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 and noise testing, and particularly relates to a method, device, medium and program for predicting the noise of a surface ship propeller based on excitation source reconstruction. Background Technique

[0002] The research on the rapid prediction of the 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 a prerequisite for their vibration reduction and noise reduction design. At present, the research on the propeller noise of surface ships is mainly based on computer simulation calculations, which require a large amount of time for modeling and calculation. Moreover, the prediction results can only reflect the vibration and acoustic characteristics of the propeller-shaft-ship to a certain extent, lack the verification of experimental data, and are difficult to obtain strong support.

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

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

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

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

[0007] Step 1: Determine the distribution of vibration sensing point positions and the positions of acoustic field assessment points;

[0008] Step 2: Determine the layout and size of the reconstruction source according to the distribution of vibration sensing point positions in Step 1;

[0009] Step 3: Obtain the vibration-acoustic transfer function from the reconstruction source to the acoustic field assessment points according to the positions of the acoustic field assessment points in Step 1, and number them in sequence;

[0010] Step 4: Based on the principle of transfer function invariance, establish a method for predicting the coupled vibration noise of the propeller shaft and hull structure based on the reconstructed excitation source according to the vibration-acoustic transfer function in Step 3;

[0011] Step 5: Based on the principle of energy superposition, realize the rapid prediction of the structural noise of the propeller-shaft-ship under multiple reconstruction sources according to Step 4;

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

[0013] Further, in Step 1 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 rotational speeds, and the vibration measurement points are numbered in sequence, i = 1:M, and the measured vibration acceleration is set as a P (p j , ω) and use this as the data input of the prediction system.

[0014] Further, in Step 2, determine the layout of the reconstruction sources: for the noise of the surface ship thruster, reconstruction sources are established at the main acting structure positions of the hull structure and numbered, j = 1:K, and the main acting structures of the hull structure include stern bearings, thrust bearings, and high-elastic couplings;

[0015] Determine the size of the reconstruction source: regard the thruster structure as a linear system, and establish the relationship between the acceleration of the excitation source p j on the reconstruction source to the vibration acceleration response A P (p j , ω) of the vibration at the measurement point r i on the shafting structure: P (r i , ω) of the vibration acceleration response A

[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 vibration transfer relationship matrix of dimension M*K between the excitation point p j and the shafting structure measurement point r i ;

[0018] Introduce the generalized inverse matrix and correct the inverse matrix 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, acoustic field assessment points are established. By applying a unit force to the reconstructed excitation source, the radiated sound pressure at the acoustic field assessment points is calculated based on FEM / BEM. The radiated sound pressure divided by the unit force gives the vibration-acoustic transfer function H from the reconstructed excitation source to the acoustic field assessment points j pa .

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

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

[0023]

[0024] In the formula, W rad is the radiated sound power of the propeller, ρc is the acoustic impedance of the propeller structure, S is the underwater radiating surface area of the structure, i.e., the wetted surface area of the propeller; σ rad is the radiation efficiency of the surface ship; is the root mean square vibration velocity of the wetted surface area of the propeller. By converting the reconstructed vibration response A p (r i , ω), the root mean square vibration velocity of the propeller main body structure is realized reconstruction;

[0025] There is the following relationship between the reconstructed excitation source F and the root mean square vibration velocity on the outer surface of the main body:

[0026]

[0027] In the formula, is the vibration-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 the above equation (3):

[0029]

[0030] Convert the radiation sound power calculation formula into a sound pressure calculation formula, establish the relationship between the sound pressure and the vibro-acoustic transfer function from the reconstructed source to the sound field assessment point, and according to the excitation source a P (p j , ω), the radiation sound pressure under the pulsating pressure of the thruster can be obtained through formula (6):

[0031] P(Q) = H1 pa |a1| + H2 pa |a2| +... H j pa |a P (p j , ω)| (6)

[0032] where P(Q) is the sound pressure of the noise generated by the thruster exciting the hull structure, and H j pa is the vibro-acoustic transfer function from the reconstructed excitation source to the sound field assessment point.

[0033] Furthermore, in step 5, according to the magnitude, quantity, and transfer function between the structures of the reconstructed excitation source, the vibro-acoustic transfer function between the reconstructed source and the reconstructed sound field is described as a complex-valued function containing real and imaginary part information, and the vibro-acoustic transfer function from the reconstructed source to the sound field assessment point and the equipment excitation source are subjected to matrix operations to achieve a rapid assessment of the underwater radiated noise under the action of thrust.

