A method for predicting in-water flow-induced structure-borne sound radiation of a flexible layer

Abstract

A method for predicting the sound radiation of a flexible layer laid water flow structure, the sound radiation calculation model of the flexible layer laid water flow structure is divided into model one and model two, the four-terminal acoustic impedance parameters are used to describe the relationship between the sound pressure and the vibration velocity of the inner and outer surfaces of the flexible layer, and the non-coherent wall plane wave superposition method is used to process the fluctuating pressure excitation of the turbulent boundary layer. Model one solves the vibration response of the outer surface and the excitation force transmitted to the inner surface under the assumption that the inner surface of the flexible layer is fixed; model two establishes a coupling equation to solve the vibration response by taking the excitation force as the structure input and considering the sound radiation reaction of the outer surface; and the complete sound radiation power is obtained by linearly superimposing the results of the two models. The present application can accurately describe the physical process of the flow-induced load transmitted to the surface of the structure through the flexible layer, realize the unified vibration-sound coupling solution of the flexible layer laid structure under the action of the outer surface flow-induced load, and provide an efficient and accurate new method for predicting the sound radiation of the flexible layer laid water flow structure in engineering.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic radiation calculation and fluid-structure acoustic coupling analysis technology for ships or underwater vehicles, and in particular to a method for predicting the acoustic radiation of underwater flow-induced structures with flexible layers. Background Technology

[0002] In the control of radiated noise from underwater structures such as ships and underwater vehicles, flexible layers (such as sound insulation layers and sound absorption layers) are often applied to the surface of the structure to reduce underwater radiated noise caused by reflected sound from the target or excited vibrations of the structure. The presence of the flexible layer transforms the structural surface from a single "structure-fluid" coupling interface into a dual-interface coupling system consisting of the inner surface of the flexible layer (connected to the structure) and the outer surface of the flexible layer (connected to the fluid), which significantly complicates its dynamic and acoustic behavior.

[0003] In existing technologies, underwater acoustic radiation analysis methods for flexible layer structures mainly include the following categories: 1) The flexible layer is equivalent to a modified structural model with added mass or added damping; 2) Simplify the flexible layer to an equivalent acoustic impedance boundary condition and perform acoustic boundary correction; 3) Use numerical methods such as finite element-finite element and finite element-boundary element combination for overall modeling and calculation.

[0004] However, the above method has the following technical problems: 1) Some methods only consider the additional mass or additional damping effect of the flexible layer on the structure, making it difficult to describe the acoustic and vibration transmission relationship between the inner and outer surfaces of the flexible layer at the same time; 2) When flow-induced loads (such as turbulent boundary layer pulsating pressure) act directly on the outer surface of the flexible layer, existing models cannot accurately depict the real physical process of the excitation being transmitted through the flexible layer to the surface of the structure. 3) In the calculation of sound radiation, the vibration sound radiation of the outer surface of the flexible layer and the reaction of the inner surface of the flexible layer on the structure are often treated separately, lacking a unified and closed solution framework. 4) In the prediction of flow-induced acoustic radiation at the engineering scale, the cost of directly using the full three-dimensional coupled numerical method is too high, making it difficult to promote its efficient application.

[0005] Therefore, it is necessary to develop a unified calculation method that can simultaneously describe the excitation transmission on the inner and outer surfaces of the flexible layer and the acoustic-vibration coupling effect of the structure-flexible layer-water medium, so as to improve the accuracy and engineering applicability of the prediction of flow-induced acoustic radiation of the flexible layer structure. Summary of the Invention

[0006] In response to the shortcomings of the existing production technology, the applicant provides a method for predicting acoustic radiation of a water-flow-induced structure with a flexible layer, thereby effectively solving the problem that it is difficult to model the external surface excitation and the structural vibration-acoustic radiation process in a unified manner under water-flow-induced loads on a structure with a flexible layer.

[0007] The technical solution adopted in this invention is as follows: A method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer includes the following steps: Step 101: Obtain the four-terminal acoustic impedance parameters between the inner and outer surfaces of the flexible layer; Step 102: Establish Model 1, namely the fluid pulsation excitation force transmission model. The flow-induced load is regarded as acting on the outer surface of the flexible layer. Under the assumption that the inner surface of the flexible layer is fixed, solve the vibration response of the outer surface of the flexible layer and the excitation force transmitted to the inner surface of the flexible layer. Step 103: Obtain the excitation pressure acting on the structure after the flow-induced load is transferred through the flexible layer; Step 104: Establish Model 2, namely the structure-flexible layer-water medium acoustic-vibration coupling model. Take the excitation force on the inner surface of the flexible layer obtained in Step 103 as the input excitation of the structure. At the same time, consider the acoustic radiation reaction caused by the vibration of the outer surface of the flexible layer. Establish the coupling equation between the vibration of the inner and outer surfaces of the flexible layer and the sound pressure. Solve the acoustic-vibration coupling response of Model 2. Step 105: Linearly superimpose the velocity response and sound pressure obtained from Model 1 and Model 2 to obtain the velocity and sound pressure response on the outer surface of the flexible layer in the real physical field, and then calculate the overall radiated sound power. Step 106: Complete the prediction of acoustic radiation from the water flow-induced structure with the flexible layer laid.

