Method and device for calculating modal radiation efficiency of cylindrical body structure

Abstract

The application relates to a cylindrical main body structure modal radiation efficiency calculation method and device. The method comprises the following steps: providing a cylindrical main body structure whose modal radiation efficiency is to be calculated, and obtaining a modal function of the cylindrical main body structure; determining a structure radial vibration speed of the cylindrical main body structure based on the modal function of the cylindrical main body structure; determining a spatial mean square vibration speed, a far-field radiation sound pressure and a radiation sound power of the cylindrical main body structure based on the structure radial vibration speed; and calculating the modal radiation efficiency of the cylindrical main body structure by using a spatial integration method based on the spatial mean square vibration speed, the far-field radiation sound pressure and the radiation sound power of the cylindrical main body structure. The application can effectively realize the calculation of the modal radiation efficiency of the cylindrical structure and improve the convenience of the modal radiation efficiency calculation.

Description

Technical Field

[0001] This invention relates to a calculation method and apparatus, and more particularly to a method and apparatus for calculating the modal radiation efficiency of a cylindrical main structure. Background Technology

[0002] Cylindrical shapes are common in the main structures of underwater vehicles and aircraft. When excited, cylindrical main structures vibrate and radiate sound outwards. Radiation efficiency is an important parameter connecting vibration and sound radiation in the vibration and sound radiation of the main structure. In engineering problems, as long as the vibration characteristics and radiation efficiency of the main structure are obtained, its sound radiation characteristics can be evaluated.

[0003] Currently, the modal radiation efficiency of cylindrical structures is mostly solved using wavenumber domain integration methods. However, this method involves wavenumber domain truncation, and in practical applications, selecting the appropriate wavenumber interval is a challenge.

[0004] Therefore, how to effectively calculate the modal radiation efficiency of cylindrical structures is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method and apparatus for calculating the modal radiation efficiency of a cylindrical main structure, which can effectively realize the calculation of the modal radiation efficiency of a cylindrical structure and improve the convenience of modal radiation efficiency calculation.

[0006] According to the technical solution provided by this invention, a method for calculating the modal radiation efficiency of a cylindrical main structure is provided, wherein the method for calculating the modal radiation efficiency includes: Provide a cylindrical main structure for calculating the modal radiation efficiency, and obtain the modal function of the cylindrical main structure; Based on the modal functions of the cylindrical main structure, the radial vibration velocity of the cylindrical main structure is determined. Based on the radial vibration velocity of the structure, the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure are determined. Based on the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure, the modal radiation efficiency of the cylindrical main structure is calculated using the spatial integration method.

[0007] For the modal functions of the cylindrical main structure, we have:

[0008] in, For the modal functions of the cylindrical main structure, , All are modal numbers. For the surface axial coordinates of the cylindrical main structure. For the circumferential coordinates of the cylindrical main structure. For the axial modal functions of the cylindrical main structure, For the circumferential modal functions of the cylindrical main structure.

[0009] For the radial vibration velocity of the cylindrical main structure, we have:

[0010] in, The radial vibration velocity of the cylindrical main structure. The modal vibration amplitude of the cylindrical main structure.

[0011] For the spatial mean square vibration velocity of the cylindrical main structure, we have:

[0012] in, Let be the spatial mean square velocity.

[0013] For the far-field radiated sound pressure of the cylindrical main structure, we have:

[0014] in, This refers to the far-field radiated sound pressure. For the field point coordinates, The density of the acoustic medium, The speed of sound in the acoustic medium. The radius of the cylindrical main structure is... This refers to the length of the column in the cylindrical main structure. Angular frequency, It is the azimuth angle.

[0015] For the radiated sound power of the cylindrical main structure, we have:

[0016] in, This represents the radiated acoustic power.

[0017] For the modal radiation efficiency of the cylindrical main structure, we have:

[0018] in, For modal radiation efficiency, Let be the surface area of ​​the cylindrical main structure. .

[0019] Axial mode functions of the cylindrical main structure Configured as ; Circumferential modal functions of the cylindrical main structure Configured as .

