A self-hydrofoil craft body shape for reducing additional hydrodynamic loads of a ship lift

Abstract

The application relates to a self-air cushion ship compartment type for reducing additional water dynamic load of a launching type ship lift, which principle is that a ship compartment bottom deck is arranged as a flat bottom structure, an outer ring beam, an inner ring beam, a grid beam longitudinal beam, a grid beam transverse beam, an exhaust hole and the like are arranged under the bottom deck, part of gas at the bottom of the ship compartment is locked, an air cushion is automatically formed, direct force of water body on the ship compartment bottom deck is isolated, and thus additional water dynamic load such as adsorption force and beating force during water entering and leaving of the ship compartment is reduced. The ship compartment type can greatly improve water entering and leaving running speed of the launching type ship lift, solves the problem of low docking efficiency of the downstream, meanwhile, adsorption force and beating force during water entering and leaving are zero after the ship compartment type is adopted, the load does not increase with the increase of the ship compartment size, and thus the ship compartment type can also be applied to large-scale launching type ship lift compartment structures, and the problem of large adsorption force and beating force during water entering of the large-scale ship lift compartment is solved.

Description

Technical Field

[0001] This invention belongs to the field of navigation facility ship lift technology, specifically relating to a self-cushioned ship body type that reduces the additional hydrodynamic load of a launching ship lift. Background Technology

[0002] The submersible ship lift is a uniquely Chinese design developed by Chinese engineers to address the significant and rapid fluctuations in water levels downstream of mountainous rivers in China. It connects to the downstream dam via a direct entry of the ship's compartment into the water, allowing for rapid adjustments to the docking position based on downstream water level changes. The docking is accurate and reliable, and it eliminates the need for a lower lock head and its associated auxiliary equipment, including tightening and sealing mechanisms, significantly reducing the operational process and shortening the time for ships to pass through the dam. However, due to the additional hydrodynamic load during the entry and exit processes, the largest currently constructed submersible ship lift is a 500-ton class (the first and third stage ship lifts at Goupitan, and the ship lift at Jinghong).

[0003] The most significant characteristic of a launching ship lift is that the ship chamber enters the water and docks, with the chamber door opening when the water level in the chamber equals the water level in the chamber pool. During entry, the chamber interacts directly with the water, generating impact loads. During exit, the bottom of the chamber experiences suction from the water, generating suction loads. The impact force and suction force are positively correlated with the entry velocity and the area of ​​the chamber's bottom decking; that is, the greater the entry velocity, the greater the impact and suction forces; and the larger the area of ​​the chamber's bottom decking, the greater the impact and suction forces. Figure 1 and Figure 2 The force process lines for the flat plate entering and exiting the water show that the peak values ​​of adsorption force and impact force are relatively large during the entry and exit processes, which may affect the stability and safe operation of the ship.

[0004] To reduce the impact force during entry into the water and the suction force during exit, the current engineering approach involves reducing the speed of the hull while designing the hull deck in a wedge shape. (See...) Figure 3 The current engineering projects utilize the following ship lift bottom structure diagrams. For example, the maximum water entry speed of the Jinghong ship lift is 1.4 m / min, and the bottom elevation angle (the angle between the ship lift bottom and the horizontal plane) is 4°. The first and third stage ship lifts at Goupitan use a water entry speed of 0.8 m / min, with the same 4° bottom elevation angle. Typically, the height between the lowest point of the ship lift's exterior and the water level inside is approximately 5 meters. During the water entry or exit process, the ship lift takes about 5 minutes to descend or ascend 5 meters. In contrast, the ship lift's aerial operation typically operates at 12 m / min, and its ascent of 60 meters also takes about 5 minutes. It is evident that the inefficient operation of the submersible ship lift during water entry and exit processes indicates significant room for improvement and optimization.

[0005] To improve the operating speed of a launching ship lift during the water entry and exit process, it is necessary to further reduce the impact and suction forces of the ship lift's cargo box during this process. Current engineering solutions are no longer effective in further reducing the suction and impact forces of the cargo box. Therefore, a new technical solution is urgently needed to solve this technical problem. Summary of the Invention

[0006] The technical problem to be solved by this invention is to reduce the impact force and suction force during the rapid entry and exit of the ship chamber, thereby improving the operating efficiency of the launching ship lift, and to provide a technical solution for the design of the ship chamber of a large-scale launching ship lift.