[0008] Its further technical solution lies in: In step 101, the four-terminal acoustic impedance parameters are obtained using the finite element method or the underwater acoustic tube test method.

[0009] In step 102, the flow-induced load is transformed into an excitation on a specific node using the incoherent wall plane wave superposition method. The acoustic radiation results are calculated by repeatedly constructing the load synthesized by L incoherent wall plane wave superposition, and the calculation results are averaged.

[0010] Take L 30-50 times.

[0011] In step 104, the acoustic-vibration coupling response of Model 2 is calculated using the three-dimensional acoustic-elastic method for ships.

[0012] The flexible layer can be an acoustic covering layer, a damping rubber layer, a multi-layer composite flexible acoustic laying layer, an equivalent acoustic impedance layer, or a combination thereof.

[0013] In step 101, the four-terminal acoustic impedance parameter matrix of the flexible layer is represented as: .

[0014] The underwater flow structure is a ship or underwater vehicle.

[0015] The beneficial effects of this invention are as follows: 1. This invention achieves a unified acoustic-vibration coupling solution for flexible layer structures under flow-induced loads on their outer surfaces: In existing technologies, when flexible layer structures are subjected to flow-induced loads such as turbulent boundary layer pulsating pressure, the excitation transmission on the outer surface of the flexible layer and the acoustic-vibration coupling response of the structure-flexible layer-water medium are often treated separately, lacking a unified solution framework. This invention innovatively proposes a dual-model linear decomposition and superposition strategy, decomposing the complete physical problem into a "fluid pulsating excitation force transmission model (Model 1)" and a "structure-flexible layer-water medium acoustic-vibration coupling model (Model 2)". After solving each model separately, the complete acoustic-vibration response is obtained through linear superposition. This method maintains the integrity of the physical process and achieves closed-loop solution of the models, overcoming the deficiency in existing technologies where excitation transmission and acoustic-vibration coupling are difficult to describe in a unified manner.

[0016] 2. This invention employs a four-terminal acoustic impedance parameter model to accurately characterize the physical process of flow-induced load transmission through the flexible layer: This invention employs a four-terminal acoustic impedance parameter matrix to describe the relationship between sound pressure and vibration velocity on the inner and outer surfaces of a flexible layer. These parameters can be accurately obtained through finite element analysis or underwater acoustic tube experiments. Compared to existing techniques that simplify the flexible layer to additional mass, additional damping, or equivalent acoustic impedance boundary conditions, the four-terminal parameter model can comprehensively describe the propagation, reflection, and dissipation characteristics of sound waves within the flexible layer, accurately depicting the actual physical process of flow-induced loads being transferred from the outer surface of the flexible layer to the inner surface (structural surface). Model 1 solves for the excitation force transferred to the structural surface under the assumption that the inner surface of the flexible layer is fixed. Model 2 then uses this excitation force as input and considers the acoustic radiation reaction from the outer surface, achieving the separation and unification of excitation transmission and acoustic-vibration coupling, significantly improving prediction accuracy.

[0017] 3. This invention efficiently handles the randomness of fluctuating pressures in the turbulent boundary layer, balancing accuracy and computational cost: Turbulent boundary layer pulsating pressure exhibits typical stochastic characteristics, making direct simulation of its acoustic radiation response using full three-dimensional numerical methods at the engineering scale extremely computationally expensive. This invention employs an incoherent wall-plane wave superposition method to transform the stochastic turbulent pulsating pressure field into a finite number (30-50 recommended) superposition of deterministic loads, calculating the acoustic radiation response separately and then statistically averaging. This method effectively characterizes the stochastic characteristics of turbulent boundary layer excitation while avoiding the enormous computational overhead of direct numerical simulation or large eddy simulation, offering significant computational efficiency advantages in engineering applications. Furthermore, this method is flexibly adaptable to different types of turbulent wall pressure spectrum models or CFD calculation results, demonstrating good versatility.

