Improved underwater device

Abstract

There is disclosed an underwater material moving device or excavator (10a, b) comprising an outlet (15), wherein the outlet (15) comprises an elongate shape or slot (16). In preferred implementations the device (15; 315; 415) comprises a nozzle (150; 350; 450) having one or more guide vanes or blades (175; 375; 425) which can act to reduce fluid swill and / or provide a more coherent fluid output. There is also disclosed an underwater material moving apparatus (105) comprising first and 10 second underwater material moving devices (10a, 10b). In preferred implementations the nozzle (450) is dimensioned such that a width (W) of the nozzle (450) decreases or tapers. Further a length (L) of the nozzle (450) increases or flares in a direction from an inlet end to an outlet end of the nozzle (450).

Description

FIELD OF INVENTION

[0001] The present invention relates to a device, apparatus and method for moving underwater or subsea material or spoil, such as on a floor of a body of water.

[0002] A device according to the present invention may be referred to as an underwater "blower" or as a "water blade" or "water rake".

[0003] The invention pertains to excavation, and in particular, though not exclusively, to underwater or subsea excavation and / or to an underwater or subsea excavator.BACKGROUND TO INVENTION

[0004] There is often a desire or need to move underwater material. For example, if a trench has been formed on a floor of a body of water, such as a sea bed, there may be a desire to backfill the trench. This may be the case after laying a cable, pipeline or the like in the trench. This may also be the case if or when reburying a cable, pipeline or the like which has been deburied.

[0005] When a trench is formed, a ridge or ridges (also known as a berm or berms) of spoil may be formed on either or both sides of the trench. The trench may, therefore, be back-filled or refilled from such ridge(s) or berm(s).

[0006] WO 2018 / 037232 A2 (ROTECH GROUP LIMITED) discloses improvements in and relating to underwater excavation apparatus, the content of which is incorporated herein by reference. The apparatus comprises at least one rotor and an arrangement for dampening reactive torque on the excavation apparatus caused by rotation of the rotor, in use, wherein the excavation apparatus further comprises at least one stator comprising stator blades, the torque dampening arrangement comprising the stator blades, the stator blades comprising a plurality of primary stator blades and a plurality of secondary or splitter blades provided between adjacent pairs of primary stator blades.

[0007] The apparatus of WO 2018 / 037232 A2 further comprises a housing comprising an inlet and an outlet, a rotor having a rotor rotation axis, the rotor comprising a first body and a plurality of impeller blades provided within the housing, such that, in use, flow of fluid passed or across the rotor is at a first angle from the axis of rotation.

[0008] The apparatus of WO 2018 / 037232 A2 further comprises the housing comprising an inlet and an outlet; at least one rotor comprising an impeller provided within the housing; at least one stator provided within the housing; and an arrangement for producing at least one vortex in a flow of fluid; wherein, the or each at least one vortex producing arrangement comprises a planar member provided adjacent the outlet of the housing, an edge of the planar member being attached to the housing or to a body within the housing.

[0009] The device / apparatus of the present invention hereinafter described may incorporate one or more features of the apparatus disclosed in WO 2018 / 037232 A2.

[0010] Mass Flow Excavation (MFE) is a means of creating cavities in the seabed with relatively low pressure(s) (Kilopascals, KPa), e.g. in sand and / or pre-loosened or disturbed material. Mass flow excavators typically comprise a hollow body housing and at least one impeller or rotor provided within the housing which draws fluid into the housing and directs the fluid out of the housing towards the seabed.

[0011] Known mass flow excavators comprise impellers designed to draw in large volumes of fluid and to discharge the fluid at relatively low speed and low pressure - typically less than 6m / s and less than 25 KPa. Due to the relatively low pressure and low fluid flow speed of mass flow excavation, many passes may be required to effectively excavate an area, as with each pass only a limited penetration of the seabed may be achieved. It is a further characteristic of mass flow excavation that trenches created in the seabed may be wide but shallow. This is because the mass flow excavator may first move looser material on the surface due to pressure limitations before penetrating firmer material underneath, creating a wide and ill-defined or uncontrolled excavation profile.

[0012] Further, mass flow excavation apparatus are primarily suitable for excavation by directing fluid at the seabed, but due to the low pressure nature of the apparatus, such are of limited use in the collection and removal of seabed material by suction. Thus, after the mass flow device has disturbed the seabed material, a separate tool - such as a centrifugal pump - may require to be deployed to suck-up and remove the material.

[0013] To distinguish from "mass flow" or "Mass Flow Excavators" (MFE) the terms "controlled flow" or "Controlled Flow Excavator" (CFE) are hereinafter used in connection with use of the present invention which may be configured to produce and / or direct a flow of fluid (water) at a pressure of typically around 35 to 120 KPa and volume flow of typically around 1 m 3< / s to 8 m 3< / s.

[0014] It is an object of at least one embodiment of at least one aspect of the present invention to obviate or mitigate one or more problems and / or disadvantages in the prior art.