[0007] The principle by which this invention solves the above technical problems is: The impact and suction forces generated during the entry and exit of the ship's compartment from the water are due to the interaction between the compartment's floorboards and the water. If the water and the floorboards did not contact each other, would these suction and impact forces not occur? Therefore, an air cushion can be installed between the water and the floorboards to isolate them from contact. (See...) Figure 4 To verify this idea, the pressure curves at the bottom of the ship's compartment before and after the air cushion was installed were measured experimentally. (See attached data.) Figure 7 and Figure 8 It can be seen that under this method, no suction force or impact force occurs during the process of the ship entering and exiting the water.

[0008] The technical solution of this invention to solve the above technical problems is: (1) The bottom lining of the ship's compartment no longer adopts the usual wedge-shaped scheme, but adopts a flat bottom lining scheme with a bottom lift angle of 0°.

[0009] (2) Two ring beams are arranged under the boundary of the bottom deck of the ship compartment. The outer ring beam is located at the boundary of the bottom deck of the ship compartment. The distance between the outer ring beam and the inner ring beam is 10cm. The grid beam is arranged under the bottom deck of the ship compartment surrounded by the inner ring beam. The grid beam is composed of steel of equal width that is staggered longitudinally and laterally. The grid beam distributed along the longitudinal direction of the ship compartment is called the grid beam longitudinal beam, and the grid beam distributed perpendicular to the longitudinal direction of the ship compartment is called the grid beam transverse beam. The preferred beam width of the outer ring beam, inner ring beam and grid beam is 1cm, and the preferred beam height is 5cm (considering factor (1) the height of the grid beam that does not contact the bottom deck of the water body is calculated based on the maximum tilt of the ship compartment during the water entry and exit process and a certain margin is taken; considering factor (2) the buoyancy generated by the gas between the grid beams cannot be significantly greater than the original scheme. After calculation, the same 2.5m water entry is used. Since this scheme adopts a flat bottom, the total buoyancy generated by water entry is less than the 4° wedge angle scheme). The preferred grid beam longitudinal beam spacing is 3m, and the preferred grid beam transverse beam spacing is 5m.

[0010] (3) The top of the vent holes of the main structural longitudinal beams and the main structural transverse beams under the bottom deck of the ship compartment are located 5cm above the bottom deck, ensuring that only a 5cm air cushion is generated under the bottom deck during the entry and exit of the water, and the remaining gas in the cavity at the bottom of the ship compartment can be freely discharged. At the same time, in order to meet the gas communication between the outer ring beam and the inner ring beam, the main structural longitudinal beams and the main structural transverse beams under the bottom deck of the ship compartment have holes in the space enclosed between the outer ring beam and the inner ring beam. The top of the hole is at the bottom deck of the ship compartment, and the hole is 5cm high and 10cm wide.

[0011] (4) To monitor the airtightness of the ship compartment, four pressure sensors are installed between the outer and inner ring beams upstream and downstream of the longitudinal centerline of the ship compartment. Two sensors are installed on the upstream side and two on the downstream side. The pressure sensors on the upstream and downstream sides are arranged in layers vertically, with one sensor at the top of the outer ring beam and one at the bottom of the outer ring beam, i.e., the height difference is 5 cm. (If only one pressure sensor is used, it cannot be determined whether the pressure change after the ship compartment enters the water is due to air leakage in the outer ring beam or changes in the downstream water level.) (5) Pressure changes during the descent of the ship compartment into the water can be obtained by monitoring the pressure sensors. The pressure measuring point at the top of the outer ring beam on the upstream side is named P1, the pressure measuring point at the bottom of the outer ring beam on the upstream side is named P2, the pressure measuring point at the top of the outer ring beam on the downstream side is named P3, and the pressure measuring point at the bottom of the outer ring beam on the downstream side is named P4. The pressure change of the measuring points over time after the ship compartment enters the water is P(t). When the ship compartment enters the water horizontally and the outer ring beam does not leak air, the values ​​of the four pressure sensors are equal, that is, P1(t)=P2(t)=P3(t)=P4(t)=constant value (490Pa), and P1(t)-P2(t)=0 and P3(t)-P4(t)=0. If the ship compartment enters the water at an angle (lower upstream and higher downstream), but the outer ring beam does not leak air, then P1(t)=constant value 1>P3(t)=constant value 2>P2(t)=constant value 3>P4(t)=constant value 4. If the ship compartment leaks air, then P1(t), P2(t), P3(t), and P4(t) will not be constant values, or P1(t) - P2(t) = constant value (490Pa) and P3(t) - P4(t) = constant value (490Pa).

