Cavitating anchors and associated methods

Abstract

This disclosure relates to dynamically installable anchor for installation in the bed of a body of water by being driven down through the water and into the bed. The anchor comprises a body having a surface and a cavitation inducer. The cavitation inducer is configured to induce cavitation adjacent to the surface of the anchor body to reduce friction between the outer surface and the water. Also disclosed is a system for creating a column of bubbles within a body of water. An anchor positioned within the created column would experience reduced friction. These systems allow the anchors to attain a higher velocity within the water and embed more securely in the bed.

Description

Cavitating Anchors and Associated MethodsTECHNICAL FIELD

[0001] The invention relates to methods and apparatus for embedding anchors in the floor below a water body. In particular, the invention relates to reducing friction between an anchor as it passes through the water, sediment, or any other medium (e.g. ice, seaweed) using bubble cavities.BACKGROUND

[0002] Subsea anchors are used in a variety of industries including the offshore wind energy sector, floating solar farms, aquaculture, defence, and oil and gas. There is significant commercial value to performant solutions which can operate quickly, especially in short seasonal and weather windows, and cost-effectively in a variety of substrate types, sedimentary profiles, and water depths. Existing solutions that work well for very deep water often do not work in shallow water, and vice versa. Successful solutions must be cost effective throughout the entire life cycle of fabrication, inventory, transportation, installation, use, and removal where required. Increasingly, solutions are sought that have low environmental impact on the marine ecosystem.

[0003] In the field of torpedo piles and other kinetic impact anchors, also known as dynamic embedment anchors, the gravitational potential energy of typically massive and slender bodies is converted into kinetic energy as the pile falls through the water column. The pile impacts the bed of the water body with significant energy, embedding itself into the substrate. The embedment of the pile gives the anchor its load holding capacity / pull out strength / resisting force.

[0004] The total axial pull-out capacity of a driven pile is made up of contributions from the gravitational force on the mass of the pile, a pull-out resistance from forces acting on the side wall of the pile, a pull-out resistance from bearing forces acting on the heel or top of the pile, and suction forces acting on the lower surfaces of the pile. These forces combine to safely anchor the asset, such as the floating wind turbine, in place. It can be appreciated by those skilled in the field that anchors and piles can be interchangeable terms in this context.SUMMARY

[0005] In accordance with the present disclosure, there is provided a dynamically installable tool (e.g., anchor or recoverable device) for installation in the bed of a body of water dynamically by being driven down through the water and into the bed, the tool (or anchor) comprising:a body having an outer surface,a cavitation inducer, the cavitation inducer configured to induce cavitation adjacent to the outer surface of the body to reduce friction between the outer surface and the water, sediment, or ice through which it is passing.

[0006] The tool may be an anchor (e.g., a dynamically installable anchor). The tool may be a recoverable device - e.g., a recoverable device which is temporarily installed in the bed of a body of water in order to determine parameters of the bed (e.g., how far the body can penetrate into the bed for a given velocity, how much force is required to remove the body etc.). In this disclosure, it will be appreciated that an anchor and a recoverable tool may share similar characteristics so the terms tool and anchor will be used interchangeably unless the function of the apparatus mean that they are being used differently. A tool may be a dynamically installable tool. A tool may or may not comprise a cavitator. A tool may comprise an elongate body. A tool may comprise fins. A tool may comprise flukes.

[0007] It will be appreciated that an outer surface is the surface which is adjacent to the medium surrounding the anchor (e.g. air, water, ice, or sediment). The outer surface may be interior in the context of the geometry of the anchor. For example, the interior wall of a hollow cylinder may still be an outer surface of the anchor because it comes in contact with the medium through which the anchor is travelling. The cavitation inducer may be indistinguishable from the body in some embodiments, that is cavitation may be induced by the body, or part of it, itself.

[0008] The body may comprise a tip, and the cavitation inducer is configured to generate bubbles (or a cavity or supercavity) at or adjacent to the tip. Bubbles may also be generated further aft on the body. The tip may be at the fore end of the body. The tip may be configured to pierce the water. The tip may be in the shape of a cavitator and be configured to generate bubbles as the tip is driven through the water. The body may be elongate. The gas cavity generated may extend further aft on the anchor.

[0009] Bubbles may merge to form a cavity. A cavity may be a supercavity if it substantially envelops the anchor or tool.

[0010] The anchor may comprise a dynamically installable anchor. The anchor may comprise a pile.

[0011] The cavitation inducer may be configured to generate gas through a chemical reaction.

[0012] The cavitation inducer may comprise a cavitator, the cavitator being a shaped component configured to generate bubbles via cavitation of the water as the anchor moves through the water.

[0013] The cavitation inducer may comprise a heated component, the heated component being configured to induce cavitation via boiling (e.g., the Leidenfrost effect). The heatedcomponent may be at least a portion of the outer surface of the anchor body. It will be appreciated that a heated component would help in penetration of ice.

[0014] The heated component may be configured to be in contact with the water in the body of water.

[0015] The temperature of the heated component may be at least 100 °C. The temperature of the heated component may be at most 4000 °C.

[0016] The required skin temperature for cavitating drag reduction via the Leidenfrost effect depends on the specific design conditions required of a given anchor. The Leidenfrost effect takes place across the film boiling regime of a typical pool boiling curve. In certain embodiments, a goal is to maintain film boiling but other embodiments may be able to achieve positive drag reduction results within other boiling regimes (i.e. nucleate or transition boiling). These pool boiling regimes are to be understood for this application by analogy as the anchor being in motion is subject to flow boiling. Nevertheless, the same effect is known to occur with heat flux from a solid moving surface into a fluid or a fluid moving against a solid surface (i.e. heat exchanger). For example, it is seen with heated ball bearings dropped into water. It is known in the literature that the Leidenfrost point corresponds to the location of minimum heat flux in the pool boiling curve. This feature facilitates its empirical determination for a given experimental setup. The Leidenfrost point, particularly in a dynamic (flow) context, will certainly vary with pressure, fluid properties, and anchor properties - thermophysical, microstructure (e.g., on the external surface of the anchor), and other factors which are relevant to anchors, as well as potentially mechanical vibration (e.g., ultrasonic vibration), gravitational acceleration, and electric field. In the present application an empirical approach to setting appropriate temperature parameters is likely required given the design objectives (target anchor depth, pressure, ambient temperature, fluid characteristics, anchor composition).

[0017] For the purposes of illustration only, for pooling boiling, the Leidenfrost point for water (initiation of film boiling regime) at 1 atm may be seen at and above a wall superheat (surface temperature minus saturated water temperature) of approximately 120 °C.

[0018] The heated component may be electrically heated. The anchor may comprise an electrical energy storage device (e.g., a battery) for providing power for electrical heating. The battery capacity of a heated system will similarly depend on the mass, thermal properties, and surface area of the skin that is heated, the depth of the water body bed, water conditions, the heat transfer characteristics between the anchor and the water, and the desired time varying or invariant temperature profile of the anchor as the system sheds energy. In one embodiment, the battery may have a capacity of 500-2000 MJ. It will be appreciated that the anchor may be preheated prior to launch.

[0019] The heated component may be heated by being thermally connected to a heat sink which may be a solid, liquid, or another phase material.

[0020] The heat energy dissipated by the heatsink of an anchor will vary depending on the size, thermal properties and surface area of the anchor, the depth of the water body bed, water conditions, the heat transfer characteristics between the anchor and the water, and the desired time-varying temperature profile of the anchor as it sheds heat. The excess temperature required to operate in the film boiling regime is large and significantly increases with depth. This excess thermal energy might be in the vicinity of 1000-2000 MJ, though it could vary significantly.

[0021] The anchor may comprise a mass which can be separated from the body after the anchor has been installed in the bed.

[0022] The anchor may comprise hydrodynamic guide surfaces.

[0023] The cavitation inducer may comprise a hydrophobic surface configured to entrain gas when the anchor is introduced into the water. A hydrophobic surface may have a static contact angle with water of greater than 90°. The hydrophobic surface may be microstructured. A hydrophobic surface may become more hydrophobic when microstructured.

[0024] The anchor may be configured to be driven through the water by a combination of one or more of: gravity (e.g., within the water and / or when launched in the air above the water); a propulsion system and providing an initial velocity to the anchor (e.g., by launching from a barrel, released at a tangent of a circular trajectory). It will be appreciated that an airdrop (or other methods to drive the tool) could facilitate the penetration of a medium on the surface of the body of water (e.g. ice, or biological matter, such as seaweed).

[0025] The anchor may comprise a propulsion unit.

[0026] The anchor may comprise anchoring flukes for engaging with the bed.

[0027] The anchor may comprise a controller configured to control the cavitation inducer to increase or decrease the rate of gas emission as depth of the anchor increases.

[0028] The anchor body may comprise an embedding portion and a detachable portion, wherein the embedding portion is separable from the detachable portion, such that the detachable portion can be retrieved while the embedding portion remains embedded in the bed of the water body.

[0029] The detachable portion may comprise one or more of the following:• Additional mass, which would increase the anchor’s gravitational potential energy while it is attached;• Fins for guidance and / or stability;• A heat sink for providing thermal energy to the anchor body during transit through the water (e.g., to the outer surface of the embedding portion and / or the detachable portion);• An electrical power source for heating the anchor body during transit through the water (e.g., for heating the outer surface of the embedding portion and / or the detachable portion);• A gas source for the gas inducer;• A drogue for retarding the movement of the detachable portion relative to the embedding portion during and after separation;• A control system for controlling the cavitation inducer (e.g., for controlling heating and / or gas emission);• A control system for guidance control;• A connector for connecting to a retrieval line;• A sabot for sealing the anchor in the barrel of a propulsive cannon;• A propulsion unit;• An explosive charge to contribute kinetic energy; and• An encapsulating body that cavitates and also envelops the anchor and which releases the anchor from within.

[0030] According to a further aspect, there is provided a method of installing an anchor as described herein, wherein the method comprises:dropping the anchor from the air, or from within the waterbody such that it passes through the body of water towards the bed of the water; andgenerating bubbles using the bubble source to reduce friction between the outer surface of the body and the water.