[0015] EP 2317016 A2 describes an underwater excavation apparatus comprising mass flow excavation means and jet flow excavation means. The mass flow excavation means causes a mass flow at a pressure less than that of a jet flow of the jet flow excavation means. The mass flow excavation means causes a mass flow at a volume flow rate greater than that of a jet flow volume rate of the jet flow excavation means. An outlet of the jet flow means is provided within an outlet of the mass flow means.

[0016] GB 2554522 A describes an excavation apparatus, such as an underwater excavation apparatus, having means for producing, in use, at least one vortex, spiral or turbulent flow in a laminar flow of fluid, e.g. water. The excavation apparatus comprises a rotor having a rotor rotation axis, wherein, in use, flow of fluid passed or across the rotor is at a first angle from the axis of rotation. The excavation apparatus comprises the rotor and means or an arrangement for dampening reactive torque on the apparatus caused by rotation of the rotor, in use. The turbulent flow is provided within, such as within a (transverse) cross-section, of the laminar flow.

[0017] GB 2368560 A describes a vessel having means at its bow to direct a water flow ahead of the vessel downwardly towards the seabed in front of and to either side of the path of the vessel to displace material from the seabed including any weapon system or obstacles on or buried in the seabed away from the path of the vessel. The means may comprise a duct of rectangular cross-section having an upright portion with a water inlet at its upper end, an arcuate portion sweeping forwardly of the vessel and an outlet facing forwardly and downwardly from the vessel. Impeller means may be provided in the inlet of the duct to draw water into the duct. The duct means may be mounted on a boom which extends forwardly of the vessel and may be lowered or raised by a hoist on the bow of the vessel.

[0018] WO 97 / 32091 A1 describes a dredging apparatus comprising a body mounting thrust means to direct, in use, a wash of water downwards towards an area of sea bed or the like, connection means to connect said dredging apparatus to a support means above the sea bed, said connection means including attitude adjusting means to selectively adjust the attitude of the dredging apparatus in a side to side (roll) orientation.SUMMARY OF INVENTION

[0019] According to a first aspect of the present invention there is provided an underwater material moving device according to claim 1.

[0020] The device of the present invention may be referred to as a "blower", "water blade" or "water rake".

[0021] The inlet may be substantially circular.

[0022] The inlet and outlet may be aligned substantially parallel to or with one another.

[0023] In one implementation the elongate shape or slot may comprise at least one, and preferably two, full radiussed end(s). The end(s) of the slot may be at least part circular, e.g. beneficially semi-circular.

[0024] In another implementation the elongate slot may comprise at least one, and preferably two, ends which may be linear and / or may be substantially parallel to one another.

[0025] First and second sides of the slot may be substantially parallel to one another. First and second sides of the slot may be linear.

[0026] In said one implementation first and second sides of the slot may extend, for example, tangentially extend, from ends of the slot.

[0027] In said another implementation first and second sides of the slot may extend, for example, substantially perpendicularly, from ends of the slot.

[0028] The outlet of the device is provided on an outlet portion, for example, an outlet portion of the body or of a nozzle. The outlet portion or nozzle may be detachably attached to the body. The outlet portion or nozzle may comprise a fluid passageway extending linearly between the inlet end and the outlet end. The inlet end of the nozzle may be substantially circular.

[0029] The inlet end and the outlet end / outlet may be aligned substantially parallel to or with one another.

[0030] Beneficially a length of the outlet end / outlet may increase, flare and / or taper outwards in a direction from the inlet end to the outlet end / outlet.

[0031] Beneficially the inlet end may be circular and / or the outlet end / outlet maybe of an elongate (slot) shape.

[0032] Beneficially a width of the outlet end / outlet may be less than a width / diameter of the inlet end.

[0033] Advantageously a ratio of outlet end / width to inlet end width / diameter maybe in the range of 0.25 to 0.5, for example, 0.3.

[0034] Beneficially a length of the outlet end / outlet may be greater than a width / diameter of the inlet end. Advantageously a ratio of outlet end / outlet length to inlet end width / diameter may be in the range of 1.1 to 2.5, for example, 2.1.

[0035] The device comprises one or more guide blades or vanes, for example, beneficially at or adjacent the outlet portion / outlet. The blade(s) or vane(s) are arranged so as to provide a substantially even fluid flow (distribution) across and / or along the outlet portion or nozzle.

[0036] A width (or length) of each blade or vane may taper, decrease or narrow in a direction towards the outlet. Such arrangement may act to facilitate or encourage an improved or even fluid (water) flow distribution.

[0037] The one or more blades or vanes comprise one or more primary or guide blades or vanes.

[0038] The one or more blades or vanes may comprise one or more secondary or splitter blades or vanes. The secondary or splitter blades or vanes may be provided between adjacent primary or guide vanes. The one or more blades or vanes may be substantially symmetrically dispersed around a centre of the device.

[0039] One or more of the one or more blades or vanes are curved in cross- section.

[0040] The one or more blades or vanes may extend to the outlet.

[0041] The primary or guide blades or vanes may be longer (e.g. in a direction extending between the inlet and the outlet) than the secondary or splitter blades or vanes.

[0042] The / each primary or guide blade(s) or vane(s) comprise a first curved portion and a second curved portion.

[0043] For each primary or guide blade or vane, the first curved portion is curved or bent in an opposite disposition or direction to the second curved portion.