[0020] The cylindrical main structure also includes the bow and stern structures at both ends of the cylindrical main structure, wherein... When calculating the modal radiation efficiency of the cylindrical main structure, the bow and stern structures are treated as rigid baffles.

[0021] A device for calculating the modal radiation efficiency of a cylindrical main structure includes a modal radiation efficiency calculator, wherein... For any cylindrical main structure, the modal radiation efficiency calculator uses the method described above to calculate the modal radiation efficiency.

[0022] The advantages of this invention are: the calculation method for modal radiation efficiency is clear, simple and quick, and can easily and accurately obtain the modal radiation efficiency of the cylindrical main body. It can be used to evaluate the acoustic radiation characteristics of the cylindrical main body, effectively realize the calculation of modal radiation efficiency of cylindrical structures, improve the convenience of modal radiation efficiency calculation, and thus guide the acoustic design of underwater vehicles and other structures with cylindrical main body configuration. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating one embodiment of the modal radiation efficiency calculation of the present invention.

[0024] Figure 2 This is a schematic diagram of one embodiment of the cylindrical main structure of the present invention.

[0025] Figure 3 This is a schematic diagram illustrating the establishment of cylindrical coordinates for the cylindrical main structure according to the present invention.

[0026] Figure 4 This is a simulation diagram of the modal radiation efficiency of the cylindrical main structure of the present invention.

[0027] Explanation of reference numerals in the attached drawings: 1-cylindrical main body, 2-first bow and stern body, and 3-second bow and stern body. Detailed Implementation

[0028] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0029] To effectively calculate the modal radiation efficiency of a cylindrical structure and improve the convenience of modal radiation efficiency calculation, in one embodiment of the present invention, the method for calculating the modal radiation efficiency of a cylindrical main structure includes: Provide a cylindrical main structure for calculating the modal radiation efficiency, and obtain the modal function of the cylindrical main structure; Based on the modal functions of the cylindrical main structure, the radial vibration velocity of the cylindrical main structure is determined. Based on the radial vibration velocity of the structure, the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure are determined. Based on the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure, the modal radiation efficiency of the cylindrical main structure is calculated using the spatial integration method.

[0030] Figure 2 An embodiment of a cylindrical main body structure is shown, consisting of... Figure 2 It can be seen that the cylindrical main structure is cylindrical, that is, it includes a cylindrical main body 1; generally, at both ends of the cylindrical main body 1, there are a first bow and stern body 2 and a second bow and stern body 3. The calculation of the modal radiation efficiency of the cylindrical main structure specifically refers to the calculation of the modal radiation efficiency of the cylindrical main body 1.

[0031] Figure 1 The diagram illustrates the calculation process for the modal radiation efficiency of a cylindrical main structure. During the calculation, for a given cylindrical main structure, it is necessary to obtain its modal functions. Specifically, for the modal functions of the cylindrical main structure, we have:

[0032] in, The modal functions are for the cylindrical main structure. For the axial modal functions of the cylindrical main structure, For the circumferential modal functions of the cylindrical main structure; , These are all modal numbers. For common simply supported structures, the modal number values ​​are: , ; For the surface axial coordinates of the cylindrical main structure. The coordinates are the circumferential coordinates of the cylindrical main structure.

[0033] When calculating modal radiation efficiency, a coordinate system needs to be established for the cylindrical main structure. Figure 3 The diagram illustrates one embodiment of the established coordinate system, where the origin is the center of one end face of the cylindrical main structure, and the Z-axis runs along the length of the cylindrical main structure. In specific implementation, the axial modal functions of the cylindrical main structure are... Can be Circumferential modal functions of the cylindrical main structure Can be .

[0034] In one embodiment of the present invention, the radial vibration velocity of the cylindrical main structure is as follows:

[0035] in, The radial vibration velocity of the cylindrical main structure. The modal vibration amplitude of the cylindrical main structure.

[0036] As can be seen from the following description, the modal velocity amplitude of the cylindrical main structure It is an intermediate value; its specific value does not affect subsequent calculations.

[0037] In one embodiment of the present invention, the spatial mean square vibration velocity of the cylindrical main structure is as follows:

[0038] in, Let be the spatial mean square velocity.

