Noise reduction method for stern shell structure of underwater vehicle

Abstract

The invention provides an underwater vehicle stern shell structure noise reduction method, and relates to the technical field of underwater vehicle noise reduction, and the method comprises the steps: obtaining the structure data of an underwater vehicle and a vibration signal in the operation process; determining a noise reduction target for the underwater vehicle according to the vibration signal; obtaining constraint conditions for the underwater vehicle; analyzing stern flow field characteristics and horseshoe vortex formation of the underwater vehicle on the basis of fluid dynamics analogue simulation; the method comprises the following steps: arranging a transition part of the underwater vehicle, vortex eliminating rectiblocks and reinforcing ribs; simulating vibration sound radiation of the underwater vehicle under fluid excitation by applying a finite element method in combination with sound-structure interaction analysis; optimizing the size of the transition part and the mounting position of the vortex elimination rectifying piece, and further optimizing the design parameters and the mounting position of the reinforcing rib by using a genetic algorithm; and outputting the target setting position of the reinforcing rib when the vibration sound radiation reaches the noise reduction target. According to the invention, systematic noise reduction analysis of the underwater vehicle structure can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of underwater vehicle noise reduction, and in particular to a method for reducing the noise of a stern shell structure of an underwater vehicle. Background Art

[0002] Unmanned underwater vehicle (UUV) is a kind of exploration vehicle that can be unmanned and intelligent underwater. It needs to maintain low noise during the mission to obtain high concealment. Therefore, how to reduce the navigation noise of UUV has become the focus of current attention. The main sources of noise during UUV navigation are: noise during propeller propulsion, mechanical noise during power unit transmission, and noise caused by fluid disturbance caused by the stern shell, etc. These noises have a significant impact on the stealth and comprehensive performance of the navigation body. Among them, propeller noise is mainly high-frequency noise, mechanical noise is mainly generated at low speed, and stern shell noise is mainly mid-frequency noise, among which propeller noise is the largest.

[0003] Therefore, in the existing technology, researchers have reduced propeller noise through various measures such as increasing the propeller diameter, reducing the rotation speed, increasing the number of blades and blade area. The existing technology usually focuses on a single method, such as reducing noise by adjusting the propeller design or adding components, and lacks a systematic method for overall noise reduction of underwater vehicles. Summary of the Invention

[0004] The present application provides a method for reducing the noise of the stern shell structure of an underwater vehicle, which can realize systematic noise reduction analysis of the underwater vehicle structure.

[0005] In a first aspect of the present application, a method for reducing noise of a stern hull structure of an underwater vehicle is provided, the method comprising:

[0006] Obtain the structural data of underwater vehicles and vibration signals during operation;

[0007] determining a noise reduction target for the underwater vehicle based on the vibration signal;

[0008] Obtaining constraints for the underwater vehicle, the constraints including structural total weight limit constraints, prescribed strength and stiffness requirement constraints, and navigation stability and maneuverability;

[0009] Based on fluid dynamics simulation, the flow field characteristics at the stern of the underwater vehicle and the formation of horseshoe vortices are analyzed;

[0010] According to the structural data, a transition component, a vortex-eliminating fairing, and a reinforcing rib are provided for the underwater vehicle, wherein the transition component is used to suppress the formation of horseshoe vortices, and the vortex-eliminating fairing and the reinforcing rib are used to destroy the expansion of the longitudinal horseshoe vortex;

[0011] The finite element method is combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation;

[0012] Under the premise of satisfying the constraints, the size of the transition component and the installation position of the vortex-eliminating rectifier are optimized, and the design parameters and installation position of the reinforcing rib are further optimized using a genetic algorithm. According to the simulation results, the horseshoe vortex is suppressed and the vibration sound radiation is reduced;

[0013] When the vibration sound radiation reaches the noise reduction target, the target setting position of the reinforcing rib is determined and output.

[0014] On the basis of the above technical solution, preferably, the analysis of the flow field characteristics of the stern of the underwater vehicle and the formation of the horseshoe vortex based on fluid dynamics simulation specifically includes:

[0015] Acquire the created geometric model of the underwater vehicle;

[0016] Meshing the computational domain of the geometric model and refining the mesh in the horseshoe vortex formation region to capture key flow phenomena, wherein the horseshoe vortex formation region includes the stern transition region and the stern wing region of the vehicle;

[0017] Determining the fluid properties and boundary conditions of the fluid dynamics simulation;

[0018] Performing fluid dynamics simulation analysis on the geometric model according to a turbulence model to obtain a velocity distribution of the stern flow field;

[0019] Determining, based on the results of the fluid dynamics simulation analysis, a change in pressure gradient in a geometric area between the stern wing and the hull of the underwater vehicle, and identifying alternating high-pressure and low-pressure areas generated by horseshoe vortices;

[0020] The position, strength and structure of the horseshoe vortex are identified based on the vorticity distribution diagram and streamline diagram of the fluid dynamics simulation analysis.

[0021] Based on the above technical solution, preferably, before performing fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field, the method further includes:

[0022] The standard k-ε model is used, assuming that the turbulent viscosity is isotropic, which is suitable for simulation under high Reynolds number conditions. The k-ε model is the turbulence model, and the K equation in the k-ε model is expressed as follows:

[0023]

[0024] Where ρ is the fluid density, μ is the fluid dynamic viscosity coefficient, and u j is the component of the average fluid velocity in the j direction, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr K is the Prandtl number of turbulent kinetic energy, p K is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, G b is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, ρε is the dissipation term, and Y M is the compressibility correction term;

[0025] The ε equation in the k-ε model is expressed as follows:

[0026]

[0027] Where ρε is the dissipation term, ρ is the fluid density, and u j is the component of the average fluid velocity in the j direction, μ is the fluid dynamic viscosity coefficient, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr ε is the Prandtl number of turbulent dissipation rate, C1 is an empirical constant, S ε is the effect of turbulent shear on turbulent dissipation rate ε, C2 is an empirical constant, ν is molecular viscosity, C ε1 is the empirical constant, C ε3 is the empirical constant, G b is the generation term of turbulent kinetic energy K caused by the mean water velocity gradient.

[0028] Based on the above technical solution, preferably, performing fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field further includes:

[0029] The control equations used to calculate the geometric model in the fluid dynamics simulation analysis include the momentum equation, wherein the momentum equation is expressed as follows:

[0030]

[0031] Where ρ is the fluid density, u iis the velocity component of the fluid in the i direction, u j is the velocity component of the fluid in the j direction, x i and x j is the Cartesian coordinate, P is the total pressure, τ ij is the stress tensor, pg i is gravity, F i For external force.

[0032] On the basis of the above technical solution, preferably, setting the reinforcement ribs of the underwater vehicle according to the structural data specifically includes:

[0033] Identify, through the fluid dynamics simulation analysis, areas in the stern flow field where eddies and pressure changes meet preset conditions, and determine locations where the reinforcement ribs need to be optimized for noise reduction;

[0034] Obtaining preset design principles for the reinforcement, wherein the design principles include optimizing fluid transition, structural adaptability, and structural durability;

[0035] The size of the reinforcement rib is adjusted through fluid simulation iteration to match the geometric features of the shell and the stern wing.

[0036] On the basis of the above technical solution, preferably, the application of the finite element method combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation specifically includes:

[0037] Importing the flow field velocity and direction data output by the fluid dynamics simulation into the acoustic finite element model;

[0038] In the acoustic finite element model, select a solver suitable for vibration and acoustic coupling analysis;

[0039] Setting the frequency range of the solver and setting the step sampling frequency to ensure that the calculation resolution is suitable for the target analysis;

[0040] An acoustic-structure coupling analysis is performed to calculate the vibration response of the stern shell of the underwater vehicle under fluid excitation, including the amplitude and frequency of the stiffener.