[0044] The first curved portion of the / each primary or guide blade or vane may be provided proximal the inlet. The second curved portion of the / each primary or guide blade or vane may be provided proximal outlet.

[0045] The / each secondary or splitter blade(s) or vane(s) may comprise a first curved portion.

[0046] The first curved portion of the / each primary or guide blade or vane may be provided proximal the inlet end. The second curved portion of the / each primary or guide blade or vane may be provided proximal the outlet end outlet.

[0047] The / each secondary or splitter blade(s) or vane(s) may comprise a first curved portion.

[0048] The first curved portion of a / each secondary or splitter blade may be provided between and / or be disposed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes.

[0049] The primary or guide blades or vanes may be "s" shaped. The secondary or splitter blades or vanes may be "r" shaped.

[0050] The outlet portion or nozzle comprises a first dimension, a second dimension and third dimension.

[0051] The first dimension comprises a width or breadth dimension or direction. The second dimension comprises a length dimension or direction. The third dimension comprises a height dimension or direction. The third dimension may extend between the / an inlet end and the / an outlet end of the outlet portion or nozzle.

[0052] The first dimension decreases or tapers along at least a portion of the third dimension, e.g. in a direction towards the outlet end.

[0053] The second dimension may increase or flare along at least a portion of the third dimension e.g. in a direction towards the outlet end.

[0054] According to a second aspect of the present invention there is provided an underwater material moving apparatus comprising at least one underwater material moving device according to the first aspect of the present invention.

[0055] The apparatus may comprise a pair of devices according to the first aspect of the present invention.

[0056] According to a third aspect of the present invention there is provided a method of moving underwater material according to claim 16.

[0057] Moving said underwater material may comprise filling or back-filling an underwater trench, for example, with material comprising spoil or berm.

[0058] According to the present invention there is provided an outlet portion or nozzle for use in or with an underwater material moving device according to a first aspect of the present invention.

[0059] The outlet portion or nozzle may be termed a "tool" or "attachment".

[0060] Also described is an (underwater) material moving apparatus or excavator comprising first and second or at least one pair of underwater material moving devices (or excavators).

[0061] Beneficially said devices may be symmetrically disposed on a yoke or frame.

[0062] Beneficially each device may be substantially the same or identical.

[0063] Each device may comprise a blower or "controlled flow" device as hereinbefore described and / or defined.

[0064] The / each device may be referred to as a "blower", "water blade" or "water rake". Each device may comprise a device according to the first aspect of the present invention.

[0065] Each device comprises an outlet. The outlet comprises an elongate shape or slot.

[0066] The / each device comprises a body. The outlet is provided on or at an end of the body or on an outlet portion or nozzle or tool or attachment connected or (releasably) connectable to the body. The body comprises a body outlet, which may be circular. The outlet portion / nozzle / tool / attachment comprises a inlet end which may be circular. The device comprises an inlet. The inlet may be substantially circular. The inlet may be provided on or at another (e.g. opposite) end of the body.

[0067] The body comprises a through-passage, for example, extending from inlet to body outlet. The inlet / body inlet and the outlet / body outlet are disposed substantially along an axis of the body. The inlet / body inlet and outlet / body outlet are aligned substantially parallel to or with one another.

[0068] In one implementation the elongate shape or slot may comprise at least one, and preferably two, full radiussed end(s). The end(s) of the slot may be at least part circular e.g. beneficially semi-circular.

[0069] In another implementation the elongate slot may comprise at least one, and preferably two, ends which may be linear and / or may be substantially parallel to one another.

[0070] First and second sides of the slot may be substantially parallel to one another. First and second sides of the slot may be linear.

[0071] In said one implementation first and second sides of the slot may extend, for example, tangentially extend, from ends of the slot.

[0072] In said another implementation first and second sides of the slot may extend, for example, substantially perpendicularly, from ends of the slot.

[0073] The outlet of the device may be provided on an outlet portion of the body or on a nozzle. The outlet portion or nozzle may be detachably attached to the body. The outlet portion or nozzle may comprise an inlet end. The outlet portion or nozzle may comprise a fluid passageway extending linearly between the inlet and the outlet. The inlet end of the nozzle may be substantially circular.

[0074] The / each device comprises one or more guide blades or vanes, for example, beneficially at or adjacent the outlet.

[0075] A width (or length) of each blade or vane may taper, decrease or narrow in a direction towards the outlet. Such arrangement may act to facilitate or encourage an improved or even fluid (water) flow distribution.

[0076] The one or more blades or vanes comprise one or more primary or guide blades or vanes.

[0077] The one or more blades or vanes may comprise one or more secondary or splitter blades or vanes. The secondary or splitter blades or vanes may be provided between adjacent primary or guide vanes. The one or more blades or vanes may be substantially symmetrically dispersed around a centre of the device.

[0078] One or more of the one or more blades or vanes may be curved in cross-section.

[0079] The one or more blades or vanes may extend to the outlet.

[0080] The primary or guide blades or vanes may be longer (e.g. in a direction extending between the inlet and the outlet) than the secondary or splitter blades or vanes.