[0018] 4. This invention can simultaneously obtain structural vibration response and radiated acoustic power, meeting the needs of multi-objective evaluation: This invention, in its solution process, can obtain both the vibration response of the structural surface under the influence of the flexible layer (which can be used for structural strength, fatigue, and vibration control assessment) and the acoustic power radiated into the water by the structure (which can be used for acoustic stealth performance assessment). Model 1 provides the vibration velocity and sound pressure of the outer surface of the flexible layer, while Model 2 provides the vibration and sound pressure response after the structure-flexible layer coupling. By linearly superimposing these, complete information on structural vibration and sound radiation can be obtained simultaneously, meeting the comprehensive assessment needs of multiple objectives and multiple physics fields in engineering.

[0019] 5. This invention is based on a rigorous physical model, resulting in high prediction accuracy and strong engineering applicability: The three-dimensional acoustoelastic method for ships used in this invention can accurately reflect the elastic vibration characteristics of complex structures (such as ships and underwater vehicles) under fluid loads and their coupling effect with the fluid. It is a mature and reliable method for predicting acoustic radiation from underwater structures. The four-terminal acoustic impedance parameters can be accurately calibrated based on the actual flexible layer configuration through finite element calculations or underwater acoustic tube experiments. The incoherent wall plane wave superposition method can reasonably set the wavenumber domain range and superposition number according to the actual flow field conditions. The entire technical solution is based on a rigorous physical model and mature numerical methods, and its prediction accuracy is better than that of empirical formulas or simplified equivalent models.

[0020] 6. This invention can be easily integrated into existing engineering software, and has high application value: The technical solution of this invention features modularity: the four-terminal acoustic impedance parameters can be independently acquired and formed into a database; the solution of Model 1 can be encapsulated as an independent module; Model 2 can directly call existing ship three-dimensional acoustic elasticity calculation programs; the generation of incoherent wall plane wave loads and the statistical averaging of results can be written as pre- and post-processing scripts. Therefore, this invention can be easily integrated into existing ship underwater acoustic radiation prediction and control analysis software systems without requiring disruptive changes to the core software architecture, and has good engineering promotion value and commercialization prospects.

[0021] 7. This invention has a wide range of applications, extending to air media and other structural forms: This invention describes a typical application scenario using underwater structures (ships, underwater vehicles), but its technical principles are equally applicable to the prediction of acoustic radiation from flow-induced structures in air. Furthermore, this invention does not limit the specific configuration of the flexible layer; it is applicable to acoustic covering layers, damping rubber layers, multi-layer composite flexible acoustic laying layers, equivalent acoustic impedance layers, and any combination thereof, exhibiting good versatility and scalability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the acoustic radiation calculation model of a water flow-induced structure with a flexible layer provided by the present invention.

[0023] Figure 2 This is a schematic diagram of the fluid pulsation excitation force transmission model (Model 1) of the present invention.

[0024] Figure 3 This is a schematic diagram of the acoustic-vibration coupling model (Model 2) of the structure-flexible layer-water medium of the present invention.

[0025] Figure 4 The flowchart for calculating the acoustic radiation of a water-flow-induced structure with a flexible layer provided by the present invention is shown.

[0026] Wherein: 100, structure; 200, flexible layer; 300, fluid pulsation; 400, fixed boundary; 500, load synthesized by superposition of single incoherent wall plane waves. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0028] like Figures 1-4 As shown in the figure, this embodiment provides a method for predicting acoustic radiation of a water flow-induced structure with a flexible layer 200, the specific steps of which are as follows: Step 101: Obtain the four-terminal acoustic impedance parameters between the inner and outer surfaces of the flexible layer 200; The acoustic impedance parameters at four ends between the inner and outer surfaces of the flexible layer 200 were obtained using calculation methods such as the finite element method or by underwater acoustic tube testing. The definitions of sound pressure (pressure) and vibration displacement are provided in [reference needed]. Figure 2 and Figure 3 As shown. The four-terminal acoustic impedance parameter matrix of the flexible layer 200 is represented as follows. .

[0029] Step 102: Solve for Model 1 to obtain the displacement and sound pressure on the upper surface of the flexible layer 200 and the sound pressure (pressure) on the lower surface. Will Figure 1The calculation model for acoustic radiation of a water-flow-induced structure with a flexible layer of 200 shown is decomposed into Model 1 (see...). Figure 2 ) and Model 2 (see Figure 3 ).