[0031] Dropping the anchor first in air to build up an initial speed prior to entering water, for example dropping from a crane, or aircraft, maximizes the low drag characteristics and higher terminal velocity potential of a cavitating anchor relative to the same anchor without cavitation. The same anchor without cavitation has a velocity ceiling which is much lower. The higher initial velocity allows the cavitating anchorto fulfill more of its maximum potential kinetic energy for water depths that otherwise do not allow sufficient acceleration time.

[0032] According to a further aspect, there is provided a method of installing an anchor in the bed of a body of water, the method comprising:placing a bubble source at a first depth within the body of water below a surface, the bubble source being configured to emit bubbles which form a column of bubbles as they float towards the surface;driving the anchor downwards from a second depth within the column of bubbles, the second depth being shallower than the first depth.

[0033] The anchor may be driven by gravity.

[0034] The bubble source may be configured to eject bubbles laterally.

[0035] The bubble source may be configured to eject bubbles at a range of depths.

[0036] According to a further aspect, there is provided an anchor installation system for installing an anchor in the bed of a body of water, the system comprising:a bubble source positionable at a first depth within the body of water below a surface, the bubble source being configured to emit bubbles which form a column of bubbles as they float towards the surface; andan anchor being positionable at a second depth within the column of bubbles, the second depth being shallower than the first depth, the anchor being drivable downwards within the column of bubbles.

[0037] According to a further aspect, there is provided a retrofit apparatus attached to a dynamically installable anchor, the retrofit apparatus comprising some or all of the following:attachment grips (including but not limited to welds, adhesives, fasteners, magnets, pressure clamps) for connecting to a body of the dynamically installable anchor, the body having a fore end and an aft end; and / ora cavitation inducer, the cavitation inducer configured to induce cavitation adjacent to the fore end of the body or elsewhere on the body (e.g. using boiling) when the retrofit apparatus is attached to the anchor, and the anchor is moving through a body of water.

[0038] The retrofit apparatus may comprise one or more of: a cavitator and a gas generator.

[0039] According to a further aspect, there is provided a method of retrofitting a dynamically installable anchor, the method comprising:connecting a retrofit apparatus to a body of the dynamically installable anchor, the body having a fore end and an aft end; anddriving the retrofitted anchor through a body of water,inducing cavitation adjacent to the fore end of the body or elsewhere on the body (e.g. using boiling) when the anchor is driven through a body of water.

[0040] The retrofit apparatus may comprise a heater for inducing cavitation via the Leidenfrost effect.

[0041] Gas generating processes may be configured to generate a relatively high first volumetric flow rate to initiate cavity followed by a relatively lower second flow rate to sustain the cavity.

[0042] Gas generating processes may be configured to generate the cavity in different ways over time. For example, the anchor may be configured to induce cavitation using the Leidenfrost first, then gas generator second or vice versa.

[0043] In the context of this disclosure, aft relates to the rear of the anchor relative to the direction of travel. As anchors are installed by driving them downwardly into the bed below a body of water, the aft will generally be towards the top of the anchor during installation. Likewise, in the context of this disclosure, fore relates to the front of the anchor relative to the direction of travel. The fore end of the anchor will generally be towards the bottom of the anchor during installation.

[0044] A cavitator may be considered to be a device which induces cavitation in a liquid by reducing the static pressure of the liquid below the liquid’s vaporization pressure. A cavitator may comprise a solid component which induces cavitation when the relative velocity of the liquid passing around it exceeds a cavitation threshold. The cavitator may be a passive device (e.g., not driven, vibrated, spun, rotated) or active (e.g., driven, vibrated, spun, and / or rotated). The cavitator may be rigidly attached to the anchor, or may have one or more degrees of freedom relative to the anchor (e.g. for steering).

[0045] For small anchors, for example to be used with scientific equipment (with integral or attached sensors payloads anchored into sediment layers, or moored scientific buoys), or smaller vessel mooring, anchors may be of the order of magnitude of 0.2m (spherical body type embodiments) to 1m (or to 10m) meter long (elongated body types) with masses on the order of magnitude of 20 to 100kg (or to 10000kg). More typical anchors may be in the range of 3-25m or 10-25m long with masses on the order of magnitude of 1-120 or 10-120 tonnes. For example, for large industrial applications, e.g. oil and gas applications, anchors may be 120 tonnes and 25m long.

[0046] A torpedo anchor may comprise a body having a tubular steel shaft, with or without vertical steel fins (e.g., along the long axis of the anchor body). An anchor may be up to 50 meters long.

[0047] A deep-penetrating anchor (DPA) is similar to a torpedo anchor. A DPA may comprise a dart-shaped, thick-walled, steel cylinder body with fins attached to the upper section of the anchor. A DPA may be approximately 10-25 meters in length. A DPA may be 0.5-2 meters in diameter. A DPA may have a mass of 50,000-100,000 kg or 10,000-100,000 kg.

[0048] The speed of the anchor upon impact with the bed below the water body may be between 15 and 300 m / s.

[0049] Anchor transit time (e.g., between launch and embedding) varies with depth and anchor size characteristics. Anchors in shallow applications may transit in less than 1 secondor less than 5 seconds. Anchors travelling beyond 1000m may take 15-20 seconds or 15-30 seconds to reach the waterbody bed.

[0050] Means may be provided to monitor the cavity around the anchor via cameras, flowmeters, or other sensors (e.g. temperature, pressure, velocity, cavity orientation, anchor orientation and / or depth). These may be located at a single or multiple locations, for example along the anchor length or around its circumference to discern which areas lie inside and outside the cavity envelope. A controller, based on sensor data, may be used to vary the cavitation mode during different parts of the travel or acceleration of the anchor (for example to preserve gas or heat energy) or to make control decisions as to ventilation gas flow rates for example to maintain full cavitation. The controller may be part of the anchor or may be a remote controller communicating with the anchor (e.g., via a cable or wirelessly from a vessel on the surface or a remote operated vehicle).

[0051] For example, the ventilation gas flow rates required to initiate cavitation are higher than those required to sustain it, and data from these sensors may be used to optimize system performance and gas or heat use. Likewise, the anchor may adjust for different conditions as the anchor descends (variations in pressure, currents, and water temperature).

[0052] These sensors may also be used to respond to gravitational and buoyant effects on the cavity, for example if the anchor moves away from vertical and the bubble pulls away from the anchor along the lower surface under the influence of buoyancy. Nozzles in the cavitator on this side may expel a higher volumetric flow rate of gas to compensate, or the total volume may be increased to enlarge the cavity everywhere.

[0053] The bottom of a body of water may be considered to be the bed or floor.

[0054] In the context of this disclosure, cavitation may be considered to relate to generating a cavity of gas (potentially multiple cavities) within a body of liquid. Cavitation may comprise: natural cavitation (generating the cavity of vapour by changes in velocity of the liquid); ventilated cavitation (generating the cavity by introducing gas into the liquid); heated cavitation (generating the cavity by boiling the liquid by heating) and / or entrained cavitation (capturing gas adjacent to the surface of the anchor).

[0055] Supercavitation may be considered to be when there is a clear supercavity. A supercavity may be considered to be a coherent and (substantially) stable bubble which is attached to and surrounds at least a portion of a body.

[0056] Cavitation may comprise the formation of a cavity of gas, vapour or supercritical fluid.

[0057] Methods of Leidenfrost heating may include one or more of: inductive, resistive, external, and internal heating. The anchor may be preheated before launch and / or during transit.

[0058] The anchor may be connected to an external device (e.g., a vessel) using a data tether, e.g., for transmitting sensor data and / or control signals.

[0059] Cavitation may be induced using mechanical vibration and / or an electromagnetic field. This may be used to induce or enhance the Leidenfrost effect.

[0060] The anchor may be launched above the surface. This may allow the anchor to accelerate to a greater speed before entering the water.

[0061] The anchor may be stabilized by being spun around an axis aligned with the direction of travel.

[0062] Sensors may be used to monitor cavity or environment for control and embedment data.

[0063] The anchor may be fired out of cannon, or otherwise propelled to an initial velocity. The method of launching may comprise firing the anchor from a cannon or propelling the anchor to an initial velocity.BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In the Detailed Description section below, one or more embodiments of the present technology are described in relation to the attached figures. These embodiments are intended to provide a better understanding of the invention, how the invention may be put into practice, and to demonstrate some of the advantages of the invention. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.Figure 1a-d are schematic cross-section views of an embodiment of an anchor as it is inducing cavitation during transit through a water body prior to embedding in the water body bed.Figures 2a-c taken together is a flow diagram showing how an anchor could be installed in the seabed.Figure 3 is a perspective view of two floating wind turbine assets secured to the seabed using anchors.Figure 4 is side view of a further embodiment of an anchor configured to induce cavitation using heat.Figure 5a is a cross-section view of a further embodiment of an anchor with a heated skin.Figure 5b is a cross-section view of a further embodiment of an anchor in which the skin is heated using an electrical power source.Figure 5c is a cross-section view of a further embodiment of an anchor in which the skin is heated using a heat sink.Figure 6a is a side view of a further embodiment of an anchor with a substantially spherical shape.Figure 6b is a side view of a further embodiment of an anchor wherein the body is in the shape of fins.Figure 7 is a schematic side view of a further embodiment of an anchor which has a hydrophobic coating for entrapping gas next to the anchors surface.Figure 8 is a schematic side view of a further embodiment of an anchor embedded within the layers of the seabed.Figure 9 is a schematic side view of an embodiment of an anchor installation system comprising a bubble generator configured to create a column of bubbles within which the anchor can travel.Figure 10 is a schematic side view of a further embodiment of an anchor installation system comprising a bubble generator configured to create a column of bubbles within which the anchor can travel.Figure 11 is a schematic side view of an embodiment of an anchor installation system.Figures 12a-g are perspective views of various embodiments of anchors showing their guidance systems.Figure 13 are two side views of embedded anchors, one installed using the present cavitation method and one installed without using the present cavitation method. Figures 14a and 14b are schematic cross section views of two embodiments of anchors showing how gas may be generated and expelled to induce cavitation.Figures 15a is a schematic cross-section view of a further embodiment of anchors showing how gas may be generated and expelled to induce cavitation.Figures 15b is a schematic cross-section view of a further embodiment of anchors showing how gas may be generated and expelled to induce cavitation.Figure 16 is a cross-section view of how gas would coat an embodiment of an anchor during transit through the water.Figure 17 shows two cross-section views of an embodiment of an anchor with detachable recoverable components.Figure 18 shows two cross-section views of an embodiment of an anchor with detachable recoverable components.Figures 19a and 19b show typical pile anchors, one configured without using the present invention and a retrofit device to configure the typical pile anchor to use the present cavitation method.Figure 20a-d shows cross-section views of two variants of an anchor embodiment launched out of a cannon with detachable recoverable components.Figure 21a is a cross-section view of an embodiment of a hollow cavitating anchor.Figure 21b is a top view of the anchor of figure 21a.DETAILED DESCRIPTIONIntroduction

[0065] Dynamically installed anchors are anchors intended for waterbody use (e.g., at sea, in a reservoir, in a tailing pond, in a flooded mine, in a river or in a lake) that derive their holding capacity from the frictional, or bearing, resistance of the surrounding soil as well as their weight, as opposed to gravity anchors, which derive their holding capacity largely from their weight.