[0081] The / each primary or guide blade(s) or vane(s) comprise a first curved portion and a second curved portion.

[0082] For each primary or guide blade or vane, the first curved portion is curved or bent in an opposite disposition or direction to the second curved portion.

[0083] The first curved portion of the / each primary or guide blade or vane may be provided proximal the inlet end. The second curved portion of the / each primary or guide blade or vane may be provided proximal the outlet end / outlet.

[0084] The / each secondary or splinter blade(s) or vane(s) may comprise a first curved portion.

[0085] The first curved portion of a / each secondary or splitter blade may be provided between and / or be dispersed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes.

[0086] The primary or guide blades or vanes may be "s" shaped. The secondary or splitter blades or vanes may be "r" shaped.

[0087] The outlet portion or nozzle comprises a first dimension, a second dimension and a third dimension.

[0088] The first dimension being a width or breadth dimension of the outlet portion.

[0089] The second dimension being a length dimension of the outlet portion. The third dimension being a height dimension of the outlet portion which extends between the inlet end and the outlet end of the outlet portion of the nozzle.

[0090] The first dimension decreases or tapers along at least a portion of the third dimension, e.g. in a direction towards the outlet end.

[0091] Beneficially the outlet of the / each device may face or may be angled at least partially away (outwardly away) from the frame or yoke and / or from the other device, for example, at an angle of between 30° and 60°, for example, 45°.

[0092] The frame or yoke may comprise an arrangement for retaining or supporting each device, for example, for pivotally retaining each device. The frame or yoke may have a centre or central axis. The devices may be disposed symmetrically about the centre or central axis of the frame or yoke. This may provide for balance of force on the apparatus, in use, for example, if the devices are used simultaneously, and are driven at the same flow rates and / or pressure.

[0093] The outlets of the devices may be angled away from a centre of the frame or yoke, e.g. so as to face partially downwardly, in use.

[0094] An angle between a body of the / each device and the frame or yoke may be around between 30° and 60°, and beneficially around 45°.

[0095] Beneficially, the flared out nature of the devices of the present invention allows for provision of a relatively short / small frame / yoke.

[0096] Also described is a method of moving underwater material comprising: providing an underwater material moving apparatus according to the fourth aspect of the present invention; using or deploying said apparatus to move underwater material.

[0097] Moving said underwater material may comprise filling or back-filling an underwater trench, for example, with material comprising spoil or berm.

[0098] Back-filling said trench may bury or rebury a cable, conduit or the like.BRIEF DESCRIPTION OF DRAWINGS

[0099] Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, which are: Figure 1 a view from one side and to one end of an underwater material moving apparatus according to a first embodiment of the present invention comprising a pair of underwater material moving devices according to the present invention; Figure 2 a schematic illustration of a water flow output from a preferred outlet nozzle of one of the underwater material moving devices of Figure 1; Figure 3 a schematic illustration of a water flow output from a less preferred outlet nozzle; Figure 4 a further view from one side to one end of the underwater material moving apparatus of Figure 1; Figure 5 a top view of the underwater material moving apparatus of Figure 1; Figure 6 a cross-sectional end view of the underwater material moving apparatus of Figure 1; Figure 7 a schematic end view of the underwater material moving apparatus of Figure 1, in use, back-filling a trench on a floor of a body of water; Figure 8 a view from one side and to one end of an underwater material mooring apparatus according to a second embodiment of the present invention comprising a pair of underwater material moving device according to the present invention; Figure 9 a side view of an underwater material mooring apparatus according to a third embodiment of the present invention; Figure 10 a view from one side, to one end and below of an underwater material moving apparatus accordingly to a fourth embodiment of the present invention comprising a pair of underwater material moving devices according to the present invention; Figure 11 a sectional view of one of the underwater material moving devices of Figure 10; Figures 12(a) and (b) pictorial representations of flow performance of one of the underwater material moving devices of Figure 10; Figure 13 a view from one end of an underwater moving apparatus according to a fifth embodiment of the present invention comprising a pair of underwater material moving devices according to the present invention; Figure 14 a view from above, to one end and to one side of one of the underwater material moving devices of Figure 13; Figure 15 a sectional view of the underwater material moving device of Figure 14; Figure 16 a view from below, to one end and to one side of the underwater material moving device of Figure 14; and Figure 17 an end view of the underwater material moving apparatus of Figure 13, in use. DETAILED DESCRIPTION OF DRAWINGS

[0100] Referring to Figures 1 to 7, there is shown an underwater material moving apparatus or excavator, generally designated 5, according to an embodiment of the present invention. The apparatus 5 comprises first and second underwater material moving devices or excavators 10a, 10b.

[0101] The / each device 10a, 10b comprises a controlled flow underwater excavation (CFE) apparatus as disclosed in WO 2018 / 037232 A2 (ROTECH GROUP LIMITED), the content of which is incorporated herein by reference, and is not repeated herein merely for reasons of brevity.

[0102] Each device comprises an outlet 15, wherein the outlet 15 comprises an elongate shape or slot 16. The device 10a, 10b can be referred to as a "blower" or as a "water blade".