[0041] On the basis of the above technical solution, preferably, under the premise of satisfying the constraint conditions, the design parameters and installation position of the reinforcing rib are further optimized using a genetic algorithm, and according to the simulation results, the horseshoe vortex is suppressed and the vibration sound radiation is reduced, specifically including:

[0042] Setting the genetic algorithm, including setting the population size, number of iterations, crossover probability, and mutation probability;

[0043] Defining a weight value of a primary objective and a weight value of a secondary objective according to a fitness function, wherein the primary objective is to reduce the vibration acoustic radiation, and the secondary objective is to suppress horseshoe vortices;

[0044] randomly generating multiple sets of initial design parameters and installation positions, and forming a geometric model of the reinforcement according to the decoding results;

[0045] By performing fluid dynamics simulation on the geometric model under each set of initial design parameters and installation positions, the strength and position changes of the horseshoe vortex are obtained;

[0046] Import the results of each fluid dynamics simulation into the acoustic-solid coupling model to calculate the total sound source level and distribution characteristics of vibration sound radiation;

[0047] Calculating the fitness value for each set of initial design parameters and installation positions based on the results of the fluid dynamics simulation and the calculation results of the acoustic-solid coupling model, combined with the weight value of the primary objective and the weight value of the secondary objective;

[0048] When the differences between the fitness values ​​of any adjacent groups of initial design parameters and installation positions are all less than a preset threshold, the size, shape and installation position parameters of the reinforcement rib are determined.

[0049] In a second aspect of the present application, a noise reduction device for a stern hull structure of an underwater vehicle is provided, the device comprising an acquisition module, an analysis module, a control module, a simulation module, a processing module, and an output module, wherein:

[0050] The acquisition module is used to acquire structural data of the underwater vehicle and vibration signals during operation;

[0051] The analysis module is configured to determine a noise reduction target for the underwater vehicle based on the vibration signal;

[0052] The acquisition module is used to acquire constraints for the underwater vehicle, wherein the constraints include a total structural weight limit constraint, a prescribed strength and stiffness requirement constraint, and navigation stability and maneuverability;

[0053] The analysis module is used to analyze the flow field characteristics of the stern of the underwater vehicle and the formation of the horseshoe vortex based on fluid dynamics simulation;

[0054] The control module is configured to set a transition component, a vortex-eliminating fairing, and a reinforcing rib of the underwater vehicle according to the structural data, wherein the transition component is configured to suppress the formation of horseshoe vortices, and the vortex-eliminating fairing and the reinforcing rib are configured to disrupt the expansion of longitudinal horseshoe vortices;

[0055] The simulation module is used to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation by applying the finite element method combined with acoustic-solid coupling analysis;

[0056] The processing module is configured to optimize the size of the transition component and the installation position of the vortex-eliminating rectifier under the premise of satisfying the constraint conditions, and further optimize the design parameters and installation position of the reinforcing rib using a genetic algorithm, so as to suppress the horseshoe vortex and reduce the vibration acoustic radiation according to the simulation results;

[0057] The output module is used to determine and output the target setting position of the reinforcing rib when the vibration sound radiation reaches the noise reduction target.

[0058] On the basis of the above technical solution, preferably, the acquisition module is used to acquire the created geometric model of the underwater vehicle;

[0059] The control module is configured to mesh the computational domain of the geometric model and refine the mesh in a horseshoe vortex formation region to capture key fluid phenomena, wherein the horseshoe vortex formation region includes a stern transition region and a stern wing region of the vehicle;

[0060] The processing module is used to determine the fluid properties and boundary conditions of the fluid dynamics simulation;

[0061] The simulation module is used to perform fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field;

[0062] The analysis module is configured to determine, based on the results of the fluid dynamics simulation analysis, changes in pressure gradients in the geometric regions of the stern wing and the hull of the underwater vehicle, and identify alternating regions of high and low pressure generated by horseshoe vortices;

[0063] The analysis module is used to identify the position, strength and structure of the horseshoe vortex based on the vortex distribution diagram and streamline diagram analyzed by the fluid dynamics simulation.

[0064] On the basis of the above technical solution, preferably, the processing module is used to use a standard k-ε model, assuming that the turbulent viscosity is isotropic, suitable for simulation under high Reynolds number conditions, wherein the k-ε model is the turbulence model, and the K equation in the k-ε model is expressed as follows:

[0065]

[0066] Where ρ is the fluid density, μ is the fluid dynamic viscosity coefficient, and u j is the component of the average fluid velocity in the j direction, x i and x j is the Cartesian coordinate, μt is the turbulent viscosity, Pr K is the Prandtl number of turbulent kinetic energy, p K is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, G b is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, ρε is the dissipation term, and Y M is the compressibility correction term;

[0067] The ε equation in the k-ε model is expressed as follows:

[0068]

[0069] Where ρε is the dissipation term, ρ is the fluid density, and u j is the component of the average fluid velocity in the j direction, μ is the fluid dynamic viscosity coefficient, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr ε is the Prandtl number of turbulent dissipation rate, C1 is an empirical constant, S ε is the effect of turbulent shear on turbulent dissipation rate ε, C2 is an empirical constant, ν is molecular viscosity, C ε1 is the empirical constant, C ε3 is the empirical constant, G b is the generation term of turbulent kinetic energy K caused by the mean water velocity gradient.

[0070] On the basis of the above technical solution, preferably, the processing module is used to calculate the control equation of the geometric model in the fluid dynamics simulation analysis, including the momentum equation, wherein the momentum equation is expressed as follows:

[0071]

[0072] Where ρ is the fluid density, u i is the velocity component of the fluid in the i direction, u j is the velocity component of the fluid in the j direction, x i and x j is the Cartesian coordinate, P is the total pressure, τ ij is the stress tensor, pg i is gravity, F i For external force.

[0073] Based on the above technical solution, preferably, the analysis module is used to identify, through the fluid dynamics simulation analysis, areas in the stern flow field where the vortex and pressure changes meet preset conditions, and determine the noise reduction positions of the reinforcement ribs that need to be optimized;

[0074] The acquisition module is used to acquire the preset design principles of the reinforcement rib, wherein the design principles include optimizing fluid transition, structural adaptability, and structural durability;

[0075] The control module is used to adjust the size of the reinforcement rib through fluid simulation iteration so that the reinforcement rib matches the geometric features of the shell and the stern wing.

[0076] On the basis of the above technical solution, preferably, the output module is used to import the flow field velocity and direction data output by the fluid dynamics simulation into the acoustic finite element model;

[0077] The control module is used to select a solver suitable for vibration and acoustic coupling analysis in the acoustic finite element model;

[0078] The control module is used to set the solving frequency range of the solver and set the step sampling frequency to ensure that the calculation resolution is suitable for the target analysis;

[0079] The processing module is used to perform acoustic-solid coupling analysis to calculate the vibration response of the stern shell of the underwater vehicle under fluid excitation, including the amplitude and frequency of the stiffener.

[0080] On the basis of the above technical solution, preferably, the control module is used to set the genetic algorithm, including setting the population size, number of iterations, crossover probability and mutation probability;

[0081] The processing module is used to define a weight value of a primary objective and a weight value of a secondary objective according to a fitness function, wherein the primary objective is to reduce the vibration acoustic radiation, and the secondary objective is to suppress horseshoe vortices;

[0082] The control module is used to randomly generate multiple sets of initial design parameters and installation positions, and form a geometric model of the reinforcement according to the decoding results;

[0083] The simulation module is used to obtain the strength and position changes of the horseshoe vortex by performing fluid dynamics simulation on the geometric model under each set of initial design parameters and installation positions;

[0084] The processing module is used to import the results of each fluid dynamics simulation into the acoustic-solid coupling model to calculate the total sound source level and distribution characteristics of vibration sound radiation;

[0085] The processing module is configured to calculate the fitness value for each set of initial design parameters and installation positions based on the results of the fluid dynamics simulation and the calculation results of the acoustic-solid coupling model, in combination with the weight value of the primary objective and the weight value of the secondary objective;

[0086] The processing module is used to determine the size, shape and installation position parameters of the reinforcing rib when the differences between the fitness values ​​of any adjacent multiple groups of initial design parameters and installation positions are less than a preset threshold.