[0066] For embedded anchors, the holding resistance against load can be expected to be higher whenever an anchor is driven deeper into a substrate relative to an identical installation that is shallower; the undrained shear strength of a given substrate type is typically higher at greater depth, and this translates into larger resistive shear and bearing forces. In addition, for deeper installations the energy required to mobilize a failure surface in the sediment increases, yielding higher pullout capacity.

[0067] An anchor driven deeper also may allow for different substrates in a sedimentary profile to be accessed, as different substrates can have widely varying mechanical properties (i.e. sand vs clay). Accessing an otherwise inaccessible substrate for embedment can result in significant shear and bearing strength improvements.

[0068] Consequently, attaining higher kinetic energy for a given dynamically embedded anchor is desirable because it is very likely to result in deeper embedment. Terminal velocity is “the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration” (Oxford English Dictionary). Terminal velocity can be increased by decreasing drag. Even anchors that are propelled or launched toward the bed of a waterbody will experience significant drag as they travel through water. After the propulsive force is removed, this drag will gradually diminish their speed until they also reach their terminal velocity. If propulsion is supplied throughout, the attained terminal velocity will remain high, but it will be limited by viscous drag. If viscous drag can be reduced the propelled anchor will achieve even higher kinetic energy.

[0069] Reducing the friction between the water and the anchor can increase the terminal velocity of the anchor, thereby increasing the kinetic energy that the anchor can attain. Embodiments disclosed herein relate to reducing the friction between the anchor and the water using bubbles to create a low viscosity cavity between the anchor and the water. For the purposes of this description the term ‘cavitating’ means ‘developing a cavity’ (from the verb ‘cavitate’); likewise ‘cavitation’ can refer to the action of creating a cavity from the same verb, or can refer to the well-known hydrodynamics term to mean the generation of vapour frommotion of a liquid. Cavitating can therefore include hydrodynamic cavitation of a fluid, but can arise from pure ventilation or other means.

[0070] To attain significantly higher terminal velocities embodiments are disclosed herein which enable the anchor to be placed substantially inside a cavitated bubble. This cavitated bubble may also be referred to as a supercavity, analogous to its use in the field of hydrodynamics (e.g., in which the bubble extends (either naturally or augmented with generated gas) past the aft end of the object). The goal is to dramatically reduce viscous drag on the anchor and increase its kinetic energy. The source of the gas cavity can be the ambient fluid itself, or it can be an introduced gas source, or both.

[0071] From the frame of reference of the anchor, natural cavitation can be induced by localized reduction of the fluid static pressure from higher-than-freestream fluid velocities near the anchor as water accelerates to move around it. This is a consequence of Bernoulli’s principle. Fluid static pressure below the local vaporization pressure causes water vapour to form. It will be appreciated that references in this document to freestream fluid motion are understood to mean from the reference frame of a moving object moving through substantially quiescent fluid.

[0072] When natural cavitation is attempted at increased depth the hydrostatic pressure in the vicinity of the object attempting to naturally cavitate increases which makes vapour generation much more difficult.

[0073] A solution therefore requires steps to help initiate or synthesize a comparable gas, vapour, or supercritical fluid pocket in this context. That can be achieved by using chemical reactions to drive gas-generating reactions that ventilate exhaust around the anchor body, by overcoming the higher ambient vaporization pressure barrier by increasing the local fluid temperature such as by heating the anchor surface, or by initially accelerating the anchor significantly, with an affixed cavitator to induce cavitation that arises from high local fluid motion around the cavitator. These methods can also be used in combination.

[0074] The benefits of subsea cavitating anchors are numerous. They can achieve comparable performance to conventional anchors at smaller sizes, therefore they are more economical even after accounting for additional required components, processes, and subsystems (some of which can be re-used in certain embodiments). They can correspondingly achieve much greater pull-out capacity to conventional anchors at the same size. Because of their size-efficiency they are comparably lower cost and lower environmental impact to fabricate, store, handle, and transport than the current state of the art. They can be installed very rapidly and the installation can be done from smaller vessels or even aircraft. Unlike driven or drilled piles which are installed slowly with heavy equipment, greater fuel emissions, and significant noise, cavitating anchors have only a very short term acoustic andsediment-disturbing impact on the local ecosystem through which they travel and embed. They are also able to reach effective embedment speeds in shallower water depths and are also able to embed at the bottom of very deep water which is less feasible for existing anchor technologies that are drilled, driven, suctioned or dragged into place. Because of their high kinetic energy, they can also penetrate some sediment types that other anchors cannot. These features make them a more versatile and cost-effective solution.

[0075] Various aspects of the invention will now be described with reference to the figures. For the purposes of illustration, components depicted in the figures are not necessarily drawn to scale. Instead, emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects of the invention. A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgment of persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present invention.Anchor with Natural and Ventilated Cavitation

[0076] Figures 1a-d show an embodiment of a subsea cavitating anchor 100. In this embodiment, cavitation is induced through natural cavitation and ventilated cavitation. Natural cavitation is induced using a disc cavitator. Ventilated cavitation is induced using peroxide decomposition and catalyst to create a pressure regulated gas flow. In this embodiment this combination induces a supercavity, and the combination is referred to as ventilated supercavitation. Bubble evolution is shown developing in figures 1a through to 1d from foamy partial cavity to clear supercavity.

[0077] The anchor has a body 101, and it may have fins and lugs, padeyes, or shackles to attach it to mooring equipment or chains / lines / tethers or other equipment. In this case fins 102 and line connector 103 are shown.

[0078] The anchor body 101 has an elongate form and is attached to fins at the aft end. The fins ensure that the axis of the body is aligned with the direction of travel through the water.

[0079] The anchor has mass, and so its gravitational potential energy converts to kinetic energy as it falls.

[0080] In this embodiment, cavitation is induced using a ventilated supercavitation (a combination of natural cavitation and ventilation of gas).

[0081] For natural cavitation, the anchor body comprises a cavitator 104 at the fore end. A cavitator induces cavitation in the fluid in which it travels by motion of the freestream fluid around the cavitatorwhich increases the local flow speed and reduces its pressure low enough to vaporize at ambient temperatures. The cavitator in this embodiment is a disc-type cavitator.Other embodiments may have conical cavitators, other cavitator geometries, or no distinct cavitators.

[0082] In this embodiment, ventilation cavitation is induced by a gas generating system. In this embodiment the gas generating system comprises a tank 107 for reactants and a catalyst 106. In this embodiment the catalyst is a silver mesh, and the reactant is hydrogen peroxide.

[0083] Other embodiments may use other catalysts, no catalyst, other reactants in one or more tanks and one or more reaction chambers. Other embodiments may also use solid propellants (fuel plus oxidizer mixtures) in different fuel grain and core configurations to generate gasses. The gasses emitted may be inert or of low impact to the ecology of the surroundings, e.g. air, oxygen, carbon dioxide, hydrogen. In this embodiment the hydrogen peroxide reactant decomposes into hydrogen and oxygen gas as it contacts the catalyst.

[0084] In this embodiment the anchor has a pressure regulator 108 that controls the flow rate of reaction products along fluid conducting paths that lead out of ventilation holes 105 adjacent to the cavitator.

[0085] In other embodiments the ventilation hole or holes (e.g. nozzles) may be oriented to expel gas to provide thrust to the anchor to propel it forward. In other embodiments the fluid conducting paths may include pumps, compressors, pressure transmitters, temperature transmitters, check valves, controlled actuated valves, nozzles, orifices, or heat exchangers, to sense, control, or condition the gasses. Other embodiments may use other types of valves, regulators and control systems to control the gas flow rate, including sensing upstream and ambient conditions.

[0086] Once the anchor is dropped, the reaction product gasses help initiate ventilated cavitation of the fluid flow around the anchor once they exit the ventilation holes into the freestream water, as shown in figure 1a.

[0087] The reaction product gasses and any naturally cavitated fluid vapours form a cavity 115 around the anchor. The cavity starts as a turbulent mix of fluid and bubbles as shown in figures 1a-d. The bubble cavity may grow or coalesce as the flow rate of gasses increases. The bubble cavity may grow or coalesce as the speed of the anchor increases (e.g., as the quantity of gas created by the natural and / or ventilated cavitation increases).

[0088] As shown in figure 1c, at the critical condition the cavity evolves into a clear supercavity. The clear supercavity is a substantially stable gas volume that fully or partially envelops the anchor. As shown in figure 1c, the supercavity extends beyond the aft end of the anchor body. However, the tips of the fins may continue to engage with the liquid to improve guidance. In figure 1 d, the cavity size has reduced so as not to fully extend beyond the aft end of the anchor body.

