A method and system for predicting far-field spatial directivity of underwater vehicle radiated noise

Abstract

The present application belongs to the technical field of ship radiation noise prediction, and discloses a method and system for predicting the far-field spatial directivity of underwater vehicle radiation noise. The present application obtains the surface normal frequency domain vibration velocity vector of the underwater vehicle; a plurality of equivalent sources are arranged inside the underwater vehicle to represent the noise radiation characteristics of the underwater vehicle; based on the surface normal frequency domain vibration velocity vector and the dipole matrix, the source strength vector of the equivalent source is solved; combined with the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, and the corresponding pitch angle and azimuth angle of the far-field observation point, the far-field spatial directivity information of the underwater vehicle radiation noise is calculated. The present application can realize real-time and rapid prediction of the far-field spatial directivity of underwater vehicle radiation noise under the premise of ensuring accuracy.

Description

Technical Field

[0001] This invention belongs to the field of ship radiated noise prediction technology, and more specifically, relates to a method and system for far-field spatial directivity prediction of underwater vehicle radiated noise. Background Technology

[0002] In engineering practice, predicting or calculating the far-field directivity of radiated noise from underwater vehicles faces numerous challenges. First, underwater vehicles have complex structures, containing various noise sources such as mechanical equipment and fluid-structure interaction surfaces. The distribution and interaction of these noise sources in three-dimensional space make modeling the radiated sound field exceptionally complex. More challenging is the fact that calculating the far-field directivity of radiated noise requires solving the three-dimensional Helmholtz equations and calculating the sound pressure levels at numerous field points. Traditional numerical methods, such as the boundary element method or the finite element method, while highly accurate, consume enormous computational resources, making them unsuitable for the rapid iteration requirements of engineering design. Furthermore, while some studies employ the equivalent source method, which can directly predict far-field radiated sound pressure using measured surface vibration velocity distributions and boasts relatively high computational efficiency, this method requires deploying a series of virtual distributed point sources. It cannot directly obtain the spatial directivity of the vehicle's far field from these distributed point sources; it necessitates first predicting the radiated sound pressure on the far-field spherical envelope surface using these distributed point sources, and then using these sound pressures to calculate the spatial directivity of the underwater vehicle's far field. This process involves a massive computational load, and the accuracy is limited by the number of equivalent sources.

[0003] How to significantly improve computational efficiency while ensuring accuracy, and achieve rapid prediction of the far-field spatial directivity of radiated noise from underwater vehicles, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] This invention provides a method and system for predicting the far-field spatial directivity of radiated noise of underwater vehicles, thereby solving the problem that existing technologies cannot achieve real-time and rapid prediction of the far-field spatial directivity of radiated noise of underwater vehicles while ensuring accuracy.

[0005] This invention provides a method for predicting the far-field spatial directivity of radiated noise from underwater vehicles, comprising the following steps: Obtain the surface normal frequency domain vibration velocity vector of the underwater vehicle; Multiple equivalent sources are deployed inside the underwater vehicle, and the noise radiation characteristics of the underwater vehicle are characterized by the equivalent sources. The source strength vector of the equivalent source is obtained by solving based on the surface normal frequency domain vibration velocity vector and dipole matrix. By combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the structure center of the underwater vehicle, and the pitch and azimuth angles corresponding to the far-field observation points, the far-field spatial directivity information of the underwater vehicle's radiated noise is calculated.

[0006] Preferably, obtaining the surface normal frequency domain velocity vector through experimental testing includes the following steps: The surface normal vibration displacement vector of an underwater vehicle was measured using distributed optical fiber measurement. By combining the surface normal vibration displacement vector and the circular frequency, the surface normal frequency domain vibration velocity vector of the underwater vehicle is calculated.

[0007] Preferably, obtaining the surface normal frequency domain velocity vector through numerical simulation includes the following steps: Establish an acoustic-vibration coupled finite element model of an underwater vehicle; Calculate the nodal displacement matrix of an underwater vehicle under a known excitation force; Extract the surface normal vibration displacement vector of the underwater vehicle from the nodal displacement matrix; By combining the surface normal vibration displacement vector and the circular frequency, the surface normal frequency domain vibration velocity vector of the underwater vehicle is calculated.

[0008] Preferably, the total number of equivalent sources matches the dimension of the surface normal frequency domain velocity vector.

[0009] Preferably, the source strength vector of the equivalent source is calculated using the following formula:

[0010] In the formula, This represents the source strength vector of the equivalent source. Represents a dipole matrix. express The inverse matrix, This represents the surface normal frequency domain vibration velocity vector.