[0087] In summary, one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0088] 1. This application systematically solves the noise reduction problem of underwater vehicle structures by combining multidisciplinary analysis and optimization technology. First, starting from the analysis of vibration signals, the noise characteristics and noise reduction targets are clarified; under the constraints, key noise sources (such as the formation area of ​​horseshoe vortex) are identified through fluid dynamics simulation; transition components, vortex elimination rectifiers and reinforcement ribs are set in combination with structural data to reduce fluid disturbance by optimizing the flow field; further application of finite element method and acoustic-solid coupling analysis is carried out to simulate structural vibration and sound radiation characteristics; finally, genetic algorithms are used to optimize the design parameters and installation positions of transition components, vortex elimination rectifiers and reinforcement ribs to ensure that the weight, strength and maneuverability requirements are met while suppressing noise. This multi-level process not only comprehensively considers the physical characteristics of underwater vehicles, but also organically combines simulation analysis with optimization design to achieve the systematic, scientific and efficient noise reduction goals.

[0089] 2. Through fluid dynamics simulation, the system systematically analyzes the flow field characteristics and horseshoe vortex generation mechanism at the stern of the underwater vehicle. The system accurately identifies the pressure gradient changes and vortex characteristics at the junction of the stern and hull, including the vortex intensity, location, and structure. Mesh refinement and turbulence model calculations in key areas capture the dynamic behavior of the complex flow field in detail, providing a scientific basis for optimizing the stern flow field, reducing horseshoe vortices, and improving fluid disturbances.

[0090] 3. Vibration signal analysis is used to identify noise reduction targets. Fluid dynamics simulation is used to precisely identify noise sources. Ribs are set and optimized to reduce fluid disturbances. Vibration and acoustic radiation are predicted using acoustic-solid coupling analysis. Finally, genetic algorithms are used to optimize component design parameters and installation locations to ensure effective noise reduction while meeting the vehicle's structural strength, weight, and controllability requirements.

[0091] 4. Accurately importing the data output from the fluid dynamics simulation into the acoustic finite element model and setting the frequency range and sampling accuracy suitable for the target analysis can accurately calculate the vibration response (including amplitude and frequency) of the stern shell and reinforcement, and effectively evaluate the intensity and distribution characteristics of vibration sound radiation.

[0092] 5. Set the population size, number of iterations, crossover and mutation probabilities, and combine the weights of the primary goal (reducing vibration and acoustic radiation) and the secondary goal (suppressing horseshoe vortices) to form multiple sets of initial design parameters and installation positions. Perform fluid dynamics and acoustic-solid coupling simulation analysis to gradually optimize the fitness value. When the design parameters and installation position converge to the preset threshold, determine the optimal rib size, shape, and installation position. This effectively reduces the horseshoe vortex intensity and the total sound source level of vibration and acoustic radiation, while taking into account structural performance and constraints, significantly improving the stealth and overall performance of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 This is a flow chart of a method for reducing noise of a stern hull structure of an underwater vehicle disclosed in an embodiment of the present application;

[0094] Figure 2 This is a schematic diagram of a module of a noise reduction device for the stern shell structure of an underwater vehicle disclosed in an embodiment of the present application;

[0095] Description of the accompanying drawings: 201, acquisition module; 202, analysis module; 203, control module; 204, simulation module; 205, processing module; 206, output module. DETAILED DESCRIPTION

[0096] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments.

[0097] In the description of the embodiments of this application, words such as "for example" or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "for example" or "for instance" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "for example" or "for instance" is intended to present the relevant concepts in a concrete manner.

[0098] In the description of the embodiments of the present application, the term "multiple" means two or more. For example, multiple systems refer to two or more systems, and multiple screen terminals refer to two or more screen terminals. In addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0099] The main sources of noise generated by unmanned underwater vehicles (UUVs) are propeller propulsion noise, mechanical noise from the power plant, and fluid disturbance noise from the stern hull. Propeller noise is the heaviest, particularly concentrated in the high-frequency range, while stern hull noise is concentrated in the mid-frequency range. These noises significantly impact the stealth and performance of UUVs. Existing technologies often employ single approaches, such as adjusting propeller diameter, speed, blade number, or adding additional components, to reduce noise. However, a systematic approach to overall UUV noise reduction is lacking.

[0100] This embodiment discloses a method for reducing noise of the stern shell structure of an underwater vehicle, referring to Figure 1 , including the following steps S110-S180:

[0101] S110, acquiring structural data of the underwater vehicle and vibration signals during operation.

[0102] The present invention discloses a method for reducing noise in the stern hull structure of an underwater vehicle. This method, which is applicable to the field of underwater vehicle noise reduction, collects the underwater vehicle's design documentation, including CAD drawings and 3D modeling files, to obtain key structural information about the vehicle, such as the dimensions and shape of the stern hull and stern wing, as well as the geometry of the transition components. The method also collects material parameters of the vehicle's primary structure, including density, elastic modulus, Poisson's ratio, yield strength, and corrosion resistance, with a focus on obtaining the fatigue resistance parameters of the hull material for subsequent vibration analysis.

[0103] Select highly sensitive vibration sensors (such as accelerometers) and hydrophones to collect vibration signals and underwater acoustic radiation during the operation of the underwater vehicle. Focus on installing sensors in noise-sensitive areas (such as the junction between the stern wing and the hull, the hull surface, and near the propeller) to ensure that the sensors can capture vibration signals in different frequency ranges during the operation of the underwater vehicle. Set the sensor sampling frequency to cover the main frequency range of the noise signal (such as 20Hz to 10kHz), and use a multi-channel data acquisition system to simultaneously record vibration signals at multiple locations.

[0104] S120: Determine a noise reduction target for the underwater vehicle according to the vibration signal.

[0105] Typical mission scenarios are simulated, including low-speed, medium-speed, and high-speed operating conditions, to ensure that vibration signal acquisition covers the actual operating conditions of the underwater vehicle. The collected signals are subjected to a Fourier transform (FFT) to analyze their spectral characteristics, determine the frequency range and intensity of the main noise, and use time-frequency analysis methods (such as short-time Fourier transform or wavelet analysis) to identify the dynamic characteristics of the vibration noise in time and frequency.

[0106] Calculate the vibration energy at different frequencies and identify the frequency bands that contribute most to the total acoustic radiation, focusing on the mid-frequency range (500Hz-5000Hz). Correlate the vibration signals with the flow simulation data to identify the noise sources and their characteristics, such as the flow field disturbances caused by horseshoe vortices or the vibrations at the junction of the stern wing and the hull. The primary design objective is to reduce the level of vibration and acoustic radiation from the underwater vehicle's stern hull in the mid-frequency range of 500Hz-5000Hz.

[0107] S130: Obtain the constraint conditions of the underwater vehicle.

[0108] Collect information about the underwater vehicle's mission requirements and operating environment, such as navigation depth, mission duration, and the weight of onboard equipment, to determine the vehicle's overall weight limit to meet transportation, deployment, and mission execution needs. This allows the upper limit of the total structural weight to be determined based on actual needs, ensuring that the vehicle's overall performance and endurance are not affected while meeting transportation and deployment requirements.

[0109] According to the navigation stability constraints, the underwater vehicle diameter is set to 0.5-1.5 meters, the hull length is 4-25 meters, the type is a typical four-stern wing underwater vehicle, the stern wing length is 0.4-1.2 meters, the stern wing height is 0.2-0.6 meters, the stern wing thickness is 0.04-0.12 meters, and the minimum turning radius is 100-120 meters to ensure that the underwater vehicle can still maintain good maneuverability and stability in complex sea conditions. The speed of the underwater vehicle is set to 3-20 knots to meet the rapid response and mission requirements of the underwater vehicle;

[0110] S140, based on fluid dynamics simulation, analyzes the flow field characteristics and horseshoe vortex formation at the stern of an underwater vehicle.