[0089] In some embodiments the supercavity may oscillate. It may also collapse, dissipate, and be re-initiated.

[0090] The ventilated gasses, cavitated bubbles, and the supercavity dramatically reduce the anchor’s viscous drag as it travels through the fluid and through the waterbody bed during embedment. The supercavity reduces the anchor’s drag the most which allows it to attain very high speed (e.g., 15-300 m / s) through the fluid and reach the bed of the waterbody with very high kinetic energy. The reaction product gases exit the anchor with high temperature and pressure ensuring that they do not condense even as the anchor experiences very high pressure and low temperature deep below the sea, e.g. 1000m below sea level.

[0091] The very high speed of travel of the anchor results in deep embedment into the waterbody floor. This deep embedment places the anchor in strong de-watered sediments. These sediments have high undrained shear strength. The entry of the anchor with cavitation also reduces the water entrained into the sediment by displacing that water with vapour. The deep placement and strength of surrounding sediments makes the anchor a very strong anchor. The strength or pull-out capacity of the anchor comes from side shear / pull-out capacity (surfaces along the long axis of the anchor) and side bearing capacity, end (or heel) shear / pull-out and bearing capacity, suction acting on the lower surfaces of the anchor, and the mass of the anchor. The end / heel pull-out capacity is influenced by the depth and / or the undrained strength of the sediment above. The side pull-out capacity is influenced by the undrained shear strength of the adjacent sediment. Bearing capacities are influenced by the undrained shear strength of adjacent sediment. The ease of operation of the supercavity and concomitant speed allows the anchor to be installed quickly, in diverse substrates, in diverse fluid depths, very economically.Flowchart

[0092] Figures 2a-c together form a generalised flowchart that illustrates how some embodiments of the cavitating anchor are installed to create a subsea anchor foundation. It will be appreciated that some embodiments may or may not use all of the steps shown in figures 2a-c.

[0093] As shown in figure 2a, the anchor is taken to the launch location, typically by boat, though it could be done by aircraft. The anchor may be handled on the deck of the vessel to put it into position.

[0094] A series of optional steps are then performed based on:• Whether the anchor requires an external separable fuel or detachable guidance module.• whether the anchor requires a chemical process fuel or batteries.• whether the anchor requires an external pre-heating for boiling, e.g. Leidenfrost effect• whether the anchor requires require an external source of gas.• whether the launching of the anchor requires a guidance system.

[0095] Any required components, materials and / or systems are provided. Then the anchor is positioned in or above the water column, hanging or in a launching device. If the anchor needs to be positioned at a specific height or depth, this is done.

[0096] Figure 2b relates to launching the anchor downwards. If the anchor has a propulsion system, this an activated. If an external gas source is required, this is activated. It will be appreciated that the external gas source may be used to induce cavitation and / or propel the anchor.

[0097] Then the anchor is released or launched, and it descends downwardly through air and then water, or just through the water column. During its decent, if gas generation processes are being used, these are activated at the appropriate time. If the anchor is guided, the guidance instructions are communicated to the anchor to control its trajectory. This can include adjusting the speed and / or direction of the anchor as it is descending. It will be appreciated that the anchor may be configured to control the direction of guidance surfaces of the anchor (e.g., the fins) based on received guidance control signals. It will be appreciated that other embodiments may be guided based on information stored onboard (e.g., a target location), or the anchor may be unguided.

[0098] Figure 2c relates to the anchor when it embeds in the sea floor. Before or after embedding, the anchor may be configured to determine whether there is a separation module to be jettisoned before the anchor embeds in the sea floor. If so, this is done, and the separation module or other material can be recovered. It will be appreciated that the detachment of a separation module may also be done after embedment, or after validation of embedment.

[0099] After the anchor is embedded, there may be an analysis of embedment data. This may include data relating to the lateral position of the anchor on the seabed (e.g., longitude and latitude), the depth of the anchor in the seabed, the angle of the anchor relative to the horizon, and / or the pressure of the seabed on the anchor etc. If the data is not satisfactory, the anchor may be retrieved and the process restarted. If the data is satisfactory, any post-embedment processes are undertaken. Again, a status check of the anchor may be carried out based on data for the anchor.

[0100] After settling of sediment, the anchor may be connected to external equipment (e.g., floating assets such as a floating wind turbine) and used.

[0101] Cavitating anchors will have a shorter settling time by entraining less water during sediment penetration which will maintain a higher undrained shear strength of the adjacent sediment. Anchors which cavitate using boiling, e.g. heated Leidenfrost anchors may haveresidual heat that can be dissipated into sediment after they are embedded which may favourably accelerate the restoration of sediment shear strength via accelerated dewatering.

[0102] The most common use of these anchors is as a connection point to secure assets to the bed of the water body (e.g., the sea floor). Other anchors may be used as a probe, for example, to determine the characteristics of the water body bed for other uses including other anchors. These probe anchors may be used as penetrometers. For example, a smaller anchor may be driven into the water body bed in order to determine factors such as penetration depth for particular impact conditions, and / or to directly measure or sample sediment properties using on-board sensors or devices. This allows the user to determine how securely attached an anchor will be to the water body bed. The user may carry out a number of such tests at different positions before deciding on a location for the final anchor installation.Anchoring Offshore Assets

[0103] Figure 3 shows an embodiment of installed subsea cavitating anchors anchoring offshore floating assets 390 (wind turbines in this case) with taut mooring lines 391a.

[0104] The floating assets float on the water at sea level 312 and are tethered to anchors 300a embedded below the seabed 311.

[0105] The taut mooring lines may include sections of chains or load reduction devices.

[0106] Other embodiments may use catenary or slack mooring systems to attach to the anchors, for example plain catenary, multi-catenary, semi-taut, and other variations. The anchor foundations may also be used in other embodiments to anchor floating solar generation facilities, aquaculture facilities, floating desalination facilities, floating buildings, oil and gas processing, transportation or storage facilities, oil and gas floating vessels, tidal and wave energy generating facilities, energy storage facilities, floating or submerged data centres, ocean waste collecting equipment, fishing equipment or vessels, military vessels or equipment, scientific vessels, transportation or shipping equipment or vessels, submerged vessels of all types, submerged scientific equipment, offshore mining vessels or equipment. Different embodiments may vary the size, orientation, number, depth, relative placement, shape and features of anchors for different applications.Preheated Anchor using Leidenfrost Effect

[0107] Figure 4 shows an embodiment of a cavitating anchor 400. The anchor has a body 401 , fins 402, and a lug 403 which is attached to a tether line 491.

[0108] This embodiment is configured to induce cavitation using film boiling, i.e. the Leidenfrost effect. The anchor has a thermal mass. The anchor, in this case, is at least partially made of a thermally conductive metal material. Other embodiments may be made with other thermally conductive materials.

[0109] In this case, the thermal mass of the anchor is heated to a temperature above the Leidenfrost point of the freestream fluid at the highest pressure the anchor will experience (corresponding to the deepest point that the anchor will travel). In this embodiment the thermal mass will be heated far above this temperature. Heat from the anchor’s thermal mass is conducted, convected, and radiated to the fluid as it flows past the anchor. This heat vaporizes the fluid and surrounds the anchor in a cavity or film of gasses - this is a type of manifestation of the Leidenfrost effect.

[0110] The cavity 415 of vapour fully encloses the anchor body; in other embodiments or at different times the cavity may only partially enclose the anchor. The motion of the freestream fluid around the anchor may also increase the local flow speed and reduce its pressure low enough to vaporize at ambient temperatures contributing so-called ‘natural’ cavitation. The vaporized fluid surrounding the anchor reduces its viscous drag during travel through the freestream and during embedment in watered sediments such as are found in the beds of waterbodies. The vaporized fluid reduces the entrainment of water into the sediment during embedment, resulting in better strength properties in the sediment adjacent to the anchor.

[0111] As shown in figure 4, the anchor’s fins protrude beyond the supercavity contributing to stability of travel by interacting with the freestream flow; other embodiments may not have fins protrude beyond the supercavity.

[0112] In this embodiment the anchor is pre-heated before it travels through the fluid and its temperature decays as it sheds heat to the fluid, at all times the anchor remains at sufficient temperature to remain in the film boiling regime.

[0113] In other embodiments the anchor may be continuously heated by an onboard battery or electrical power source, and / or by an exothermic chemical reaction, and / or by a heat sink such as molten salt. In this embodiment the anchor is made of a ferrous material and is heated inductively through inductive coils as it is oriented and positioned for deployment. In other embodiments the anchor may be heated resistively, by contact with hot fluid, or by contact with flames. The anchor in this embodiment has similar benefits to the anchor embodiment in Figure 1 in terms of simplicity of operation of the supercavity, concomitant speed, strength of resultant anchor, quick installation in diverse substrates at diverse fluid depths, and favourable economics.Heated Skin Embodiment

[0114] Figure 5a shows an embodiment of a subsea cavitating pile anchor 500a. The anchor has a body 501 , fins 502, and a lug 503 connected to an anchor line 591. The body 501 has a layer of outer material that constitutes a skin 521. This skin has thermal mass and is thermally conductive. The anchor has at least some volume of internal material that is massive but doesnot have high thermal mass or thermal conductivity. The internal mass may be thermally insulated from the skin and be unheated.

[0115] When the heated skin comes into contact with water, a cavity 515 is formed.

[0116] The anchor 500a operates similarly to the embodiment described in Figure 4 except that only the outer material skin substantially contributes to heating fluid as it flows past the anchor.

[0117] Figures 5b-c shows two more specific embodiments of a pile anchor 500b-c with a thermally conductive and thermally massive skin.

[0118] The first embodiment 500b, as shown in figure 5b, has a power source 522 (e.g., a battery) and the skin 521 is electrically resistive. When current is applied to the skin it heats up past the vaporization point (e.g., or Leidenfrost point) of the freestream fluid at the highest pressure the anchor will experience (corresponding to the deepest point that the anchor will travel). It will be appreciated that an electrically conductive and magnetically permeable anchor skin may alternately be heated inductively through properly oriented coils adjacent to, within the skin, or sufficiently close to the skin (e.g. coils with turns substantially aligned around a normal that is locally perpendicular to the skin).

