Water surface ship propeller noise forecasting method and device based on excitation source reconstruction, medium and program

Abstract

The invention discloses a method, a device, a medium and a program for forecasting noise of a water surface ship propeller based on excitation source reconstruction. The method comprises the following steps: firstly, determining vibration sensing point location distribution and sound field assessment point positions; determining the arrangement and size of a reconstruction source; obtaining vibration and sound transfer functions from the reconstruction source to the sound field assessment point, and numbering the functions in sequence; according to a transfer function invariance principle, establishing a propeller noise forecasting method based on a reconstructed excitation source; rapid prediction of the structural noise of the propeller shaft ship under multiple reconstruction sources is realized; the direct sound production coherence of the propeller is judged, if the direct sound production coherence is strong coherence, correction continues to be carried out to obtain vibration sound transfer functions from the reconstruction source to the sound field assessment point, and numbering is carried out in sequence; if the signal is weak coherence, a direct sound production noise source model is established based on a sound-sound transfer function, radiation noise under direct sound production of the propeller is obtained through calculation, and prediction of the propeller noise considering direct sound production is achieved based on the vector superposition principle. The method is suitable for ship thruster shafting vibration monitoring and thruster noise rapid forecasting and evaluation.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship vibration noise testing, and in particular relates to a method, device, medium and program for predicting surface ship propeller noise based on excitation source reconstruction. Background Art

[0002] The rapid prediction of propeller noise of surface ships is of great significance for improving the acoustic stealth performance of ships. Understanding the vibration and acoustic characteristics of surface ships is the prerequisite for their vibration and noise reduction design. At present, the research on propeller noise of surface ships is mainly based on computer simulation calculations, which requires a lot of time to model and calculate, and the prediction results can only reflect the vibration and acoustic characteristics of propeller-shaft-ship to a certain extent. It lacks the verification of experimental data and is difficult to obtain strong support.

[0003] Therefore, providing a method for surface ship propeller shaft vibration testing and propeller noise prediction is crucial to understanding surface ship propeller noise, thereby providing support for the development of surface ship vibration and noise reduction design. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of high cost and low accuracy of existing surface ship propeller noise testing technology, and to provide a surface ship propeller noise prediction method, device, medium and program based on excitation source reconstruction.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for predicting propeller noise of a surface ship based on excitation source reconstruction comprises the following steps:

[0007] Step 1: Determine the distribution of vibration sensing points and the locations of sound field assessment points;

[0008] Step 2: According to the distribution of vibration sensing points in step 1, determine the layout and size of the reconstruction source;

[0009] Step 3: According to the position of the sound field test point in step 1, obtain the vibration-acoustic transfer function from the reconstructed source to the sound field test point, and number them in sequence;

[0010] Step 4: According to the vibration-acoustic transfer function of step 3 and the principle of transfer function invariance, a propeller shaft system and hull structure coupled vibration noise prediction method based on reconstructed excitation source is established;

[0011] Step 5: According to step 4, based on the energy superposition principle, the propeller shaft ship structure noise rapid prediction under multiple reconstruction sources is realized;

[0012] Step 6: According to step 5, determine the coherence of the direct sound of the thruster. If it is strongly coherent, correct it back to step 3; if it is weakly coherent, establish a direct sound noise source model based on the acoustic transfer function, calculate the radiated noise under the direct sound of the thruster, and based on the principle of vector superposition, realize the prediction of thruster noise taking into account the direct sound.

[0013] Furthermore, in step 1, for the propeller-shaft ship structure, the vibration response of the vehicle at different speeds and rotation speeds is measured by evenly distributing the vibration sensing points on the surface of the stern cabin structure, and the vibration measuring points are numbered in sequence, i=1:M, and the measured vibration acceleration is set to a P (p j ,ω) and use it as the data input of the forecast system.

[0014] Furthermore, in step 2, the arrangement of the reconstruction source is established: for the surface ship propeller noise, the reconstruction source is established at the position of the main functional structure of the hull structure, and is numbered, j=1:K, the main functional structure of the hull structure includes the stern bearing, the thrust bearing and the high elastic coupling;

[0015] Establish the size of the reconstruction source: Consider the propeller structure as a linear system, and establish the vibration transfer function from the reconstruction source to the surface of the hull structure. j The acceleration is a P (p j ,ω) vibration and measuring point r on the shaft structure i Vibration acceleration response A P (r i ,ω) are related to each other:

[0016] A P (r i ,ω)=H vP (r i p j ,ω)*a P (p j ,ω) (1)

[0017] In the formula, H vP (r i p j ,ω) is the excitation point p j And shaft structure measuring point r i The vibration transfer relationship matrix with dimension M*K between them;

[0018] The generalized inverse matrix is ​​introduced, and the inverse matrix is ​​modified based on the least squares method to obtain the excitation source vector:

[0019] a P (p j ,ω)=[[H vP (ri p j ,ω)] H [H vP (r i p j ,ω)]] -1 [H vP (r i p j ,ω)] H *A P (r i ,ω) (2).