[0111] Propeller noise and mechanical noise are closely related to the structural dynamics of underwater vehicles, making modification and adjustment difficult. Therefore, in existing technologies, suppressing the horseshoe vortex in the stern hull of an underwater vehicle is an effective method for reducing noise. Researchers have proposed various devices and methods for controlling horseshoe vortices. For example, Liu Zhihua et al. proposed the technical concept of installing vortex-eliminating straightening blades, which achieves a rectifying effect by disrupting the generation of horseshoe vortices and suppressing their development. Davenport et al. studied the rectification method of setting appendage fillets, and found that appropriate fillets can significantly suppress the intensity and size of horseshoe vortices. Jin Yeqing et al. studied the effect of reinforcing plate ribs on acoustic radiation characteristics, which has practical significance for the field of far-field radiated sound pressure. Batcho invented an appendage device to eliminate horseshoe vortices, which offsets the horseshoe vortex by generating vortices rotating in the opposite direction of the original horseshoe vortex. Zhang Nan et al. conducted research on submarine jet technology, and the results showed that submarine jets can reduce horseshoe vortices at the main / appendage junction.

[0112] In one possible implementation, based on fluid dynamics simulation, the flow field characteristics at the stern of the underwater vehicle and the formation of horseshoe vortex are analyzed, specifically including: obtaining a created geometric model of the underwater vehicle; meshing the computational domain of the geometric model, and meshing the horseshoe vortex formation region to capture key fluid phenomena, the horseshoe vortex formation region including the stern transition region and the stern wing region of the vehicle; determining the fluid properties and boundary conditions of the fluid dynamics simulation; performing fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field; determining the pressure gradient change in the geometric region of the stern wing and the shell of the underwater vehicle according to the results of the fluid dynamics simulation analysis, and identifying the high-pressure and low-pressure alternating regions generated by the horseshoe vortex; and identifying the position, intensity and structure of the horseshoe vortex according to the vortex distribution diagram and streamline diagram of the fluid dynamics simulation analysis.

[0113] Specifically, a 3D modeling software (such as SolidWorks or CATIA) is used to create a geometric model of the underwater vehicle, including the hull, stern, transition components, and other appendages. The modeling process ensures that the geometric dimensions and shape of the model are consistent with the actual vehicle, especially the details of the stern and stern areas. Minor structures can be appropriately simplified (e.g., removing small components) to reduce simulation complexity without affecting key fluid properties.

[0114] Import the geometry into meshing software (such as ANSYS Meshing) to generate a global computational mesh. Ensure high mesh quality to avoid excessive distortion or uneven distribution. Locally refine the mesh in areas prone to horseshoe vortices (such as the stern, transition components, and the stern wing junction) to capture vortex details. Use smaller mesh elements (such as tetrahedral or hexahedral meshes) to cover these areas and ensure simulation accuracy.

[0115] Next, define the physical properties of water in the fluid dynamics simulation process (such as density, dynamic viscosity, and sound speed, for example, the density of water is 1000 kg / m3, the dynamic viscosity is 1.01×10-3 Pa·s, and the speed of sound is 1500 m / s) to ensure that it conforms to the actual operating environment. At the same time, set the boundary conditions, including setting a fixed speed inlet to simulate the actual navigation speed of the underwater vehicle during operation, setting the outlet condition to free outflow to allow the fluid to naturally leave the calculation domain, and setting a no-slip boundary condition (No-slip condition) to simulate the real interaction between the fluid and the solid surface. Select a calculation domain that is 2-3 times the length of the underwater vehicle in front, behind, left, and right to ensure that the simulation results are not affected by the boundary.

[0116] The standard k-ε turbulence model is used, which is suitable for high Reynolds number fluid simulation. If higher accuracy is required, the SST turbulence model can be used to capture the near-wall vortex characteristics. The standard k-ε model is a turbulence model based on the average fluid velocity gradient. It assumes that the turbulent viscosity is isotropic and is suitable for flow analysis at high Reynolds numbers. This model describes turbulent characteristics through two transport equations. K represents the turbulent kinetic energy, which measures the turbulence intensity, and ε represents the turbulent dissipation rate, which measures the dissipation rate of turbulent energy. Among them, the K equation in the k-ε model is expressed as follows:

[0117]

[0118] Where ρ is the fluid density, μ is the fluid dynamic viscosity coefficient, and u j is the component of the average fluid velocity in the j direction, x i and x j is the Cartesian coordinate used to describe the position and motion of the fluid, μ t is the turbulent viscosity, turbulent viscosity μ t Calculated by turbulent kinetic energy K and turbulent dissipation rate ε, the formula is:

[0119]

[0120] Pr K is the Prandtl number of turbulent kinetic energy, p K is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, and the calculation formula is:

[0121]

[0122] G b is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, which represents the generation of turbulent kinetic energy caused by buoyancy. It is usually small in incompressible fluids and can be ignored. ρε is the dissipation term, Y M is the compressibility correction term, K represents the turbulent kinetic energy, which measures the turbulence intensity, and ε represents the turbulent dissipation rate, which measures the dissipation rate of turbulent energy.

[0123] in, is the temporal variation of turbulent kinetic energy, It is the convective transport of turbulent kinetic energy in space through fluid motion. is the diffusion term, which represents the diffusion of turbulent kinetic energy in the flow field through molecular viscosity and turbulent viscosity.

[0124] The ε equation in the k-ε model is expressed as follows:

[0125]

[0126] Where ρε is the dissipation term, ρ is the fluid density, and u jis the component of the average fluid velocity in the j direction, μ is the fluid dynamic viscosity coefficient, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr ε is the Prandtl number of turbulent dissipation rate, C1 is an empirical constant, S ε is the effect of turbulent shear on turbulent dissipation rate ε, C2 is an empirical constant, ν is molecular viscosity, C ε1 is the empirical constant, C ε3 is the empirical constant, G b is the generation term of turbulent kinetic energy K caused by the mean water velocity gradient.

[0127] where ρC1Sε represents the generation term of the turbulent kinetic energy dissipation rate, which originates from the production of turbulent kinetic energy (i.e., ε is related to turbulent shear), C represents the quadratic nonlinear term of the dissipation rate, which is used to limit the excessive growth of ε. ε3 G b is the change in dissipation rate caused by buoyancy, C ε3 is an empirical constant related to buoyancy.

[0128] The K equation describes the source, diffusion, and dissipation of turbulent kinetic energy and is the energy foundation for turbulence modeling. The ε equation, by describing the energy dissipation rate, establishes the mechanism by which turbulent kinetic energy is converted into internal energy. These two equations are tightly coupled through the calculation of turbulent viscosity and form the core of turbulence models, used to quantify the turbulent properties of high-Reynolds-number fluids. Numerically solving these two equations accurately simulates turbulent behavior in fluids, such as flow field distribution, pressure gradients, and vortex generation, providing a basis for subsequent calculations and optimization.

[0129] The governing equations used to calculate the geometric model in fluid dynamics simulation analysis include the momentum equation, which is expressed as follows:

[0130]

[0131] Where ρ is the fluid density, u i is the velocity component of the fluid in the i direction, u j is the velocity component of the fluid in the j direction, x i and x j is the Cartesian coordinate, P is the total pressure, pg i is gravity, F i is the external force, τ ij is the stress tensor, in Pa, which describes the viscous force inside the fluid. The specific calculation is:

[0132]

[0133] Among them, δ ijis the Kronecker symbol (identity matrix element).