[0119] The second embodiment 500c, as shown in figure 5c, has an internal heat source 524 which may be a heat sink and / or an exothermic reaction vessel. The heat source is in thermal contact with the skin 521 which heats the skin as described for the previous embodiment. In this case, the thermal contact is facilitated via thermal conductors 523.

[0120] In other embodiments the heated skin may cover only a portion of the anchor. In other embodiments there may be a control system to control the temperature of the heated skin as it travels deeper to optimize the heating.Alternative Leidenfrost Effect Anchors

[0121] Figures 6a-b show two embodiments of cavitating anchors.

[0122] Figure 6a shows an anchor 600a which has a body 601a, a lug 603a attached to an anchor line 691a, and no fins.

[0123] Figure 6b shows an anchor has a body in the shape of fins 601b made of metal plate, a lug 603b attached to an anchor line 691 b.

[0124] Similar to Figure 4, the anchors have thermal mass. The anchors are at least partially made of a thermally conductive metal material; other embodiments may be made with other thermally conductive materials. The thermal masses of the anchors are heated to a temperature above the vaporization point of the freestream fluid at the highest pressure the anchor will experience (corresponding to the deepest point that the anchor will travel).

[0125] Heat from the anchors’ thermal mass is conducted, convected, and radiated to the fluid as it flows past the anchors. This heat vaporizes the fluid and surrounds the anchors in a cavity 615a-b or film of gasses - this is a type of manifestation of the Leidenfrost effect.

[0126] In this example, the cavity of vapour fully encloses the anchors; in other embodiments or at different times the cavity may only partially enclose the anchors. The motion of the freestream fluid around the anchors may also increase the local flow speed and reduce its pressure low enough to vaporize at ambient temperatures contributing so-called ‘natural’ cavitation.

[0127] The vaporized fluid surrounding the anchors reduces their viscous drag during travel through the freestream and during embedment in watered sediments such as are found in the beds of waterbodies. In this embodiment the anchors rely on the drag of the anchor lines to be a significant contributing factor to stability of travel.

[0128] In these embodiments the anchors are pre-heated before they travel through the fluid and their temperatures decay as they shed heat to the fluid, at all times the anchors remain at sufficient temperature exploit the Leidenfrost effect.

[0129] In other embodiments the anchors may be continuously heated by an onboard battery or electrical power source, or by an exothermic chemical reaction. In this embodiment the anchors are made of a ferrous material and are heated inductively through inductive coils as they are oriented and positioned for deployment. In other embodiments the anchors may be heated resistively, by contact with hot fluid, by contact with flames, or by contact with other phases of matter (e.g. plasma).

[0130] The anchors in these embodiments enjoy very similar benefits to the embodiments in Figures 1 and 4 in terms of simplicity of operation of the supercavity, concomitant speed, strength of resultant anchor, quick installation in diverse substrates at diverse fluid depths, and favourable economics. Their simple geometry makes them very cost effective to manufacture.Anchor with Hydrophobic Coating

[0131] Figure 7 shows a further embodiment of a subsea cavitating anchor 700. The anchor has a cylindrical body 701 with a hemispherical end. Other embodiments may have other geometries of bodies and ends. The anchor has a lug 703 attached to a chain tether 791.

[0132] The anchor body 701 in this case is substantially coated with a hydrophobic coating such as a commercially available microscopic silica crystal coating that cannot be wetted.

[0133] Other embodiments may be coated with other low surface energy microstructure composite materials (e.g. zinc oxide / polystyrene, carbon nanotubes or others) or the anchor itself may have a micro or nano-structure at its surface creating a so-called lotus effect which gives it a high liquid-solid contact angle.

[0134] The anchor entrains a volume of air while entering the fluid 712 with speed as shown in figure 7. As the volume of entrained air becomes submerged it is pinched off to form a stable teardrop shaped gas cavity around the anchor. The teardrop sheds bubbles from its tail (shallowest end) and reaches an optimal shape and size. The gas cavity reduces the tangential stress at the gas-fluid interface and approaches a free-slip condition and minimal drag.

[0135] The entrained gas cavity allows the anchor to accelerate quickly within the fluid even if the gas cavity is eventually shed such that the anchor can reach its non-cavitating terminal velocity earlier, even in shallow depths of water. This helps ensure successful embedment. In other embodiments the anchor can travel in the un-shed gas cavity and water column a greater distance / depth and attain higher kinetic energy, embedding deeply into strong sedimentary layers of the waterbody bed. The gas cavity is shed during embedment in the sediment.

[0136] Features of other embodiments described above may be used together with this embodiment to sustain a gas cavity during embedment or during other parts of the anchor’s travel, for example, the Leidenfrost effect may be used or ventilated cavitation may be used. Several gas cavities may also act together to reduce the drag of the anchor during travel, for example, using a superhydrophobic coating to establish and sustain a layer of microbubbles, an air plastron, adjacent to the anchor surface. The anchor enjoys a high pull-out strength as a result of its deep embedment and placement in typically stronger de-watered sediments which are located deeper in the waterbody bed. Like other embodiments described, the anchor can be deployed much faster than other types of piles and anchors (screwed, hammered, dragged, suction anchors) at lower fabrication, transportation and installation cost for comparable anchor capacity owing to its reduced material use, reduced size, lower complexity and reduced installation time.Embedding into De-Watered Sediment

[0137] Figure 8 shows an embodiment of a subsea cavitating anchor 800 that is embedded into deep de-watered sediment layers 811a-c. The anchor has embedded into the sediment and travelled through the fluid inside a supercavity.

[0138] The upper layer 811a of the seabed is the least de-watered and the resultant shear strength of the sediment is the lowest. A middle layer 811b is more de-watered and the resultant shear strength of the layer is higher. A lower layer 811 c of sediment is the most dewatered and the resultant shear strength of the sediment is highest.

[0139] The anchor has been able to embed in deep layers on account of its high kinetic energy on embedment. This was enabled by the low viscous drag that it experienced in travel. The low viscous drag was enabled by the cavitation bubble or bubbles in which it traveled.

[0140] It will be appreciated that sediment layers may not always progressively get more dewatered and stronger with increased depth, though embedding deeper has the advantagethat the mass of sediment above the bearing surfaces of the anchor is greater. The sedimentary profile is driven by geological processes and can consist of different combinations of sediment types, some of which may impede de-watering of lower layers. For example, a clay overburden may impede dewatering of other sediments below.

[0141] Nonetheless the embedment energy of the anchor maximizes the probability of it reaching the strongest layers at a given location. The high kinetic energy also allows the anchor to embed in substrates that kinetic anchors cannot typically penetrate, or penetrate with difficulty, for example rocky or coarse sediments. The low drag and stability afforded by cavitation also allows optimization of anchor geometry to maximize penetration in sediments. The low viscous drag on the anchor arising from cavitation also allows the anchor to attain a high kinetic energy in a short water column. This allows the anchor to be embedded into waterbody beds that lie in shallow water. This increases the number of possible applications for this type of anchor.External Bubble Source from Seabed

[0142] Figure 9 shows an embodiment of a subsea cavitating anchor pile that is being deployed from a ship 951 , for example an anchor handling tug supply vessel. The anchor has no specific cavitator. Other embodiments may have cavitators. Other embodiments may be deployed from other vessel types.

[0143] The pile anchor 900 in this case is lowered into the water column before it is released. The pile anchor will be released with a slack tether that keeps it connected to the vessel without substantially impeding its speed. The tether is flaked on the ship’s deck. In other embodiments it may also be flaked or suspended in the water column or wound around a drum or capstan or payed out from the rear of the pile anchor. The anchor will be released into a column of bubbles that are emitted by an external source 961.

[0144] The external bubble source 961 contributes ventilated gasses to initiate ventilated supercavitation which can be generated at much lower speeds and higher ambient pressures by injection of non-condensable gas or supercritical fluid around a cavitating object.

[0145] In this embodiment, the external bubble source 961 is a hollow device, such as a tube, with one or more outlets. Gas is supplied to the external bubble source 961 via a tube, pipe, or hose 962 from the surface. As shown in figure 9, the bubble source is placed at a first depth within the body of water below a surface. The bubble source is configured to emit gas received from the tube, pipe, or hose to create bubbles which form a column of bubbles 963 as they float towards the surface.

[0146] The anchor is propelled or driven downwards from a depth above the bubble source within the column of bubbles.

[0147] In this case, the bubble source is arranged in a ring to provide a cylindrical column of bubbles. In this case, the bubble source has outlets configured to emit the gas laterally such that as the bubbles start to rise, the column of bubbles is not directly above a component of the bubble source. This allows the anchor to experience the drag reduction due to the bubbles, while not impinging on the bubble source when it embeds in the bed below the body of water.

[0148] In this case, the gas for the bubbles is generated on the ship 951. It will be appreciated that, in other embodiments, the bubble source may comprise a gas generator (e.g., reactants for a gas producing reaction) and / or a gas source (e.g., a tank of compressed gas).

[0149] The ventilated gasses decrease the viscous drag around the anchor. This allows the anchor to reach high speeds. At high speeds natural cavitation conditions can be met in the fluid moving past the anchor. The external gas bubbles can contribute to the anchor’s supercavity. The external gas bubbles may be used for only a part of the travel of the anchor, for example to help initiate natural cavitation. In this embodiment the gas is emitted from apertures or nozzles in a gas or fluid conducting structure that rests at a desired depth. In other embodiments this structure may be suspended in the water column below a vessel, or the external structure may travel through the fluid. In this embodiment the gas is compressed air pumped from the vessel toward the nozzles.