[0012] With the above design, the new hull shape automatically traps air during water entry, creating a 5cm air cushion. This air cushion isolates the hull from the water and provides excellent cushioning, significantly reducing suction and impact forces during entry and exit. Pressure monitoring allows for real-time monitoring of the air cushion's status, ensuring the safe operation of the hull.

[0013] The specific technical solution adopted by this invention is as follows: A self-cushioned hull design for reducing the additional hydrodynamic load on a launching ship lift is disclosed. The self-cushioned hull design includes a hull bottom deck, an outer ring beam, an inner ring beam, longitudinal and transverse grid beams, longitudinal and transverse main structural beams under the hull bottom deck, an exhaust port, and a pressure sensor. The hull bottom deck, along with the outer ring beam, inner ring beam, longitudinal and transverse grid beams, longitudinal and transverse main structural beams under the hull bottom deck, and transverse main structural beams under the hull bottom deck, forms an open-bottom cavity. During the hull's descent into the water, an air cushion automatically forms at the bottom of the hull bottom deck. This air cushion isolates the hull bottom deck from the water, significantly reducing the suction and impact forces during the hull's descent.

[0014] In a preferred embodiment, the bottom rise angle of the ship compartment floor is 0°, that is, the bottom floor of the ship compartment is flat.

[0015] In a preferred embodiment, the outer ring beam is located at the boundary of the bottom deck of the ship compartment, the inner ring beam is 10cm away from the outer ring beam, and the grid beam is arranged under the bottom deck of the ship compartment surrounded by the inner ring beam. The grid beam is composed of steel of equal width that are staggered longitudinally and laterally. The grid beams distributed along the longitudinal direction of the ship compartment are called grid beam longitudinal beams, and the grid beams distributed perpendicular to the longitudinal direction of the ship compartment are called grid beam transverse beams. The width of the outer ring beam, inner ring beam, grid beam longitudinal beam, and grid beam transverse beam is 1cm, the beam height is 5cm, the spacing between grid beam longitudinal beams is 3m, and the spacing between grid beam transverse beams is 5m.

[0016] In a preferred embodiment, the top of the vent holes of the main structural longitudinal beams and main structural transverse beams under the bottom deck of the ship compartment are located 5cm above the bottom deck, ensuring that only a 5cm air cushion is generated under the bottom deck during water entry and exit, allowing the remaining gas in the bottom cavity of the ship compartment to be freely discharged. At the same time, to ensure gas communication between the outer and inner ring beams, the main structural longitudinal beams and main structural transverse beams under the bottom deck of the ship compartment have holes in the space enclosed between the outer and inner ring beams, with the top of the holes being the bottom deck of the ship compartment, and the holes being 5cm high and 10cm wide.

[0017] In a preferred embodiment, a total of four pressure sensors are arranged, two on the upstream side and two on the downstream side. The pressure sensors on the upstream and downstream sides are arranged in layers in terms of vertical height, with one sensor on the top of the outer ring beam and one sensor on the bottom of the outer ring beam. The height difference between the top and bottom pressure sensors is 5 cm, and the airtightness of the outer ring beam is determined by the measurement values ​​of the top and bottom pressure sensors.

[0018] In a preferred embodiment, the method for determining the airtightness of the outer ring beam is as follows: The pressure measuring point at the top of the upstream outer ring beam is designated P1, the pressure measuring point at the bottom of the upstream outer ring beam is designated P2, the pressure measuring point at the top of the downstream outer ring beam is designated P3, and the pressure measuring point at the bottom of the downstream outer ring beam is designated P4. The pressure measurement point changes over time after the ship compartment is submerged, and the value is P(t). When the ship compartment is submerged horizontally and the outer ring beam is airtight, the values ​​of the four pressure sensors are equal, i.e., P1(t) = P2(t) = P3(t) = P4(t) = a constant value of 490 Pa. Simultaneously, P1(t) - P2(t) = 0 and P3(t) - P4(t) = 0. If the ship compartment is submerged at an angle with the upstream lower than the downstream, but the outer ring beam is airtight, then P1(t) = constant value 1 > P3(t) = constant value 2 > P2(t) = constant value 3 > P4(t). =Constant value 4. If the ship compartment leaks air, then P1(t), P2(t), P3(t), and P4(t) will not be constant values, or P1(t)-P2(t) = constant value 490Pa and P3(t)-P4(t) = constant value 490Pa.