[0020] Furthermore, in step 3, the sound field assessment point is established, and the radiation sound pressure of the sound field assessment point is obtained by applying a unit force to the reconstructed excitation source based on FEM / BEM calculation. The radiation sound pressure is divided by the unit force to obtain the vibration-acoustic transfer function H from the reconstructed excitation source to the sound field assessment point. j pa .

[0021] Furthermore, the step 4 is specifically as follows:

[0022] According to the acoustic principle of surface ships, the relationship between the surface vibration velocity of the propeller body and its radiated sound power is as follows:

[0023]

[0024] Where W rad is the propeller radiated acoustic power, ρc is the acoustic impedance of the propeller structure, S is the underwater radiation surface area of ​​the structure, i.e., the propeller wet surface area; σ rad is the radiation efficiency of surface ships; is the root mean square vibration velocity of the propeller wet surface area, and the reconstructed vibration response A p (r i ,ω) to achieve the root mean square vibration velocity of the propeller main structure Reconstruction of

[0025] Reconstructed excitation source F and the root mean square vibration velocity of the outer surface of the main body The following relationship exists:

[0026]

[0027] In the formula, is the vibration transfer function from the reconstructed source to the outer surface of the main body, and a is the excitation magnitude of the reconstructed source.

[0028] Substitute equation (4) into equation (3) above:

[0029]

[0030] The calculation formula of radiated sound power is converted into the calculation formula of sound pressure, and the relationship between sound pressure and the vibration-acoustic transfer function from the reconstruction source to the sound field test point is established. P (p j ,ω), the radiated sound pressure under the thruster pulsating pressure is obtained by formula (6):

[0031]

[0032] Where P(Q) is the noise pressure generated by the propeller exciting the hull structure, H j pa To reconstruct the vibration-acoustic transfer function from the excitation source to the sound field assessment point.

[0033] Furthermore, in step 5, according to the transfer function between the size, number and structure of the reconstructed excitation source, the acoustic vibration transfer function between the reconstructed source and the reconstructed sound field is described as a complex function containing real and imaginary part information, and the acoustic vibration transfer function from the reconstructed source to the sound field assessment point is combined with the equipment excitation source through matrix operation to achieve rapid evaluation of underwater radiated noise under thrust.

[0034] Furthermore, in step 6, based on solving the vibration reconstruction excitation source, the coherence relationship of the propeller at different speeds or frequencies under the typical ship speed and loading state is calculated by numerical simulation method;

[0035] When there is a strong coherence between the two, the vibration component of the stern structure caused by the direct acoustic noise source of the propeller is used to correct the reconstruction source of the propeller-excited stern coupled vibration, and the vibration transfer relationship between the distributed mechanical equipment reconstruction source and the radiation surface is established considering the ship's speed, draft and propeller speed factors.

[0036] When the two are weakly correlated, differentiated solutions are implemented according to the magnitude: when the noise source magnitude is large and has a significant impact on the sound field characteristics, the vibration source reconstruction sound field method is used to calculate the noise characteristics caused by the direct sound of the propeller based on the sound-to-sound transfer function, and the excitation of the direct sound noise source of the propeller is calculated. and the acoustic transfer function H′ between it and the underwater acoustic field n1 The vector product of the noise source is used to obtain the underwater sound field characteristics induced by the direct sound source of the propeller. On the contrary, when the magnitude difference between the noise source and the vibration source is large, the influence of the noise source on the underwater sound field is directly ignored.

[0037] Based on the principle of vector superposition, the propeller noise taking into account the direct sound is obtained as follows:

[0038]

[0039] In the formula, A n To take into account the sound pressure of the propeller noise that emits direct sound.

[0040] A computer device / equipment / system comprises a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of a method for predicting surface ship propeller noise based on excitation source reconstruction.

[0041] A computer-readable storage medium stores a computer program / instruction, which, when executed by a processor, implements the steps of a method for predicting noise of a surface ship propeller based on excitation source reconstruction.

[0042] A computer program product includes a computer program / instruction, which, when executed by a processor, implements the steps of a method for predicting noise of a surface ship propeller based on excitation source reconstruction.

