Ship draft detection device and detection method

Abstract

The invention relates to the technical field of ships, in particular to a ship draft detection device and detection method.The ship draft detection device comprises a wave stabilizing tube assembly vertically penetrating through a ship body, and the wave stabilizing tube assembly comprises a fluid stabilizing area communicated with an external water area; the non-linear eddy current energy dissipater is arranged at the bottom of the wave stabilizing tube assembly, a rotational flow dissipation cavity is defined in the non-linear eddy current energy dissipater, a tangential throttling channel is formed in the side wall of the rotational flow dissipation cavity, and an axial overflow opening is formed in the top of the rotational flow dissipation cavity; the following assembly is arranged in the fluid stable area and comprises a guide mechanism and a following body; the non-linear eddy current energy dissipater is arranged at the bottom, the flow resistance is automatically switched through the kinetic energy difference of fluid, non-contact guiding is achieved in combination with the magnetic suspension following assembly, self-adaptive isolation of high-frequency waves and real-time following of draught changes are achieved, resonance interference and mechanical friction are eliminated, and the measurement precision under the complex sea condition is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of marine technology, specifically to a device and method for detecting the draft of a ship. Background Technology

[0002] In the field of shipbuilding and marine engineering equipment, draft is a core parameter characterizing a ship's buoyancy, calculating displacement, and ensuring navigational safety. In existing technologies, to achieve high-precision draft detection, non-contact radar or laser rangefinders are typically used in conjunction with a wave-stabilizing tube. The wave-stabilizing tube is usually a vertical metal tubular structure that penetrates the ship's deck and extends to the bottom, with a through-hole at the bottom connecting to the outside seawater. The main function of this structure is to act as a mechanical low-pass filter, using the physical isolation of the tube walls to shield against direct interference from sea surface waves, foam, and floating debris, thereby creating a relatively calm liquid surface environment within the tube for accurate sensor measurements. For example, in a typical bulk carrier draft monitoring system, a radar level gauge is installed at the top of the wave-stabilizing tube, and the ship's draft is deduced by measuring the liquid level height within the tube.

[0003] However, in practical applications, especially under normal sea conditions, while the aforementioned technologies can isolate most high-frequency wave interference, they still face the conventional problems of response lag and residual small fluctuations. To balance connectivity and damping effect, existing wave stabilizers typically use a single-aperture circular throttling orifice or a simple grid structure at the bottom. This conventional design often struggles to address the conflicting requirements of "rapidly following draft changes" and "effectively filtering wave noise": if the orifice is too large, the filtering effect is poor; if the orifice is too small, changes in water level within the pipe can lag significantly behind the actual draft of the ship, affecting real-time loading decisions during loading and unloading operations. Therefore, existing technologies often rely on backend electronic algorithms for long-period moving average filtering, but this does not solve the fluid disturbance problem at its physical source.

[0004] In particular, when a ship is in an open anchorage or encounters swells with wave heights exceeding 2 meters, conventional wave stabilizer structures can experience severe measurement failures due to the resonance effect of the fluid inside the pipe. Specifically, when the frequency of external waves is close to or coincides with the natural frequency of the liquid column inside the wave stabilizer, the straight-through or simple throttling pipe structure cannot dissipate fluid energy. Instead, it induces violent reciprocating oscillations in the liquid level inside the pipe, leading to breakage of the radar signal reflector, the generation of multipath effects or parasitic echoes. Consequently, the data collected by the sensor under adverse sea conditions becomes distorted due to the extremely low signal-to-noise ratio, severely restricting the accuracy of draft monitoring and navigation safety of ships under dynamic navigation and complex sea conditions.