[0150] In other embodiments the gas may be generated by the reaction of chemicals that are pumped toward the apertures, with or without the use of catalysts. In yet other embodiments the gas may be generated from self-contained standalone systems that are not connected to the anchor handling vessel. The gas may be at an elevated temperature relative to the ambient water temperature. This will help prevent the gas bubbles from condensing at high pressure in deep water. The gasses emitted may be inert or of low impact to the ecology of the surroundings, e.g. air, oxygen, carbon dioxide, hydrogen.Vertical Emission of Bubbles

[0151] Figure 10 shows an embodiment of a subsea cavitating anchor pile that is similar to Figure 9.

[0152] The pile anchor 1000 in Figure 10 is being lowered for release into a veil or column of bubbles 1062 emitted by a substantially vertical gas conducting structure or bubble source 1061. The gas conducting structure is supplied with gas by the vessel via a tube or pipe 1064. In this embodiment, the gas conducing structure has gas outlets configured to direct gas laterally outwards below the anchor 1000.

[0153] It will be appreciated that, in some embodiments, the bubble source may be configured to close outlets which are above the anchor. For example, in this case, the vertical gas conducting structure may have openable and closeable valves in the outlets such that bubbles are only created below the anchor. This may reduce the use of gas. Likewise, someembodiments may be configured to only emit gas within a predetermined distance below the anchor. For example, valves more than the predetermined distance may be closed until the anchor approaches. The opening and closing of valves may be controlled from the surface (e.g., electronically using a computer with memory and a processor), mechanically (e.g., in response to the position of the anchor with respect to the guide rail or line), and / or in response to sensor data received on the position of the anchor (e.g., one or more of: depth sensor, pressure sensor, and location sensor).

[0154] In this embodiment the pile anchor 1000 is physically guided by the vertical gas conducting structure 1061. The anchor is connected to the vertical gas conducting structure by a supplementary mass 1063 which moves with the anchor translationally in one degree of freedom (up and down) until it disconnects from the anchor. The supplementary mass disconnects from the anchor before embedment. The supplementary mass is connected to the gas conducing structure via a low friction linear guidance device, for example a linear rail carriage. The supplementary mass rides in the anchor’s cavitation bubble or bubbles and does not substantially increase the viscous drag on the anchor. When connected it contributes greater mass to the anchor which increases the gravitational force on the anchor-mass system and increases its terminal velocity. This guidance ensures accurate insertion of the anchor in the waterbody bed.

[0155] It will be appreciated that attaching the anchor to the bubble source in this way addresses issues with the anchor impinging upon the bubble source during transit through the water and / or during embedding on the seabed.

[0156] In other embodiments the gas conducting structure may be suspended above the waterbody bed. The gas conducting structure may span the entire path of travel of the anchor, or a part of it. In other embodiments the anchor may be physically guided by the gas conducting structure without a supplementary mass.Anchor Inspection

[0157] Figure 11 shows a subsea cavitating anchor pile. The pile anchor 1100 has a cavitator 1104, fins 1102, and a multi-degree of freedom lug 1103, and is attached to a tether 1191. The tether is connected to a buoy 1195.

[0158] The buoy may be separately anchored or not separately anchored and / or connected to the installation vessel. The buoy keeps the anchor’s line clear from self-entanglement. The anchor has been released from a crane line on a vessel 1151 via a mechanical latch or disconnect 1153.

[0159] The vessel employs a remote operated vehicle (ROV 1154) to target, inspect, maintain, gather data from, or repair the anchor. Data collected from the anchor may be used to characterize the sediment at different embedment depths. The ROV may also inspect,service, or use the anchor’s lug or tether equipment. The anchor’s supercavity 1115 envelops the anchor and its fins. The anchor is actively guided to stabilize its travel and improve its placement accuracy using one or more of the embodiments described in Figure 12.

[0160] In other embodiments the anchor may be released by an ROV or autonomous underwater vehicle (AUV) if the ROV / AUV is large or the anchor is small.Guidance Systems

[0161] Figure 12 shows a set of subsea cavitating anchors. Each anchor has a body, and a cavitator. Each anchor illustrates embodiments of guidance systems. The guidance systems all work to target the anchor to the correct location in the correct orientation.

[0162] The guidance systems include:• Figure 12a: The anchor has no fins. It can be actively guided using a steerable cavitator 1204a. The steerable cavitator pitches in at least two degrees of freedom to create guidance pitching moments for the anchor. In other embodiments the cavitator may have more degrees of freedom.• Figure 12b: The anchor also has a steerable cavitator 1204b which operates the same way. This anchor also has fins 1202b for passive stability. The fins provide passive stability when they are not fully enveloped by the supercavity.• Figure 12c: The anchor has, in addition to optional fins 1202c, reaction control thrusters 1219c which create pitching moments about the anchor’s centre of gravity in at least two degrees of freedom. In other embodiments the anchor may have additional sets of reaction control thruster or sets of reaction control thrusters in different locations. The reaction control thrusters may expel fluids generated by a chemical or physical reaction, or driven by compressed gasses, or they may propel fluid from the freestream using propellers or other fluid motion devices, ora combination of all three.• Figure 12d: The anchor is guided along a guidance cable, line, or rail 1217d. The anchor has a guidance lug 1218d. The guidance lug in this case comprises a running surface made of a low friction material such as a bushing of polytetrafluoroethylene, ultra-high molecular weight polyethylene, graphite or other material. The guidance lug may partially or completely surround the guidance cable cross section. The guidance lug may be fully or partially enveloped by the supercavity and may be hydrodynamically shaped to minimize its hydrodynamic drag. The guidance lug is located at or near the centre of pressure of hydrodynamic force on the anchor to minimize moments that will pitch the anchor as it travels. Other embodiments of the anchor may have multiple guidance lugs or lugs located in different positions along the length of the anchor. Yet other embodiments may use more than one guidance cable, line, or rail. The guidance cable or system may be suspended along the path of travel of the anchor, for examplewith a weight on one end. The guidance system may have one end embedded into the waterbody bed near the anchor target location. When the anchor reaches the end of the guidance cable it can simply break free of the guidance system by disconnecting at the guidance lug or by travelling off the end of the guidance system if the anchor which holds the cable, for example, can pass through the guidance lug. The lug could also break free or automatically disconnect from the anchor and remain attached to the guidance cable.• Figure 12e: The anchor is connected to a control system which provides guidance information via a data tether 1213e. The data tether may be an optical cable, ora cable for electrical signals, e.g. long-distance ethernet. The other anchors may be internally guided. These may use artificial intelligence, or pre-programmed trajectories and internal processors and sensors to reach their target. These sensors may include pressure sensors, inertial sensors, accelerometers, magnetometers, and timers. Other embodiments may receive guidance information wirelessly. These may use acoustic signals or electromagnetic signals emitted at sufficient power and proximity to reach the anchor even with significant signal attenuation in fluid. In other embodiments the cable may be stored in the anchor and payed out of the anchor as it descends in order to reduce the load on the data tether and reduce drag loads.• Figure 12f: The anchor has fin tabs on its fins 1202f that can be independently actuated to create pitching or rolling moments in at least two degrees of freedom. The pitching of tabs may be actively actuated or passively actuated, e.g. rollerons.• Figure 12g: The anchor has fins 1202g that are fully actuated independently to create pitching or rolling moments in at least two degrees of freedom.

[0163] Other embodiments may use a combination of one or more of these guidance systems.

[0164] Guidance systems may be integral to the anchor or connected to the anchor and jettisoned for re-use. Yet other embodiments may use no guidance systems at all and may rely on passive stability from fins, or spin stabilization. Spin stabilization may be created by the geometry of the cavitator, the geometry and orientation of ventilation gas orifices, by the geometry of the anchor body or fins, by releasing the anchor with high angular momentum that persists during its travel, or by ejection of propulsion gasses, for example gasses generated by the same gas generating system as is employed for ventilated cavitation. Embodiments that use spin stabilization may have attachment points for tethers that have a degree of freedom aligned with the spin axis.

[0165] Embodiments may have no vessel-attached tether, but a length of tether and a drogue contained within the anchor which is ejected before embedment to remain above thewaterbody floor, and which can later be used to guide an additional tether through a connection point on the anchor or otherwise be connected to.Effect of Cavitation on Embedding

[0166] Figure 13 shows two subsea dynamic embedment anchors embedded into sediment. The anchors have a body, fins, a lug attached to a tether. The embodiment on the left 1300a has ventilation orifices and cavitates. It has penetrated into the sediment 1311 within a supercavity. The embodiment on the right 1300b has penetrated into the sediment 1311 without any cavitation.

[0167] Penetration without cavitation of an anchor into sediment entrains water with the anchor as it embeds. The sediment immediately adjacent to the anchor reconstitutes at higher moisture content with a lower undrained shear strength (dark gray, sparse dots). For the embodiment on the left that penetrates within a supercavity, we can expect the sediment immediately adjacent to the anchor to be less subject to reconstitution at higher moisture content as the gas displaces entrained water (light gray, dense dots).

[0168] Furthermore, empirical data indicates that undrained shear strength in sediment adjacent to kinetically embedded anchors increases with increased sediment shear rate, that is with higher velocity embedment. The embodiment on the left which embeds with higher energy and velocity, and lower viscous drag through the moist sediment will do so at a higher shear rate.

[0169] Thus, even ignoring the advantageous deeper embedment of the cavitating anchor in further dewatered sediments, the cavitating anchor should experience greater pull-out strength from the locally higher undrained shear strength of adjacent sediments alone. The sediment adjacent to the embodiment on the right without cavitation may eventually reach comparable levels of undrained shear strength to undisturbed sediments at the same depth if the soils have the capacity to increase in strength over time at constant water content. This would likely be the case for some marine clays. However, this process would delay the full loading of the anchor by a considerable and possibly unpredictable amount of time which would add cost and uncertainty to its use. The cavitating anchor has no such impediment. If the anchor 1300a achieves cavitation via boiling, the heat from the anchor may beneficially contribute to accelerated dewatering of any sediments that are disturbed and reconstituted with entrained water.Ventilation Cavitation

[0170] Figure 14a-b shows two subsea cavitating anchors. The anchor 1400a of figure 14a has a conical cavitator 1404a, a body, fins, and an eye for the attachment of a chain. In this embodiment, gas from tanks 1407aa-1407an is emitted from the anchor body adjacent to and behind the cavitator via an outlet.