[0103] The device 10a, 10b comprises a body 20. The outlet 15 is provided on or at an end of the body 20. The device 10a, 10b comprises an inlet 25. The inlet 25 is substantially circular. The inlet 25 is provided on or at another (opposite) end of the body 20.

[0104] The body 20 comprises a through-passage 21. The inlet 25 and the outlet 15 are substantially disposed along an axis A of the body 20. The inlet 25 and outlet 15 are aligned substantially parallel with one another. The elongate shape or slot 16 comprises at least one, and in this embodiment two, full radiussed end(s) 30, 35, i.e. the end(s) of the slot 16 are at least part circular, i.e. are semi-circular.

[0105] First and second sides 40, 45 of the slot 16 are substantially parallel to one another. The first and second sides 40, 45 of the slot 16 are linear. First and second sides 40, 45 of the slot 16 extend, i.e. tangentially extend, from ends 30, 35 of the slot 16.

[0106] The outlet 15 of the device 10a, 10b is provided on a nozzle 50. The nozzle 50 is detachably attached to the body 20. The nozzle 50 comprises an inlet end 55. The nozzle 50 comprises an outlet end. The outlet end of the nozzle comprises the outlet 15 of the device 10a, 10b. The nozzle 50 comprises a fluid passageway 60 extending linearly between inlet end 55 and the outlet 15 / outlet end. The inlet end 55 of the nozzle 50 is substantially circular.

[0107] The present invention further provides the underwater material moving apparatus 5 comprising at least one underwater material moving 10a, 10b. The apparatus 5 comprises a pair of devices 10a, 10b.

[0108] According to the present invention there is provided a method of moving underwater material comprising: providing an underwater material moving device 10a, 10b and / or an underwater material moving apparatus 5; using or deploying said device (5) 10a, 10b or apparatus 5 to move underwater material 65.

[0109] Moving said underwater material 65 can comprise filling or back-filling an underwater trench 60, for example, with material 65 comprising spoil or berm.

[0110] The present invention provides an underwater material moving apparatus (or excavator) 5 comprising first and second underwater material moving devices (or excavators) 10a, 10b.

[0111] Said devices 10a, 10b are symmetrically disposed on a yoke or frame 70. Each device 10a, 10b is substantially the same or identical. Each device 10a, 10b comprises a blower or controlled flow device as hereinbefore described and / or defined. Each device 10a, 10b comprises outlet 15, the outlet 15 comprising elongate shape or slot 16.

[0112] The / each device 10a, 10b of the present invention can be referred to as a "blower" or "water blade".

[0113] The / each device 10a, 10b comprises body 20. The outlet 15 is provided on or at an end of the body 20. The device 10a, 10b comprises inlet 25. The inlet 25 is substantially circular. The inlet 25 is provided on or at said another (opposite) end of the body 20.

[0114] The body 20 comprises through-passage 21. The inlet 25 and the outlet 15 are substantially disposed along axis A of the body. The inlet 25 and outlet 15 are aligned substantially parallel with one another.

[0115] The elongate shape or slot 16 comprises at least two ends 30, 35, which in this embodiment comprises at least two full radiussed end(s) 30, 35. The end(s) 30, 35 of the slot 16 are at least part circular, and beneficially semi-circular.

[0116] Beneficially the outlet 15 of the / each device 10a, 10b face or is angled at least partially away (outwardly away) from the frame or yoke 20 and / or from the other device 10a, 10b.

[0117] The frame or yoke 70 comprises an arrangement for retaining or supporting each device 10a, 10b, for example, for adjustably pivotally retaining each device 10a, 10b. The frame or yoke 70 has a centre or central axis C. The devices 10a, 10b are disposed symmetrically about the centre C of the frame or yoke 70. This provides for balance of force on the apparatus 5, in use, for example, if the devices 10a, 10b are used simultaneously, and are driven at the same flow rates and / or pressure.

[0118] The outlets 15 of the devices 10a, 10b are angled away from centre C of the frame or yoke 70, e.g. so as to face partially downwardly, in use.

[0119] An angle α between a body 20 of the / each device 10a, 10b and the frame or yoke 70 is around between 30° and 60° and beneficially around 45°.

[0120] Beneficially, the flared out nature of the devices 10a, 10b of the present invention allows for provision of a relatively short / small frame / yoke 70.

[0121] The present invention provides a method of moving underwater material comprising: providing an underwater material moving apparatus 5; using or deploying said apparatus 5 to move underwater material 65.

[0122] Moving said underwater material 65 can comprise filling or back-filling underwater trench 60, for example, with material comprising spoil or berm. Beneficially said trench 60 is used to bury or rebury a cable, conduit or the like (not shown).

[0123] Referring now to Figure 8, there is shown an underwater moving apparatus or excavator, generally designated 105, according to a second embodiment of the present invention. The apparatus 105 is similar to the apparatus 5 of Figures 1 to 7, like parts being denoted by like numerals, but incremented by "100".