[0043] The beneficial effects of the present invention are:

[0044] The present invention proposes a propeller noise prediction method based on excitation source reconstruction, aiming to provide a method and application device for rapid prediction of ship propeller noise, and solve the problem of real-time monitoring of propeller shaft vibration and rapid evaluation of radiation noise. A surface ship propeller-shaft-ship vibration and acoustic radiation noise testing method of the present invention can effectively solve the measurement problem of surface ship vibration and acoustic radiation noise. The present invention is suitable for ship propeller shaft vibration monitoring and rapid prediction and evaluation of propeller noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the calculation flow of a method for predicting surface ship propeller noise based on excitation source reconstruction in the implementation of the present invention;

[0046] Figure 2 It is a schematic diagram of a surface ship propeller noise prediction method based on excitation source reconstruction and a specific implementation of the application in the implementation of the present invention;

[0047] Figure 3 The invention is a schematic diagram of the results of a surface ship propeller noise assessment. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings.

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0050] Embodiment 1: A method for predicting surface ship propeller noise based on excitation source reconstruction, the method comprising:

[0051] Step 1: Determine the distribution of vibration sensing points and the locations of sound field assessment points;

[0052] Step 2: Determine the layout and size of the reconstruction source based on the vibration sensing points;

[0053] Step 3: In step 3, the sound field assessment point is established. By applying a unit force to the reconstructed excitation source, the radiation sound pressure of the sound field assessment point is calculated based on FEM / BEM. The radiation sound pressure is divided by the unit force to obtain the vibration-acoustic transfer function H from the reconstructed excitation source to the sound field assessment point. j pa , and number them in sequence;

[0054] Step 4: According to the transfer function invariance principle, a prediction method for the coupled vibration noise of the propeller shaft system and hull structure based on the reconstructed excitation source is established;

[0055] Step 5: Based on the above method, the rapid prediction of propeller shaft ship structure noise under multiple reconstruction sources is realized;

[0056] Step 6: According to step 5, determine the coherence of the direct sound of the propeller. If it is strongly coherent, correct it back to step 3; if it is weakly coherent, establish a direct sound noise source model based on the acoustic transfer function, calculate the radiated noise under the direct sound of the propeller, and based on the vector superposition principle, realize the prediction of the propeller noise taking into account the direct sound; Figure 3 This is a comparison chart of the thruster noise source level calculated using this method and numerical simulation. It can be seen from the figure that the noise calculated by this method is consistent with the simulation calculation results in the 10-500Hz frequency band.

[0057] This embodiment provides a propeller noise prediction method based on excitation source reconstruction, aiming to provide a method and application device for rapid prediction of ship propeller noise, solve the difficult problem of real-time monitoring of ship propeller shaft vibration and rapid evaluation of radiated noise, and can effectively solve the measurement problem of surface ship vibration and acoustic radiation noise.

[0058] Embodiment 2: This embodiment further defines the surface ship propeller noise prediction method based on excitation source reconstruction described in embodiment 1. In this embodiment, step 1 is further defined, specifically including:

[0059] For the propeller-shaft ship structure, the vibration response of the vehicle at different speeds and rotation speeds is measured by evenly distributing the vibration sensing points on the surface of the stern cabin structure, and the vibration measurement points are numbered in sequence, i = 1: M, and the measured vibration acceleration is set to a P (p j,ω) is used as the data input of the forecasting system.

[0060] Specifically, the sound field assessment point is selected according to actual needs, generally 1 meter behind the thruster.

[0061] This embodiment provides a method for determining the distribution of vibration sensing points and the locations of sound field assessment points.

[0062] Embodiment 3: This embodiment further limits the surface ship propeller noise prediction method based on excitation source reconstruction described in embodiment 1. In this embodiment, the arrangement of the reconstruction source established in step 2 is further limited, specifically including:

[0063] In step 2, the establishment of the arrangement of the reconstruction sources specifically includes:

[0064] The reconstructed sources are established at the main action positions of the stern bearing, thrust bearing, high elastic coupling, etc. and the hull structure, and are numbered, j=1:K.

[0065] In this embodiment, for the propeller noise of the surface ship, the exciting force of the propeller in the stern wake field is the bearing force generated by the fluid in the wake field acting on the propeller, which is transmitted to the hull structure through structures such as the shaft system and bearings. Therefore, a reasonable arrangement method of the reconstruction source is provided.

