Wave-current combined simulation system and method in low-pressure environment

Abstract

The invention discloses a wave-current combined simulation system and method in a low-pressure environment, and relates to the technical field of underwater vehicle hydrodynamic model tests. The defects that in the prior art, sealing and strength are difficult to guarantee in a low-air-pressure environment, and accurate flow velocity and shear gradient control of a multi-layer flow channel cannot be achieved are overcome. According to the technical scheme, the device comprises a low-pressure pool, a plurality of layers of layered water inlet galleries, a plurality of layers of layered water outlet galleries, a rectifying wall, a rectifying baffle, a flow guide grid, a wave absorbing bank, an in-cabin rocking plate type wave maker, a plurality of bottom flow making pump flow making systems, an electric butterfly valve, a high-voltage frequency conversion cabinet, a three-phase asynchronous motor, a gear box, an impeller shaft system and the like. All the devices work cooperatively, and accurate coupling simulation of a multi-layer flow field and high sea condition waves under low air pressure is achieved. The device is suitable for wave-current combined hydrodynamic characteristic simulation and test research of deep-sea navigation bodies and ocean engineering equipment in a low-pressure environment.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrodynamic model testing of aircraft, and in particular to a method for joint simulation of waves and flows in multi-layer flow channels under low pressure conditions. Background Art

[0002] In the field of experimental hydrodynamics for vehicles, the navigation process involves the interaction between the effects of gas-liquid two-phase flow coupling and complex wave-current environments. Scaled-scale model testing, a core method for revealing the hydrodynamic characteristics of vehicles and guiding engineering design, is a crucial research tool in this field. Currently, conventional test facilities (such as circulating water tanks and water tunnels) employ a single-layer homogeneous flow channel design in a normal-pressure environment. These can only simulate constant-velocity flow fields and are unable to reproduce the pressure gradients and laminar shear effects of low-pressure environments. This significantly reduces the accuracy of the wave-current coupled load simulation during the variable-speed motion of the vehicle. Furthermore, existing wave-current combined simulation devices commonly suffer from technical bottlenecks such as low flow field uniformity, limited wave-generating capabilities, and poor adaptability to low-pressure environments, making them difficult to simulate and test hydrodynamics of vehicles in low-pressure environments. Therefore, it is urgent to develop test methods that are compatible with low-pressure environments, capable of controlling gradient shear in stratified flow channels, and capable of dynamically coupling wave and current parameters. This can overcome the challenges of existing technologies, which currently suffer from insufficient fidelity in complex sea state simulation and the lack of multi-physics coordinated control.

[0003] Patent CN113418677A discloses a combined wave and current simulation test tank. This tank integrates a wave-generating device, a flow-generating device, and a control system to achieve wave-current coupled simulation. It is equipped with measurement equipment to collect hydrodynamic parameters such as wave height and flow velocity. While this device can conduct conventional hydrodynamic studies, it has significant technical limitations: the tank's atmospheric pressure design results in insufficient compressive strength in its sealing structure, making it unsuitable for deep-sea low-pressure conditions. The flow-generating system can only generate a single-layer uniform flow field, and the flow field stability deteriorates significantly under low-pressure conditions, manifested by excessive velocity fluctuations and lateral uniformity deviations, making it difficult to accurately simulate low-pressure flow fields. Furthermore, the wave-generating device lacks an extreme sea condition simulation module, resulting in large errors in the reproduction of complex wave surface morphologies due to the wave phase transition effects caused by low pressure. Patent CN109580168B proposes a test tank and method for strong wave-current coupling simulation. By optimizing the spatial layout of the wave-generating and flow-generating devices and employing advanced control algorithms, this system achieves dynamic matching of wave and current parameters and strong coupled simulation. Although this technology has improved the accuracy of wave-current interaction simulation under conventional working conditions, it has the following defects: the pool structure has not been designed for low-pressure adaptability, and the airtightness index does not meet the deep-sea experiment specifications; the flow field uniformity decay rate is large in low-pressure environments, and the control parameters are not maintained in a steady state for an insufficient time; the energy conversion efficiency of the wave-making system is low in low-pressure environments, and it cannot effectively simulate the wave characteristics of sea conditions under various circumstances.

[0004] Existing technologies have failed to effectively address issues such as seal compatibility, precise control of flow field parameters, and wave generation efficiency in high sea conditions in low-pressure environments, particularly in the combined scaled-down simulation of uniform flow fields and wave conditions above level 6 in low-pressure environments. Therefore, developing a method suitable for combined simulation of uniform flow fields in multi-layer flow channels and level 6 sea conditions in low-pressure environments is urgently needed to address engineering challenges such as navigation attitude prediction for vehicles and vortex-induced vibrations of deep-sea platforms. This is crucial for enhancing my country's independent research and development capabilities for marine equipment.

[0005] In summary, existing technologies have difficulty ensuring sealing and strength under low air pressure, and cannot achieve precise flow velocity and shear gradient control in multi-layer flow channels. The wave-current coupling accuracy is insufficient, and high sea conditions cannot be simulated, resulting in difficulty in truly restoring the load on the navigation body, which limits the reliability of hydrodynamic experiments. Summary of the Invention

[0006] In order to solve the technical defects in the prior art, which are that it is difficult to ensure sealing and strength under low pressure and it is also difficult to achieve precise flow rate and shear gradient control of multi-layer flow channels, the technical solution provided by the present invention is as follows: A wave and current joint simulation system in a low-pressure environment, comprising: low-pressure pools; The layered water inlet corridor is connected to the low-pressure water pool and is divided into several layers of flow channels in the vertical direction; The layered outlet corridor is connected to the low-pressure water pool and is divided into several layers of flow channels in the vertical direction; Rectification walls are arranged at the connection between the water inlet gallery, the water outlet gallery and the low-pressure water pool; The rectifying baffle is located behind the rectifying wall; The guide grille is arranged behind the rectifying baffle; The wave-breaking bank is located at the end of the low-pressure pool; The shaking plate wave maker is installed in the negative pressure cabin at one end of the low-pressure water tank; The flow-making system is located at the bottom of the low-pressure water pool and includes several flow-making pumps corresponding to several layers of flow channels. Electric butterfly valves are installed at the connection between the outlet of each flow pump and the flow channels of each layer of the water inlet gallery; High-voltage frequency conversion cabinet, electrically connected to the three-phase asynchronous motor of each flow pump; Three-phase asynchronous motors, each connected to a corresponding gearbox; Gearbox, the output end of which is connected to the impeller shaft system; The impeller shaft system is installed at the impeller end of the flow pump.