[0039] As can be seen from the above explanation, the spatial mean square velocity can be obtained. .

[0040] In one embodiment of the present invention, the far-field radiated sound pressure of the cylindrical main structure is as follows:

[0041] in, This refers to the far-field radiated sound pressure. For the field point coordinates, The density of the acoustic medium, The speed of sound in the acoustic medium. The radius of the cylindrical main structure is... This refers to the length of the column in the cylindrical main structure. It is the imaginary unit. It is the first derivative of the Hankel function of the first kind.

[0042] field point coordinates , Figure 3 The diagram shows the situation of a field point, where R is the distance between the field point and the origin, and the azimuth angle is... Let r be the angle between the line connecting the field point and the origin and the z-axis, and let r be the distance between the projection of the field point in the xoy plane and the origin O.

[0043] In practice, With angular frequency Speed ​​of sound and azimuth Related to this are:

[0044] Among them, angular frequency The range of values ​​for is generally selected based on the needs of the calculation; speed of sound The magnitude depends on the medium in which the structure is located. The first derivative of the Hankel function of the first kind... Specifically, it can be: , This is the first kind of Hankel function, and its value is... and Related to the first kind of Hankel function For details, please refer to page 264 of "Mathematical Physics Equations" (4th edition, edited by Liang Kunmiao), published by Higher Education Press.

[0045] In one embodiment of the present invention, the radiated acoustic power of the cylindrical main structure is as follows:

[0046] in, This represents the radiated acoustic power.

[0047] In practical implementation, angular frequency Speed ​​of sound and azimuth For details, please refer to the above explanation; it will not be repeated here. As can be seen from the sound radiation power, the radiated sound power is determined by the far-field sound pressure... It comes from points.

[0048] In one embodiment of the present invention, the modal radiation efficiency of the cylindrical main structure is as follows:

[0049] in, For modal radiation efficiency, Let be the surface area of ​​the cylindrical main structure. .

[0050] As can be seen from the above explanation, the modal radiation efficiency It can be determined by radiated acoustic power Surface area of ​​the cylindrical main structure Speed ​​of sound The density of the acoustic medium and spatial mean square vibration velocity The modal radiation efficiency can be calculated based on the corresponding expression above. The specific calculation expression can eliminate the spatial mean square velocity. and the modal vibration amplitude of the cylindrical main structure These two intermediate quantities.

[0051] In one embodiment of the present invention, the cylindrical main body structure further includes bow and stern structures at both ends of the cylindrical main body structure, wherein... When calculating the modal radiation efficiency of the cylindrical main structure, the bow and stern structures are treated as rigid baffles.

[0052] Figure 2 The illustration shows an embodiment of a cylindrical main structure and bow and stern structures at both ends. The specific treatment of the bow and stern structures as rigid baffles is the same as that of the existing method, which does not affect the calculation of the modal radiation efficiency of the cylindrical main structure.

[0053] In summary, a modal radiation efficiency calculation device for a cylindrical main structure can be obtained. In one embodiment of the present invention, it includes a modal radiation efficiency calculator, wherein... For any cylindrical main structure, the modal radiation efficiency calculator uses the method described above to calculate the modal radiation efficiency.

[0054] Specifically, the modal radiation efficiency calculator can be any commonly used computer equipment. The specific type of modal radiation efficiency calculator can be selected according to actual needs, based on its ability to meet the calculation requirements of modal radiation efficiency. For any cylindrical main structure, when calculating the corresponding modal efficiency using the modal radiation efficiency calculator, the specific calculation process can refer to the calculation process described above, and will not be repeated here.

[0055] Example Taking a cylindrical section of an underwater vehicle as an example, this paper details the calculation process of the corresponding modal radiation efficiency of the cylindrical section.

[0056] against Figure 2 and Figure 3 The diagram shows that the characteristic parameters of the cylindrical section are: length. ,radius Modal number And modal numbering At this point, the available mode functions for: .

[0057] Characterizing the radial vibration velocity of the cylindrical section using modal functions yields the structural radial vibration velocity. for: .