[0171] The anchor 1400b of figure 14b has a conical nose and no distinct cavitator, a body, fins, and an eye for the attachment of a chain. In this embodiment, reactants from tanks 1407ba-1407bn are reacted in the presence of a catalyst 1406b (if required). The produced gas is emitted from the anchor body adjacent to and behind the nose of the anchor body via ventilation nozzles 1405b.

[0172] Both anchors have schematically represented internal components to enable ventilated cavitation. Together these components may be thought of as a gas generator. These anchors employ a chemical or physical reaction to generate ventilation gasses. These gas generator components consist of fluid conducting structures inside the anchor; tanks, enclosed volumes, or voids for reagents (including catalysts); and valves to control the flow of reagents. Other embodiments may have fluid conducting structures, reagent volumes, reagent injectors, regulators, pumps, turbines, flow control valves, flow conditioning components such as heat exchangers, heat sinks or insulation, nozzles, orifices, either inside or outside the anchor, or both. These embodiments generate gas through the decomposition of hydrogen peroxide with a supported silver catalyst. Other embodiments may use the same reaction but different catalysts or catalyst structures (e.g. nanoparticles).

[0173] Other embodiments may generate gas via the vaporization of dry ice, the vaporization of liquid nitrogen, the reaction of sodium bicarbonate and acid, the thermal decomposition of sodium azide with or without other chemicals such as potassium nitrate or silicon dioxide to mitigate harmful byproducts, the decomposition of ammonium nitrate with or without catalysts, the decomposition of potassium chlorate with or without catalysts, the reaction of zinc with hydrochloric acid, the combustion of solid propellants. Some of these reactions may be undesirable owing to their detrimental impact on marine ecosystems.

[0174] Figure 15a shows an embodiment, similar to that of figure 14a, comprising an elongated body, cavitator 1504a, round nose, fins, fixed position lug and an internal pressurized gas generation system. This gas generation system may be pre-pressurized. The gas generation system, in this embodiment, has one or more reagents stored in one or more vessels 1507aa-1507an. The gas generation system has one or more reagent compounds stored in one or more vessels 1507aa-1507an. This embodiment includes an inline static mixer 1534 (see expanded detail in oval within figure 15a) to provide thorough mixing of the reagent(s).

[0175] Other embodiments might just house compressed gas and not have the static mixer. The gas is exhausted out of the cavitator. As depth in the water column increases so does the ambient pressure. An increase in ambient pressure may change the phase of the cavitating gas or vapour back to a liquid as it exits the cavitator. A phase change from gas or vapour to liquid would hinder the formation or maintenance of the cavity. One method to overcome thisissue is to have the skin or body of the anchor heated to an elevated temperature to heat the immediate surroundings so that the exhausted cavitating fluid remains at a desired temperature and phase.

[0176] Figure 15b shows an embodiment, similar to that of figure 14b, comprising an elongated body, ventilation nozzles 1505b, round nose, fins, fix position lug and an internal pressurized gas generation system.

[0177] The embodiment of figure 15b shows an inline heat exchanger 1536 (see expanded detail in circle within figure 15b) to heat the cavitation fluid that is to be exhausted prior to exhausting. This is to achieve a similar result as discussed above for the external heat source for the cavitation fluid. It will be appreciated that heating the gas may be used in conjunction with heating the external surface of the anchor body or skin.

[0178] The heat exchanger may source the input heat from a large heated thermal mass. The heat exchanger may generate heat electrically. The heat exchanger may transfer the heat to the cavitation fluid using another fluid that circulates in a closed loop system bringing heat from a heat source to the cavitation fluid. The heat exchanger may transfer the heat to the cavitation fluid using a fluid that mixes with the cavitation fluid before both are exhausted out of the cavitator.Leidenfrost effect

[0179] Figure 16 shows a detail view of a subsea cavitating anchor 1600 and adjacent water 1699. The anchor uses the Leidenfrost effect to generate water vapour. The anchor is heated and maintained above the required temperature to transfer sufficient heat to the water to maintain film boiling and sustain a vapour pocket or cavity 1615 around the anchor, even deep underwater at high pressure. If the anchor is to travel to a depth corresponding to a pressure above the critical pressure (>2km), the anchor may conceivably be heated above the critical temperature to generate a cavity of supercritical fluid. The resultant cavity would yield similar viscous drag reduction benefits as the viscosity of supercritical water is still very low.

[0180] For the water that the anchor is passing through, example conditions are as follows:• 5°C• 400m depth• ambient pressure of 40.22 bara• vaporization temperature / boiling point of water of 251 °C• Density 1000kg / m3

[0181] For the anchor body or skin, example conditions are as follows:• 370°C (or more - hot enough to continuously vaporize the water it is passing through forming a vapor film / pocket around the body)

[0182] For the water vapour pocket, example conditions are as follows:• Min temp: 251°C• Max density: <16.57kg / m3Detachable Components

[0183] Figure 17 shows a subsea cavitating anchor 1700 that has two connected bodies. Both bodies use the Leidenfrost effect on outer skins to create a supercavity 1715 during travel. Other embodiments may use the Leidenfrost effect or other effects mentioned here in one or the other body.

[0184] The first body 1700a in this embodiment has fins, a lug is attached to a tether. The second body 1700b has fins, an eye attached to a separate tether. Other embodiments may have different features on each body. The two bodies can be mated and selectively released.

[0185] In this case, the first body 1700a leads the travel through the fluid and becomes the embedded load-resisting portion of the anchor.

[0186] The second body 1700b which is mated to the first is recovered once jettisoned or unmated. This second body contains a power source 1722 which provides energy for heating both body’s skins. The power source, e.g. a battery or supercapacitor, may be rechargeable. The body containing the power source is re-usable with another mated body.

[0187] This reduces the overall cost of the installation of anchors. It also increases the terminal velocity of the first body as the second body has mass but resides substantially inside the same supercavity.

[0188] Other embodiments may have more than two connected bodies each providing different masses, recovery means, guidance equipment, instrumentation, communication equipment, energy sources for heating or conditioning the anchor or its gasses, or propulsion sources such as propulsive nozzles, propellants, and gasses to reach very high speeds and very high kinetic energies.

[0189] In this embodiment, the second body, when mated, surrounds the end of the body of the first body. In other embodiments, the second body may be inserted into the end of the first body, or otherwise attached to the first body.

[0190] Other embodiments may have a second retrievable body comprising a heat sink for inducing cavitation through heating instead of, or in addition to, the power source 1722.

[0191] Figure 18 shows a subsea cavitating anchor 1800 that has two connected bodies 1800a, b.

[0192] The first body 1800a in this embodiment has fins, a lug, a disk cavitator and is attached to a tether 1891.

[0193] The first body contains the gas generating systems to achieve ventilated supercavitation and its supercavity envelops itself and the connected body. Other implementations may locate some of the gas generating systems inside the connected body,yet other implementations may have no gas generating systems at all and may rely on natural supercavitation only.

[0194] The second, connected body 1800b, has fins, a large mass 1841, multiple eyes, and a drogue 1840, and is connected to a retrieval line 1894. Other implementations may have no drogue. The second body contributes more mass to the first body without significantly increasing its drag. Therefore, it helps the first body achieve a higher terminal velocity before and after the initiation of cavitation at the cavitator.

[0195] In this embodiment, the second body 1800b can be jettisoned or released from the first body before embedment as shown on the right-hand side view. The drogue 1840 slows the jettisoned second body after release. The second body can be recovered by its tether retrieval line 1894.

[0196] Other embodiments may recover the second body after embedment by pulling it out of the sediment. Other embodiments may have more than two connected bodies each providing different masses, recovery means, gas generating means, guidance equipment, instrumentation, communication equipment, energy sources for heating or conditioning the anchor or its gasses, or propulsion sources such as propulsive nozzles, propellants, and gasses to reach very high speeds and very high kinetic energies.Retrofit Cavitator

[0197] Figure 19a and 19b shows a subsea cavitating anchor. The anchor is made up of a conventional non-cavitating anchor body 1901 (figure 19a) to which a cavitation system is retrofitted. The retrofit comprises the cavitator 1904, fluid conducting structure, gas generator 1942, releasable coupling, and a lug 1903.

[0198] The retrofitted anchor 1900 (figure 19b) has a cavitator, a fluid conducting structure, a gas generator, a releasable coupling, fins and two lugs. The fluid conducting structure conveys gas generated by the gas generator to outlets adjacent to and behind the cavitator. The cavitator and emitted gas induce cavitation around the retrofitted anchor as it moves through the water.

[0199] Figure 19b shows how other types of anchor can be retrofitted to become subsea cavitating anchors with or without reusable parts.Other Options

[0200] Other embodiments may have other components or numbers of components, for example, heat sources to cavitate using the Leidenfrost effect, or fins. The cavitation system may be fully or partially re-usable. Embodiments may comprise a releasable coupling which may detach just before or after embedment, separating the cavitation system from the rest of the anchor.

[0201] The cavitator may split into halves along a substantially vertical plane, allowing its parts to be slid off the conventional non-cavitating anchor portion of the system, to be recovered.

[0202] Other embodiments may leave the cavitator in place and might recover the remainder of the cavitation system, or other subsets of it.

[0203] Two tethers would be used, one for the cavitation system and one for the conventional non-cavitating anchor portion of the now subsea cavitating anchor. Other embodiments may have a different tether configuration, for example the portion of the anchor that remains in the sediment may have a finite length tail extending upward from it whose upper end lies above the seabed surface. This tail can conduct gas or fluid to the embedded portion of the anchor.

[0204] The fluid is subsequently further ejected around the embedded portion of the anchor to reconstitute the adjacent soil with greater moisture and lubricate the removal of the anchor by pulling it out from above at end-of-life. Subsea cavitating anchors thus constructed have all of the same benefits of cavitating anchors described in this document.