[0019] The advantages of this invention are: 1) The bottom lining of the ship compartment no longer needs to use wedge-shaped bodies, which reduces the amount of steel used in the ship compartment and reduces the difficulty of ship compartment construction.

[0020] 2) A grid beam is laid at the bottom of the cabin to divide the gas into independent small air cushion blocks, so that large air bubbles will not be generated during the cabin's entry and exit from the water, affecting the cabin's stability.

[0021] 3) The air automatically bound between the ship chamber and the water forms an air cushion, which effectively isolates the direct effect of water on the ship chamber structure. This greatly reduces the suction and impact forces during the ship chamber's entry and exit from the water, and reduces the maximum load on components such as the ship lift's wire rope, synchronous shaft, drum, and hydraulic cylinder, thereby improving the safety of each component and extending its fatigue cycle.

[0022] 4) The process of the ship chamber entering and leaving the water is no longer subject to suction and impact forces, and the speed of entering and leaving the water can be greatly increased, which greatly improves the operating efficiency of the ship lift.

[0023] 5) The suction and impact forces during the entry and exit of the ship chamber no longer increase with the increase of the ship chamber size, which is suitable for the structural design of large-scale launching ship lifts.

[0024] 6) This scheme generates less total buoyancy when entering the water compared to the wedge-shaped scheme with a bottom lift angle of 4°. Attached Figure Description

[0025] Figure 1 Bottom pressure process line during the plate immersion process.

[0026] Figure 2 Bottom pressure process line of the flat plate water outlet process.

[0027] Figure 3 The current engineering project uses the bottom structure diagram of the ship compartment.

[0028] Figure 4 A schematic diagram of the principle of this invention (front view).

[0029] Figure 5 Schematic diagram of the beam grid and sensor arrangement under the bottom deck of the ship compartment (bottom view).

[0030] Figure 6 Schematic diagram of the beam grid and sensor layout under the bottom deck of the ship's compartment (front view) Figure 7 After the air cushion is installed, the pressure process line at the bottom of the ship's compartment is set for water entry.

[0031] Figure 8 After setting the air cushion, the pressure process line at the bottom of the ship's compartment is set above water.

[0032] Figure 9 The structural diagram of the ship compartment of this invention (bottom view).

[0033] Figure 10 Cross-sectional view of the main structural beam under the bottom deck of the ship's compartment (AA).

[0034] Figure 11 Cross-sectional view of the grid beam (BB).

[0035] Figure 12 Cross-sectional view of the main structural longitudinal beam under the bottom deck of the ship's compartment (CC).

[0036] Figure 13 Detailed diagram of the upstream pressure measurement point layout.

[0037] In the diagram: 1-bottom deck of the ship compartment, 2-outer ring beam, 3-inner ring beam, 4-longitudinal beam of the grid beam, 5-transverse beam of the grid beam, 6-longitudinal beam of the main structure under the bottom deck of the ship compartment, 7-transverse beam of the main structure under the bottom deck of the ship compartment, 8-vent hole, 9-pressure sensor. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] Please see Figure 1-13As shown, the present invention provides a self-cushioned boat body shape that reduces the additional hydrodynamic load of a launching ship lift. The self-cushioned boat body shape includes a grid beam, a bottom deck, an exhaust port, a main structural longitudinal beam under the bottom deck, a main structural longitudinal beam, side decks, and a main structural transverse beam. The bottom deck and the bottom grid beam form an open-bottom cavity. During the process of the boat entering the water, an air cushion is automatically formed at the bottom of the bottom deck. The air cushion isolates the bottom deck from the water, greatly reducing the suction force and impact force during the process of the boat exiting the water.