[0124] The device 110a, 110b comprises guide vanes or blades 175 within the nozzle 150. The outlet guide vanes or blades 175 can act to reduce fluid swirl and / or provide a more coherent output fluid flow or jet. In particular, the guide vanes or blades 175 can be arranged so as to provide a substantially even fluid flow (distribution) across and / or along the outlet portion or nozzle. The vanes or blade 175 can extend into the nozzle 50 as far as a quarter or a half of the length of the nozzle 1 from the outlet 115, with none or one blade 175 in the middle of a long axis of theoutlet 115 and either two (as shown) or three vanes or blades 175 across a short axis of the outlet 115.

[0125] Referring now to Figure 9, there is shown an underwater material moving apparatus, generally designated 205, according to a third embodiment of the present invention. The apparatus 205 is similar to the apparatus 5 of Figures 1 to 7, like parts denoted by like numerals, but incremented by "200".

[0126] As can be seen from Figure 9 in the apparatus 205, the devices 210a, 210b are angled inwards so that the berms 265 on either side of thread 266 are blown simultaneously.

[0127] Referring now to Figures 10 to 12(b), there is shown an underwater moving apparatus, generally designated 305, according to a fourth embodiment of the present invention. The apparatus 305 is similar to the apparatus of Figures 1 to 7, like parts denoted by like numerals, but incremented by "300".

[0128] The inlet end 355 and the outlet end / outlet 315 are aligned substantially parallel to or with one another. A width of the outlet end / outlet 315 decreases, narrows and / or tapers inwardly in a direction from the inlet end 355 to the outlet end / outlet 315.

[0129] A length of the outlet end / outlet 315 increases, flares and / or tapers outwardly in a direction from the inlet end 355 to the outlet end / outlet 315.

[0130] The inlet end 355 is circular and / or the outlet end / outlet 315 is of an elongate (slot) shape.

[0131] A width of the outlet end / outlet 315 is less than a width / diameter of the inlet end 355.

[0132] A ratio of outlet end 315 width to inlet end 355 width / diameter is beneficially in the range of 0.25 to 0.5, for example, 0.3.

[0133] A length of the outlet end / outlet 315 is greater than a width / diameter of the inlet end 355. A ratio of outlet end / outlet 315 length to inlet end 355 width / diameter is beneficially in the range of 1.1 to 2.5, for example, 2.1.

[0134] A width (or length) W of each blade or vane 375a, 375b tapers, decreases or narrows in a direction towards the outlet 315. Such arrangement acts to facilitate or encourage an improved or even fluid (water) flow distribution (see Figures 12(a) and 12(b)).

[0135] Similar to the apparatus 105 of Figure 8, the apparatus 305 comprises guide vanes or blades 375a, b.

[0136] The one or more blades or vanes 375a, b may comprise one or more primary or guide blades or vanes 375a. The one or more blades or vanes 375a, b comprise one or more secondary or splitter blades or vanes 375b. The secondary or splitter blades or vanes 375b are provided between adjacent primary or guide vanes 375a. The one or more blades or vanes 375 are substantially symmetrically dispersed around a longitudinal axis A of the device 310a, 310b.

[0137] All but one of the one or more blades or vanes 375a, b are curved in cross-section. A central blade or vane 376 disposed at the longitudinal axis A is straight. The one or more blades 375a, b extend to the outlet 315.

[0138] The primary or guide blades or vanes 375a are longer (e.g. in a direction extending between the inlet 355 and the outlet 315) than the secondary or splitter blades or vanes 375b.

[0139] The / each primary or guide blade(s) or vane(s) 375a comprises a first curved portion and / or a second curved portion.

[0140] For each primary or guide blade or vane 375a, the first curved portion is curved or bent in an opposite disposition or direction to the section curved portion.

[0141] The first curved portion of the / each primary or guide blade 375a or vane is provided (more) proximal the inlet 355. The second curved portion of the / each primary or guide blade or vane 375a is provided (more) proximal outlet 315.

[0142] The / each secondary or splinter blade(s) or vane(s) 375b comprise a first curved portion.

[0143] The first curved portion of a / each secondary or splitter blade 375b is provided between and / or is dispersed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes 375a.

[0144] The primary or guide blades or vanes 375a can be said to be "s" shaped. The secondary or splitter blades or vanes 375b can be said to be "r" shaped.

[0145] The outlet portion or nozzle 350 comprises a first dimension, and / or a second dimension, and / or a third dimension.

[0146] The first dimension comprises a width or breadth dimension or direction W. The second dimension comprises a length dimension or direction L. The third dimension comprises a height dimension or direction H. The third dimension H extends between an inlet end 355 and an outlet end 315 of the outlet portion or nozzle 350.

[0147] Beneficially the first dimension W decreases or tapers along at least a portion of the third dimension H in a direction towards the outlet end 315.

[0148] Beneficially also the second dimension L increases or flares along at least a portion of the third dimension H in a direction towards the outlet end 315.

[0149] Referring now to Figures 13 to 17, there is shown an underwater material moving apparatus, generally designated 405, according to a fifth embodiment of the present invention. The apparatus 405 is similar to the apparatus 305 of Figures 10 to 12(b), like parts denoted by like numerals, but incremented by "100". In particular the apparatus 405 is the same as the apparatus 305 in respect of the blades or vanes 475a, b, i.e. the primary or guide blades or vanes 475a and the secondary or splitter blades or vanes 475b.