[0134] Define the fluid calculation domain range, including the calculation domain of the front end of the underwater vehicle as 1 times the length of the underwater vehicle shell, the diameter is 16 times the diameter of the underwater vehicle, and the calculation domain of the rear end of the underwater vehicle is 2 times the length of the underwater vehicle shell, to ensure that the fluid calculation domain is fully covered. The wall boundary condition is set to a no-slip boundary condition (No-slip condition). This type of model setting is very suitable for fluid turbulence models with high Reynolds numbers. According to the actual navigation speed U1 of the vehicle, the inlet velocity V1=U1 is set, the outlet velocity is set to free outflow, and the inlet pressure P1=P is set at the underwater depth h. 大气 +ρgh, outlet pressure P atm. Using coordinate positioning, two receivers are set up on the stern wall of the underwater vehicle to collect flow field velocity magnitude and direction fluctuation signals. Two receivers are set up at left-right symmetrical positions outside the computational domain to accurately monitor and receive underwater acoustic radiation noise signals from the stern of the underwater vehicle.

[0135] Set up a transient solver to capture the dynamic changes of the fluid, especially the generation and dissipation of the horseshoe vortex, define a reasonable time step (such as 0.01s), and ensure that the number of time steps is large enough to simulate the complete vortex generation cycle.

[0136] Then, based on the results of the fluid dynamics simulation analysis, the velocity distribution diagram of the stern of the underwater vehicle is output to observe the spatial distribution and variation of the fluid velocity, focusing on analyzing the flow velocity gradient at the junction of the stern wing and the shell. At the same time, a pressure distribution diagram is output to analyze the pressure gradient in the junction area of ​​the stern wing and the shell, identify the alternating areas of high and low pressure, and clarify the generation location and intensity of the horseshoe vortex. Based on the simulation results, the impact of the current geometric design on the flow field is evaluated, especially the effect of the reinforcement on the horseshoe vortex suppression, to determine whether it is necessary to adjust the geometric parameters or add noise reduction devices. For areas with higher horseshoe vortex intensity, new reinforcements are designed and their size and position are adjusted. After optimizing the geometric model, the simulation is rerun to verify the improvement effect.

[0137] S150: Arrange the transition components, vortex-eliminating fairings, and reinforcement ribs of the underwater vehicle according to the structural data.

[0138] To address the large flow field fluctuations and high acoustic radiation noise at the transition between the stern and the hull, the stern structure was redesigned to create a smooth and stable transition between the stern and the hull. The transition section is approximately 1 / 5 of the stern's height, and its length along the hull is approximately twice its height. Its maximum width is set to approximately 1 / 2 of the stern's width. For example, the rib has a length of x = 16 cm, a width of y = 8 cm, and a height of z = 4 cm. The front end of the transition is a pointed streamlined shape. This transition component reduces the front contact area of ​​the stern and serves to weaken the horseshoe vortex core in the flow field at the corner where the stern and hull meet. The size of the vortex suppressor blades should be adjusted according to the size of the underwater vehicle structure. For example, they can be set to 10 cm long, 2.5 cm high, and only a few millimeters thick. They can be installed on both sides of the stern to suppress the initial formation of horseshoe vortices along the longitudinal direction of the underwater vehicle hull, thereby preventing the increase of the horseshoe vortex effect.

[0139] In one possible implementation, stiffeners for the underwater vehicle are provided based on the structural data, specifically including: identifying, through fluid dynamics simulation analysis, areas in the stern flow field where the severity of vortices and pressure changes meet preset conditions, and determining the noise reduction positions where the stiffeners need to be optimized; obtaining preset design principles for the stiffeners, which include optimizing fluid transition, structural adaptability, and structural durability; and iteratively adjusting the size of the stiffeners through fluid simulation to match the geometric features of the shell and stern wing.

[0140] Specifically, reinforcing ribs can be installed on the shells on both sides of the stern wing. On the one hand, they can enhance the stability of the stern wing and reduce the vibration caused by fluid impact. On the other hand, they can enhance the suppression effect of horseshoe vortex.

[0141] According to the results of fluid dynamics simulation analysis, draw the vortex distribution diagram, identify the areas with higher vortex intensity in the flow field, determine the generation location of horseshoe vortex and other vortices and the range of their disturbance to the flow field. At the same time, draw the pressure distribution diagram and analyze the pressure gradient changes at the junction of the stern wing and the shell. Identify areas with drastic pressure changes, which are usually the main contribution points of the noise source. According to the simulation results, select areas that meet the following conditions as the focus of noise reduction optimization, including vortex intensity exceeding a certain threshold (such as high turbulent kinetic energy value), or drastic pressure gradient, which easily produces fluid separation and turbulence. Combine the above analysis results to mark the specific locations on the stern shell that need to be optimized, such as the transition area where the stern wing and the shell are combined.

[0142] When designing the stiffeners, ensure smooth geometric transitions to reduce sudden changes in fluid flow. By adjusting the shape and size of the components to weaken the generation and development of horseshoe vortices, the flow velocity and pressure distribution of the fluid near the stiffeners tend to be uniform, reducing fluid disturbances. At the same time, the geometric design of the stiffeners must be precisely matched with the shape and size of the shell and stern wing to avoid new structural interference. In addition, lightweight, high-strength, corrosion-resistant materials (such as titanium alloys) are used to ensure that the stiffeners can withstand long-term water flow impact and vibration, ensuring that the components do not suffer fatigue failure during long-term operation and meet the design life requirements.

[0143] Based on the noise reduction location and design principles, the initial dimensions of the ribs were defined: their length matched the junction of the hull and stern wing, covering the critical noise reduction area, and their thickness and width were initially set at 1 / 40 to 1 / 20 of the hull size to ensure effective suppression of fluid disturbances. The initial rib model was then incorporated into the fluid dynamics simulation to verify its effect on optimizing the flow field. The ribs' fluid transition performance was evaluated, including the degree of vortex attenuation, pressure gradient reduction, and improvement in flow field uniformity. Changes in noise sources, particularly changes in the total sound pressure level, were recorded.

[0144] Adjust key rib parameters (such as length, width, and mounting angle) to optimize the following: minimize the strength of horseshoe vortices; reduce local pressure fluctuations; and improve flow field uniformity to avoid new disturbances. Rerun the simulation after each optimization until the desired results are achieved. Output the optimized rib geometry, including size, shape, and mounting position. Ensure the final rib design meets noise reduction objectives while also satisfying structural fit and durability requirements.

[0145] An initial number of reinforcements was determined as a baseline. Starting from the preliminary design, a total of ±8 reinforcements were added along the longitudinal direction of the AUV's stern hull. The distribution pattern was adjusted by varying the spacing (uniform or variable). The reinforcements could be straight or curved. Within each iteration, the number, distribution, and size of reinforcements were adjusted within the pre-set iteration range. For each revised design, the finite element analysis method was re-used to update the AUV's stern hull model and evaluate the horseshoe vortex suppression effect. The fluid dynamics simulation settings were maintained consistent to allow for accurate comparison between the different designs. The acoustic-structure interaction analysis was then re-run based on the fluid excitations obtained from the fluid dynamics simulation.

[0146] S160, using the finite element method combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of underwater vehicles under fluid excitation.

[0147] In one possible implementation, the finite element method is combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of an underwater vehicle under fluid excitation, specifically including: importing the flow field velocity and direction data output by the fluid dynamics simulation into an acoustic finite element model; selecting a solver suitable for vibration and acoustic coupling analysis in the acoustic finite element model; setting the solver's solution frequency range and the step sampling frequency to ensure that the calculation resolution is suitable for the target analysis; and performing acoustic-solid coupling analysis to calculate the vibration response of the underwater vehicle's stern hull under fluid excitation, including the amplitude and frequency of the stiffeners.

[0148] Specifically, fluid dynamics simulations are used to obtain flow field velocity and direction data on the underwater vehicle surface, typically including key parameters such as velocity distribution, pressure distribution, and turbulence intensity. Flow field data is specifically extracted for the stern hull and the areas near the stiffeners, as these areas are the primary sources of fluid excitation. The fluid simulation data is then mapped onto the surface mesh of the finite element model, ensuring that the flow field velocity and direction are consistent with the structural geometry.