[0040] The bottom of the ship's compartment has a 0° rise angle, meaning the bottom of the ship's compartment is flat. The grid beams are made of steel of equal width that are staggered longitudinally and laterally. The outermost beam of the grid beam is welded to the bottom deck of the ship compartment. In order to reduce the buoyancy caused by the air cushion during the ship compartment's entry into the water, and to avoid the generation of large air bubbles that cause instability in the ship compartment, the preferred beam width is 1cm, the beam height is 5cm, and the beam grid spacing is 5m along the longitudinal direction of the ship compartment and 3m along the transverse direction of the ship compartment. The top of the air holes in the main structural longitudinal beams and main structural transverse beams under the bottom deck of the ship compartment is located 5cm above the bottom deck of the ship compartment, ensuring that only a 5cm air cushion is generated under the bottom deck during the process of entering and leaving the water, and the remaining gas in the cavity at the bottom of the ship compartment can be freely discharged. In this invention, the ship compartment of the Jinghong ship lift is modified into the ship compartment of this invention as an example: The bottom structure of the Jinghong ship lift consists of a wedge-shaped bottom plate, main structural crossbeams, main structural longitudinal beams, and structural spur beams. Large-sized exhaust holes are opened on the main structural crossbeams and main structural longitudinal beams, and small-diameter round holes are opened at the contact points between the top of the structural spur beams and the bottom plate, so that gas can be freely introduced and discharged during the water entry and exit process.

[0041] The steps for modifying the ship chamber of the Jinghong ship lift into the ship chamber of this invention are as follows: 1. Replace the wedge-shaped bottom paving with a flat bottom paving; 2. Under the bottom deck, arrange outer ring beams, inner ring beams, and grid beams with a width of 1cm and a height of 5cm. The outer ring beams are located at the boundary of the bottom deck of the ship compartment. The distance between the inner ring beams and the outer ring beams is 10cm. The longitudinal beam spacing of the grid beams is 3m, and the transverse beam spacing of the grid beams is 5m. 3. Adjust the positions of the vent holes on the main structural longitudinal beams and main structural transverse beams under the bottom deck of the ship compartment. The top of these holes should be 5cm above the bottom deck to ensure that only a 5cm air cushion is generated under the bottom deck during entry and exit from the water, allowing the remaining gas in the bottom cavity of the ship compartment to escape freely. Simultaneously, to ensure gas communication between the outer and inner ring beams, holes are made in the main structural longitudinal beams and main structural transverse beams under the bottom deck of the ship compartment within the space enclosed by the outer and inner ring beams. The top of these holes should be at the bottom deck, with a height of 5cm and a width of 10cm. 4. Four pressure sensors are installed on the outer ring beam under the bottom deck of the ship's compartment. Two sensors are installed on the upstream side and two on the downstream side. The pressure sensors on the upstream and downstream sides are arranged in layers vertically, with one sensor at the top of the outer ring beam and one at the bottom, i.e., the height difference between them is 5 cm. The airtightness of the outer ring beam is determined by the pressure measurements from the top and bottom pressure sensors. 5. The method for determining the airtightness of the outer ring beam is as follows: Name the pressure measuring point at the top of the upstream outer ring beam as P1, the pressure measuring point at the bottom of the upstream outer ring beam as P2, the pressure measuring point at the top of the downstream outer ring beam as P3, and the pressure measuring point at the bottom of the downstream outer ring beam as P4. The pressure measurement point changes over time as the ship enters the water as P(t). When the ship enters the water, if the ship enters horizontally and the outer ring beam is airtight, the values ​​of the four pressure sensors are equal, i.e., P1(t) = P2(t) = P3(t) = P4(t) = constant value (490 Pa), and simultaneously P1(t) - P2(t) = 0 and P3(t) - P4(t) = 0. If the ship enters the water at an angle (upstream lower than downstream), but the outer ring beam is airtight, then P1(t) = constant value 1 > P3(t) = constant value 2 > P2(t) = constant value 3 > P4(t) = constant value 4. If the ship compartment leaks air, then P1(t), P2(t), P3(t), and P4(t) will not be constant values, or P1(t) - P2(t) = constant value (490Pa) and P3(t) - P4(t) = constant value (490Pa).

[0042] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A self-cushioned vessel body design for reducing the additional hydrodynamic load of a launching ship lift, characterized in that: The self-cushioned boat body includes a bottom deck (1), an outer ring beam (2), an inner ring beam (3), a grid beam longitudinal beam (4), a grid beam transverse beam (5), a main structural longitudinal beam (6) under the bottom deck, a main structural transverse beam (7) under the bottom deck, an exhaust port (8), and a pressure sensor (9). The bottom deck (1) and the outer ring beam (2), inner ring beam (3), grid beam longitudinal beam (4), grid beam transverse beam (5), main structural longitudinal beam (6), and main structural transverse beam (7) under the bottom deck form an unsealed cavity. During the process of the boat entering the water, an air cushion is automatically formed at the bottom of the bottom deck (1). The air cushion isolates the bottom deck (1) from the water, greatly reducing the adsorption force and impact force during the process of the boat leaving the water.