[0066] Embodiment 4: This embodiment further limits the surface ship propeller noise prediction method based on excitation source reconstruction described in embodiment 3. In this embodiment, the size of the reconstructed source established in step 2 is further limited, specifically including:

[0067] In step 2, the establishment of the size of the reconstruction source specifically includes:

[0068] The propeller structure is regarded as a linear system, and the vibration transfer function from the reconstructed source to the hull structure surface is established. The acceleration of the excitation source pj on the structure is a P (p j ,ω) and the measuring point r on the shaft structure i Vibration acceleration response A P (r i ,ω).

[0069] A P (r i ,ω)=H vP (r i p j ,ω)*a P (p j ,ω) (1)

[0070] H vP (ri p j ,ω) is the excitation point p j And shaft structure measuring point r i The vibration transfer relationship matrix with dimension M*K between them.

[0071] Specifically, in practical engineering applications, in order to meet the unique solution condition, the generalized inverse matrix is ​​introduced, and the inverse matrix is ​​modified based on the least squares method to obtain the excitation source vector:

[0072] a P (p j ,ω)=[[H vP (r i p j ,ω)] H [H vP (r i p j ,ω)]] -1 [H vP (r i p j ,ω)] H *A P (r i ,ω) (2)

[0073] Embodiment 5: This embodiment further defines the surface ship propeller noise prediction method based on excitation source reconstruction described in embodiment 1. In this embodiment, step 4 is further defined, specifically including:

[0074] According to the acoustic principle of surface ships, the relationship between the surface vibration velocity of the propeller body and its radiated sound power is as follows:

[0075]

[0076] Where W rad is the propeller radiated acoustic power, ρc is the acoustic impedance of the propeller structure, S is the underwater radiation surface area of ​​the structure, i.e., the propeller wet surface area; σ rad is the radiation efficiency of surface ships; is the root mean square vibration velocity of the propeller wet surface area, and the reconstructed vibration response A p (r i ,ω) to achieve the root mean square vibration velocity of the propeller main structure reconstruction.

[0077] It can be seen that the reconstructed excitation source F and the root mean square vibration velocity of the outer surface of the main body The following relationship exists:

[0078]

[0079] In the formula, is the vibration transfer function from the reconstructed source to the outer surface of the main body, and a is the excitation magnitude of the reconstructed source.

[0080] Substituting formula (4) into the above formula (3), we can get:

[0081]

[0082] The calculation formula of radiated sound power is converted into the calculation formula of sound pressure, and the relationship between sound pressure and the vibration-acoustic transfer function from the reconstruction source to the sound field test point is established. According to the known excitation source a of S2 P (p j ,ω), the radiated sound pressure under the thruster pulsating pressure can be obtained by formula (6):

[0083] P(Q)=H1 pa |a1|+H2 pa |a2|+...H j pa |a P (p j ,ω)|(6)

[0084] Where P(Q) is the noise pressure generated by the propeller exciting the hull structure, H j pa To reconstruct the vibration-acoustic transfer function from the source to the sound field test point.

[0085] This embodiment provides a propeller noise prediction method based on a reconstructed excitation source according to the transfer function invariance principle.

[0086] Embodiment 6: This embodiment further defines the surface ship propeller noise prediction method based on excitation source reconstruction described in embodiment 1. In this embodiment, step 5 is further defined, specifically including:

[0087] The acoustic field characteristics under multi-source coupling should be the vector sum of the products of multiple reconstructed sources and their matching transfer functions in the complex domain. According to the size, number and transfer function between the structures of the reconstructed excitation sources, the acoustic vibration transfer function between the reconstructed source and the reconstructed sound field is described as a complex function containing real part (amplitude) and imaginary part (phase) information. The acoustic vibration transfer function from the reconstructed source to the sound field assessment point and the equipment excitation source are combined through matrix operations to achieve rapid evaluation of underwater radiated noise under thrust.

[0088] Embodiment 7: This embodiment further defines the surface ship propeller noise prediction method based on excitation source reconstruction described in Embodiment 1. In this embodiment, step 6 is further defined, specifically including:

[0089] The propeller noise mainly includes propeller rotation noise and cavitation noise. Rotation noise is the noise caused by the propeller running in an uneven flow field (its frequency is mainly determined by the blade frequency). Once the shaft system reaches the critical speed of cavitation, the propeller noise becomes the main noise source of surface ships. The characteristics of cavitation noise are related to factors such as blade shape, area, and blade pitch distribution. At a specific speed, the vortex frequency generated by the propeller blade is close to the natural frequency of the blade, which will produce propeller noise.