[0030] Figure 1 The pressure of the fluid pulsations 300 acting on the outer surface of the flexible layer 200 can be obtained by computational fluid dynamics methods, such as direct numerical simulation and large eddy simulation, or it can be described by semi-empirical formulas, such as the Corcos model and the Chase model. This invention employs an incoherent wall plane wave superposition method to transform the fluid pulsations 300 pressure into excitation at deterministic nodes. This method determines the wavenumber domain range by using flow field characteristics or structural filtering characteristics, and based on this wavenumber domain, a second wavenumber domain can be constructed. Load generated by superposition of incoherent wall plane waves with random phases , By repeatedly building L Next (in practical applications, it is recommended to take) L The acoustic radiation results of the load synthesized by superposition of incoherent wall plane waves (30-50 times) are calculated, and the calculation results are averaged to obtain the statistical results of acoustic radiation under pressure excitation of fluid pulsation 300.

[0031] With the first Load generated by superposition of incoherent wall plane waves with random phases For example: like Figure 2 In Model 1 shown, the load synthesized by the superposition of incoherent wall plane waves is... (abbreviated as) The force acts on the outer surface of the flexible layer 200, while the inner surface is a rigid, fixed boundary 400. Calculations are performed in the frequency domain, and for Model 1, the following matrix equations exist: (1) in, This represents the excitation pressure exerted on the inner surface of the flexible layer 200 under a load 500 generated by the superposition of a single incoherent wall plane wave. The acoustic pressure reaction force of the water medium on the outer surface of the flexible layer 200; For the outer surface of flexible layer 200 at the first Load generated by the superposition of sub-incoherent wall plane waves Normal vibration displacement caused by excitation This represents the corresponding normal vibration velocity; The normal vibration displacement of the inner surface of the flexible layer 200 is 0 in Model 1; , The excitation angular frequency.

[0032] From equation (1), we obtain the following two relations: (2) (3) The sound pressure level on the outer surface of the acoustic covering layer can be directly constructed using the acoustic boundary integral equation. Its vibration velocity The relationship, combined with equations (2) and (3), can be used to solve for the pressure on the inner surface of the acoustic covering layer. The sound pressure on the outer surface of the acoustic covering layer Vibration velocity of the outer surface of the acoustic coating .

[0033] Step 103: Obtain the excitation pressure acting on the structure 100 after the flow-induced load is transmitted through the flexible layer 200; The inner surface of the flexible layer 200 is laid on the structure 100, and there is a force-reaction relationship between it and the surface of the structure 100, which is calculated by Model 1. The reaction force is applied to the surface of structure 100, and is used as the excitation pressure on structure 100 after the flow-induced load is transmitted through the flexible layer 200, denoted as . .

[0034] Step 104: Calculate the acoustic-vibration coupling response of Model 2; Will The acoustic-vibration coupling response of Model 2 is calculated using the three-dimensional acoustoelastic method for ships, with the external excitation load applied to the surface of structure 100 in Model 2.

[0035] Based on the four-terminal acoustic impedance parameter model of flexible layer 200, the relationship between the normal vibration velocity and dynamic pressure of the inner and outer surfaces of flexible layer 200 can be established and transformed into the form of the following matrix equation: (4) In the formula, and These are the sound pressure (dynamic pressure) at the inner and outer surfaces of the flexible layer 200 in Model 2. and These are the normal vibration velocities of the inner and outer surfaces of the flexible layer 200 in Model 2.

[0036] From equation (4), we obtain the following two relations: (5) (6) By applying the three-dimensional acoustic elasticity calculation method of ships and combining the relationships (5) and (6), the vibration response of the inner and outer surfaces of the flexible layer 200 and the sound pressure at the inner and outer surfaces can be obtained.

[0037] Step 105: Calculation of overall radiated sound power; By linearly superimposing the velocity responses and sound pressures obtained from Model 1 and Model 2, the velocity response on the outer surface of the flexible layer 200 in the real physical field under flow-induced load excitation can be obtained. Harmony and sound pressure : (7) (8) Furthermore, by integrating along the outer surface of the flexible layer 200, the overall radiated acoustic power of the underwater flow-induced structure with the flexible layer 200 laid on it can be obtained as follows: (9) In the formula, To denote the real part of a complex number, the superscript " " indicates taking the conjugate of a complex number.

[0038] For the wall pressure field realized by the incoherent wall plane wave method used here, Equation (9) is only the calculation result of the load 500 under the superposition and synthesis of a single incoherent wall plane wave. Equations (1)-(9) are calculated repeatedly. L Second-rate, And take the average of the final sound radiation result (9). ,when When the value is sufficiently large, the equation converges to the statistical results of acoustic radiation under the excitation of real turbulent boundary layer pulsating pressure.

[0039] Step 106: Complete the prediction of acoustic radiation of the underwater flow-induced structure with the flexible layer 200 laid.