[0011] Preferably, the far-field spatial directivity information is calculated using the following formula:

[0012] In the formula, Represents far-field spatial directional information. N Indicates the total number of equivalent sources. Indicates the first t Equivalent source The source of strength, j Represents the imaginary unit. k Indicates wave number, Indicates the first t The coordinate information of an equivalent source relative to the center of the underwater vehicle structure. i Indicates pitch angle, Indicates the azimuth angle.

[0013] Preferably, after obtaining the source strength vector of the equivalent source, the method further includes: By combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation point, the far-field radiated sound pressure of the underwater vehicle is calculated.

[0014] Preferably, the far-field radiated sound pressure is calculated using the following formula:

[0015] In the formula, This represents the far-field radiated sound pressure. j Represents the imaginary unit. oh Represents angular frequency. Indicates fluid density, N Indicates the total number of equivalent sources. Indicates the first t Equivalent source The source of strength, k Indicates wave number, Indicates the first t The coordinate information of an equivalent source relative to the center of the underwater vehicle structure. i Indicates pitch angle, Indicates azimuth. This represents the position vector of the far-field observation point. This represents the position vector of the structural center of the underwater vehicle.

[0016] On the other hand, the present invention provides a far-field spatial directivity prediction system for radiated noise of underwater vehicles, comprising: The vibration velocity acquisition unit is used to acquire the surface normal frequency domain vibration velocity vector of the underwater vehicle; The source strength calculation unit is used to solve for the source strength vector of the equivalent source based on the surface normal frequency domain vibration velocity vector and dipole matrix. The spatial directivity calculation unit is used to combine the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the structure center of the underwater vehicle, and the pitch and azimuth angles corresponding to the far-field observation points to calculate the far-field spatial directivity information of the underwater vehicle's radiated noise. The underwater vehicle radiated noise far-field spatial directivity prediction system is used to perform the steps in the underwater vehicle radiated noise far-field spatial directivity prediction method described above.

[0017] Preferably, the underwater vehicle radiated noise far-field spatial directivity prediction system further includes: The far-field radiated sound pressure calculation unit is used to calculate the far-field radiated sound pressure of the underwater vehicle by combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation point.

[0018] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention first obtains the surface normal frequency domain vibration velocity vector of an underwater vehicle; then, multiple equivalent sources are deployed inside the underwater vehicle to characterize its noise radiation features; based on the surface normal frequency domain vibration velocity vector and dipole matrix, the source strength vector of the equivalent source is obtained; subsequently, combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the structural center of the underwater vehicle, and the pitch and azimuth angles corresponding to the far-field observation points, the far-field spatial directivity information of the underwater vehicle's radiated noise is calculated. In other words, this invention proposes a novel scheme for calculating the far-field spatial directivity of radiated noise based on a distributed point source model. It can directly calculate the far-field spatial directivity of the underwater vehicle using surface vibration velocity data, without requiring the radiated sound pressure to be obtained first and then used to calculate the spatial directivity, as in existing research. Therefore, this invention can significantly reduce the computational load and greatly improve computational efficiency, enabling real-time and rapid prediction of the far-field spatial directivity of underwater vehicle radiated noise while maintaining accuracy. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a far-field spatial directivity prediction method for radiated noise of an underwater vehicle provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram illustrating the principle of a far-field spatial directivity prediction method for radiated noise of an underwater vehicle provided in Embodiment 1 of the present invention. Detailed Implementation

[0020] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0021] Example 1: Example 1 provides a method for predicting the far-field spatial directivity of radiated noise from underwater vehicles. See [link to example]. Figure 1 This includes the following steps: S1. Obtain the surface normal frequency domain vibration velocity vector of the underwater vehicle; S2. Multiple equivalent sources are deployed inside the underwater vehicle, and the noise radiation characteristics of the underwater vehicle are characterized by the equivalent sources. Based on the surface normal frequency domain vibration velocity vector and dipole matrix, the source strength vector of the equivalent source is obtained. S3. Combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation points, the far-field spatial directivity information of the underwater vehicle's radiated noise is calculated.

[0022] Example 1 can directly calculate the far-field spatial directivity of an underwater vehicle using surface vibration velocity data, instead of obtaining the radiated sound pressure first and then using the radiated sound pressure to calculate the spatial directivity as in existing research. Therefore, this invention can greatly reduce the amount of calculation and significantly improve the calculation efficiency, enabling real-time and rapid prediction of the far-field spatial directivity of underwater vehicle radiated noise while ensuring accuracy.