[0005] To address this, a device and method for detecting ship draft are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a ship draft detection device and method, which solves the problem that ship wave stabilizers cannot simultaneously achieve filtering and fast response. By setting a nonlinear eddy current energy dissipator at the bottom, the flow resistance is automatically switched by utilizing the difference in fluid kinetic energy, and a magnetic levitation following component is combined to achieve non-contact guidance. This enables adaptive isolation of high-frequency waves and real-time tracking of draft changes, eliminates resonance interference and mechanical friction, and ensures measurement accuracy under complex sea conditions.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A ship draft detection device includes a wave-stabilizing tube assembly vertically penetrating the hull, the wave-stabilizing tube assembly including a fluid stabilization zone communicating with external water; a nonlinear eddy current energy dissipator disposed at the bottom of the wave-stabilizing tube assembly, the nonlinear eddy current energy dissipator internally defining a swirling dissipation cavity, the sidewall of the swirling dissipation cavity having a tangential throttling channel to force high-velocity inflowing fluid to form a high-resistance rotating vortex, the top of the swirling dissipation cavity having an axial overflow port communicating with the fluid stabilization zone to allow low-velocity fluid to flow through laminarly; when external waves... During high-frequency surges (high flow velocity), the fluid is forced to form a high-resistance rotating vortex, which dissipates wave kinetic energy by using centrifugal pressure drop and prevents it from entering the wave stabilizer. When the ship's draft changes substantially (low flow velocity), the fluid cannot form a vortex and passes through the axial overflow port in a low-resistance laminar flow form. This achieves an adaptive effect of "blocking strong waves (filtering out waves) and allowing weak waves to pass (rapidly responding to draft changes)," which not only ensures wave stabilization capability in severe sea conditions but also avoids the problem of delayed loading draft readings caused by traditional small-hole throttling.

[0008] The following assembly, located within the fluid stabilization zone, includes a guiding mechanism and a following body. The guiding mechanism is configured to establish a non-contact magnetic levitation constraint field between the following body and the inner wall of the fluid stabilization zone. This isolates mechanical friction and suppresses parasitic vibrations caused by the following body's swaying with the hull. This not only eliminates mechanical friction caused by seawater corrosion, biological adhesion, or salt crystallization, and solves the viscous error caused by static friction during small liquid level changes in traditional floats, thus improving detection sensitivity, but also suppresses lateral parasitic vibrations caused by the following body's swaying with the hull using the radial constraint force provided by the magnetic levitation field. This ensures that the reflecting surface remains stably centered in the tube, preventing collisions with the tube wall, thus protecting the structure and improving the accuracy of the detection data.

[0009] Traditional straight-through wave stabilizers are prone to resonance of the liquid column inside the tube at specific wavelengths. This invention, through a combination of bottom eddy current energy dissipation and internal magnetic levitation damping, disrupts the energy accumulation conditions for standing wave formation, effectively attenuating the resonance amplitude of the liquid level inside the tube. This ensures that even when encountering swells close to the tube's natural frequency, the device maintains a relatively stable fluid calm zone, thereby establishing a stable wave reflection reference surface across all sea states and ensuring navigational safety.

[0010] Preferably, the inner wall of the vortex dissipation cavity is constructed as a rotating body structure that gradually contracts upward along the axial direction; by utilizing the principle of conservation of angular momentum, the rotational angular velocity of the vortex is forcibly increased during the fluid ascent, thereby increasing the fluid shear resistance without increasing the external dimensions.

[0011] Preferably, the cross-section of the tangential throttling channel has a convergent, gradually changing structure along the fluid inflow direction, and the inlet cross-sectional area of ​​the tangential throttling channel is larger than its own outlet cross-sectional area; in order to form a nozzle effect, accelerate the fluid velocity entering the vortex dissipation chamber, and ensure that even in low wave height (low pressure difference) sea states, the rotating vortex can be effectively triggered, improving the sensitivity of low frequency filtering; and the resistance of the fluid flowing out in the reverse direction is much greater than the resistance of the fluid flowing in in the forward direction, preventing the water in the pipe from being rapidly lost due to the pressure difference between the inside and outside, and maintaining a stable change in liquid level.

[0012] Preferably, the nonlinear eddy current energy dissipator is arranged in multiple stages along the axial direction of the wave stabilizer assembly, and the vortex dissipation cavities of adjacent nonlinear eddy current energy dissipators are connected; each stage dissipates wave energy in different frequency ranges step by step, thus widening the wave-dissipation bandwidth of the device; and the multi-stage structure shares the pressure of the single-stage structure, avoiding structural cavitation or damage due to excessive pressure difference under extreme sea conditions.

[0013] Preferably, the axial overflow port is provided with a flow-rectifying grid, which includes several radially distributed guide vanes; it forcibly cuts off the rotational component of the rising fluid, converts the rotational kinetic energy of the turbulence into heat energy dissipation, ensures that the fluid entering the upper fluid steady zone returns to a stable laminar flow state, and prevents large floating objects or marine organisms from entering the wave-stabilizing tube assembly through the axial overflow port, thus playing a filtering and protection role.