[0149] Import the 3D structural model of the underwater vehicle (including the stiffeners and stern fin) into the Acoustics Analysis Module. Generate a convex mesh for the acoustic computational domain, ensuring that the mesh quality is high enough to capture the propagation characteristics of the sound waves. In critical areas (such as near noise sources), refine the mesh, typically using tetrahedral elements.

[0150] Select the Harmonic Acoustics solver, which supports acoustic-structure interaction analysis, to calculate the interaction between structural vibration and the acoustic field. Based on the noise characteristics of the underwater vehicle, set the solution frequency range (e.g., 500Hz-5000Hz) and the step sampling frequency (e.g., 50Hz) to ensure the frequency resolution of the calculation. Apply fluid excitation to the structure surface, including the distribution of flow field velocity and direction. Set non-reflecting boundary conditions (Absorbing Boundary) at the boundaries of the computational domain to simulate the propagation of sound waves into the infinite field.

[0151] Run an acoustic-structure interaction analysis to calculate the vibration response of the underwater vehicle structure. This includes calculating the displacement amplitude at each point on the structure's surface, identifying the areas of strongest vibration, and determining the dominant frequency range to match the flow field excitation frequency. Applying the Rayleigh Integral formula or similar methods, the acoustic radiation intensity caused by surface vibration is calculated, predicting the far-field sound pressure level distribution and sound wave propagation characteristics. Finally, the vibration response (amplitude and frequency) distribution of the stiffeners and stern hull is output.

[0152] S170 optimizes the size of the transition component and the installation position of the vortex-eliminating rectifier. A genetic algorithm is used to further optimize the design parameters and installation position of the stiffener. Based on the simulation results, the horseshoe vortex is suppressed and the vibration and acoustic radiation are reduced.

[0153] Based on the results of fluid dynamics simulation, the noise reduction effects of the transition piece and the vortex rectifier were evaluated and compared, and possible improvement areas were identified. The size of the transition piece and the installation position parameters of the vortex rectifier were fine-tuned. For example, the size of the transition piece can be introduced into the size coefficient C (existing size / original size, i.e., proportional scaling, C = 0.8-1.2). When C = 0.9, that is, x = 14.4cm, y = 7.2cm, z = 3.6cm, the installation position parameters of the vortex rectifier are changed to m = 10 ± 2cm, n = 2.5 ± 0.5cm (m = 6-14cm, n = 1.5-3.5cm) to further optimize the noise reduction effect. The adjusted parameters are used to re-grid and re-simulate the calculations to ensure that the previously set parameters are the same. The lowest sound pressure level signal is searched, and the optimal size parameters of the transition piece and the installation position of the vortex rectifier are determined within a small range. The optimization scheme of the transition piece and the vortex rectifier is obtained.

[0154] In a possible implementation, under the premise of satisfying the constraint conditions, a genetic algorithm is used to further optimize the design parameters and installation position of the reinforcement rib, and according to the simulation results, the horseshoe vortex is suppressed and the vibration sound radiation is reduced, specifically including: setting the genetic algorithm, including setting the population size, number of iterations, crossover probability and mutation probability; defining the weight value of the main goal and the weight value of the secondary goal according to the fitness function, the main goal is to reduce the vibration sound radiation, and the secondary goal is to suppress the horseshoe vortex; randomly generating multiple groups of initial design parameters and installation positions, and forming the geometric model of the reinforcement rib according to the decoding results; by The results of each fluid dynamics simulation are imported into the acoustic-structure coupling model to calculate the total sound source level of vibration sound radiation and its distribution characteristics. According to the results of the fluid dynamics simulation and the calculation results of the acoustic-structure coupling model, the fitness value of each set of initial design parameters and installation position is calculated in combination with the weight value of the primary target and the weight value of the secondary target. When the difference between the fitness values ​​of any adjacent sets of initial design parameters and installation positions is less than the preset threshold, the size, shape and installation position parameters of the reinforcement rib are determined.

[0155] Specifically, based on the results of fluid dynamics simulation and finite element analysis, a symmetrically installed stiffener layout was determined, with one stiffener on each side of the underwater vehicle's stern hull. This meant ±8 stiffeners were placed longitudinally along the stern hull. This ensured the stiffeners were distributed to effectively cover the critical vibration area of ​​the stern hull. The stiffener length was set to 1 / 5-1 / 2 of the stern hull height, the width to 1 / 40-1 / 15 of the stern hull length, and the thickness to 1 / 40-1 / 20 of the stern hull thickness. Excessive size would affect the overall quality of the underwater vehicle, while too small would have a poor effect on suppressing longitudinal horseshoe vortices. The bottom of the stiffener was mounted on the underwater vehicle hull, and the top of the stiffener was mounted on the stern hull. The initial installation position of the bottom was set at a distance from the stern hull, with corresponding installation angles and spacings set. The material selected is titanium alloy, which has high strength, low density and good corrosion resistance, and is suitable as a structural material for underwater vehicles. The three-dimensional model of the reinforcement is accurately drawn according to the design parameters in the three-dimensional modeling software, and then integrated and installed into the model of the stern shell of the underwater vehicle.

[0156] First, initialize the parameters and set the population size (e.g., 50 individuals) to ensure the breadth of the design space and enhance global search capabilities. Set the maximum number of iterations (e.g., 100) to allow the algorithm to fully converge. Set the crossover probability (e.g., 0.8) to increase the speed of generating new designs. Set the mutation probability (e.g., 0.05) to maintain population diversity and prevent regression into local optima.

[0157] Then, the target weights are defined, including the main target and the secondary target. The main target is to reduce the total sound source level of vibration sound radiation (such as reducing it to below a certain sound pressure level), and the secondary target is to suppress the intensity of the horseshoe vortex (such as reducing eddy currents or reducing the fluctuation of the vortex core position). According to the design requirements, the target weights in the fitness function are assigned. The main target weight prioritizes reducing vibration sound radiation (such as 0.7), and the secondary target weight prioritizes suppressing the horseshoe vortex (such as 0.3). According to the results of the fluid dynamics simulation and the calculation results of the acoustic-solid coupling model, combined with the weight value of the main target and the weight value of the secondary target, the fitness value for each set of initial design parameters and installation position is calculated. The fitness function formula is:

[0158]

[0159] Among them, D is the fitness value, S is the total sound source level of the vibration sound radiation of the current design, T is the horseshoe vortex intensity of the current design, S ref and T ref For reference benchmark value.

[0160] Binary or real number coding is used to represent the design parameters and installation location of the stiffener. The parameters include length, width, thickness, installation angle, and location, forming a total of n parameters, each of which is normalized to the interval [0,1]. Multiple sets of initial design parameters and installation locations (populations) are randomly generated. After decoding, each set of parameters generates a geometric model of the stiffener. For each set of design parameters and installation location generated geometric model, a fluid dynamics simulation is run to obtain the strength (e.g., eddy current) and position variation of the horseshoe vortex, as well as the flow field uniformity. The fluid dynamics simulation results for each set of design parameters and installation location are then imported into the acoustic-solid coupling model to calculate the total sound source level (e.g., far-field sound pressure level) and its distribution characteristics of the vibration sound radiation.

[0161] Based on the simulation results, the fitness value is calculated. The fluid dynamics simulation results (such as horseshoe vortex intensity) and the acoustic-solid coupling analysis results (such as total sound source level) are substituted into the fitness function to obtain the comprehensive fitness value of each design group.

[0162] S180, when the vibration sound radiation reaches the noise reduction target, determining and outputting the target setting position of the reinforcement rib.