[0040] The "flexible layer" mentioned in this embodiment refers to a flexible acoustic component laid on the outer surface of a structure to regulate the vibration characteristics of the structure and its underwater acoustic radiation characteristics. It can be manifested as an acoustic covering layer, a damping rubber layer, a multi-layer composite flexible acoustic laying layer, an equivalent acoustic impedance layer, or a combination thereof.

[0041] This embodiment innovatively proposes to decompose the calculation model of the acoustic radiation of the structure in water with a flexible layer into a fluid pulsation excitation force transmission model (i.e., the excitation model of the outer surface of the flexible layer, referred to as Model 1) and a structure-flexible layer-water medium acoustic vibration coupling model (i.e., the coupling model of the inner surface of the flexible layer-structure, referred to as Model 2).

[0042] In this embodiment, for underwater structures with flexible layers, an excitation model of the outer surface of the flexible layer and a coupling model of the inner surface of the flexible layer and the structure are established respectively. The acoustic impedance parameters at the four ends of the flexible layer are used to describe the relationship between the sound pressure (pressure) and vibration velocity on its inner and outer surfaces.

[0043] In this embodiment, the flow-induced load is regarded as acting on the outer surface of the flexible layer in the excitation model. Under the assumption that the inner surface of the flexible layer is fixed, the vibration response of the outer surface of the flexible layer and the excitation force transmitted to the inner surface (structural surface) are solved.

[0044] In this embodiment, the calculated excitation force of the inner surface of the flexible layer is used as the input excitation of the structure in the coupled model of the inner surface of the flexible layer. At the same time, the acoustic radiation reaction caused by the vibration of the outer surface of the flexible layer is considered, and the coupling equation between the vibration of the inner and outer surfaces of the flexible layer and the sound pressure is established.

[0045] This embodiment achieves the real transfer of flow-induced load from the outer surface of the flexible layer to the structure by linearly superimposing and uniformly solving the sound pressure and vibration velocity in the two models mentioned above. Based on this, the acoustic-vibration coupling response and the sound power radiated into the water after the flexible layer is laid on the structure are obtained.

[0046] This embodiment is also extended to physical scenarios in the air, and is a calculation method for acoustic radiation caused by the pulsating pressure of the turbulent boundary layer in water, under the condition that a flexible layer is laid on the wet surface of the structure.

[0047] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer, characterized in that: The following steps are included: Step 101: Obtain the four-terminal acoustic impedance parameters between the inner and outer surfaces of the flexible layer; Step 102: Establish Model 1, namely the fluid pulsation excitation force transmission model. The flow-induced load is regarded as acting on the outer surface of the flexible layer. Under the assumption that the inner surface of the flexible layer is fixed, solve the vibration response of the outer surface of the flexible layer and the excitation force transmitted to the inner surface of the flexible layer. Step 103: Obtain the excitation pressure acting on the structure after the flow-induced load is transferred through the flexible layer; Step 104: Establish Model 2, namely the structure-flexible layer-water medium acoustic-vibration coupling model. Take the excitation force on the inner surface of the flexible layer obtained in Step 103 as the input excitation of the structure. At the same time, consider the acoustic radiation reaction caused by the vibration of the outer surface of the flexible layer. Establish the coupling equation between the vibration of the inner and outer surfaces of the flexible layer and the sound pressure. Solve the acoustic-vibration coupling response of Model 2. Step 105: Linearly superimpose the velocity response and sound pressure obtained from Model 1 and Model 2 to obtain the velocity and sound pressure response on the outer surface of the flexible layer in the real physical field, and then calculate the overall radiated sound power. Step 106: Complete the prediction of acoustic radiation from the water flow-induced structure with the flexible layer laid.

2. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: In step 101, the four-terminal acoustic impedance parameters are obtained using the finite element method or the underwater acoustic tube test method.

3. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: In step 102, the flow-induced load is transformed into an excitation on a specific node using the incoherent wall plane wave superposition method. The acoustic radiation results are calculated by repeatedly constructing the load synthesized by L incoherent wall plane wave superposition, and the calculation results are averaged.

4. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 3, characterized in that: Take L 30-50 times.

5. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: In step 104, the acoustic-vibration coupling response of Model 2 is calculated using the three-dimensional acoustic-elastic method for ships.

6. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: The flexible layer can be an acoustic covering layer, a damping rubber layer, a multi-layer composite flexible acoustic laying layer, an equivalent acoustic impedance layer, or a combination thereof.

7. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: In step 101, the four-terminal acoustic impedance parameter matrix of the flexible layer is represented as: 。 8. The method for predicting acoustic radiation from a water-flow-induced structure with a flexible layer as described in claim 1, characterized in that: The underwater flow structure is a ship or underwater vehicle.

Images