[0014] Preferably, the bottom of the follower is provided with a protrusion, which is a streamlined hemispherical or parabolic structure; this minimizes the resistance of the follower during vertical movement, enabling it to respond quickly to minute changes in the liquid level in the pipe and eliminate mechanical lag; and when the liquid level fluctuates violently and the follower hits the liquid surface due to inertia, the protrusion structure can effectively break the water, preventing the formation of an airbag effect that could cause false liquid level readings.

[0015] Preferably, the follower body has a plurality of damping holes penetrating its upper and lower surfaces, with the opening area of ​​the damping holes decreasing from top to bottom; the damping holes connect the air pressure and water pressure above and below the follower body, preventing the formation of a closed air cushion below the follower body that would hinder its descent with the liquid surface, ensuring consistent bidirectional following performance; and the fluid flowing through the damping holes generates viscous damping, providing appropriate damping characteristics for the vertical movement of the follower body, further smoothing high-frequency fluctuations in the liquid level; the change in the opening area of ​​the damping holes ensures that the center of gravity of the follower body is located below its center of buoyancy, ensuring that the follower body can automatically recover its horizontal attitude after tilting due to lateral wave forces, and preventing the follower body from overturning or tipping over in extreme sea conditions that cause the liquid surface inside the tube to break, thus ensuring the stability of the measurement system.

[0016] Preferably, the guiding mechanism includes a permanent magnet array evenly distributed along the circumference of the follower and a magnetically guided track extending axially along the inner wall of the fluid steady zone; it restricts the follower to move only along the trajectory defined by the magnetically guided track, prevents it from rotating circumferentially, ensures that the polarization direction of the radar reflector remains constant, and enhances the lateral constraint force, thereby improving the anti-overturning stability of the follower.

[0017] Preferably, the nonlinear eddy current energy dissipator and the wave stabilizer assembly adopt a detachable modular connection structure, and the connection between the nonlinear eddy current energy dissipator and the wave stabilizer assembly is provided with a sealed interface; this allows for the replacement of energy dissipator modules with different damping parameters according to the typical wave period characteristics of the ship's navigation area, thereby achieving customized filtering; and it facilitates the separate disassembly of the bottom energy dissipator for cleaning or maintenance during dry dock repairs, without having to remove the entire detection device that runs through the hull.

[0018] The detection method for the aforementioned ship draft depth detection device includes the following steps: 1. The nonlinear eddy current energy dissipator is used as the only flow channel between the external water area and the fluid stabilization zone. The flow resistance mode is automatically switched according to the inflow velocity of the external fluid: when the external wave impact causes the fluid to flow in at a high velocity, the fluid is guided to enter the vortex dissipation chamber tangentially, which excites the fluid to generate a high-speed rotating vortex. The centrifugal pressure gradient generated by the rotation is used to build a high-impedance barrier to block the transfer of wave energy to the fluid stabilization zone; when the ship's draft changes and the fluid flows in at a low velocity, the fluid is kept in a laminar state and passes through the axial overflow port to form a low-impedance channel so that the liquid level in the fluid stabilization zone follows the external draft depth in real time.

[0019] 2. By using the guiding mechanism, a non-contact magnetic levitation constraint field is established between the follower and the inner wall of the fluid steady zone, so that the follower is suspended on the liquid surface of the fluid steady zone, and the magnetic repulsion force is used to suppress the lateral parasitic vibration generated by the follower as the hull sways, thereby establishing a stable radar wave reflection reference surface.

[0020] 3. Using a ranging sensor mounted on top of the waveguide assembly, a probe beam is emitted toward the reflective reference surface of the follower and the echo is received. The real-time height of the follower in the steady fluid zone is calculated, and then the draft of the ship is calculated.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention incorporates a nonlinear eddy current energy dissipator at the bottom of the wave stabilizer tube, utilizing a tangential throttling channel to guide fluid tangentially into the vortex dissipation chamber. When external waves cause a high fluid velocity, the fluid rotates within the chamber, generating a centrifugal pressure drop and creating high impedance, thus preventing wave energy from entering. When draft changes cause a lower fluid velocity, the fluid does not rotate and flows directly out through the axial overflow port, forming a low-impedance channel. Furthermore, the flow resistance is automatically switched based on the fluid velocity difference, filtering high-frequency wave interference while ensuring the fluid level in the tube follows changes in the ship's draft, thus solving the data lag problem caused by fixed-aperture throttling.