[0034] Furthermore, in step 6, on the basis of solving the vibration reconstructed excitation source, the coherence relationship under different rotational speeds or different frequency conditions of the thruster under typical ship speeds and loading conditions is calculated by means of numerical simulation;

[0035] When there is strong coherence between the two, the vibration component of the stern structure caused by the direct sound noise source of the thruster is used to correct the reconstructed source of the coupled vibration of the thruster exciting the stern, and the vibration transfer relationship between the distributed mechanical equipment reconstructed source considering the ship speed, draft depth, and thruster rotational speed factors and the radiation surface is established;

[0036] In the case of weak coherence between the two, a differential scheme is implemented according to the magnitude: when the magnitude of the noise source is large and has a significant impact on the sound field characteristics, the method of reconstructing the sound field from the vibration source is used for reference, and the noise characteristics caused by the direct sound of the thruster are calculated based on the sound-to-sound transfer function, and the direct sound noise source of the thruster is excited and the vector product of its sound-to-sound transfer function H' n1 with the underwater sound field is obtained 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;

[0037] Based on the vector superposition principle, the thruster noise considering the direct sound is obtained according to the following formula:

[0038]

[0039] wherein, A n is the sound pressure of the propeller noise considering the direct sound.

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

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

[0042] A computer program product, comprising a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of a method for predicting the noise of a surface ship propeller based on excitation source reconstruction are implemented.

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

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

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

[0046] Figure 2 is a schematic diagram of the specific execution of a method for predicting the noise of a surface ship propeller based on excitation source reconstruction and its application in an embodiment of the present invention;

[0047] Figure 3 is a schematic diagram of the evaluation result of the noise of a surface ship propeller in an embodiment of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0049] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

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

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

[0052] Step 2: Based on the vibration sensing points, determine the layout and size of the reconstruction source;

[0053] Step 3: Establish the sound field assessment points in Step 3. By applying a unit force to the reconstruction excitation source, the radiated sound pressure at the sound field assessment points is calculated based on FEM / BEM. The radiated sound pressure divided by the unit force is the vibration-acoustic transfer function H j pa from the reconstruction excitation source to the sound field assessment points, and number them in sequence;

[0054] Step 4: According to the principle of transfer function invariance, establish a method for predicting the coupled vibration noise of the propeller shafting and hull structure based on the reconstruction excitation source;

[0055] Step 5: According to the above method, realize the rapid prediction of the structural noise of the propeller shaft ship under multiple reconstruction sources;

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

[0057] This embodiment provides a method for predicting the noise of a propeller based on excitation source reconstruction, aiming to provide a method and application device for the rapid prediction of the noise of a ship propeller, solve the problems of real-time monitoring of the vibration of the propeller shafting of a ship and the rapid assessment of the radiated noise, and can effectively solve the measurement problems of the vibration and sound radiation noise of a water surface ship.

[0058] Embodiment 2. This embodiment further limits the method for predicting the noise of a water surface ship propeller based on excitation source reconstruction described in Embodiment 1. In this embodiment, Step 1 is further limited, specifically including:

[0059] For the propeller shaft ship structure, the vibration response of the vehicle at different speeds and rotational 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. The measured vibration acceleration is set as a P (p j , ω), which is used as the data input of the prediction system.

[0060] Specifically, the sound field assessment points are selected according to actual needs, and are generally selected 1 meter behind the propeller.

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

[0062] Embodiment 3 is a further limitation of the method for predicting the noise of a surface ship propeller based on the reconstruction of the excitation source 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 arrangement of the reconstruction source is specifically as follows:

[0064] Reconstruction sources are established at the main acting positions of the stern bearing, thrust bearing, high-elastic coupling, etc. with the hull structure, and these are numbered, j = 1:K.

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

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

[0067] In step 2, the size of the reconstruction source is specifically as follows:

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

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

[0070] H vP (r i p j , ω) is the vibration transfer relationship matrix with dimension M*K between the excitation point p j and the measurement point r of the shafting structure i .

[0071] Specifically, in practical engineering applications, to meet the unique solution condition, a generalized inverse matrix is introduced, and the inverse matrix is corrected 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 limits a method for predicting the noise of a surface ship propeller based on excitation source reconstruction described in Embodiment 1. In this embodiment, step 4 is further limited, specifically including:

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

[0075]

[0076] In the formula, W rad is the radiated sound power of the propeller, ρc is the acoustic impedance of the propeller structure, S is the underwater radiation surface area of the structure, i.e., the wetted surface area of the propeller; σ rad is the radiation efficiency of the surface ship; is the root mean square vibration velocity of the wetted surface area of the propeller. The reconstructed vibration response A p (r i , ω) is converted to realize the reconstruction of the root mean square vibration velocity of the propeller main body structure.