[0007] Based on the same inventive concept, the present invention also provides a method for joint simulation of waves and currents in a low-pressure environment, which is implemented based on the system described above and includes: Steps to create a low-pressure environment; The steps of starting the flow-generating system to generate a plurality of stratified flow fields; The steps of adjusting the guide grid and the rectifying baffle to correct the uniformity of the stratified flow field; The step of starting the shaking plate wave maker to generate target sea condition waves; The step of correcting the generated waves in real time under the closed-loop control of wave height; Steps for coupling and matching control of stratified flow field and waves; The step of compensating the reflected wave to reduce the reflection interference; Steps for collecting and storing experimental data on flow velocity, wave height, and impact force in a water tank.

[0008] Furthermore, a preferred embodiment is provided, in which the air tightness of the negative pressure cabin is continuously monitored by multiple sealing detection devices, and spare sealant is automatically injected when sealing failure is detected.

[0009] Furthermore, a preferred embodiment is provided, in which a high-voltage frequency conversion cabinet is used to drive a three-phase asynchronous motor, which in turn drives a gearbox and an impeller shaft system, so that the flow pump outputs the stratified flow rate of each layer according to the flow velocity target values ​​of several layers pre-stored in the CFD simulation database.

[0010] Furthermore, a preferred embodiment is provided to ensure that the error of uniformity of the flow velocity at the outlet of each layer of the flow channel does not exceed ±3% when correcting the stratified flow field.

[0011] Furthermore, a preferred embodiment is provided, in which, in the wave height closed-loop control, when the deviation between the actual wave height and the target wave height is greater than 5%, the PID algorithm is called to dynamically adjust the swing angle to complete the wave correction.

[0012] Based on the same inventive concept, the present invention also provides a wave-current combined simulation device in a low-pressure environment, which is implemented based on the above system and includes: Module for establishing low-pressure environment; Start the flow generation system to generate several layers of stratified flow fields; A module for adjusting the guide grid and the rectifying baffle to correct the uniformity of the stratified flow field; A module for activating a shaking plate wave maker to generate target sea condition waves; A module for real-time correction of generated waves under closed-loop control of wave height; A module for coupling and matching control of stratified flow fields and waves; A module that compensates for reflected waves to reduce reflection interference; A module that collects and stores experimental data on flow velocity, wave height, and impact force in a water pool.

[0013] Based on the same inventive concept, the present invention also provides a computer storage medium for storing a computer program. When the computer program is read by a computer, the computer executes the method described above.

[0014] Based on the same inventive concept, the present invention also provides a computer, comprising a processor and a storage medium. When the processor reads the computer program stored in the storage medium, the computer executes the method described above.

[0015] Based on the same inventive concept, the present invention also provides a computer program product, which is a computer program. When the computer program is executed, the method described above is implemented.

[0016] Compared with the prior art, the technical solution provided by the present invention is beneficial in that: This solution utilizes an independent layered flow channel structure, with each layer equipped with an independent high-voltage variable frequency drive system, a three-blade spiral impeller, a gradient aperture rectifier grid, and an angle-adjustable guide plate, achieving multi-stage flow velocity regulation and precise control of the flow field shear gradient. This approach effectively improves the lateral uniformity of the flow field, controlling the outlet flow velocity uniformity error to within ±3%, and stably maintaining the vertical flow shear gradient below 0.3 (m / s) / m, significantly improving existing single-layer uniform flow channel designs that suffer from large flow velocity fluctuations and shear discontinuities.

[0017] Through a unique sealing structure design and custom composite seals, combined with multiple seal detection and emergency glue injection mechanisms, the entire system ensures airtightness and structural stability in low-pressure environments. Unlike existing sealing structures that are unable to adapt to low-pressure environments and are prone to leakage and structural damage, this design achieves long-term stable operation under significantly reduced pressure conditions, providing reliable support for fluid experiments in low-pressure environments.

[0018] This system utilizes a dual-pivot suspended rocker structure and an energy loss correction model for low-pressure environments. Through external servo motor drive, real-time feedback force control, and a wave height correction formula, precise adjustment and closed-loop compensation of wave height and period are achieved. Compared to traditional atmospheric pressure wave-making systems, which suffer from reduced energy transfer efficiency and difficulty controlling wave height due to thin air, this approach significantly improves wave-making energy conversion efficiency and output stability, achieving effective wave height control accuracy better than ±5%, and supporting the generation of complex waveforms.

[0019] By constructing a wave-current coupling control module, combining the Navier-Stokes modified equations, a wave height correction model, and the flow field velocity coupling relationship, and using a control program to dynamically match the wave spectrum with the flow field velocity, this method achieves precise coupling of waves and flow fields in low-pressure environments. Compared to existing technologies that face difficulties in wave-current phase matching and large simulation errors due to large phase differences, this method controls the wave-current phase difference to within 5°, ensuring the accuracy of the coupled simulation.

[0020] The system utilizes a sloped wave-breaking bank design combined with absorbing materials, and incorporates periodic reflection wave detection and reverse compensation control mechanisms. This system actively attenuates reflected wave energy and enables real-time correction of wave height. This approach effectively reduces reflected wave interference, achieving a wave height attenuation rate of less than 10%, significantly improving upon the slow response and insufficient attenuation of traditional wave-breaking devices for complex wave systems.

[0021] The control system utilizes a multi-parameter collaborative strategy and a standardized interface closed-loop control structure. The host computer dynamically accesses a CFD database via the Modbus protocol to optimize the deflector angle and servo motor motion curve. Compared to existing devices with low control precision and weak coordination between subsystems, this approach significantly improves the overall system response speed and control accuracy. The system stability and experimental repeatability both meet high-standard testing requirements.

[0022] In summary, this technical solution is significantly superior to existing technologies in terms of flow field control accuracy, sealing assurance, wave generation capability, wave-flow coupling control, reflected wave processing and overall system coordination, and can effectively support high-precision, high-fidelity hydrodynamic scale model experiments in low-pressure environments.