[0022] 2. This invention, by setting up a permanent magnet array and a magnetically guided track, forms a non-contact magnetic levitation gap between the follower and the inner wall of the waveguide, avoiding the frictional jamming caused by seawater corrosion, biological adhesion, or salt crystallization that occurs with traditional mechanical pulleys or sliders. Furthermore, the hemispherical or parabolic protrusions at the bottom of the follower reduce water resistance during vertical movement. Simultaneously, the damping orifices with decreasing opening areas running vertically through the follower balance the upper and lower air pressures, preventing the formation of air pockets below the follower. These structures work together to ensure smooth movement of the follower under minute liquid level changes and prevent the follower from tipping over when tilted.

[0023] 3. This invention employs a multi-stage series nonlinear eddy current energy dissipator to disperse a large single-stage pressure difference into multiple smaller pressure differences, thereby dissipating wave energy stage by stage and preventing external surge waves of a specific frequency from inducing standing wave resonance within the pipe. Simultaneously, radially distributed guide vanes are installed at the axial overflow port to cut off the rotational component of the rising fluid, allowing the fluid entering the steady-state zone to return to a laminar flow state. This prevents the inner liquid surface from forming a depression due to residual rotation, providing a flat reflective reference surface for the sensor at the top. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall isometric structure of the present invention; Figure 2 This is a schematic diagram of the isometric structure with internal section of the present invention; Figure 3 This is a schematic diagram of the front half-section structure of the present invention; Figure 4 For the present invention Figure 3 Schematic diagram of the AA section structure; Figure 5 For the present invention Figure 3 Schematic diagram of the cross-sectional structure of the middle BB; Figure 6 This is a schematic diagram of the follower structure of the present invention; Figure 7 For the present invention Figure 3 Enlarged diagram of section C; Figure 8 For the present invention Figure 3 Enlarged schematic diagram of part D in the middle.

[0025] In the figure: 1. Wave stabilizing tube assembly; 2. Fluid stabilization zone; 3. Nonlinear eddy current energy dissipator; 4. Swirl dissipation cavity; 5. Tangential throttling channel; 6. Axial overflow port; 61. Rectifying grid; 7. Follower assembly; 8. Guide mechanism; 81. Permanent magnet array; 82. Magnetic guide track; 9. Follower body; 91. Protrusion; 92. Damping orifice; 10. Sensor. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figures 1 to 8 This invention provides a device and method for detecting ship draft, the technical solution of which is as follows: A ship draft detection device includes a wave-stabilizing tube assembly 1 that vertically penetrates the hull. The wave-stabilizing tube assembly 1 includes a fluid stabilization zone 2 that communicates with the external water area. The inner wall of the fluid stabilization zone 2 is provided with a spiral guide groove to disrupt the standing wave resonance mode within the tube. This dissipates acoustic standing wave energy by changing the fluid boundary conditions and guides condensate on the tube wall to slide down along a spiral path in a controlled manner, preventing random dripping of water droplets from causing secondary disturbance to the liquid surface. A nonlinear eddy current energy dissipator 3 is disposed at the bottom of the wave-stabilizing tube assembly 1. The nonlinear eddy current energy dissipator 3 has a streamlined spindle-shaped outer profile to reduce the navigation resistance when the device protrudes outside the hull, reduce ship fuel consumption, improve the flow field distribution at the bottom of the ship, and reduce turbulence at the stern induced by the presence of the device. The shell materials of the wave-stabilizing tube assembly 1 and the nonlinear eddy current energy dissipator 3 are preferably 316L stainless steel or duplex stainless steel to resist seawater corrosion; or high-strength composite materials (such as carbon fiber reinforced polymer) with a surface coating of antifouling paint can be used. The spiral guide grooves on the inner wall of the fluid stabilization zone 2 have a pitch preferably 1.5-2.0 times the pipe diameter, a groove depth of 1 / 3 to 1 / 2 of the pipe wall thickness, and a circular arc cross-section to minimize fluid residue adhering to the wall during downward flow. The length-to-diameter ratio (length to maximum diameter ratio) of the streamlined spindle-shaped outer profile is set to 2:1 to 3:1 to reduce the drag coefficient during navigation to below 0.3. The nonlinear vortex energy dissipator 3 internally defines a swirling dissipation cavity 4. The sidewall of the swirling dissipation cavity 4 is provided with a tangential throttling channel 5 to force the high-velocity inflowing fluid to form a high-resistance rotating vortex. The top of the swirling dissipation cavity 4 is provided with an axial overflow port 6 connecting to the fluid stabilization zone 2 to allow low-velocity fluid to flow through laminarly. In a preferred embodiment, the geometric relationship between the tangential throttling channel 5 and the swirling dissipation cavity 4, as well as the arrangement of the axial overflow port 6, ensures that when the external seawater changes slowly at a rate much higher than the draft, When the flow velocity caused by the chemical reaction surges in, the fluid entering the cavity tends to form a flow state dominated by rotation, thus exhibiting a flow resistance at the axial overflow port 6 that is significantly higher than that of the laminar flow state; while when the external seawater flows slowly at a lower velocity mainly due to changes in draft, the fluid entering the cavity passes through the axial overflow port 6 in a form close to laminar flow; the following component 7 is set in the fluid stabilization zone 2, and the following component 7 includes a guide mechanism 8 and a following body 9; the guide mechanism 8 is configured to establish a non-contact magnetic levitation constraint field between the following body 9 and the inner wall of the fluid stabilization zone 2 to isolate mechanical friction and suppress parasitic vibrations generated by the following body 9 as it sways with the hull.