[0150] The apparatus 405 provides a plate member or baffle (or further blade or vane) 490 which spans between the first and second ends 430, 435, is parallel to the first and second sides 440, 445, and divides each blade or vane 475a, b into first and second blade or vane portions 475a , 475b.

[0151] In this embodiment there is provided a tool or attachment or nozzle, generally designated 450, comprising a water rake which is a water-jet nozzle attachment for a subsea mass-flow excavator (MFE) or controlled-flow excavator (CFE). The rake is designed to create a flatter, smoother seabed profile than conventional MFE or CFE nozzles. Generally, MFE and CFE nozzles have simple circular outlets and are designed primarily to produce excavations which are as deep and narrow as possible, for example for the burial or de-burial of subsea cables or pipes. The water rake is used where the seabed is to be levelled out, producing a more or less flat seabed profile. This is useful, for example, in preparing the seabed for the placing of mattresses, jack-up rig spud-cans, or other structures, and for clearing a path through sand-waves for tracked vehicles. Achieving such a flat seabed profile with circular MFE or CFE nozzles is challenging.

[0152] The water rake achieves this by producing a substantially linear water jet with a substantially uniform jet speed along the exit rather than the more usual circular water jet typical of MFE and CFE devices. The inlet of the water rake attaches to a circular outlet of a conventional CFE tool. The circular jet at the water rake inlet 455 is converted into a substantially linear jet at the water rake outlet 415. Operational constraints require a CFE device to be as short as practical, for stability while stored on the deck of a moving vessel, for safety during launch and recovery, and to allow it to operate in as shallow water as possible. The water rake, therefore, employs a series of internal guide blades or vanes 475a, b to direct the flow through the tool or nozzle 450, allowing the jet to be converted from circular to linear in a relatively short distance. The rake tapers, reduces in width, from inlet 425 to outlet 415 and increases in length from inlet 425 to outlet 415. In the embodiment shown the outlet 415 is rectangular for ease of manufacture, but could also incorporate semi-circular ends.

[0153] In a preferred implementation: a length of the outlet 415 is 2.1 times a diameter of the inlet 425, a width of the outlet 415 is 0.3 times the diameter of the inlet 425, a height of the tool 450 is 0.6 times the diameter of the inlet 425.

[0154] The spacing of the vanes 475a, b accounts for two phenomena. Firstly, the tendency of fluid flow to take the shortest, easiest route between inlet 425 and outlet 415, in particular the tendency for flow to concentrate near the centre of the outlet 415. This provides motivation to make the inner passages narrower than the outer passages to encourage more flow to the extremities of the tool 450.

[0155] Secondly, flow exiting a CFE device 405 generally has higher energy towards an outer diameter of the device, with a lower energy region towards the centre. This mitigates the first phenomenon, as the outer passages are proportionally more exposed to higher energy flow regions of an incoming jet, whereas the inner passages have greater exposure to a low energy central region.

[0156] In a preferred implementation, the ratio of passage widths (not areas) at the inlet 425, symmetrically from inner passage to outer passage is 20:20:15:45 (a:b:c:d) (see Figure 15). An alternative implementation has passage width ratios of 20:15:20:45.

[0157] Splitter guide vanes 475b are used to seek to improve fluid flow towards the outlet 415 of the tool 450. As a fluid passage expands linearly from inlet 425 to outlet 415, the splitter guide vanes 475b help to evenly distribute flow across the outlet 415. Splitter guide vanes 475b are used as another set of full-length guide vanes 475a would result in increased energy loss due to skin friction and too much restriction in the narrow passages towards the inlet 425.

[0158] At the outlet 415, the guide vanes 475a, b are uniformly spaced. A central guide vane or baffle 490 extends longitudinally through the device 450 from inlet 425 to outlet 415, to reduce secondary circulating flows and to increase the structural rigidity of the guide vanes 475a and splitter guide vanes 475b.

[0159] The water rake can be used individually, or can be deployed with two excavators side by side, e.g. to increase (double) a length of the rake. In this case, the rakes / excavators can be mechanically connected, e.g. bolted together using brackets on an end of each.

[0160] It will be understood that the embodiments of the invention hereinbefore described are given by way of example only, the scope of protection is defined by the appended claims.

Claims

1. An underwater material moving device (10a, 10b; 110a, 110b; 210a, 210b; 310a, 310b; 410a, 410b) comprising: a body (20; 120; 220; 320; 420); an inlet (25; 125; 225; 325; 425) provided on or at an end of the body (20;125;225; 325;425); and an outlet (15; 115; 215; 315; 415) provided on or at another, opposite, end of the body to the inlet, wherein the body comprises a through-passage (21; 121; 221; 321; 421) extending from the inlet to the outlet, wherein the outlet is provided on an outlet portion comprising an inlet end (55; 155; 255; 355; 455) and an outlet end, the outlet end comprising the outlet of the device, the outlet portion comprising a first dimension (W), a second dimension (L) and a third dimension (H), the first dimension (W) being a width or breadth dimension of the outlet portion, the second dimension (L) being a length dimension of the outlet portion, and the third dimension (H) being a height dimension of the outlet portion which extends along a direction of a longitudinally extending axis (A) of the body, the first dimension of the outlet portion decreases or tapers along at least a portion of the third dimension in a direction from the inlet end towards the outlet end of the outlet portion, and the outlet comprises an elongate shape or slot (16; 116; 216; 316; 416), the inlet and the outlet are substantially disposed along the longitudinally extending axis (A) of the body such that the inlet and outlet are aligned with one another, characterized in that the device further comprises one or more primary or guide blades or vanes (375a; 475a), and each primary or guide blade or vane comprises a first curved portion and a second curved portion, the first curved portion being curved or bent in an opposite disposition or direction to the second curved portion.