[0023] The present invention is applicable to the simulation and experimental research of wave-current combined hydrodynamic characteristics of deep-sea navigation bodies and marine engineering equipment in a low-pressure environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the longitudinal section of the inlet and outlet corridor of the wave and current simulation system; Figure 2 This is a top view of the wave and current simulation system; Figure 3 Diagram of the flow pump for the wave and current simulation system; Figure 4 Schematic diagram of the rectification wall; Figure 5 Schematic diagram of the rectifier baffle; Figure 6 Schematic diagram of the diversion grille.

[0025] Among them, 1. Water inlet gallery; 2. Water outlet gallery; 3. Rectification wall; 4. Rectification baffle; 5. Guide grille; 6. Wave-breaking bank; 7. Rocking plate wave maker; 8. Flow-making system; 9. Electric butterfly valve; 10. High-voltage frequency conversion cabinet; 11. Three-phase asynchronous motor; 12. Gearbox; 13. Impeller shaft system. DETAILED DESCRIPTION

[0026] In order to make the advantages and benefits of the technical solution provided by the present invention more clearly reflected, the technical solution provided by the present invention is now further described in detail with reference to the accompanying drawings, specifically: Embodiment 1: This embodiment provides a wave-current joint simulation system in a low-pressure environment, including: low-pressure pools; The layered water inlet gallery is connected to the low-pressure water pool and is divided into three layers of flow channels in the vertical direction; The layered outlet gallery is connected to the low-pressure water pool and is divided into three layers of flow channels in the vertical direction; Rectification walls are arranged at the connection between the water inlet gallery, the water outlet gallery and the low-pressure water pool; The rectifying baffle is located behind the rectifying wall; The guide grille is arranged behind the rectifying baffle; The wave-breaking bank is located at the end of the low-pressure pool; The shaking plate wave maker is installed in the negative pressure cabin at one end of the low-pressure water tank; The flow-making system is located at the bottom of the low-pressure pool and includes three flow-making pumps; Electric butterfly valves are installed at the connection between the outlet of each flow pump and the flow channels of each layer of the water inlet gallery; High-voltage frequency conversion cabinet, electrically connected to the three-phase asynchronous motor of each flow pump; Three-phase asynchronous motors, each connected to a corresponding gearbox; Gearbox, the output end of which is connected to the impeller shaft system; The impeller shaft system is installed at the impeller end of the flow pump.

[0027] Based on the same inventive concept, the present invention also provides a method for joint simulation of waves and currents in a low-pressure environment, which is implemented based on the system described above and includes: Steps to create a low-pressure environment; Steps for starting the flow-generating system to generate a three-layered flow field; The steps of adjusting the guide grid and the rectifying baffle to correct the uniformity of the stratified flow field; The step of starting the shaking plate wave maker to generate target sea condition waves; The step of correcting the generated waves in real time under the closed-loop control of wave height; Steps for coupling and matching control of stratified flow field and waves; The step of compensating the reflected wave to reduce the reflection interference; Steps for collecting and storing experimental data on flow velocity, wave height, and impact force in a water tank.

[0028] The air tightness of the negative pressure cabin is continuously monitored through multiple sealing detection devices, and backup sealant is automatically injected when seal failure is detected.

[0029] A high-voltage frequency conversion cabinet is used to drive a three-phase asynchronous motor, which in turn drives the gearbox and impeller shaft system, so that the flow pump outputs the stratified flow rate of each layer according to the three-layer flow velocity target values ​​pre-stored in the CFD simulation database.

[0030] When correcting the stratified flow field, ensure that the uniformity error of the flow velocity at the outlet of each layer does not exceed ±3%.

[0031] In the wave height closed-loop control, when the deviation between the actual wave height and the target wave height is greater than 5%, the PID algorithm is called to dynamically adjust the swing angle to complete the wave correction.

[0032] Implementation Method 2: This implementation method further describes the technical solution provided in Implementation Method 1 in detail. Specifically: A high-precision test system for combined wave and current simulation in low-pressure environments is suitable for studying the hydrodynamic performance of navigable objects or marine structures in deep-sea conditions. Through layered flow generation, sealed structural design, precise wave generation, and wave-current coupling control, the system achieves realistic simulation of complex sea conditions in low-pressure environments. Its implementation process includes the following steps: Step 1: Build a sealed low-pressure water pool system and establish a basic water flow structure First, a closed, low-pressure water tank for wave and current simulation was constructed. Its outer walls were constructed from high-strength steel and fitted with a transparent, pressure-resistant observation window. Once the tank structure was complete, a flow channel system for water inlet and outlet was installed. This system includes an inlet and outlet gallery, each vertically divided into three independent levels. Pressure-through holes were installed at the inlet and outlet of each level to guide fluid into and out of the corresponding channel.

[0033] To ensure sealing stability in low-pressure environments, composite gaskets are installed at corridor connections, flange joints, and pipeline nodes. These gaskets, composed of a polytetrafluoroethylene and rubber composite, are combined with nitrile rubber sealing rings and specialized sealant to effectively prevent air infiltration in low-pressure environments, ensuring that the system meets airtightness standards. Once the seal is established, the system establishes a low-pressure environment using a vacuum pump assembly and maintains stable pressure using a pressure monitoring device.

[0034] Step 2: Establish a three-layer stratified flow field system and control the flow rate After the low-pressure environment in the pool is established, three flow pumps corresponding to the three levels are activated. Each flow pump has its drive frequency controlled by an independent high-voltage frequency converter cabinet. A three-phase asynchronous motor, gearbox, and self-lubricating bearing drive the three-blade spiral impeller, causing water to flow from the flow pump through the water inlet gallery into the corresponding flow channel level.

[0035] Water enters the main body of the pool through rectifying facilities such as rectifying walls, rectifying baffles, and guide grilles. Each flow channel's inner wall is equipped with a gradient aperture rectifying grid, and angle-adjustable guide plates are placed at the guide grilles. The system pre-establishes a database of matching guide plate angles with flow velocities. Using CFD simulation data, the system adjusts the guide plate angle (adjustable from 15° to 75°) to achieve a single-layer outlet flow velocity uniformity error of less than ±3%, while also maintaining a stable shear gradient of flow velocity between adjacent layers within 0.3 meters per second per meter.