[0028] As one embodiment of the present invention, refer to Figure 1 and Figure 2 The inner wall of the swirling dissipation cavity 4 is constructed as a rotating body structure that gradually contracts upward along the axial direction; specifically, the generatrix trajectory of the inner wall of the swirling dissipation cavity 4 has various types to adapt to different sea conditions, such as... Figure 2As shown, this invention comprises two stages of waveguide assemblies 1. The generatrix trajectory of the inner wall of the swirling dissipation cavity 4 of the upper waveguide assembly 1 is close to a sine curve, while the generatrix trajectory of the inner wall of the swirling dissipation cavity 4 of the lower waveguide assembly 1 is similar to an exponential function curve. The ratio of the bottom diameter to the top axial overflow port 6 diameter is controlled between 3:1 and 5:1, so as to force the rotation radius of the rising fluid to decrease and the tangential velocity to increase through the principle of conservation of angular momentum, thereby constructing a centrifugal pressure gradient that increases sharply from the center to the outer wall. In addition, the surface roughness Ra of the inner wall of the swirling dissipation cavity 4 should be less than 1.6 μm to reduce frictional resistance in laminar flow and ensure smooth fluid rotation in vortex flow.

[0029] As one embodiment of the present invention, refer to Figures 3 to 5 The cross-section of the tangential throttling channel 5 has a convergent, gradually changing structure along the fluid inflow direction, and the inlet cross-sectional area of ​​the tangential throttling channel 5 is larger than its own outlet cross-sectional area. The number of tangential throttling channels 5 is preferably 2-4, evenly distributed along the circumference; and their opening directions are consistent. The angle deviation between the axis of the tangential throttling channel 5 and the tangent of the inner wall of the swirling dissipation cavity 4 should be less than 5 degrees. The contraction ratio (inlet area / outlet area) of the convergent, gradually changing structure is 1.5 to 2.0 to form a high-speed jet, inducing a shear layer and a rotating flow field within the cavity. A rounded transition is provided at the channel inlet to prevent unnecessary inlet separation vortices from forming during low-velocity intake.

[0030] As one embodiment of the present invention, refer to Figure 3 and Figure 7 The nonlinear eddy current energy dissipator 3 is arranged in multiple stages along the axial direction of the wave stabilizer assembly 1, and the swirling dissipation cavities 4 of adjacent nonlinear eddy current energy dissipators 3 are connected. The adjacent stages are connected by standard flanges or threads. When multiple stages are arranged, the volume of each swirling dissipation cavity 4 can be designed to decrease from bottom to top, for example, by decreasing by 10% to 20% step by step, so as to achieve graded filtering for wave energy of different frequency bands (the bottom filters out the large energy of long waves, and the upper part filters out the residual energy of short waves).