[0205] Other embodiments may turn a non-cavitating anchor with suitable thermal properties into a cavitating anchor by heating them to use boiling, e.g. the Leidenfrost effect.Launched Cavitating Anchor

[0206] Figures 20a-d show a cavitating anchor 2000 launched from a vessel 2051. Figures 20a-b show a first variant and figures 20c-d show a second variant.

[0207] In Figure 20a, the anchor 2000 to be launched is in the barrel of pneumatic cannon 2061. Other embodiments may use an explosively charged cannon, or may propel the anchor using a different device, including a drop through air. The cannon allows the anchor to start with a higher initial velocity providing a higher kinetic energy at impact for a given depth relative to an anchor which is not propelled outof a cannon. This increase is enhanced when combined with the cavitating anchor as it has a higher terminal velocity capability.

[0208] In this embodiment, the anchor has a sabot 2062 to seal around the irregular anchor shape and to the smooth bore of the barrel. In other embodiments, the anchor may be shaped to fit closely with the interior bore of the cannon. The anchor may have extendable fins which extend when the anchor is ejected from the cannon.

[0209] In this embodiment, the anchor is attached to a line 2091 and a buoy and which is packed in the chamber. The line and buoy will be fired out with the anchor and can be later connected to (e.g., with a tether securing a floating asset). The barrel is evacuated of water. The body may be preheated with intention of inducing cavitation using film boiling.

[0210] In figure 20b the sabot 2062 separates from the anchor 2000 after leaving the muzzle (in this case by splitting into two halves which detach from the anchor). The anchor continues to accelerate towards the bed of the waterbody (driven by gravity) in its cavity of water vapour. If the anchor is propelled out of the cannon at a speed higher than its terminal velocity it mayslowly decelerate. In this embodiment the sabot pieces are net positively buoyant and will surface to be collected and reused.

[0211] The embodiment of figures 20 c and d are similar to that of figures 20a and b with the exception that the tether 2091c for the anchor is fed through the sabot 2062 and coiled up in the water and then attached to the anchor launching vessel. It will be appreciated that the cannon launch method can be operate above water as well.

[0212] Dropping the anchor first in air to build up an initial speed prior to entering water maximizes the low drag characteristics and higher terminal velocity potential of a cavitating anchor relative to the same anchor without cavitation. The same anchor without cavitation has a velocity ceiling which is much lower. The higher initial velocity allows the cavitating anchor to fulfill more of its maximum potential kinetic energy for water depths that otherwise do not allow sufficient acceleration time.Hollow Anchor

[0213] Figure 21a is a cross-section view of an embodiment of a hollow cavitating anchor 2100. The anchor has a body 2101, fins 2102, and a lug 2103 which is attached to a tether line 2191. Figure 21b is a top view of the anchor showing the hollow cavity within the tube body 2101.

[0214] This embodiment is configured to induce cavitation using film boiling, i.e. the Leidenfrost effect. The anchor has a thermal mass. The anchor, in this case, is at least partially made of a thermally conductive metal material. Other embodiments may be made with other thermally conductive materials.

[0215] In this case, the thermal mass of the anchor is heated to a temperature above the Leidenfrost point of the freestream fluid at the highest pressure the anchor will experience (corresponding to the deepest point that the anchor will travel). In this embodiment the thermal mass will be heated far above this temperature. Heat from the anchor’s thermal mass is conducted, convected, and radiated to the fluid as it flows past and through the anchor. This heat vaporizes the fluid and surrounds the anchor in a cavity or film of gasses - this is a type of manifestation of the Leidenfrost effect.

[0216] The cavity 2115 of vapour fully encloses the anchor body; in other embodiments or at different times the cavity may only partially enclose the anchor. The motion of the freestream fluid around the anchor may also increase the local flow speed and reduce its pressure low enough to vaporize at ambient temperatures contributing so-called ‘natural’ cavitation. The vaporized fluid surrounding the anchor reduces its viscous drag during travel through the freestream and during embedment in watered sediments such as are found in the beds of waterbodies. The vaporized fluid reduces the entrainment of water into the sediment during embedment, resulting in better strength properties in the sediment adjacent to the anchor.

[0217] As shown in figure 21, the anchor’s fins protrude beyond the supercavity contributing to stability of travel by interacting with the freestream flow; other embodiments may not have fins protrude beyond the supercavity.

[0218] In this embodiment the anchor is pre-heated before it travels through the fluid and its temperature decays as it sheds heat to the fluid, at all times the anchor remains at sufficient temperature to remain in the film boiling regime.

[0219] It will be appreciated that the geometry of the hollow part of the anchor may be manipulated to allow fluid to enter the interior of the anchor where it is vapourized and expelled preferentially from the rear of the anchor, contributing a net forward thrust to its direction of travel.

[0220] In other embodiments the anchor may be continuously heated by an onboard battery or electrical power source, and / or by an exothermic chemical reaction, and / or by a heat sink such as molten salt. In this embodiment the anchor is made of a ferrous material and is heated inductively through inductive coils as it is oriented and positioned for deployment. In other embodiments the anchor may be heated resistively, by contact with hot fluid, or by contact with flames. The anchor in this embodiment has similar benefits to the anchor embodiment in Figure 1 in terms of simplicity of operation of the supercavity, concomitant speed, strength of resultant anchor, quick installation in diverse substrates at diverse fluid depths, and favourable economics.

[0221] Other embodiments might use other methods for propulsion such as explosives.

[0222] The anchor could be loaded through the breach or loaded through the muzzle of the cannon.

[0223] Other embodiments may use a rifled bore.

[0224] In other embodiments the sabot could potentially remain as one piece and slide off.

[0225] Other embodiments may have muzzle breaks to reduce recoil.

[0226] Other embodiments may have other recoil absorption system.

[0227] Other embodiments may store the line / tetherforthe anchor differently.

[0228] Other embodiments may have tethers on the sabot pieces.

[0229] Other variations may use a spin-launcher to launch the anchor at elevated initial velocity.

[0230] Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.

Claims

CLAIMS1. A dynamically installable tool for penetrating into the bed of a body of water by dynamically being driven through the water and into the bed, the tool comprising:a body having an outer surface,a cavitation inducer, the cavitation inducer configured to induce cavitation adjacent to the outer surface of the body.

2. The tool according to claim 1, wherein the body comprises a tip, and the cavitation inducer is configured to generate one or more gas cavities at and / or adjacent to the tip and / or further aft on the body.

3. The tool according to any one of claims 1-2, wherein the cavitation inducer is configured to generate gas through a chemical or physical reaction.

4. The tool according to any one of claims 1 -3, wherein the cavitation inducer comprises a cavitator, the cavitator being a shaped component configured to generate vapour via hydrodynamic cavitation of water as the tool moves through the medium.

5. The tool according to any one of claims 1 -4, wherein the cavitation inducer comprises a heated component, the heated component being configured to induce cavitation via boiling.

6. The tool of claim 5, wherein the heated component is part of, or is thermally connected with, the outer surface of the body.

7. The tool according to any one of claims 1-6, wherein the tool comprises a mass which can be separated from the body after the tool has been installed in the bed.

8. The tool according to any one of claims 1 -7, wherein the cavitation inducer comprises a hydrophobic surface configured to entrain gas.

9. The tool according to any one of claims 1-8, wherein the tool is configured to be driven by gravity.

10. The tool according to any one of claims 1-9, wherein the tool comprises a propulsion unit.

11. The tool according to any one of claims 1-10, wherein the tool comprises anchoring flukes for engaging with the bed.

12. The tool according to any one of claims 1-11, wherein the tool comprises a controller configured to control the cavitation inducer to steer and / or increase or decrease the volume of cavitating gas as a depth of the tool increases.

13. The tool according to any one of claims 1-12, wherein the body comprises an embedding portion and a detachable portion, wherein the embedding portion is separable from the detachable portion, such that the detachable portion can be retrieved while the embedding portion remains embedded in the bed of the water body.

14. A method of installing the tool according to anyone of claims 1-13, wherein the method comprises:launching the tool such that it passes through the body of water towards the bed of the water; andgenerating a cavity adjacent to the outer surface of the body using a cavitation inducer.

15. The method of claim 14, wherein the tool is launched by releasing the tool from rest.

16. The method according to any one of claims 14, wherein the tool is launched at an initial velocity.

17. A method of installing a tool in the bed of a body of water, the method comprising: placing a bubble source at a first depth within the body of water below a surface, the bubble source being configured to emit bubbles which form a column of bubbles as they float towards the surface; anddriving the tool downwards from a second position above the source of the column of bubbles such that the column of bubbles reduces the hydrodynamic drag on the tool.

18. The method according to claim 17, wherein the bubble source is configured to eject bubbles laterally.

19. The method according to any one of claims 17-18, wherein the bubble source is configured to eject bubbles at a range of depths.

20. A tool installation system for installing a tool in the bed of a body of water, the system comprising:a bubble source positionable at a first depth within the body of water below a surface, the bubble source being configured to emit bubbles which form a column of bubbles as they float towards the surface; anda tool being positionable at a second depth within the column of bubbles, the second depth being shallower than the first depth, the tool being drivable downwards within the column of bubbles such that the column of bubbles reduces the hydrodynamic drag on the tool.

21. A retrofit apparatus attachable to a dynamically installable tool, the retrofit apparatus comprising:attachment grips for connecting to a body of the dynamically installable tool; and a cavitation inducer, the cavitation inducer configured to induce cavitation adjacent to the body when the retrofit apparatus is attached to the tool, and the tool is driven through a body of water.

22. The retrofit apparatus according to claim 21 , wherein the retrofit apparatus comprises one or more of: a cavitator, a heated component, a hydrophobic surface and a gas generator.

23. A method of retrofitting a dynamically installable tool, the method comprising:connecting a retrofit apparatus to a body of the dynamically installable tool, the body having a fore end and an aft end;driving the retrofitted tool through a body of water; andinducing cavitation adjacent to the body when the tool is driven through a body of water.

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