[0036] Step 3: Start the wave-making system to generate complex wave conditions and implement feedback correction After the flow field is established and stabilized, the system activates the rocking plate wave generator. This device utilizes a dual-pivot suspension structure. The wave generator is covered with a flexible rubber pad to mitigate impact loads. The servo motor is located outside the cabin to prevent low air pressure from affecting its stability. Based on the input target wave spectrum parameters (such as wave height and period), the wave generator control system generates a sinusoidal or irregular wave drive signal, which drives the wave generator to generate waves.

[0037] During the wave-making process, high-frequency force sensors at the joints monitor the force on the wave-making plate in real time. The system dynamically adjusts the servo motor drive parameters using the principle of force balance. If the actual wave height deviates by more than 5% from the target, the control system generates a compensation signal based on a PID algorithm. This signal adjusts the servo motor's swing angle to correct the wave height in real time, maintaining the stability and accuracy of the wave output.

[0038] Step 4: Realize wave-current coupling and perform dynamic matching control Once waves are generated and stabilized, the system activates the wave-current coupling control module. Based on linear wave theory, the modified Navier-Stokes equations, and a coupling model, this module analyzes the interaction between flow velocity and wave height in real time. Using the Modbus protocol, the system adjusts the deflector angle and servo motor motion parameters to achieve dynamic matching of the flow field and wave parameters.

[0039] The system monitors wave propagation characteristics and air pressure changes in real time and, in conjunction with experimental fitting models, corrects wave height to ensure that wave height propagation errors do not exceed ±5% in low-pressure environments. By regulating the servo motor's input energy, energy loss due to air resistance is reduced, improving energy efficiency. Ultimately, encoder feedback and phase analysis mechanisms stabilize the wave-current phase difference within 5°, ensuring simulation accuracy.

[0040] Step 5: Implement reflection wave elimination and compensation mechanism To prevent interference from wave reflections, a sloped bank is installed at the end of the pool, and high-efficiency wave-absorbing materials are adhered to its surface, attenuating the reflected wave energy through a multi-stage dissipation method. When the system detects periodic interference characteristics in the wave echo signal through the force sensor, it immediately calculates the phase information of the reflected wave and generates a compensation waveform with an opposite phase, which is superimposed on the wave-making board control command. This effectively suppresses the wavefront disturbance caused by the reflected wave and keeps the effective wave height attenuation rate within 10%.

[0041] Step 6: Complete data acquisition and system closed-loop control Throughout the combined wave and current simulation process, the system continuously collects PIV velocity data, wave height data from a wave gauge, and wave-making force sensor data from each layer, storing them at high speed via a host computer. If any parameter exceeds a set threshold, the system automatically activates a coordinated correction mechanism, synchronously fine-tuning the deflector angle and servo motor motion curve until the simulation parameters return to the target range.

[0042] All subsystems are connected to the host computer via standardized data interfaces, forming a complete closed-loop control network. The control system dynamically adjusts test parameters based on a pre-stored database and real-time feedback, ensuring high-precision wave-current coupling simulations at varying low-pressure depths and in varying sea conditions.

[0043] In terms of experimental systems: Figure 1 Description of the longitudinal section view This figure is a side longitudinal section of the system, with the water tank in the middle and the layered corridors and auxiliary devices for water inlet and outlet on both sides. The main structure and numbering are as follows: The pool is located in the center of the picture and is used for wave and current combined simulation experiments. The surrounding walls of the pool are made of high-strength steel.

[0044] The water inlet gallery 1 is located on the right side of the pool and has a layered structure. Water flows from the flow generation system 8 through the pipeline into the water inlet gallery 1, and is divided into three layers of vertical flow channels, which are sequentially introduced into the pool.

[0045] The outlet corridor 2 is located on the left side of the pool and is also a three-layered design. It is used to divert the water flow formed by the flow field in the pool and transport it to the flow generation system for recycling.

[0046] The straightening walls 3 are installed on the walls between the inlet and outlet corridors 1 and 2 and the pool, arranged in sections along the vertical direction. Their function is to eliminate instantaneous vortices caused by water impact, ensuring a smooth flow of water entering or leaving the pool.

[0047] The rectifying baffles 4 are arranged behind the rectifying wall 3 and are directly connected to the water pool. The angle of each layer of rectifying baffles 4 can be adjusted to further reduce water flow pulsation and optimize flow velocity distribution.

[0048] The guide grid 5 is located behind the rectifying baffle 4. The grid-like structure is arranged along the width direction and is used to evenly distribute the water flowing through the rectifying baffle 4 to each flow pipe outlet to ensure uniform lateral flow velocity in the three-layer flow channel.

[0049] The wave-breaking bank 6 is set on both sides of the top of the pool and connected to the pool surface. The wave-breaking bank 6 adopts a sloped structure and is paved with wave-absorbing materials on the surface to reduce the energy of reflected waves and reduce the interference of wave reflections on the system.

[0050] The rocking plate wave maker 7 is located in the upper right corner of the pool, mounted on top of the negative pressure cabin just before the water inlet corridor 1 enters the pool. Its wave maker, a dual-pivot suspension structure driven by an off-cabin servo motor, swings up and down to generate sinusoidal or irregular waves.

[0051] Figure 2 Floor plan diagram This figure is a top view of the system, showing the spatial layout of the pool surface and the bottom flow-generating room. The main components and their numbers are as follows: The inlet corridor 1 is located on the right side of the figure, connecting the flow room and the pool. It is divided into three flow pipes that extend horizontally to the pool. Each flow pipe is connected to the internal flow field of the pool through a guide grid 5 on the side close to the pool.

[0052] The outlet gallery 2 is located on the left side of the figure, symmetrically distributed with the inlet gallery 1. It is also divided into three flow pipes corresponding to the pool, which are used to transport the flow field water from the pool back to the flow generation system.

[0053] The flow-generating system 8 is located in the flow-generating room area at the bottom of the figure and consists of two independent flow-generating pump devices. Each flow-generating system 8 includes a pump body, an impeller shaft system 13, a gearbox 12, a three-phase asynchronous motor 11, and corresponding pipes and support frames.

[0054] The electric butterfly valve 9 is installed on the connection section between the outlet pipe of each set of flow pump and the water inlet gallery 1. Each flow pipe corresponds to an electric butterfly valve 9, which is used to adjust the flow rate of each layer to cooperate with the angle adjustment of the guide grid 5 to achieve fine control of the flow rate of the three layers.

[0055] The outlet corridor 2 is connected to the water intake of the flow generation system 8 below by three branch pipes for recycling the fluid in the pool.