[0077] It can be seen from this that there is the following relationship between the reconstructed excitation source F and the root mean square vibration velocity of the outer surface of the main body :

[0078]

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

[0080] Substituting Equation (4) into the above Equation (3), we can obtain:

[0081]

[0082] Convert the radiation sound power calculation formula to the sound pressure calculation formula, establish the relationship between the sound pressure and the vibration-sound transfer function from the reconstruction source to the sound field assessment point. According to the known excitation source a P (p j , ω) magnitude, the radiation sound pressure under the propeller pulsating pressure can be obtained through Equation (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 sound pressure of the noise generated by the propeller exciting the hull structure, and H j pa is the vibration-sound transfer function from the reconstruction source to the sound field assessment point.

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

[0086] Embodiment 6, this embodiment further limits the method for predicting the noise of a surface ship propeller based on excitation source reconstruction described in Embodiment 1. In this embodiment, step 5 is further limited, specifically including:

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

[0088] Embodiment 7. This embodiment further limits a method for predicting the noise of a water surface ship propeller based on the reconstruction of the excitation source described in Embodiment 1. In this embodiment, Step 6 is further limited, specifically including:

[0089] The propeller noise mainly includes propeller rotation noise and cavitation noise. Rotation noise is the noise caused by the propeller operating in a non-uniform flow field (its frequency is mainly determined by the blade frequency). Once the shafting reaches the cavitation critical speed, the propeller noise becomes the main noise source of the water surface ship. The characteristics of cavitation noise are related to factors such as blade shape, area, and pitch distribution. At a specific rotational speed, the vortex frequency generated by the propeller blade is close to the natural frequency of the blade, and blade singing will occur.

[0090] On the basis of solving the vibration reconstruction source, due to the coherence between the direct sound "noise source" of the propeller and the excitation-coupled noise "vibration source" of the propeller, the coherence at different rotational speeds and different frequencies of the propeller under typical ship speeds and loading conditions is calculated by numerical simulation. When there is strong coherence between the two, the vibration component of the stern structure caused by the direct sound "noise source" of the propeller is used to correct the excitation-coupled vibration reconstruction source of the stern of the propeller, and further establish the vibration transfer relationship between the distributed mechanical equipment reconstruction source considering ship speed, draft depth, and propeller rotational speed factors and the radiation surface. In the case of weak coherence between the two, a differential scheme is implemented according to the magnitude: when the magnitude of the "noise source" is large and has a significant impact on the sound field characteristics, the method of reconstructing the sound field from the vibration source is used for reference, and the noise characteristics caused by the direct sound of the propeller are calculated based on the "sound-sound" transfer function, and the vector product of the direct sound noise source excitation of the propeller and the "sound-sound" transfer function H' between it and the underwater sound field n1 is obtained to obtain the underwater sound field characteristics induced by the direct sound noise 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.

[0091] Based on the vector superposition principle, the propeller noise considering the direct sound is obtained according to the following formula.

[0092]

[0093] In the formula, A n is the sound pressure of the propeller noise considering the direct sound.

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

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

[0096] In step S1, determine the distribution of vibration sensing points and the positions of acoustic field assessment points.

[0097] In step S101, first determine the distribution of vibration sensing points. For the propeller - shaft - ship structure, by evenly distributing the vibration sensing points on the surface of the stern cabin structure, measure the vibration responses of the vehicle at different speeds and rotational speeds, and sequentially number the vibration measurement points, i = 1:M. Let the measured vibration acceleration be a P (p j , ω), which is used as the data input of the prediction system.

[0098] In step S102, determine the positions and distributions of the acoustic field assessment points, and select the acoustic field assessment points according to actual needs.

[0099] In step S2, establish a reconstruction source based on the vibration sensing points established in S1.

[0100] In step S201, first determine the distribution and quantity of the reconstruction sources. For the noise of the water surface ship propeller, the exciting force of the propeller in the wake flow field is the bearing force generated by the fluid in the wake flow field acting on the propeller, and is transmitted to the hull structure through structures such as the shafting and bearings. Therefore, establish reconstruction sources at the main acting positions of the stern bearing, thrust bearing, high - elastic coupling, etc. with the hull structure, and number them, j = 1:K.

[0101] In step S202, determine the size of the reconstruction source. Consider the propeller structure as a linear system, and establish the relationship between the acceleration a P (p j , ω) of the excitation source pj on the structure of the reconstruction source to the hull surface and the vibration acceleration response A i of the measurement point r P (r i , ω) on the shafting structure.

[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 transfer function from the excitation point p j to the measurement point r iThe vibration transfer relation matrix with dimensions of M*K between them.