[0023] In step S1, the surface normal frequency domain velocity vector can be obtained through experimental testing, including the following steps: (1) The surface normal vibration displacement vector of the underwater vehicle was measured using distributed optical fiber measurement.

[0024] (2) The surface normal frequency domain vibration velocity vector of the underwater vehicle is calculated by combining the surface normal vibration displacement vector and the circular frequency.

[0025] Specifically, the surface normal frequency domain velocity vector of the underwater vehicle (that is, the global velocity vector of the underwater vehicle surface) is calculated using the following formula:

[0026] In the formula, This represents the surface normal frequency domain vibration velocity vector. j Represents the imaginary unit. oh Represents angular frequency. This represents the surface normal vibration displacement vector.

[0027] In S1, the surface normal frequency domain velocity vector can also be obtained through numerical simulation, including the following steps: (1) Establish an acoustic-vibration coupled finite element model of the underwater vehicle.

[0028] Specifically, an acoustic-vibration coupled finite element model of the underwater vehicle is established using the finite element method, as shown in the following equation.

[0029]

[0030] In the formula, The mass matrix of the structure (i.e., the underwater vehicle). The mass matrix of the fluid; Here is the damping matrix of the structure. Here is the acoustic damping matrix; Here is the stiffness matrix of the structure. Here is the stiffness matrix of the fluid; Here is the nodal displacement matrix. For sound pressure matrix, The coupling matrix between fluid and structure. for The transpose of the matrix, For fluid density, This represents the external excitation matrix of the structure.

[0031] Based on the above formula, the underwater vehicle acoustic-vibration coupled finite element model established in Example 1 includes the following model parameters: (a) Structural (i.e., underwater vehicle) parameters: mass matrix of the structure, damping matrix of the structure, stiffness matrix of the structure, nodal displacement matrix, external excitation matrix of the structure; (b) Fluid parameters: mass matrix of the fluid, acoustic damping matrix, stiffness matrix of the fluid, acoustic pressure matrix, fluid density; (c) Coupling parameters: coupling matrix between fluid and structure.

[0032] (2) Calculate the underwater vehicle under known excitation force The nodal displacement matrix below .

[0033] (3) From the nodal displacement matrix Extracting the surface normal vibration displacement vector of the underwater vehicle .

[0034] (4) Combining the surface normal vibration displacement vector and angular frequency oh The surface normal frequency domain vibration velocity vector of the underwater vehicle was calculated. .

[0035] Specifically, using the same method The surface normal frequency domain velocity vector is calculated.

[0036] Based on the above description, it can be seen that the surface normal frequency domain vibration velocity vector of the underwater vehicle can be obtained in S1 by using experimental testing methods or numerical simulation technology.

[0037] In S2, multiple equivalent sources are deployed inside the underwater vehicle. The noise radiation characteristics of the underwater vehicle are characterized by the equivalent sources. That is, a set of equivalent sources (distributed point sources) is used to characterize the noise radiation characteristics of the underwater vehicle. Setting the equivalent sources inside the vehicle can avoid singularities in subsequent calculations.

[0038] Furthermore, it is preferable to set the total number of equivalent sources to match the dimension of the surface normal frequency domain velocity vector, thus ensuring the uniqueness of the calculation results. Since the number of surface velocity nodes of an underwater vehicle is equal to the dimension of the surface normal frequency domain velocity vector, it can also be understood that the total number of equivalent sources matches the number of surface velocity nodes of the underwater vehicle.

[0039] Specifically, the source strength vector of the equivalent source is calculated using the following formula:

[0040] In the formula, This represents the source strength vector of the equivalent source. Represents a dipole matrix. express The inverse matrix.

[0041] The dipole matrix describes the linear mapping between the vibration velocity nodes on the structural surface and the equivalent source; that is, the dipole matrix characterizes the sound field transmission relationship between the vibration velocity nodes and the equivalent dipole source.

[0042] Dipole matrix The elements are calculated using the following formula:

[0043] In the formula, The first in the dipole matrix i line, number t Column matrix elements, For the surface of the underwater vehicle i The position vector of each vibrational velocity node For the first t Position vectors of equivalent sources; , Indicates position The unit's external normal direction; k Indicates wave number, , c The medium wave velocity.