[0163] According to the fitness value ratio, excellent individuals are selected to enter the next generation, and two groups of high fitness individuals are randomly selected to perform crossover operations to generate new individuals. The crossover method can be single-point crossover or multi-point crossover. The generated new individuals are mutated, and the gene bit is randomly selected to flip (if binary coded) or add a small disturbance (if real number coded). Combined with selection, crossover and mutation operations, the next generation population is generated and the population fitness value is updated. The algorithm terminates when the fitness value difference of any adjacent groups of individuals is less than the preset threshold or the maximum number of iterations is reached. Finally, the individual with the highest fitness value is extracted to determine the design parameters of the optimal reinforcement, including size, shape and installation position. The optimal design parameters and installation position can be used to rerun the fluid dynamics simulation and acoustic-solid coupling analysis to verify the optimized horseshoe vortex suppression effect and the degree of reduction in vibration sound radiation.

[0164] This embodiment also discloses a noise reduction device for the stern shell structure of an underwater vehicle, referring to Figure 2 The device includes an acquisition module 201, an analysis module 202, a control module 203, a simulation module 204, a processing module 205 and an output module 206, wherein:

[0165] The acquisition module 201 is used to acquire the structural data of the underwater vehicle and the vibration signal during operation.

[0166] The analysis module 202 is configured to determine a noise reduction target for the underwater vehicle based on the vibration signal.

[0167] The acquisition module 201 is used to acquire the constraints for the underwater vehicle, where the constraints include the total weight limit constraint, the specified strength and stiffness requirement constraint, and the navigation stability and maneuverability.

[0168] The analysis module 202 is used to analyze the flow field characteristics at the stern of the underwater vehicle and the formation of horseshoe vortices based on fluid dynamics simulation.

[0169] The control module 203 is used to set the transition components, vortex-eliminating fairings and reinforcing ribs of the underwater vehicle according to the structural data. The transition components are used to suppress the formation of horseshoe vortices, and the vortex-eliminating fairings and reinforcing ribs are used to destroy the expansion of longitudinal horseshoe vortices.

[0170] The simulation module 204 is used to apply the finite element method in combination with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation.

[0171] The processing module 205 is used to optimize the size of the transition component and the installation position of the vortex-eliminating rectifier under the premise of satisfying the constraint conditions, and use the genetic algorithm to further optimize the design parameters and installation position of the reinforcement rib, and suppress the horseshoe vortex and reduce the vibration sound radiation according to the simulation results.

[0172] The output module 206 is used to determine and output the target setting position of the reinforcement rib when the vibration sound radiation reaches the noise reduction target.

[0173] In a possible implementation, the acquisition module 201 is configured to acquire a created geometric model of the underwater vehicle.

[0174] The control module 203 is used to mesh the computational domain of the geometric model and to refine the mesh in the horseshoe vortex formation region to capture key fluid phenomena. The horseshoe vortex formation region includes the stern transition region and the stern wing region of the vehicle.

[0175] The processing module 205 is used to determine the fluid properties and boundary conditions for fluid dynamics simulation.

[0176] The simulation module 204 is used to perform fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field.

[0177] The analysis module 202 is used to determine the pressure gradient change in the geometric area between the stern wing and the hull of the underwater vehicle based on the results of the fluid dynamics simulation analysis, and identify the high-pressure and low-pressure alternating areas generated by the horseshoe vortex.

[0178] The analysis module 202 is used to identify the position, strength and structure of the horseshoe vortex based on the vortex distribution diagram and streamline diagram analyzed by fluid dynamics simulation.

[0179] In one possible implementation, the processing module 205 is configured to use a standard k-ε model, assuming isotropic turbulent viscosity, suitable for simulations under high Reynolds number conditions. The k-ε model is a turbulence model, and the K equation in the k-ε model is expressed as follows:

[0180]

[0181] Where ρ is the fluid density, μ is the fluid dynamic viscosity coefficient, and u j is the component of the average fluid velocity in the j direction, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr K is the Prandtl number of turbulent kinetic energy, p K is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, G b is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, ρε is the dissipation term, and Y M is the compressibility correction term.

[0182] The ε equation in the k-ε model is expressed as follows:

[0183]

[0184] Where ρε is the dissipation term, ρ is the fluid density, and u j is the component of the average fluid velocity in the j direction, μ is the fluid dynamic viscosity coefficient, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr ε is the Prandtl number of turbulent dissipation rate, C1 is an empirical constant, S ε is the effect of turbulent shear on turbulent dissipation rate ε, C2 is an empirical constant, ν is molecular viscosity, C ε1 is the empirical constant, C ε3 is the empirical constant, G b is the generation term of turbulent kinetic energy K caused by the mean water velocity gradient.

[0185] In one possible implementation, the processing module 205 is configured to process the control equations for calculating the geometric model in the fluid dynamics simulation analysis, including the momentum equation, wherein the momentum equation is expressed as follows:

[0186]

[0187] Where ρ is the fluid density, u i is the velocity component of the fluid in the i direction, u j is the velocity component of the fluid in the j direction, x i and xj is the Cartesian coordinate, P is the total pressure, τ ij is the stress tensor, pg i is gravity, F i For external force.

[0188] In a possible implementation, the analysis module 202 is configured to identify, through fluid dynamics simulation analysis, areas in the stern flow field where vortexes and pressure variations meet preset conditions, and determine noise reduction positions of the reinforcement ribs that require optimization.

[0189] The acquisition module 201 is used to obtain the preset design principles of the reinforcement ribs, where the design principles include optimizing fluid transition, structural adaptability, and structural durability.

[0190] The control module 203 is used to adjust the size of the reinforcement ribs through fluid simulation iterations so that the reinforcement ribs match the geometric features of the shell and the stern wing.

[0191] In a possible implementation, the output module 206 is configured to import the flow field velocity and direction data output by the fluid dynamics simulation into the acoustic finite element model.

[0192] The control module 203 is used to select a solver suitable for vibration and acoustic coupling analysis in the acoustic finite element model.

[0193] The control module 203 is used to set the solving frequency range of the solver and set the step sampling frequency to ensure that the calculation resolution is suitable for the target analysis.

[0194] The processing module 205 is used to perform acoustic-solid coupling analysis to calculate the vibration response of the stern hull of the underwater vehicle under fluid excitation, including the amplitude and frequency of the stiffeners.

[0195] In a possible implementation, the control module 203 is used to set the genetic algorithm, including setting the population size, the number of iterations, the crossover probability, and the mutation probability.

[0196] The processing module 205 is used to define the weight value of the main goal and the weight value of the secondary goal according to the fitness function. The main goal is to reduce vibration and acoustic radiation, and the secondary goal is to suppress horseshoe vortex.

[0197] The control module 203 is used to randomly generate multiple sets of initial design parameters and installation positions, and form a geometric model of the reinforcement according to the decoding results.

[0198] The simulation module 204 is used to obtain the strength and position changes of the horseshoe vortex by performing fluid dynamics simulation on the geometric model under each set of initial design parameters and installation positions.

[0199] The processing module 205 is used to import the results of each fluid dynamics simulation into the acoustic-solid coupling model to calculate the total sound source level and distribution characteristics of the vibration sound radiation.

[0200] The processing module 205 is used to calculate the fitness value for each set of initial design parameters and installation positions based on the results of the fluid dynamics simulation and the calculation results of the acoustic-solid coupling model, combined with the weight values ​​of the primary and secondary objectives.

[0201] The processing module 205 is used to determine the size, shape and installation position parameters of the reinforcement rib when the differences in the fitness values ​​of any adjacent groups of initial design parameters and installation positions are all less than a preset threshold.