2. The self-cushioned vessel body shape for reducing the additional hydrodynamic load of a launching ship lift according to claim 1, characterized in that: The bottom rise angle of the ship compartment floor panel (1) is 0°, that is, the bottom rise angle of the ship compartment floor panel (1) is flat.

3. The self-cushioned vessel body shape for reducing the additional hydrodynamic load of a launching ship lift according to claim 1, characterized in that: The outer ring beam (2) is located at the boundary of the bottom deck of the ship compartment. The inner ring beam (3) is 10cm away from the outer ring beam. The grid beam is arranged under the bottom deck of the ship compartment surrounded by the inner ring beam. The grid beam is composed of steel of equal width that are interlaced longitudinally and laterally. The grid beam distributed along the longitudinal direction of the ship compartment is called the grid beam longitudinal beam (4), and the grid beam distributed perpendicular to the longitudinal direction of the ship compartment is called the grid beam transverse beam (5). The width of the outer ring beam (2), inner ring beam (3), grid beam longitudinal beam (4), and grid beam transverse beam (5) is 1cm, the beam height is 5cm, the spacing of the grid beam longitudinal beam (4) is 3m, and the spacing of the grid beam transverse beam (5) is 5m.

4. The self-cushioned vessel body shape for reducing the additional hydrodynamic load of a launching ship lift according to claim 1, characterized in that: The top of the vent holes (8) of the main structural longitudinal beam (6) and the main structural transverse beam (7) under the bottom deck of the ship compartment are located 5cm above the bottom deck of the ship compartment (1). This ensures that only a 5cm air cushion is generated under the bottom deck during the water entry and exit process, and the remaining gas in the bottom cavity of the ship compartment can be freely discharged. At the same time, in order to satisfy the gas communication between the outer ring beam (2) and the inner ring beam (3), the main structural longitudinal beam (6) and the main structural transverse beam (7) under the bottom deck of the ship compartment are opened in the space enclosed between the outer ring beam and the inner ring beam. The top of the hole is the bottom deck of the ship compartment, and the hole is 5cm high and 10cm wide.

5. The self-cushioned vessel body shape for reducing the additional hydrodynamic load of a launching ship lift according to claim 1, characterized in that: Four pressure sensors (9) are arranged in total, two on the upstream side and two on the downstream side. The pressure sensors (9) on the upstream and downstream sides are arranged in layers in the vertical height, one on the top of the outer ring beam (2) and one on the bottom of the outer ring beam (2). The height difference between the top and bottom pressure sensors is 5cm, and the air tightness of the outer ring beam is determined by the measurement values ​​of the top and bottom pressure sensors.

6. The self-cushioned vessel body shape for reducing the additional hydrodynamic load of a launching ship lift according to claim 5, characterized in that: The method for judging the airtightness of the outer ring beam (2) is as follows: name the pressure measuring point at the top of the outer ring beam on the upstream side as P1, the pressure measuring point at the bottom of the outer ring beam on the upstream side as P2, the pressure measuring point at the top of the outer ring beam on the downstream side as P3, and the pressure measuring point at the bottom of the outer ring beam on the downstream side as P4. The pressure measuring point changes with time after the ship compartment enters the water as P(t); when the ship compartment enters the water, if the ship compartment enters the water horizontally and the outer ring beam does not leak air, the values ​​of the 4 pressure sensors are equal, that is, P1(t)=P2(t)=P3(t)=P4(t)=constant value 490Pa, and at the same time P1(t)-P2(t)=0, P3(t)-P4(t)=0. If the ship compartment enters the water at an angle and the upstream is lower than the downstream, but the outer ring beam does not leak air, then P1(t)=constant value 1>P3(t)=constant value 2>P2(t)=constant value 3>P4(t). =Constant value 4. If the ship compartment leaks air, then P1(t), P2(t), P3(t), and P4(t) will not be constant values, or P1(t)-P2(t) = constant value 490Pa and P3(t)-P4(t) = constant value 490Pa.

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