[0044] In S3, the far-field spatial directivity information is calculated using the following formula:

[0045] In the formula, Represents far-field spatial directional information. N Indicates the total number of equivalent sources; Indicates the first t Equivalent source The source of strength, yes The first in t One element; Indicates the first t The coordinate information of an equivalent source relative to the center of the underwater vehicle structure. i Indicates pitch angle, Indicates the azimuth angle.

[0046] For details, see Figure 2 , Underwater vehicle structural center The coordinates are represented as , No. t Equivalent source The Cartesian three-dimensional coordinates are represented as Far-field observation point (i.e., field point) The Cartesian three-dimensional coordinates are represented as , i and These represent the pitch and azimuth angles in spherical coordinates, respectively.

[0047] For any given pitch and azimuth angle, the three-dimensional spatial directivity of the far-field acoustic radiation of an underwater vehicle can be calculated using the above formula.

[0048] In summary, Example 1 obtains the surface vibration velocity distribution characteristics of an underwater vehicle using either actual measurements or numerical simulations. Then, it calculates the source strength of each distributed point source on the underwater vehicle's surface based on these vibration velocity distribution characteristics. Finally, it calculates the far-field three-dimensional spatial directivity of the underwater vehicle based on the spatial coordinates and source strength of each distributed point source. Example 1 can directly calculate the far-field spatial directivity of an underwater vehicle using surface vibration velocity data, thereby significantly improving computational efficiency.

[0049] In addition to enabling real-time and rapid prediction of the far-field spatial directivity of underwater vehicle radiated noise while ensuring accuracy, Example 1 can also calculate the far-field radiated sound pressure of underwater vehicles.

[0050] Specifically, after obtaining the source strength vector of the equivalent source, the far-field radiated sound pressure of the underwater vehicle can be calculated by combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch angle and azimuth angle corresponding to the far-field observation point.

[0051] The far-field radiated sound pressure is calculated using the following formula:

[0052] In the formula, This represents the far-field radiated sound pressure (i.e., the far-field sound pressure of an underwater vehicle). (radiated sound pressure at the location). This represents the position vector of the far-field observation point. This represents the position vector of the structural center of the underwater vehicle.

[0053] In summary, the measured surface vibration velocity distribution characteristics of underwater vehicles are currently only used to establish distributed point source models of the vehicles, and cannot be used to calculate the far-field directivity of radiated noise. There is a methodological breakpoint between the distributed point source model and the directivity calculation. To address this issue, Example 1 aims to bridge the gap between the distributed point source model and the directivity method, proposing the aforementioned formula for calculating the far-field spatial directivity of radiated noise based on the distributed point source model. Using the surface vibration velocity distribution characteristics of the vehicle obtained through simulation calculations or experimental testing, an equivalent distributed point source model of the vehicle is established. Then, the proposed calculation formula is used to directly calculate the far-field spatial directivity of the underwater vehicle's radiated noise, significantly improving computational efficiency and enabling real-time and rapid prediction of the far-field spatial directivity of underwater vehicles. In other words, Example 1 optimizes the existing equivalent source method, forming a rapid calculation scheme for the far-field spatial directivity of underwater vehicle radiated noise. This solves the problems of complex calculation and low prediction efficiency in the current calculation of the spatial directivity of underwater vehicle radiated noise, and enables real-time and rapid prediction of the far-field spatial directivity of underwater vehicle radiated noise while ensuring accuracy. Furthermore, Example 1 can also calculate the far-field radiated sound pressure of the underwater vehicle.

[0054] Example 2: Example 2 provides a far-field spatial directivity prediction system for radiated noise of underwater vehicles, mainly comprising: The vibration velocity acquisition unit is used to acquire the surface normal frequency domain vibration velocity vector of the underwater vehicle; The source strength calculation unit is used to solve for the source strength vector of the equivalent source based on the surface normal frequency domain vibration velocity vector and dipole matrix. The spatial directivity calculation unit is used to calculate the far-field spatial directivity information of the underwater vehicle's radiated noise by combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation points.

[0055] In addition, Example 2 may also include: The far-field radiated sound pressure calculation unit is used to calculate the far-field radiated sound pressure of the underwater vehicle by combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation point.

[0056] The underwater vehicle radiated noise far-field spatial directivity prediction system provided in Example 2 is used to perform the steps in the underwater vehicle radiated noise far-field spatial directivity prediction method as provided in Example 1. Since the functions of each unit in Example 2 correspond to the steps in Example 1, they can be understood by referring to the description in Example 1, and will not be repeated here.