[0056] In the plan view, several auxiliary channels and support frames can be seen in the flow-generating room, but this embodiment focuses on the flow-generating and regulating devices related to wave and flow simulation.

[0057] Figure 3 Detailed description of the motor and impeller shaft system This figure is a cross-sectional view of the power transmission section of a single flow-generating system, showing the power transmission process from the control cabinet to the impeller shaft system. The main components and their numbers are as follows: The high-voltage frequency conversion cabinet 10 is located at the leftmost side of the figure, and provides variable frequency power supply for each three-phase asynchronous motor 11 in the flow creating system 8. The high-voltage frequency conversion cabinet 10 can accurately adjust the rotating speed of the motor 11 to realize accurate control of the flow output of the impeller shaft system 13.

[0058] The three-phase asynchronous motor 11 is connected with the high-voltage frequency conversion cabinet 10 and is fixedly installed on a ground base support. The output shaft of the three-phase asynchronous motor 11 is connected with the gear box 12 through a universal coupling.

[0059] The gear box 12 is adjacent to the three-phase asynchronous motor 11 and contains a reduction gear set, which converts the high-speed low-torque output of the motor 11 into a low-speed high-torque output to meet the torque requirement of the impeller shaft system 13 in the low-pressure pool for pushing water flow.

[0060] The impeller shaft system 13 is directly connected to the output end of the gear box 12, and the shaft system 13 is provided with an impeller body and a multi-stage blade structure. The impeller shaft system 13 extends into the flow creating pipeline and is responsible for converting mechanical kinetic energy into fluid kinetic energy to form a required laminar flow field. The multi-stage blade layout of the impeller shaft system 13 cooperates with the flow guide grid 5, the flow straightening baffle 4, the flow straightening wall 3 and other flow straightening devices to realize uniform outlet flow speed and maintain a predetermined flow shear gradient.

[0061] In the third embodiment, the above-mentioned technical solutions are further described in detail through specific examples. The water pool is divided into three layers in the vertical direction at the water inlet and outlet ends, and each layer is one-to-one corresponding to the water inlet and outlet. One flow creating pump is arranged in each layer to form a layered flow field system. The flow creating facility corridor is optimized and designed, and is particularly suitable for a wave and flow field combined simulation system in a low-pressure environment. The water outlet of the flow creating pump enters the water pool through the water inlet corridor, the pressure through-wall hole, the flow straightening baffle, the flow guide grid and other flow straightening measures. The water outlet of the water pool enters the suction pipe of the flow creating pump through the pressure through-wall hole and the water outlet corridor and other flow straightening measures.

[0062] A high-voltage frequency conversion driving unit is arranged at the water inlet end of each flow channel. The unit integrates a variable frequency motor, a gear reduction box and a self-lubricating bearing set, drives a three-blade spiral impeller to rotate through a rigid coupling, and realizes multi-stage flow speed regulation and control. The inner wall of the flow channel is provided with a pore diameter gradually changing flow straightening grid and an angle adjustable flow guide plate. Based on the flow guide plate angle-flow speed matching database established based on CFD pre-simulation, the opening of the flow guide plate is dynamically adjusted, so that the uniformity error of the outlet flow speed of the single layer flow channel is ≤5%, and the vertical flow shear gradient between adjacent flow layers is stably controlled at ≤0.3 (m / s) / m.

[0063] Special sealing materials and a sealing structure design are used to ensure structural sealing. The annular piping system utilizes a flange connection structure, with specially customized sealing gaskets used at the joints. These gaskets are a composite of polytetrafluoroethylene and rubber, offering excellent flexibility and sealing properties, effectively filling the tiny gaps in the joints. Nitrile rubber sealing rings are used at the sealing points, and a layer of specialized sealant is applied to the surface of the rings to further enhance the sealing effect and ensure airtightness meets standards in low-pressure environments. Regarding material selection, the various materials selected, such as the high-strength steel that constitutes the corridor and the casing material of the flow pump, all have excellent pressure resistance, capable of maintaining structural integrity and stability in low-pressure environments and resisting the effects of pressure changes caused by low pressure on the structure. In low-pressure environments, fluid dynamics properties change, such as changes in fluid viscosity and density. This design fully considers these characteristics, and through extensive preliminary experiments and theoretical analysis, a model of fluid dynamics properties in low-pressure environments was established. Based on this model, the size, shape and rectification measures of each layer of flow channels were optimized to ensure that the flow of fluid in the flow channels meets the simulation requirements, thereby ensuring the accuracy and stability of the simulation system.

[0064] In low-pressure environments, air density decreases, impacting the energy transfer and conversion of the wave-generating system. The wave-generating system utilizes a dual-pivot suspended rocker plate structure, with the plate surface covered with a flexible rubber pad to reduce impact noise. The servo motor drive mechanism is located outside the negative pressure chamber. The control program generates sinusoidal / irregular wave drive signals based on wave spectrum parameters, enabling independent adjustment of wave height and period.

[0065] To ensure the stability and accuracy of the wave-making system, we first analyze it from the energy perspective. According to fluid mechanics theory, the energy conversion relationship in the wave-making process can be expressed as: (1) in: Input energy to the servo motor, To generate wave energy, It is the energy loss caused by friction, air resistance, etc. In low pressure environment, air resistance , can be calculated according to the empirical formula: (2) in: is the air density, V is the speed of the wave-making plate, is the drag coefficient, and A is the frontal area of ​​the wave-making plate. Due to the decrease in low pressure, the air resistance is relatively reduced, which changes the proportion of energy loss. This requires corresponding adjustments in the control algorithm.

[0066] In terms of stability, high-frequency force sensors are installed at the hinges of the wave-making board to collect wave impact forces in real time and feed them back to the controller. In a low-pressure environment, the interaction force between the wave and the wave-making board will also change due to changes in air density. By monitoring the wave impact force in real time, the force balance equation is used: (3) in: is the resultant force acting on the wave-making plate, m is the mass of the wave-making plate, and a is the acceleration of the wave-making plate. The motion state of the wave-making plate is precisely controlled to ensure the stable operation of the wave-making system.

[0067] In terms of accuracy, when a deviation in wave parameters is detected, the controller generates a compensation signal through the PID algorithm, dynamically adjusting the servo motor's swing angle to form a closed-loop correction circuit. Taking into account the changes in wave propagation characteristics in low-pressure environments, a correction formula based on experimental data fitting is introduced: (4) in: is the wave height correction, is the change in air pressure, and k is the correction coefficient.