[0031] As one embodiment of the present invention, refer to Figure 2 and Figure 3 A flow-rectifying grid 61 is provided at the axial overflow port 6. The flow-rectifying grid 61 includes several radially distributed guide vanes. The flow-rectifying grid 61 is made of high-hardness engineering plastic or corrosion-resistant metal, and its thickness is 0.2-0.5 times the diameter of the axial overflow port 6. The guide vanes of the flow-rectifying grid 61 converge at the axis, dividing the axial overflow port 6 into several fan-shaped channels. This not only cuts off the rotational component of the rising fluid, but also reduces the equivalent hydraulic diameter of the overflow port, further increasing the damping ratio of high-frequency turbulence. At the same time, it also serves as a grid to prevent external marine organisms from accidentally entering the waveguide.

[0032] As one embodiment of the present invention, refer to Figure 6 The follower body 9 has a protrusion 91 at its bottom, which is a streamlined hemispherical or parabolic structure. The follower body 9 is made of closed-cell foam material (such as PMI foam) as the core material, and is covered with a fiberglass or carbon fiber shell. The overall average density is controlled at 0.4-0.6 g / cm³, ensuring that its waterline is located at 1 / 2 to 2 / 3 of the overall height. The height of the streamlined protrusion 91 at the bottom is 1 / 5 to 1 / 4 of the total height of the follower body 9. The surface of this protrusion 91 needs to be hydrophobically treated (such as by coating with PTFE), with a contact angle greater than 110 degrees, to reduce water adhesion and ensure that the follower body 9 can quickly detach from the water film without significant lag when the liquid level drops rapidly.

[0033] As one embodiment of the present invention, refer to Figure 6 The follower body 9 has several damping holes 92 penetrating its upper and lower surfaces, with the opening area of ​​the damping holes 92 decreasing from top to bottom. There are 4-8 damping holes 92, evenly distributed along a circumference centered on the axis of the follower body 9. The hole diameter shrinks linearly from top to bottom, with the ratio of the top opening diameter to the bottom opening diameter being 1.5:1 to 2.0:1. The slope angle of the sloping structure is 5-10 degrees, which not only facilitates drainage but also scatters non-perpendicularly incident radar sidelobe waves onto the radar-absorbing coating on the pipe wall. The radar wave reflector is located in the central region of the slope structure. It needs to be pasted or embedded with a metal sheet or corner reflector array with a high dielectric constant, and the diameter is not less than 1.2 times the diameter of the radar beam spot. The upper surface of the follower 9 is constructed as a slope structure with a high center and low edges. This is to utilize gravity for natural flow guidance, prevent condensation or splashed water droplets inside the pipe from accumulating on the upper surface of the follower 9, avoid draft reading drift caused by increased load mass, and this geometry can scatter stray radar waves that are not perpendicularly incident to the pipe wall for absorption, reduce multipath reflection interference, and improve the signal-to-noise ratio.

[0034] As one embodiment of the present invention, refer to Figure 2 and Figure 6The guiding mechanism 8 includes a permanent magnet array 81 evenly distributed around the circumference of the follower body 9 and a magnetically guided track 82 extending axially along the inner wall of the fluid stabilization zone 2. The permanent magnet array 81 is made of sintered neodymium iron boron magnets with a three-layer anti-corrosion coating of nickel-copper-epoxy resin. The magnetic pole arrangement can adopt a Halebeck array to enhance the magnetic field strength on one side. The magnetically guided track 82 is made of high-permeability ferritic stainless steel strips or silicon steel sheets embedded in the pipe wall. The designed air gap between the follower body 9 and the inner wall of the fluid stabilization zone 2 is 3-8 mm. Within this gap range, the radial restoring stiffness provided by the magnetic field is greater than the lateral component force generated by the full-load displacement mass of the follower body 9 (corresponding to the maximum roll angle of the ship at 30 degrees), avoiding contact between the follower body 9 and the inner wall of the fluid stabilization zone 2. The magnetic levitation constraint field generated by the guiding mechanism 8 is configured as a repulsive magnetic field, and a full-circumferential air gap is maintained between the follower 9 and the inner wall of the wave stabilizer assembly 1; the repulsive magnetic force increases nonlinearly and rapidly as the gap decreases, preventing the follower 9 from rigidly impacting the tube wall during violent swaying; and the full-circumferential air gap eliminates capillary phenomenon, preventing the follower 9 from adhering to the tube wall due to liquid surface tension.