[0058] Based on structural radial vibration velocity Determine the structural spatial mean square vibration velocity of the cylindrical module. Then we have: .

[0059] For the far-field radiated sound pressure calculation of the cylindrical section, we have: the acoustic medium is water, and the density is... speed of sound ,frequency =10~2000Hz, frequency interval 2Hz .

[0060] Based on the far-field radiated sound pressure, the radiated sound power of the cylindrical section is calculated as follows:

[0061] .

[0062] Using spatial integration to calculate the modal radiation efficiency of the cylindrical section, we have: .

[0063] Figure 4 The diagram shows a simulation of the modal radiation efficiency of a cylindrical module calculated using spatial integration. Figure 4 In the graph, the horizontal axis represents frequency, and the vertical axis represents modal radiation efficiency. Figure 4 It can be seen that, at frequency Different modal radiation efficiencies are obtained at different times.

[0064] As can be seen from the above description, the calculation method of the present invention has clear steps and is simple and quick to operate when calculating modal radiation efficiency. It can conveniently and accurately obtain the modal radiation efficiency of the cylindrical structure body, and can be used to evaluate the acoustic radiation characteristics of the cylindrical structure body. It can effectively realize the calculation of modal radiation efficiency of cylindrical structure, improve the convenience of modal radiation efficiency calculation, and thus guide the acoustic design of underwater vehicles and other structures with cylindrical main body configuration.

[0065] 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 calculating the modal radiation efficiency of a cylindrical main structure, characterized in that, The method for calculating the modal radiation efficiency includes: Provide a cylindrical main structure for calculating the modal radiation efficiency, and obtain the modal function of the cylindrical main structure; Based on the modal functions of the cylindrical main structure, the radial vibration velocity of the cylindrical main structure is determined. Based on the radial vibration velocity of the structure, the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure are determined. Based on the spatial mean square vibration velocity, far-field radiated sound pressure, and radiated sound power of the cylindrical main structure, the modal radiation efficiency of the cylindrical main structure is calculated using the spatial integration method. For the modal functions of the cylindrical main structure, we have: in, For the modal functions of the cylindrical main structure, , All are modal numbers. For the surface axial coordinates of the cylindrical main structure. For the circumferential coordinates of the cylindrical main structure. For the axial modal functions of the cylindrical main structure, For the circumferential modal functions of the cylindrical main structure; For the radial vibration velocity of the cylindrical main structure, we have: in, The radial vibration velocity of the cylindrical main structure. The modal velocity amplitude of the cylindrical main structure; For the spatial mean square vibration velocity of the cylindrical main structure, we have: in, The mean square velocity in space; For the far-field radiated sound pressure of the cylindrical main structure, we have: in, This refers to the far-field radiated sound pressure. For the field point coordinates, The density of the acoustic medium, The speed of sound in the acoustic medium. The radius of the cylindrical main structure is... This refers to the length of the column in the cylindrical main structure. Angular frequency, It is the azimuth angle. R is the imaginary unit, and R is the distance between the field point and the origin of the coordinate system. For the radiated sound power of the cylindrical main structure, we have: in, For radiated acoustic power, It is the first derivative of the Hankel function of the first kind; For the modal radiation efficiency of the cylindrical main structure, we have: in, For modal radiation efficiency, Let be the surface area of ​​the cylindrical main structure. .

2. The method for calculating the modal radiation efficiency of a cylindrical main structure according to claim 1, characterized in that, Axial mode functions of the cylindrical main structure Configured as ; Circumferential modal functions of the cylindrical main structure Configured as .

3. The method for calculating the modal radiation efficiency of a cylindrical main structure according to claim 1, characterized in that, The cylindrical main structure also includes the bow and stern structures at both ends of the cylindrical main structure, wherein... When calculating the modal radiation efficiency of the cylindrical main structure, the bow and stern structures are treated as rigid baffles.

4. A device for calculating the modal radiation efficiency of a cylindrical main structure, characterized in that, Includes a modal radiation efficiency calculator, where, For any cylindrical main structure, the modal radiation efficiency calculator uses the method of any one of claims 1 to 3 to calculate the modal radiation efficiency.

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