[0057] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for predicting the far-field spatial directivity of radiated noise from an underwater vehicle, characterized in that, Includes the following steps: Obtain the surface normal frequency domain vibration velocity vector of the underwater vehicle; Multiple equivalent sources are deployed inside the underwater vehicle, and the noise radiation characteristics of the underwater vehicle are characterized by the equivalent sources. Based on the surface normal frequency domain velocity vector and dipole matrix, the source strength vector of the equivalent source is obtained by solving. By combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the structure center of the underwater vehicle, and the pitch and azimuth angles corresponding to the far-field observation points, the far-field spatial directivity information of the underwater vehicle's radiated noise is calculated. By combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch and azimuth angles corresponding to the far-field observation point, the far-field radiated sound pressure of the underwater vehicle is calculated. The far-field spatial directivity information is calculated using the following formula: In the formula, Represents far-field spatial directional information. N Indicates the total number of equivalent sources. Indicates the first t One equivalent source The source of strength, j Represents the imaginary unit. k Indicates wave number, Indicates the first t The coordinate information of an equivalent source relative to the center of the underwater vehicle structure. θ Indicates pitch angle, Indicates the azimuth angle.

2. The method for predicting the far-field spatial directivity of radiated noise from underwater vehicles according to claim 1, characterized in that, The surface normal frequency domain velocity vector is obtained through experimental testing, including the following steps: The surface normal vibration displacement vector of an underwater vehicle was measured using distributed optical fiber measurement. By combining the surface normal vibration displacement vector and the circular frequency, the surface normal frequency domain vibration velocity vector of the underwater vehicle is calculated.

3. The method for predicting the far-field spatial directivity of radiated noise from underwater vehicles according to claim 1, characterized in that, Obtaining the surface normal frequency domain vibration velocity vector through numerical simulation includes the following steps: Establish an acoustic-vibration coupled finite element model of an underwater vehicle; Calculate the nodal displacement matrix of an underwater vehicle under a known excitation force; Extract the surface normal vibration displacement vector of the underwater vehicle from the nodal displacement matrix; By combining the surface normal vibration displacement vector and the circular frequency, the surface normal frequency domain vibration velocity vector of the underwater vehicle is calculated.

4. The method for predicting the far-field spatial directivity of radiated noise from underwater vehicles according to claim 1, characterized in that, The total number of equivalent sources matches the dimension of the surface normal frequency domain velocity vector.

5. The method for predicting the far-field spatial directivity of radiated noise from underwater vehicles according to claim 1, characterized in that, The source strength vector of the equivalent source is calculated using the following formula: In the formula, This represents the source strength vector of the equivalent source. Represents a dipole matrix. express The inverse matrix, This represents the surface normal frequency domain vibration velocity vector.

6. The method for predicting the far-field spatial directivity of radiated noise from underwater vehicles according to claim 1, characterized in that, The far-field radiated sound pressure is calculated using the following formula: In the formula, This represents the far-field radiated sound pressure. j Represents the imaginary unit. ω Represents angular frequency. Indicates fluid density, N Indicates the total number of equivalent sources. Indicates the first t One equivalent source The source of strength, k Indicates wave number, Indicates the first t The coordinate information of an equivalent source relative to the center of the underwater vehicle structure. θ Indicates pitch angle, Indicates azimuth. This represents the position vector of the far-field observation point. This represents the position vector of the structural center of the underwater vehicle.

7. A far-field spatial directivity prediction system for radiated noise of an underwater vehicle, characterized in that, include: The vibration velocity acquisition unit is used to acquire the surface normal frequency domain vibration velocity vector of the underwater vehicle; The source strength calculation unit is used to solve for the source strength vector of the equivalent source based on the surface normal frequency domain vibration velocity vector and dipole matrix. The spatial directivity calculation unit is used to combine the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the structure center of the underwater vehicle, and the pitch and azimuth angles corresponding to the far-field observation points to calculate the far-field spatial directivity information of the underwater vehicle's radiated noise. The far-field radiated sound pressure calculation unit is used to calculate the far-field radiated sound pressure of the underwater vehicle by combining the source strength vector of the equivalent source, the coordinate information of the equivalent source relative to the center of the underwater vehicle structure, the circular frequency, the fluid density, the radial distance between the far-field observation point and the center of the underwater vehicle structure, and the pitch angle and azimuth angle corresponding to the far-field observation point. The underwater vehicle radiated noise far-field spatial directivity prediction system is used to perform the steps in the underwater vehicle radiated noise far-field spatial directivity prediction method as described in any one of claims 1 to 6.

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