[0090] On the basis of solving the vibration reconstruction source, due to the coherence between the propeller direct sound "noise source" and the propeller excitation coupling noise "vibration source", the coherence of the propeller at different speeds and frequencies under the typical ship speed and loading state is calculated by numerical simulation. When there is a strong coherence between the two, the stern structure vibration component caused by the propeller direct sound "noise source" is used to correct the propeller excitation stern coupling vibration reconstruction source, and further establish the vibration transfer relationship between the distributed mechanical equipment reconstruction source and the radiation surface considering the ship speed, draft depth, and propeller speed factors. In the case of weak coherence between the two, a differentiated solution is implemented according to the magnitude: when the "noise source" magnitude is large and has a significant impact on the sound field characteristics, the vibration source reconstruction sound field method is used to refer to the noise characteristics caused by the propeller direct sound based on the "sound-sound" transfer function, and the propeller direct sound noise source excitation is calculated. and the "sound-sound" transfer function H′ between it and the underwater sound field n1 The vector product of the “noise source” and the “vibration source” is used to obtain the underwater sound field characteristics induced by the direct sound noise source of the thruster; on the contrary, when the magnitude difference between the “noise source” and the “vibration source” is large, the influence of the “noise source” on the underwater sound field is directly ignored.

[0091] Based on the principle of vector superposition, the thruster noise taking into account the direct sound is obtained as follows.

[0092]

[0093] In the formula, A n To take into account the sound pressure of the propeller noise that emits direct sound.

[0094] Embodiment 8: This embodiment is an example of a method for predicting propeller noise of a surface ship based on excitation source reconstruction as described above, and specifically includes:

[0095] Figure 1 The flowchart of a method for predicting propeller noise of a surface ship based on excitation source reconstruction according to an embodiment of the present invention comprises the following steps:

[0096] In step S1, the distribution of vibration sensing points and the locations of sound field assessment points are determined.

[0097] In step S101, the distribution of vibration sensing points is first determined. For the propeller-shaft-ship structure, the vibration sensing points are evenly distributed on the surface of the stern cabin structure to measure the vibration response of the vehicle at different speeds and rotation speeds, and the vibration measurement points are numbered in sequence, i=1:M, and the measured vibration acceleration is set to a P (p j ,ω) is used as the data input of the forecasting system.

[0098] In step S102, the positions and distribution of the sound field assessment points are determined, and the sound field assessment points are selected according to actual needs.

[0099] In step S2, a reconstruction source is established according to the vibration sensing points established in S1.

[0100] In step S201, the distribution and number of reconstructed sources are first determined. For the propeller noise of a surface ship, the exciting force of the propeller in the wake field of the stern is the bearing force generated by the fluid in the wake field acting on the propeller, which is transmitted to the hull structure through the shaft system and bearings. Therefore, the reconstructed sources are established at the main action positions of the stern bearing, thrust bearing, high elastic coupling, etc. and the hull structure, and are numbered, j=1:K.

[0101] In step S202, the size of the reconstruction source is determined. The propeller structure is regarded as a linear system, and the acceleration of the excitation source pj on the structure of the vibration-vibration transfer function from the reconstruction source to the surface of the hull structure is established as a P (p j ,ω) and the measuring point r on the shaft structure i Vibration acceleration response A P (r i ,ω).

[0102] A P (r i ,ω)=H vP (r i p j ,ω)*a P (p j ,ω) (8)

[0103] H vP (r i p j ,ω) is the excitation point p j And shaft structure measuring point r i The vibration transfer relationship matrix with dimension M*K between them.

[0104] Specifically, in practical engineering applications, in order to meet the unique solution condition, the generalized inverse matrix is ​​introduced, and the inverse matrix is ​​modified based on the least squares method to obtain the excitation source vector:

[0105] aP (p j ,ω)=[[H vP (r i p j ,ω)] H [H vP (r i p j ,ω)]] -1 [H vP (r i p j ,ω)] H *A P (r i ,ω) (9)

[0106] In step S3, the vibration-acoustic transfer function from the reconstructed source to the sound field assessment point can be obtained through actual ship testing, numerical simulation and parameter estimation, and numbered in sequence.

[0107] In step S301, if the vibration-acoustic transfer function from the reconstructed source to the sound field assessment point is obtained through the actual ship test. When the surface ship propeller is in the navigation state, after the propeller is running stably, the shaft system acceleration sensor is used to measure the time domain data of the vibration acceleration of the main shaft system structure, and the surface ship propeller propeller shaft system vibration acceleration frequency domain excitation load is obtained through time-frequency transformation. At the same time, the sound pressure of the underwater sound pressure assessment point of the surface ship propeller is measured by a hydrophone. The ratio of the sound pressure at the assessment point to the vibration acceleration of the propeller shaft system structure is the z vibration-acoustic transfer function between the two.