[0035] As one embodiment of the present invention, refer to Figure 3 and Figure 8 The nonlinear eddy current energy dissipator 3 and the wave stabilizer assembly 1 adopt a detachable modular connection structure, and a sealing interface is provided at the connection point between the nonlinear eddy current energy dissipator 3 and the wave stabilizer assembly 1. The connection interface adopts a tongue and groove flange structure and is equipped with double O-ring seals. The sealing ring material is EPDM rubber or fluororubber with a Shore A hardness of 70. The flange connection bolts are made of titanium alloy and equipped with anti-loosening washers. To facilitate operation by underwater robots or divers, the modular interface can be designed as a bayonet quick connector, which can be locked and released by rotating 90 degrees, and is equipped with a spring pin locking mechanism to prevent accidental loosening.

[0036] Working principle: The present invention utilizes the nonlinear eddy current energy dissipator 3 installed at the bottom as the only channel for external seawater to enter the wave stabilizing tube assembly 1. This structure relies on the difference in the flow velocity of external seawater entering the shell under different operating conditions to passively change the flow resistance without the need for additional sensors or control devices.

[0037] In this invention, "high flow velocity" refers to a working condition caused by wave or swell impact that is much higher than the connecting flow velocity caused by slow changes in the ship's draft; "low flow velocity" refers to a connecting flow velocity working condition mainly caused by changes in the ship's draft and not accompanied by significant wave impact.

[0038] High-velocity operation (wave impact): When external waves cause seawater to rush rapidly towards the bottom of the device, the fluid is guided by the tangential throttling channel 5 on the side wall of the shell and rushes tangentially into the internal vortex dissipation chamber 4. Since the incident angle is not pointing towards the center, the fluid rotates along the inner wall of the chamber. The rotating fluid generates centrifugal force, causing the fluid to adhere to the inner wall of the chamber, resulting in an increase in pressure flowing towards the central axial overflow port 6. This pressure difference generated by the rotation increases the resistance to the inward flow of the fluid, thereby limiting the rapid influx of water caused by external waves and keeping the liquid surface in the fluid calm zone 2 relatively stable.

[0039] Low-velocity operating conditions (draft variation): When the ship's draft changes slowly due to load variations, the external seawater velocity is low. After the fluid enters the vortex dissipation chamber 4 through the tangential throttling channel 5, it cannot form a continuous rotation due to insufficient kinetic energy. The fluid flows directly from the periphery to the axial overflow port 6 in the center, without generating a significant centrifugal pressure difference. At this time, the flow resistance is small, allowing seawater to smoothly enter or flow out of the fluid quiescent zone 2, keeping the liquid level in the pipe consistent with the external draft of the hull.

[0040] Within the fluid steady zone 2, this invention utilizes magnetic force to constrain the motion of the follower 9. The follower 9 floats on the liquid surface, and its circumferentially arranged permanent magnet array 81 interacts magnetically with the magnetically guided track 82 on the inner wall of the wave-stabilizing tube. The magnetic force maintains a fixed gap between the follower 9 and the tube wall, preventing physical contact between the follower 9 and the tube wall as it rises and falls with the liquid level, thus avoiding jamming caused by mechanical friction. Furthermore, when the hull sways, the magnetic force generates a restoring force on the follower 9, limiting its lateral swaying within the tube. Combined with the water-breaking effect of the streamlined protrusion 91 at the bottom of the follower 9 and the balancing effect of the damping orifice 92 on the upper and lower air pressures, this ensures that the reflective surface at the top of the follower 9 remains horizontal and centered within the tube, providing a stable target for measurement.