[0068] In low-pressure environments, the interaction between waves and flow is more complex. According to the basic theory of fluid dynamics, the Navier-Stokes equations need to be modified to account for the effects of low pressure. For incompressible fluids, the modified equations can be expressed as: (5) in, is the fluid density, is the velocity vector, t is the time, p is the pressure, is the dynamic viscosity, is the external body force, is the additional force caused by low air pressure.

[0069] For the coupling of wave and flow field, based on linear wave theory and flow field continuity equation, a correction coefficient is introduced and To consider the impact of low pressure environment. The coupling relationship between wave height H and flow field velocity U can be expressed as: (6) in, It is the difference between low air pressure and standard atmospheric pressure.

[0070] Based on the above-mentioned theory and correction formula of wave and flow field simulation in low pressure environment, the control program is optimized. In the control program of the wave-making system, the energy analysis formula (1) and the air resistance formula (2) are combined and the air density is monitored in real time. Dynamically adjust the servo motor input energy The set value. When the air density decreases due to low air pressure, the energy consumed due to the reduction of air resistance is reduced accordingly, so that the wave-making energy is more accurately converted into wave energy, thereby ensuring the energy utilization efficiency and accuracy of the wave-making system. Using the force balance equation (3) and the relationship between the interaction force between the wave and the wave-making board and the change of air density, the calculation model of the motion state of the wave-making board is updated in real time in the control program. When the high-frequency force sensor at the hinge of the wave-making board collects the change of wave impact force, the control program accurately calculates the acceleration and motion state adjustment of the wave-making board based on the force balance equation, and then more accurately controls the drive of the servo motor to maintain the stability of the wave-making system. According to the wave height correction formula (4), a wave height real-time correction module is established in the control program. When the pressure change is detected When the control program automatically calculates the wave height correction value according to the correction coefficient k The wave height is adjusted in real time to ensure that the wave height output by the wave-making system accurately meets the simulation requirements. For the coupled simulation of waves and flow fields, the wave-flow coupling module of the control system combines the modified Navier-Stokes equation (5) and the wave-flow field coupling relationship formula (6) to calculate the interaction between waves and flow fields in a low-pressure environment in real time. Based on these equations and formulas, the control program dynamically adjusts the matching relationship between the wave-making plate motion curve and the flow field parameters. Through encoder feedback, the wave-flow phase difference is more accurately controlled to within 5°, further improving the accuracy and stability of the system's wave and flow field simulation under low pressure.

[0071] The wave-canceling system, constructed from a combination of sloped wave-canceling plates and absorbing materials, attenuates reflected wave energy by over 80% through multi-stage dissipation. When the sensor detects reflected wave interference, the system generates a reverse compensation signal based on phase difference analysis and superimposes it on the wave-generating plate's trajectory, ensuring a target wave height error of less than 5%.

[0072] The control system employs a multi-parameter coordination strategy. The host computer controls the frequency of the inverter cabinet via the Modbus protocol and simultaneously accesses the CFD database to optimize the deflector angle. The wave-current coupling module matches the shaking plate motion curve with the flow field parameters in real time, using encoder feedback to control the wave-current phase difference to within 5°. If significant repeatability errors in wave height are detected, the system automatically adjusts the wave-making plate angle and deflector inclination until the parameters stabilize. Each subsystem interacts with data via standardized interfaces, forming a closed-loop control network that ultimately achieves high-precision simulation in low-pressure environments.

[0073] 3. Safety and stability assessment: The facility underwent comprehensive stability testing in a low-pressure environment. First, a static stability test continuously monitored the stress and deformation of various parts of the facility in a simulated low-pressure environment to ensure that the structure would not experience excessive deformation or damage due to the low pressure. Simultaneously, a dynamic stability test was conducted to simulate the combined effects of waves and flow fields under different operating conditions and observe the facility's response to complex external forces.

[0074] In terms of risk assessment, possible risks are identified, such as air leakage caused by seal failure and structural damage caused by excessive low air pressure. To address the risk of seal failure, multiple seal detection devices are set up to monitor the changes in air pressure in the sealing parts in real time. Once an abnormality is detected, an alarm is immediately issued and emergency sealing measures are initiated, such as automatically injecting spare sealant. To address the risk of low air pressure, a pressure upper limit protection device is set in the system. When it is detected that the negative pressure exceeds the safety threshold, the system operating parameters are automatically adjusted to reduce the low air pressure to a safe range. Through these stability tests, risk assessments and response measures, the safe and stable operation of the facility in a low-pressure environment is ensured, and ultimately high-precision simulation is achieved in a low-pressure environment to meet the needs of scaled-down testing of deep-sea equipment.

[0075] The benefits of this solution are: The system utilizes a multi-layered drive structure with independent flow channels. The speed of the three-blade helical impeller is controlled by a high-voltage variable frequency speed regulation mechanism. Combined with the synergistic effect of a gradually varying aperture straightening grid and angle-adjustable guide vanes, the system achieves continuously adjustable flow velocity and stable control of the flow shear gradient. The lateral flow velocity uniformity error is ≤±3%, meeting the millimeter-level precision required for reproducing wave-current coupled loads under variable speed conditions. An innovative dynamic linkage mechanism is designed between the wave-making system and the flow channel. Dynamic compensation of the wave-making plate swing angle is achieved based on a PID closed-loop control algorithm. The effective wave height simulation range is extended to 4-6 meters (corresponding to sea state 6), the wave height attenuation rate is reduced to <10%, and the period control accuracy reaches ±5%. The system supports the generation of complex wave systems such as irregular waves and multi-directional waves, with a spectral repeatability error of ≤5%. Through the synergistic effect of stratified flow field homogenization control and wave-breaking devices, the system accurately captures the wave-current coupled loads during the vehicle's entry and exit phases, providing high-confidence experimental data for vehicle trajectory prediction, intelligent control algorithm optimization, and structural strength design. This effectively addresses the technical bottlenecks of traditional simulation devices, such as large flow velocity fluctuations and high wave height attenuation rates.

[0076] The technical solution of the present invention can be widely used in scaled model tests of marine engineering equipment such as underwater vehicles and deep-sea exploration equipment. It is particularly suitable for the study of fluid dynamic characteristics under large-depth and variable working conditions. It has significant engineering value in improving the efficiency of marine equipment research and development and reducing the cost of actual sea tests, and provides a high-precision experimental platform support for deep-sea equipment performance verification.