[0202] It should be noted that the above embodiments provide devices that implement their functions using only the division of the above functional modules as examples. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the device and method embodiments provided in the above embodiments are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0203] The above is only an exemplary embodiment of the present disclosure and cannot be used to limit the scope of the present disclosure. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will easily think of other embodiments of the present disclosure. This application is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not recorded in the present disclosure. The description and examples are to be regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A method for reducing noise of the stern shell structure of an underwater vehicle, characterized in that: The method comprises: Obtain the structural data of underwater vehicles and vibration signals during operation; determining a noise reduction target for the underwater vehicle based on the vibration signal; Obtaining constraints for the underwater vehicle, the constraints including structural total weight limit constraints, prescribed strength and stiffness requirement constraints, and navigation stability and maneuverability; Based on fluid dynamics simulation, the flow field characteristics at the stern of the underwater vehicle and the formation of horseshoe vortices are analyzed; According to the structural data, a transition component, a vortex-eliminating fairing, and a reinforcing rib are provided for the underwater vehicle, wherein the transition component is used to suppress the formation of horseshoe vortices, and the vortex-eliminating fairing and the reinforcing rib are used to destroy the expansion of the longitudinal horseshoe vortex; The finite element method is combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation; Under the premise of satisfying the constraints, the size of the transition component and the installation position of the vortex-eliminating rectifier are optimized, and the design parameters and installation position of the reinforcing rib are further optimized using a genetic algorithm. According to the simulation results, the horseshoe vortex is suppressed and the vibration sound radiation is reduced; When the vibration sound radiation reaches the noise reduction target, the target setting position of the reinforcing rib is determined and output.

2. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 1, characterized in that: The analysis of the flow field characteristics of the stern of the underwater vehicle and the formation of the horseshoe vortex based on fluid dynamics simulation specifically includes: Acquire the created geometric model of the underwater vehicle; Meshing the computational domain of the geometric model and refining the mesh in the horseshoe vortex formation region to capture key flow phenomena, wherein the horseshoe vortex formation region includes the stern transition region and the stern wing region of the vehicle; Determining the fluid properties and boundary conditions of the fluid dynamics simulation; Performing fluid dynamics simulation analysis on the geometric model according to a turbulence model to obtain a velocity distribution of the stern flow field; Determining, based on the results of the fluid dynamics simulation analysis, a change in pressure gradient in a geometric area between the stern wing and the hull of the underwater vehicle, and identifying alternating high-pressure and low-pressure areas generated by horseshoe vortices; The position, strength and structure of the horseshoe vortex are identified based on the vorticity distribution diagram and streamline diagram of the fluid dynamics simulation analysis.

3. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 2, characterized in that: Before performing fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field, the method further includes: The standard k-ε model is used, assuming that the turbulent viscosity is isotropic, which is suitable for simulation under high Reynolds number conditions. The k-ε model is the turbulence model, and the K equation in the k-ε model is expressed as follows: Where ρ is the fluid density, μ is the fluid dynamic viscosity coefficient, and u j is the component of the average fluid velocity in the j direction, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr K is the Prandtl number of turbulent kinetic energy, p K is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, G b is the generation term of turbulent kinetic energy K caused by the average water velocity gradient, ρε is the dissipation term, and Y M is the compressibility correction term; The ε equation in the k-ε model is expressed as follows: Where ρε is the dissipation term, ρ is the fluid density, and u j is the component of the average fluid velocity in the j direction, μ is the fluid dynamic viscosity coefficient, x i and x j is the Cartesian coordinate, μ t is the turbulent viscosity, Pr ε is the Prandtl number of turbulent dissipation rate, C1 is an empirical constant, S ε is the effect of turbulent shear on turbulent dissipation rate ε, C2 is an empirical constant, ν is molecular viscosity, C ε1 is the empirical constant, C ε3 is the empirical constant, G b is the generation term of turbulent kinetic energy K caused by the mean water velocity gradient.

4. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 2, characterized in that: The performing of fluid dynamics simulation analysis on the geometric model according to the turbulence model to obtain the velocity distribution of the stern flow field specifically includes: The control equations used to calculate the geometric model in the fluid dynamics simulation analysis include the momentum equation, wherein the momentum equation is expressed as follows: Where ρ is the fluid density, u i is the velocity component of the fluid in the i direction, u j is the velocity component of the fluid in the j direction, x i and x j is the Cartesian coordinate, P is the total pressure, τ ij is the stress tensor, pg i is gravity, F i For external force.

5. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 1, characterized in that: The step of providing the reinforcement ribs of the underwater vehicle according to the structural data specifically includes: Identify, through the fluid dynamics simulation analysis, areas in the stern flow field where eddies and pressure changes meet preset conditions, and determine locations where the reinforcement ribs need to be optimized for noise reduction; Obtaining preset design principles for the reinforcement, wherein the design principles include optimizing fluid transition, structural adaptability, and structural durability; The size of the reinforcement rib is adjusted through fluid simulation iteration to match the geometric features of the shell and the stern wing.

6. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 1, characterized in that: The application of the finite element method combined with acoustic-solid coupling analysis to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation specifically includes: Importing the flow field velocity and direction data output by the fluid dynamics simulation into the acoustic finite element model; In the acoustic finite element model, select a solver suitable for vibration and acoustic coupling analysis; Setting the frequency range of the solver and setting the step sampling frequency to ensure that the calculation resolution is suitable for the target analysis; An acoustic-structure coupling analysis is performed to calculate the vibration response of the stern shell of the underwater vehicle under fluid excitation, including the amplitude and frequency of the stiffener.

7. The method for reducing noise of the stern hull structure of an underwater vehicle according to claim 1, characterized in that: The design parameters and installation position of the reinforcement ribs are further optimized using a genetic algorithm. According to the simulation results, the horseshoe vortex is suppressed and the vibration sound radiation is reduced, specifically including: Setting the genetic algorithm, including setting the population size, number of iterations, crossover probability, and mutation probability; Defining a weight value of a primary objective and a weight value of a secondary objective according to a fitness function, wherein the primary objective is to reduce the vibration acoustic radiation, and the secondary objective is to suppress horseshoe vortices; randomly generating multiple sets of initial design parameters and installation positions, and forming a geometric model of the reinforcement according to the decoding results; By performing fluid dynamics simulation on the geometric model under each set of initial design parameters and installation positions, the strength and position changes of the horseshoe vortex are obtained; Import the results of each fluid dynamics simulation into the acoustic-solid coupling model to calculate the total sound source level and distribution characteristics of vibration sound radiation; Calculating the fitness value for each set of initial design parameters and installation positions based on the results of the fluid dynamics simulation and the calculation results of the acoustic-solid coupling model, combined with the weight value of the primary objective and the weight value of the secondary objective; When the differences between the fitness values ​​of any adjacent groups of initial design parameters and installation positions are all less than a preset threshold, the size, shape and installation position parameters of the reinforcement rib are determined.

8. A noise reduction device for the stern shell structure of an underwater vehicle, characterized in that: The device comprises an acquisition module (201), an analysis module (202), a control module (203), a simulation module (204), a processing module (205) and an output module (206), wherein: The acquisition module (201) is used to acquire structural data of the underwater vehicle and vibration signals during operation; The analysis module (202) is used to determine a noise reduction target for the underwater vehicle based on the vibration signal; The acquisition module (201) is used to acquire the constraint conditions for the underwater vehicle, wherein the constraint conditions include the total weight limit constraint of the structure, the specified strength and stiffness requirement constraint, and the navigation stability and maneuverability; The analysis module (202) is used to analyze the flow field characteristics of the stern of the underwater vehicle and the formation of horseshoe vortices based on fluid dynamics simulation; The control module (203) is used to set a transition component, a vortex elimination fairing and a reinforcing rib of the underwater vehicle according to the structural data, wherein the transition component is used to suppress the formation of horseshoe vortices, and the vortex elimination fairing and the reinforcing rib are used to destroy the expansion of the longitudinal horseshoe vortex; The simulation module (204) is used to simulate the vibration and acoustic radiation of the underwater vehicle under fluid excitation by applying the finite element method in combination with acoustic-solid coupling analysis; The processing module (205) is used to optimize the size of the transition component and the installation position of the vortex elimination rectifier under the premise of satisfying the constraint conditions, and further optimize the design parameters and installation position of the reinforcing rib using a genetic algorithm, and suppress the horseshoe vortex and reduce the vibration sound radiation according to the simulation results; The output module (206) is used to determine and output the target setting position of the reinforcing rib when the vibration sound radiation reaches the noise reduction target.

Images