[0041] The ranging sensor 10, mounted on top of the waveguide assembly 1, emits a probe wave vertically downwards. The probe wave strikes the flat reflective reference surface of the follower 9 and is reflected back to the sensor 10. The sensor 10 records the round-trip time or phase difference of the probe wave and calculates the vertical distance between the sensor 10 and the follower 9. The system substitutes this distance value into the geometric relationship of the ship's installation height to calculate the current draft of the ship.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A ship draft detection device, characterized in that, include: A wave-stabilizing tube assembly that penetrates vertically through the hull, the wave-stabilizing tube assembly including a fluid stabilization zone communicating with external waters; A nonlinear eddy current energy dissipator is disposed at the bottom of the waveguide assembly. The nonlinear eddy current energy dissipator defines a swirling dissipation cavity. The sidewall of the swirling dissipation cavity is provided with a tangential throttling channel to force the high-velocity inflowing fluid to form a high-resistance rotating eddy. The top of the swirling dissipation cavity is provided with an axial overflow port that connects to the fluid quiescent zone to allow low-velocity fluid to flow through in laminar flow. The following component, which is disposed within the fluid stabilization zone, includes a guiding mechanism and a following body. The guiding mechanism is configured to establish a non-contact magnetic levitation constraint field between the following body and the inner wall of the fluid stabilization zone to isolate mechanical friction and suppress parasitic vibrations generated by the following body as it sways with the hull.

2. The ship draft detection device according to claim 1, characterized in that: The inner wall of the swirling dissipation cavity is constructed as a rotating body structure that gradually contracts upward along the axial direction.

3. The ship draft detection device according to claim 1, characterized in that: The cross-section of the tangential throttling channel has a convergent, gradually changing structure along the fluid inflow direction, and the inlet cross-sectional area of ​​the tangential throttling channel is larger than its outlet cross-sectional area.

4. The ship draft detection device according to claim 1, characterized in that: The nonlinear eddy current energy dissipator is arranged in multiple stages along the axial direction of the wave stabilizer assembly, and the swirl dissipation cavities of adjacent nonlinear eddy current energy dissipators are connected.

5. The ship draft detection device according to claim 1, characterized in that: The axial overflow port is provided with a flow-rectifying grille, which includes several radially distributed guide vanes.

6. The ship draft detection device according to claim 1, characterized in that: The bottom of the follower is provided with a protrusion, which has a streamlined hemispherical or parabolic structure.

7. The ship draft detection device according to claim 1, characterized in that: The follower body has several damping holes that penetrate its upper and lower surfaces, with the opening area of ​​the damping holes decreasing from top to bottom.

8. The ship draft detection device according to claim 1, characterized in that: The guiding mechanism includes an array of permanent magnets evenly distributed along the circumference of the follower and a magnetically conductive track extending axially along the inner wall of the fluid steady zone.

9. The ship draft detection device according to claim 1, characterized in that: The nonlinear eddy current energy dissipator and the wave stabilizer assembly adopt a detachable modular connection structure, and a sealed interface is provided at the connection between the nonlinear eddy current energy dissipator and the wave stabilizer assembly.

10. A method for detecting the draft of a ship, employing the ship draft detection device as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The nonlinear eddy current energy dissipator is used as the only flow channel between the external water area and the fluid stabilization zone. The flow resistance mode is automatically switched according to the inflow velocity of the external fluid: when the external wave impact causes the fluid to flow in at a high velocity, the fluid is guided to enter the vortex dissipation chamber tangentially, which excites the fluid to generate a high-speed rotating vortex. The centrifugal pressure gradient generated by the rotation is used to build a high-resistance barrier to block the transfer of wave energy to the fluid stabilization zone; when the ship's draft changes and the fluid flows in at a low velocity, the fluid is kept in a laminar state and passes through the axial overflow port to form a low-resistance channel so that the liquid level in the fluid stabilization zone follows the external draft depth in real time. S2. Using the guiding mechanism, a non-contact magnetic levitation constraint field is established between the follower and the inner wall of the fluid steady zone, so that the follower is suspended on the liquid surface of the fluid steady zone, and the magnetic repulsion force is used to suppress the lateral parasitic vibration generated by the follower as the hull sways, thereby establishing a stable radar wave reflection reference surface. S3. Using a ranging sensor located on top of the waveguide assembly, a probe beam is emitted toward the reflective reference surface of the follower and the echo is received. The real-time height of the follower in the steady fluid zone is calculated, and then the draft of the ship is calculated.

Images