[0077] In a specific embodiment: A combined wave and current simulation experimental method for deep-sea environments, based on a low-pressure water tank, achieves high-precision reproduction of the motion of a vehicle. The method includes: 1. Inlet gallery; 2. Outlet gallery; 3. Rectification wall; 4. Rectification baffle; 5. Diversion grid; 6. Wave-breaking bank; 7. Rocking plate wave generator; 8. Current generation system; 9. Electric butterfly valve; 10. High-voltage frequency conversion cabinet; 11. Three-phase asynchronous motor; 12. Gearbox; 13. Impeller shaft system. The specific implementation steps of this simulation experimental method are as follows: When implemented in a closed, low-pressure water tank, the flow generation system 8 is first activated. The output frequency of the three-phase asynchronous motor 11 (adjustable from 0 to 50 Hz) is controlled by a high-voltage frequency converter 10, driving a gearbox 12 that transmits the rotational speed to the impeller shaft 13. The impeller, supported by self-lubricating bearings, rotates within the flow generation pipeline. Water enters the pool sequentially through the inlet gallery 1, the flow straightening wall 3, the flow straightening baffle 4, and the guide grille 5, forming three independent, vertically stratified flow fields. Based on a CFD pre-simulation database, the guide plates in each layer of the guide grille are adjusted to the optimal angle of 15° to 75°. Flow velocity sensor data is simultaneously monitored. If the flow velocity in a particular layer deviates by ±3% from the set value, frequency compensation is performed by the frequency converter to stabilize the flow shear gradient within 0.3 m / s / m. Flow fields with varying gradients can also be created by opening and closing the electric butterfly valve 9. Once the flow field is established, the low pressure environment within the pool is maintained, and airtightness is ensured by the nitrile rubber seals in the annular piping system.

[0078] After the flow field stabilizes, the control software activates the rocking plate wave maker 7. Target wave spectrum parameters are input, and a servo motor drives the dual-pivot rocking plate at a preset swing angle (adjustable within ±30°) to generate initial waves. High-frequency force sensors at the wave maker's hinges collect wave impact forces in real time. When the actual wave height deviates by more than 5% from the theoretical value, the control software generates a compensation signal based on a PID algorithm and dynamically adjusts the servo motor's rotation angle. To address the interference of reflected waves at the end of the pool, the wave-breaking bank attenuates the reflected wave energy through wave climbing and breaking, as well as frictional energy dissipation. When the force sensor detects periodic fluctuations, the system automatically calculates the phase difference of the reflected wave and generates a reverse compensation waveform that is superimposed on the wave maker's motion trajectory, maintaining an effective wave height attenuation rate of ≤10%.

[0079] During the combined wave and flow simulation, based on the system's comprehensive technical design and theoretical foundation, the host computer accesses a pre-stored operating condition database optimized by incorporating relevant theories and correction formulas for wave and flow field simulation in low-pressure environments. Based on this database, the flow velocity parameters of each layer of the flow system (each layer has a flow pump, forming a stratified flow field system) are dynamically matched with the wave spectrum parameters of the wave control host computer. Specifically, the output frequency of the frequency converter cabinet and the speed of the servo motor are synchronously adjusted via the Modbus protocol based on the changes in fluid dynamics in low-pressure environments, as well as theories related to wave generation energy analysis, stability, and accuracy assurance.

[0080] During the adjustment process, the influence of low pressure on the energy transfer of the wave-making system, the interaction between waves and wave-making plates, and the wave height propagation characteristics are fully considered. For example, according to the energy conversion relationship (1) and the air resistance formula (2), the energy input is dynamically adjusted; the wave-making plate motion state is updated in real time using the force balance equation (3); and the wave height is corrected in real time according to the wave height correction formula (4), thereby ensuring that the wave-current phase difference is accurately controlled within ≤5°. The system collects flow field PIV data and wave height meter signals in real time. In a low-pressure environment, due to changes in fluid dynamics, these data are collected and analyzed based on the modified Navier-Stokes equation (5) and the wave-flow field coupling relationship formula (6). If the flow velocity fluctuation is detected to be too large, the linkage correction mechanism is immediately activated - the guide plate angle and the wave plate swing angle are fine-tuned synchronously. Among them, the adjustment of the guide plate angle is based on the guide plate angle-flow velocity matching database established by CFD pre-simulation, and the adjustment of the wave plate swing angle is combined with the stability and accuracy control theory of the wave-making system in a low-pressure environment until the parameters return to the set threshold. After the experiment, the wave-current coupled load curve was obtained by analyzing the pressure sensor data on the vehicle's surface. Thanks to the system's high-precision control of wave and current simulation in a low-pressure environment, the curve has a low relative error with the theoretical value, providing effective data support for the vehicle's trajectory prediction. During this process, all parts of the system worked closely together, fully utilizing the corrected formulas and theories for simulating wave and flow fields in low-pressure environments, ensuring the accuracy and reliability of the simulation results.

[0081] Wave-current combined simulation experiment case - underwater motion test of a vehicle. 1. Experimental Implementation: Six three-phase asynchronous motors drive the flow pumps through a reduction gearbox. The initial frequency is set to 25 Hz, corresponding to an impeller speed of 180 rpm. Based on a database, the angles of the guide vanes at each layer are adjusted: 75° at the bottom layer, 45° at the middle layer, and 15° at the top layer, to achieve vertical flow gradient stratification. The annular piping system is activated, and polyurethane coating is applied to the flow surfaces to reduce flow resistance. Nitrile rubber seals ensure airtightness. Flow field velocity is monitored in real time using an ultrasonic flowmeter. If flow velocity deviation is excessive, the frequency converter drive frequency is adjusted accordingly, and the guide vane angle is fine-tuned simultaneously. Within 5 minutes, the flow velocity is stabilized to 0.35 ± 0.01 m / s, and the shear gradient is controlled to 0.25 ± 0.02 m / s / m. Regular wave generation: Target parameters are input: wave height 0.85 m and period 5 s. A servo motor drives the dual-pivot rocker, with the initial motion curve being a 5Hz sinusoidal signal. A high-frequency force sensor at the hinge detects an actual wave height of 0.82m (with a deviation of -3.5%). A PID controller generates a compensation signal, increasing the rocking angle to ±20°. Within three cycles, the wave height is corrected to 0.85±0.02m. The terminal wave-breaking bank provides initial attenuation of reflected wave energy. When the force sensor detects periodic fluctuations, the system generates an inverse compensation waveform and superimposes it on the wave-making plate's trajectory, reducing the effective wave height attenuation rate.