2. The device as claimed in claim 1, wherein the one or more blades or vanes are provided at or adjacent the outlet.

3. The device as claimed in claim 1 or2, wherein a width or length of each blade or vane decreases or narrows in said direction from the inlet end towards the outlet end of the outlet portion.

4. The device (110a, 110b; 210a, 210b; 310a, 310b; 410a, 410b) as claimed in claim 2 or 3, wherein the one or more blades or vanes are substantially symmetrically dispersed around the longitudinal axis (A)of the device (110a, 110b; 210a, 210b; 310a, 310b;410a,410b).

5. The device as claimed in any one of claims 2 to 4, wherein the one or more blades or vanes comprise the one or more primary or guide blades or vanes and one or more secondary or splitter blades or vanes (375b; 475b), and optionally: the secondary or splitter blades or vanes (375b; 475b) are provided between adjacent primary or guide blades or vanes (375a; 475a); and / or the primary or guide blades or vanes (375a; 475a) are longer than the secondary or splitter blades or vanes (375b; 475b).

6. The device as claimed in claim 5, wherein the one or more secondary or splitter blades or vanes (375b; 475b) are curved in cross-section, and / or and wherein optionally: the or each primary or guide blades or vanes (375a; 475a) comprises a first curved portion and a second curved portion, and in such case optionally: the first curved portion of the or each primary or guide blade or vane (375a; 475a) is curved or bent in an opposite disposition or direction to the second curved portion of the or each primary or guide blade or vane (375a; 475a); and / or the first curved portion of the or each primary or guide blade or vane is provided proximal to the outlet; and / or the or each primary or guide blade or vane is "s" shaped; the or each secondary or splitter blades or vanes comprises a first curved portion, and in such case optionally: the first curved portion of the or each secondary or splitter blade is provided between and / or is disposed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes; and / or the secondary or splitter blades or vanes are "r" shaped.

7. The device as claimed in any preceding claim, wherein the second dimension of the outlet portion increases or flares along at least a portion of the third dimension in said direction from the inlet end towards the outlet end of the outlet portion.

8. The device as claimed in any preceding claim, wherein at least one of: the elongate shape or slot comprises: at least one full radiussed end; at least one semi-circular end; or at least one linear end the elongate shape or slot comprises first and second sides that are linear and / or substantially parallel to one another.

9. The device as claimed in any preceding claim, wherein: a ratio of the width of the outlet end to a width of the inlet end is in the range of 0.25 to 0.5, for example, 0.3; a length of the outlet end is greater than a width of the inlet end; a length of the outlet is greater than a width of the inlet end; a ratio of the length of the outlet end to the width of the inlet end is in the range of 1.1 to 2.5, for example, 2.1; a ratio of the length of the outlet to the width of the inlet is in the range of 1.1 to 2.5, for example, 2.1.

10. The device as claimed in any preceding claim, wherein the outlet portion comprises a nozzle (50;150;250;350;450).

11. The device as claimed in any preceding claim, wherein the outlet portion is detachably attachable to a remainder of the body.

12. The device as claimed in any preceding claim, wherein the inlet end of the outlet portion is substantially circular.

13. The device as claimed in any preceding claim, wherein the inlet is substantially circular.

14. An underwater material moving apparatus (5; 105; 205; 305; 405) comprising at least one underwater material moving device (10a, 10b; 110a, 110b, 210a, 210b;310a, 310b;410a, 410b) according to any of claims 1 to 13.

15. The apparatus as claimed in claim 14, wherein the apparatus comprises a pair of the devices according to any of claims 1 to 13.

16. A method of moving underwater material comprising: providing an underwater material moving device (10a, 10b; 110a, 110b; 210a, 210b; 310a, 310b; 410a, 410b) according to any of claims 1 to 13 or an underwater material moving apparatus (5; 105; 205; 305; 405) according to either of claims 14 or 15; using or deploying said device (10a, 10b; 110a, 110b; 210a, 210b; 310a, 310b; 410a, 410b) or apparatus (5; 105; 205; 305; 405) to move underwater material.

17. The method as claimed in claim 16, wherein moving said underwater material comprises filling or back-filling an underwater trench, such as with material comprising spoil or berm.

18. The method as claimed in claim 16, wherein, in use: there is provided a substantially linear water jet flow with a substantially uniform jet speed along the outlet; and / or the guide blades or vanes direct fluid flow through the device so as to covert a water jet flow from being circular to linear.

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