[0108] In step S302, a surface ship stern structure acoustic vibration prediction model is established based on a series of drawings such as the type value table, general layout diagram, cabin distribution diagram, propeller structure diagram and weight distribution of a specific surface ship propeller. The input load is the vibration acceleration data of the propeller shaft system structure. The frequency domain excitation load of the propeller shaft system structure vibration acceleration can come from the data obtained from the actual ship test and the bench test. Through numerical simulation, the sound pressure of the underwater test point of the surface ship propeller is calculated. The ratio of the sound pressure to the vibration acceleration at the reconstructed source position is the vibration-acoustic transfer function between the reconstructed source of the surface ship propeller and the sound pressure test point. It is also possible to directly load a unit acceleration load at the reconstructed source position of the surface ship propeller model, calculate the sound pressure of the underwater test point when the unit acceleration load of the surface ship propeller acts, and directly obtain the vibration-acoustic transfer function between the reconstructed source and the sound pressure test point.

[0109] In step S303, if the vibro-acoustic transfer function from the reconstructed source to the sound field assessment point is obtained by parameter estimation, the relevant parameters in formula (10) are estimated according to the definition of the vibro-acoustic transfer function between the ship's reconstructed source and the underwater sound pressure assessment point, and the known parameters of the ship, and the vibro-acoustic transfer function between the ship's reconstructed source c and the sound field assessment point is calculated.

[0110]

[0111] Where r is the distance from the propeller structure to the sound field assessment point, a p is the vibration acceleration at the reconstructed source.

[0112] In step S4, according to the transfer function invariance principle, a propeller noise prediction method based on the reconstructed excitation source is established.

[0113] In S401, according to the principle of ship acoustics, the vibration velocity of the propeller stern body surface and its radiated sound power have the following relationship:

[0114]

[0115] S is the underwater radiation surface area of ​​the structure, i.e. the wet surface area of ​​the propeller; σ rad is the radiation efficiency of surface ships; is the root mean square vibration velocity of the propeller wet surface area, and the reconstructed vibration response A p (r i ,ω) to achieve the root mean square vibration velocity of the propeller main structure reconstruction.

[0116] In S402, the excitation source F and the root mean square vibration velocity of the outer surface of the main body are reconstructed. The following relationship exists:

[0117]

[0118] Substituting formula (12) into the above formula (11), we can get formula (13):

[0119]

[0120] In step S403, the obtained radiated sound power calculation formula is converted into a sound pressure calculation formula, and the relationship between the sound pressure and the transfer function is established, thereby forming a rapid prediction and evaluation method for propeller-excited hull structure noise based on a reconstructed source.

[0121] P(Q)=H pa |a|(14)

[0122] Where: P(Q) is the noise pressure generated by the propeller exciting the hull structure; H pa is the vibration-acoustic transfer function from the reconstructed source to the sound field assessment point, and a is the size of the reconstructed source.

[0123] In step S5, the acoustic field characteristics under multi-source coupling should be the vector sum of the products of multiple reconstructed sources and their matching transfer functions in the complex domain. According to the transfer function between the size, number and structure of the reconstructed excitation source obtained in S2, the vibro-acoustic transfer function between the reconstructed source and the reconstructed sound field is described as a complex function containing real part (amplitude) and imaginary part (phase) information, and the vibro-acoustic transfer function between the reconstructed source and the sound pressure assessment point is combined with the equipment excitation source through matrix operation to achieve rapid evaluation of underwater radiated noise under thrust.

[0124] In step S6, combining Figure 2 , considering the direct sound of the thruster, the radiated noise under the direct sound of the thruster is obtained according to the calculation, and based on the principle of vector superposition, the rapid evaluation of the thruster noise taking into account the direct sound is realized.

[0125] In step S601, the propeller noise mainly includes propeller rotation noise and cavitation noise. Rotation noise is the noise caused by the propeller running in an uneven flow field (its frequency is mainly determined by the blade frequency). Once the shaft system reaches the cavitation critical speed, the propeller noise becomes the main noise source for surface ships. The characteristics of cavitation noise are related to factors such as blade shape, area, and blade pitch distribution. At a specific speed, the vortex frequency generated by the propeller blade is close to the blade natural frequency, which will produce propeller noise.