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

[0105] 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) (9)

[0106] In step S3, the vibration-acoustic transfer function from the reconstructed source to the sound field assessment point can be obtained through full-scale ship tests, numerical simulations, and parameter estimations, 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 full-scale ship tests. Under the navigation state of the surface ship propeller, after the propeller operates stably, the time-domain data of the vibration acceleration of the main shafting structure is measured using a shafting acceleration sensor. Through time-frequency transformation, the frequency-domain excitation load of the vibration acceleration of the surface ship propeller shafting is obtained. At the same time, the sound pressure at the underwater sound pressure assessment point of the surface ship propeller is measured using a hydrophone. The ratio of the sound pressure at the assessment point to the vibration acceleration of the propeller shafting structure is the vibration-acoustic transfer function between the two.

[0108] In step S302, based on a series of drawings such as the offset table, general arrangement plan, cabin distribution map, propeller structure diagram, and weight distribution of a specific surface ship propeller, a sound-vibration prediction model of the surface ship stern structure is established. The input load is the vibration acceleration data of the propeller shafting structure. The frequency-domain excitation load of the vibration acceleration of the propeller shafting structure can come from the data obtained through full-scale ship tests and bench tests. Through numerical simulation, the underwater sound pressure at the assessment 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 from the reconstructed source to the sound pressure assessment point of the surface ship propeller. It is also possible to directly apply a unit acceleration load at the reconstructed source position of the surface ship propeller model, calculate the underwater sound pressure at the assessment point when the unit acceleration load acts on the surface ship propeller, and directly obtain the vibration-acoustic transfer function from the reconstructed source to the sound pressure assessment point.

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

[0110]

[0111] In the formula, 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, based on the principle of transfer function invariance, a method for predicting propeller noise based on the reconstructed excitation source is established.

[0113] In S401, according to the principles of ship acoustics, there is the following relationship between the vibration velocity on the surface of the main body at the stern of the propeller and its radiated sound power:

[0114]

[0115] S is the underwater radiation surface area of the structure, i.e., the wetted surface area of the propeller; σ rad is the radiation efficiency of the surface ship; is the root mean square vibration velocity of the wetted surface area of the propeller. By converting the reconstructed vibration response A p (r i , ω), the root mean square vibration velocity of the main body structure of the propeller is realized reconstruction.

[0116] In S402, there is the following relationship between the reconstructed excitation source F and the root mean square vibration velocity on the outer surface of the main body :

[0117]

[0118] Substituting Equation (12) into the above Equation (11), Equation (13) can be obtained:

[0119]

[0120] In step S403, the obtained radiation 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 the propeller-excited hull structure noise based on the reconstructed source.

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

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

[0123] In step S5, the sound 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, quantity, and structure of the reconstructed excitation sources obtained in S2, the vibration-acoustic transfer function between the reconstructed source and the reconstructed sound field is described as a complex-valued function containing real part (amplitude) and imaginary part (phase) information. The vibration-acoustic transfer function from the reconstructed source to the sound pressure assessment point and the device excitation source are subjected to matrix operations to achieve a rapid assessment of the underwater radiated noise under the action of thrust.

[0124] In step S6, combined with Figure 2 , considering the direct sound of the propeller, calculate the radiated noise under the direct sound of the propeller according to the calculation, and based on the vector superposition principle, achieve a rapid assessment of the propeller noise considering the direct sound.

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

[0126] In step S602, select the propeller geometric model, determine the geometric key parameters; and establish the hull structure flow field domain and the propeller rotation area. Set the velocity inlet and pressure outlet in the hull structure flow field domain. The contact surface between the fluid domain and the rotation area is the interface. To eliminate the influence of boundary conditions on the numerical simulation results, expand the size of the fluid domain and set the outer boundary as a symmetric boundary; and according to the actual required flow velocity, based on the sampling theorem, determine the calculation time step from the upper limit of the calculation frequency, perform regional division, grid convergence verification, and calculation parameter setting on the calculation model; based on the large eddy simulation method (LES) combined with the FW-H equation, take the propeller blade as the sound source surface to obtain the direct sound of the propeller. Take the blade surface as the dipole sound source surface, and obtain the coherence of the propeller at different rotational speeds and different frequencies under typical ship speeds and loading conditions through the large eddy simulation method (LES) combined with the FW-H equation.

[0127] In step S603, on the basis of solving the vibration reconstruction source, due to the coherence between the "noise source" of the direct sound of the propeller and the "vibration source" of the propeller excitation coupling noise, calculate the coherence of the propeller at different rotational speeds and different frequencies under typical ship speeds and loading conditions through numerical simulation methods,

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

[0129] In the case of weak coherence between the two, a differential scheme is 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 method of reconstructing the sound field from the vibration source is used for reference, and the noise characteristics caused by the direct sound of the thruster are calculated based on the "sound-sound" transfer function, and the excitation of the direct sound noise source of the thruster is calculated and the vector product of its "sound-sound" transfer function H′ n1 with the underwater sound field 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 principle of vector superposition, the thruster noise considering the direct sound is obtained according to the following formula.

[0131]

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

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

[0134] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within 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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