[0082] Verification of Results: A flow field measurement system demonstrated a uniformity error of ≤4.2% at the outlet of the three-layer flow channel. The vertical shear gradient between adjacent channels remained stable at 0.23-0.26 m / s / m, meeting the scaled-down design requirement of 0.25 m / s / m. The flow field construction took ≤30 minutes, and the velocity deviation between repeated experiments was <2.5%, verifying the stability and repeatability of the stratified flow channel system.

[0083] The wave generator generates regular waves with a period control accuracy of ±3.5%, a wave height repeatability error of less than 6.8%, and a reflected wave height attenuation rate of >82%, meeting the scaled-down simulation requirements of the prototype 5m wave height. Measurements from the wave height meter array show a peak phase difference of less than 4° and a wavefront root mean square error of less than 0.03m, achieving high-precision reproduction under complex wave conditions.

[0084] During the combined wave and current simulation, the phase difference between the wave and current was stably controlled within 3°. The relative error between the wave-current coupling load curves collected by the pressure sensors on the vehicle model and the theoretical values ​​was less than 7.5%. The experimental data was stored in real time on a host computer via a high-speed data acquisition card, providing high-confidence data support for the vehicle's trajectory prediction.

[0085] This case study utilizes stratified flow channel design and low-pressure environment adaptation technology to achieve precise control of flow field parameters and stable simulation of complex wave conditions. The system utilizes a modular design, with standardized interfaces enabling data exchange between subsystems, supporting rapid expansion and upgrades. Experimental results demonstrate that the system effectively addresses technical bottlenecks such as large flow velocity fluctuations and high wave height attenuation rates associated with traditional simulation devices, providing a reliable, high-precision sea condition simulation method for scaled-down testing of deep-sea equipment.

[0086] The above further describes the technical solution provided by the present invention in detail through several specific embodiments in order to highlight the advantages and benefits of the technical solution provided by the present invention. However, the several specific embodiments described above are not intended to limit the present invention. Any reasonable modification and improvement of the present invention, combination of embodiments and equivalent replacement based on the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wave and current joint simulation system in a low-pressure environment, characterized by: include: low-pressure pools; The layered water inlet corridor is connected to the low-pressure water pool and is divided into several layers of flow channels in the vertical direction; The layered outlet corridor is connected to the low-pressure water pool and is divided into several layers of flow channels in the vertical direction; Rectification walls are arranged at the connection between the water inlet gallery, the water outlet gallery and the low-pressure water pool; The rectifying baffle is located behind the rectifying wall; The guide grille is arranged behind the rectifying baffle; The wave-breaking bank is located at the end of the low-pressure pool; The shaking plate wave maker is installed in the negative pressure cabin at one end of the low-pressure water tank; The flow-making system is located at the bottom of the low-pressure water pool and includes several flow-making pumps corresponding to several layers of flow channels. Electric butterfly valves are installed at the connection between the outlet of each flow pump and the flow channels of each layer of the water inlet gallery; High-voltage frequency conversion cabinet, electrically connected to the three-phase asynchronous motor of each flow pump; Three-phase asynchronous motors, each connected to a corresponding gearbox; Gearbox, the output end of which is connected to the impeller shaft system; The impeller shaft system is installed at the impeller end of the flow pump.

2. A method for joint simulation of waves and currents in a low-pressure environment, characterized in that: The system according to claim 1 is implemented, comprising: Steps to create a low-pressure environment; The steps of starting the flow-generating system to generate a plurality of stratified flow fields; The steps of adjusting the guide grid and the rectifying baffle to correct the uniformity of the stratified flow field; The step of starting the shaking plate wave maker to generate target sea condition waves; The step of correcting the generated waves in real time under the closed-loop control of wave height; Steps for coupling and matching control of stratified flow field and waves; The step of compensating the reflected wave to reduce the reflection interference; Steps for collecting and storing experimental data on flow velocity, wave height, and impact force in a water tank.

3. The method for combined wave and current simulation in a low-pressure environment according to claim 2, characterized in that: The air tightness of the negative pressure cabin is continuously monitored through multiple sealing detection devices, and backup sealant is automatically injected when seal failure is detected.

4. The method for combined wave and current simulation in a low-pressure environment according to claim 2, characterized in that: A high-voltage frequency conversion cabinet is used to drive a three-phase asynchronous motor, which in turn drives the gearbox and impeller shaft system, so that the flow pump outputs the stratified flow rate of each layer according to the flow velocity target values ​​of several layers stored in the CFD simulation database.

5. The method for combined wave and current simulation in a low-pressure environment according to claim 2, characterized in that: When correcting the stratified flow field, ensure that the uniformity error of the flow velocity at the outlet of each layer does not exceed ±3%.

6. The method for combined wave and current simulation in a low-pressure environment according to claim 2, characterized in that: In the wave height closed-loop control, when the deviation between the actual wave height and the target wave height is greater than 5%, the PID algorithm is called to dynamically adjust the swing angle to complete the wave correction.

7. A wave-current combined simulation device in a low-pressure environment, characterized in that: The system according to claim 1 is implemented, comprising: Module for establishing low-pressure environment; Start the flow generation system to generate several layers of stratified flow fields; A module for adjusting the guide grid and the rectifying baffle to correct the uniformity of the stratified flow field; A module for activating a shaking plate wave maker to generate target sea condition waves; A module for real-time correction of generated waves under closed-loop control of wave height; A module for coupling and matching control of stratified flow fields and waves; A module that compensates for reflected waves to reduce reflection interference; A module that collects and stores experimental data on flow velocity, wave height, and impact force in a water pool.

8. A computer storage medium for storing a computer program, characterized in that When the computer program is read by a computer, the computer executes the method according to claim 2 .

9. A computer comprising a processor and a storage medium, characterized in that When the processor reads the computer program stored in the storage medium, the computer executes the method according to claim 2 .

10. A computer program product, being a computer program, characterized in that When the computer program is executed, the method according to claim 2 is implemented.

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