[0126] In step S602, the propeller geometry model is selected to determine the key geometry parameters; and the hull structure flow field and the propeller rotation area are established, and the velocity inlet and pressure outlet are set in the hull structure flow field. The contact surface between the fluid area and the rotation area is the interface. In order to eliminate the influence of the boundary conditions on the numerical simulation results, the size of the fluid domain is expanded, and the outer boundary is set as a symmetric boundary; and according to the actual required flow velocity, according to the sampling theorem, the calculation time step is determined by the upper limit of the calculation frequency, and the calculation model is divided into regions, the grid convergence is verified, and the calculation parameters are set; based on the large eddy simulation method (LES) combined with the FW-H equation, the propeller blade is used as the sound source surface to obtain the direct sound of the propeller. The blade surface is used as the dipole sound source surface, and the coherence of the propeller at different speeds and frequencies under the typical speed and loading state of the ship is obtained by the large eddy simulation method (LES) combined with the FW-H equation.

[0127] In step S603, based on the solution of the vibration reconstruction source, due to the coherence between the propeller direct sound "noise source" and the propeller excitation coupling noise "vibration source", the coherence of the propeller at different speeds and frequencies under the typical speed and loading state of the ship is calculated by numerical simulation method.

[0128] When there is a strong coherence between the two, the vibration component of the stern structure caused by the thruster's direct sound "noise source" is used to correct the thruster-excited stern coupled vibration reconstruction source, and further establish the vibration transfer relationship between the distributed mechanical equipment reconstruction source and the radiation surface considering factors such as ship speed, draft depth, and thruster speed.

[0129] When the two are weakly correlated, differentiated solutions are implemented according to the magnitude of the "noise source": when the magnitude of the "noise source" is large and has a significant impact on the sound field characteristics, the vibration source reconstruction sound field method is used to calculate the noise characteristics caused by the direct sound of the thruster based on the "sound-sound" transfer function, and the excitation of the direct sound noise source of the thruster is calculated. and the "sound-sound" transfer function H′ between it and the underwater sound field n1 The vector product of the “noise source” and the “vibration source” is used to obtain the underwater sound field characteristics induced by the direct sound noise source of the thruster; on the contrary, when the magnitude difference between the “noise source” and the “vibration source” is large, the influence of the “noise source” on the underwater sound field is directly ignored.

[0130] In step S7, based on the vector superposition principle, the propeller noise taking into account the direct sound is obtained according to the following formula.

[0131]

[0132] In the formula, is the vector size of the reconstruction source.

[0133] The present invention innovatively proposes a method for rapid prediction of propeller noise of a surface ship based on excitation source reconstruction, aiming to provide a method and application device for rapid prediction of propeller noise of a ship, and solve the problem of real-time monitoring of propeller shaft vibration and rapid evaluation of radiation noise of a ship. The present invention provides a method for testing propeller-shaft-ship vibration and acoustic radiation noise of a surface ship, which can effectively solve the measurement problem of vibration and acoustic radiation noise of a surface ship.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for predicting surface ship propeller noise based on excitation source reconstruction, characterized in that: The following steps are involved: Step 1: Determine the distribution of vibration sensing points and the locations of sound field assessment points; Step 2: According to the distribution of vibration sensing points in step 1, determine the layout and size of the reconstruction source; Step 3: According to the position of the sound field test point in step 1, obtain the vibration-acoustic transfer function from the reconstructed source to the sound field test point, and number them in sequence; Step 4: According to the vibration-acoustic transfer function of step 3 and the principle of transfer function invariance, a propeller shaft system and hull structure coupled vibration noise prediction method based on reconstructed excitation source is established; Step 5: According to step 4, based on the energy superposition principle, the propeller shaft ship structure noise rapid prediction under multiple reconstruction sources is realized; Step 6: According to step 5, determine the coherence of the direct sound of the propeller. If it is strongly coherent, correct it and return to step 3; If it is weakly coherent, a direct sound noise source model is established based on the acoustic-to-acoustic transfer function, the radiated noise under the direct sound of the propeller is calculated, and based on the vector superposition principle, the prediction of the propeller noise taking into account the direct sound is realized.

2. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: In step 1, for the propeller-shaft ship structure, the vibration response of the vehicle at different speeds and rotation speeds is measured by evenly distributing the vibration sensing points on the surface of the stern cabin structure, and the vibration measuring points are numbered in sequence, i=1:M, and the measured vibration acceleration is set to a P (p j ,ω) and use it as the data input of the forecast system.

3. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: In step 2, the arrangement of the reconstruction source is established: for the surface ship propeller noise, the reconstruction source is established at the position of the main functional structure of the hull structure, and is numbered, j=1:K, the main functional structure of the hull structure includes the stern bearing, the thrust bearing and the high elastic coupling; Establish the size of the reconstruction source: Consider the propeller structure as a linear system, and establish the vibration transfer function from the reconstruction source to the surface of the hull structure. j The acceleration is a P (p j ,ω) vibration and measuring point r on the shaft structure i Vibration acceleration response A P (r i ,ω) are related to each other: A P (r i ,ω)=H vP (r i p j ,ω)*a P (p j ,oh) (1) In the formula, H vP (r i p j ,ω) is the excitation point p j And shaft structure measuring point r i The vibration transfer relationship matrix with dimension M*K between them; The generalized inverse matrix is ​​introduced, and the inverse matrix is ​​modified based on the least squares method to obtain the excitation source vector: a P (p j ,ω)=[[H vP (r i p j ,oh)] H [H vP (r i p j ,oh)]] -1 [H vP (r i p j ,oh)] H *A P (r i ,ω) (2).

4. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: In step 3, a sound field assessment point is established. By applying a unit force to the reconstructed excitation source, the radiation sound pressure of the sound field assessment point is calculated based on FEM / BEM. The radiation sound pressure is divided by the unit force to obtain the vibration-acoustic transfer function H from the reconstructed excitation source to the sound field assessment point. j pa .

5. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: The step 4 is specifically as follows: According to the acoustic principle of surface ships, the relationship between the surface vibration velocity of the propeller body and its radiated sound power is as follows: Where W rad is the propeller radiated acoustic power, ρc is the acoustic impedance of the propeller structure, S is the underwater radiation surface area of ​​the structure, i.e., the propeller wet surface area; σ rad is the radiation efficiency of surface ships; is the root mean square vibration velocity of the propeller wet surface area, and the reconstructed vibration response A p (r i ,ω) to achieve the root mean square vibration velocity of the propeller main structure Reconstruction of Reconstructed excitation source F and the root mean square vibration velocity of the outer surface of the main body The following relationship exists: In the formula, is the vibration transfer function from the reconstructed source to the outer surface of the main body, and a is the excitation magnitude of the reconstructed source. Substitute equation (4) into equation (3) above: The calculation formula of radiated sound power is converted into the calculation formula of sound pressure, and the relationship between sound pressure and the vibration-acoustic transfer function from the reconstruction source to the sound field test point is established. P (p j ,ω), the radiated sound pressure under the thruster pulsating pressure is obtained by formula (6): P(Q)=H1 pa |a1|+H2 pa |a2|+...H j pa |a P (p j ,ω)| (6) Where P(Q) is the noise pressure generated by the propeller exciting the hull structure, H j pa To reconstruct the vibration-acoustic transfer function from the excitation source to the sound field assessment point.

6. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: In step 5, according to the transfer function between the size, number and structure of the reconstructed excitation source, the acoustic vibration transfer function between the reconstructed source and the reconstructed sound field is described as a complex function containing real and imaginary part information, and the acoustic vibration transfer function from the reconstructed source to the sound field assessment point is combined with the equipment excitation source through matrix operation to achieve rapid evaluation of underwater radiated noise under thrust.

7. The method for predicting surface ship propeller noise based on excitation source reconstruction according to claim 1 is characterized in that: In step 6, based on solving the vibration reconstruction excitation source, the coherence relationship of the propeller at different speeds or frequencies under the typical ship speed and loading state is calculated by numerical simulation method; When there is a strong coherence between the two, the vibration component of the stern structure caused by the direct acoustic noise source of the propeller is used to correct the reconstruction source of the propeller-excited stern coupled vibration, and the vibration transfer relationship between the distributed mechanical equipment reconstruction source and the radiation surface is established considering the ship's speed, draft and propeller speed factors. When the two are weakly correlated, differentiated solutions are implemented according to the magnitude: when the noise source magnitude is large and has a significant impact on the sound field characteristics, the vibration source reconstruction sound field method is used to calculate the noise characteristics caused by the direct sound of the propeller based on the sound-to-sound transfer function, and the excitation of the direct sound noise source of the propeller is calculated. and the acoustic transfer function H′ between it and the underwater acoustic field n1 The vector product of the noise source is used to obtain the underwater sound field characteristics induced by the direct sound source of the propeller. On the contrary, when the magnitude difference between the noise source and the vibration source is large, the influence of the noise source on the underwater sound field is directly ignored. Based on the principle of vector superposition, the propeller noise taking into account the direct sound is obtained as follows: In the formula, A n To take into account the sound pressure of the propeller noise that emits direct sound.

8. A computer device / equipment / system comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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