CN115630446A - Rapid deduction method for real-time simulation of low-frequency radiation noise of underwater vehicle structure - Google Patents

Rapid deduction method for real-time simulation of low-frequency radiation noise of underwater vehicle structure Download PDF

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CN115630446A
CN115630446A CN202211662273.3A CN202211662273A CN115630446A CN 115630446 A CN115630446 A CN 115630446A CN 202211662273 A CN202211662273 A CN 202211662273A CN 115630446 A CN115630446 A CN 115630446A
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纪刚
张凤羽
赵鹏
唐永壮
吕晓军
潘雨村
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Naval University of Engineering PLA
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Abstract

The invention discloses a rapid deduction method for real-time simulation of low-frequency radiation noise of a structure of a submarine aircraft, which comprises the steps of firstly establishing an acoustic far-field spherical radiation noise spectrum model before dynamic simulation, and completing the prediction process of a vibration spectrum and a sound pressure spectrum on a fluid-solid coupling surface with the longest calculation time and the largest data storage requirement in advance; the underwater sound propagation rule is used as a deduction basis, an acoustic far-field spherical radiation noise spectrum model is used as input, azimuth direction factor prediction and distance attenuation factor prediction are carried out by utilizing an interpolation technology and an underwater sound attenuation rule respectively, the problem of calculation efficiency of predicting radiation noise by using large-scale fluid-solid vibration and boundary sound pressure data numerical integration is effectively solved, the used model data volume is small, and the prediction process is simple, so that the method is particularly suitable for being implanted into a yacht control dynamic simulation system. The method realizes the radiation noise forecast at a higher speed on the premise that the forecast precision is fully ensured, and meets the requirement of dynamic simulation of the radiation noise of the underwater vehicle in the sailing state.

Description

Rapid deduction method for real-time simulation of low-frequency radiation noise of underwater vehicle structure
Technical Field
The invention relates to the technical field of navigation simulation of an underwater vehicle, in particular to a rapid deduction method for low-frequency radiation noise real-time simulation of an underwater vehicle structure.
Background
The radiation noise of the structure of the underwater vehicle during underwater navigation is a concern of the research and development industry of the underwater vehicle, and in order to research and develop the underwater vehicle with low radiation noise, the radiation noise dynamic simulation of the structure of the underwater vehicle, namely the radiation noise dynamic simulation of the navigation state of the underwater vehicle, needs to be realized by matching with the boat operation control simulation in the research and development stage.
The yacht control simulation verifies the correctness of the yacht control model by forecasting the yacht control process, namely judging whether the yacht control process meets the development requirements or not by forecasting, recording and analyzing the state information of the position, the posture and the like of the underwater vehicle at each instant in real time. Because the speed of the control and forecast of the yacht is high, the forecast of each instantaneous state is measured in millisecond, so that the dynamic simulation can be adopted in a dynamic real-time simulation mode, and each instantaneous state of the underwater vehicle in the yacht control process can be recorded, and a dynamic effect is formed. The radiation noise dynamic simulation of the navigation state of the underwater vehicle needs to utilize each instantaneous position and attitude information to forecast a radiation sound pressure spectrum of a certain determined position in space of the underwater vehicle caused by vibration of the underwater vehicle under the action of mechanical excitation force, record the sound pressure spectrum and acoustic physical quantities derived from the sound pressure spectrum in a dynamic mode, and accordingly study and judge the radiation noise capability and research and development effects of the underwater vehicle.
However, the problem of radiation noise prediction of an underwater vehicle is the problem of multi-physical field coupling of interaction between an underwater structure and fluid, and at low frequency, the vibration wavelength of the underwater vehicle is much shorter than the acoustic wavelength of the fluid, so that the problem of large calculation amount and data storage amount and long prediction time exists when the radiation noise prediction is accurately carried out. This results in that the radiation noise forecast of the underwater vehicle structure can not be matched with the control forecast of the yacht, and the underwater vehicle is difficult to be implanted into a real-time simulation system to carry out dynamic simulation. Therefore, the radiation noise prediction of the underwater vehicle is separated from the control simulation of the yacht for a long time, and the radiation noise dynamic simulation of the underwater vehicle in the navigation state cannot be developed.
At present, the structural finite element coupling fluid boundary element technology is commonly used at home and abroad to forecast the low-frequency radiation noise of the underwater vehicle, and the technology is considered to be a relatively accurate forecasting technology without introducing excessive physical assumptions to a forecast object. However, this technique has a drawback of large numerical calculation amount and data storage amount: an underwater vehicle taking a plate shell as a main component generally has a vibration wavelength shorter than a fluid sound wavelength at a low frequency, and a huge number of structural finite element grids and boundary element grids are needed to characterize the vibration and sound pressure distribution characteristics of a structure on a fluid-solid coupling surface, so that large-scale matrix operation and result data storage are needed in the radiation noise prediction of the underwater vehicle. For example, for a cylindrical shell structure with the length of 36 meters and the diameter of 3.6 meters, when the excitation force frequency is 100Hz, the structural vibration wavelength is about 0.1 meter, so that the quantity of structural finite elements and fluid boundary elements which need to be used can meet the forecast accuracy requirement only when reaching 31267 units, in the corresponding fluid-solid coupling numerical operation, the occupied quantity of a magnetic disk required by intermediate storage data reaches more than 1T, and the operation of completing one frequency and one sound field position (field point) takes about 5 hours.
Therefore, if the dynamic simulation of the radiation noise of the navigation state of the underwater vehicle is to be carried out by directly utilizing the structural finite element coupling fluid boundary element technology, the dynamic simulation requirements cannot be met in both data storage capacity and forecasting speed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a rapid deduction method for real-time simulation of low-frequency radiation noise of a submarine structure, which can realize real-time synchronous matching of the submarine radiation noise simulation and the yacht control simulation and can be used for batch prediction of a radiation noise field of an underwater structure, thereby supporting dynamic simulation and technical research and development of the low-noise submarine.
In order to achieve the purpose, the invention designs a rapid deduction method for simulating the low-frequency radiation noise of a submersible vehicle structure in real time, which is characterized by comprising two stages of establishing an acoustic far-field spherical radiation noise spectrum model and rapidly deducing and forecasting the field point radiation sound pressure:
the stage of establishing the acoustic far-field spherical radiation noise spectrum model comprises the following steps:
s1, establishing a finite element and a fluid boundary element model of a submersible vehicle structure, establishing an acoustic far-field spherical radiation noise spectrum model, dividing a frequency band to be analyzed into a series of discrete frequencies, wherein the acoustic far-field spherical radiation noise spectrum model is used for representing a sound pressure spectrum of a grid node on an acoustic far-field spherical surface;
s2, aiming at each frequency omega in the frequency band to be analyzed, solving the fluid-solid coupling dynamic equation of the underwater vehicle structure to obtain a vibration displacement column vector U on a coupling surface n Predicting a sound pressure spectrum P with acoustic far-field spherical grid nodes as field points according to the sound pressure column vector P s Integrating the sound pressure spectrum P at each frequency omega s Acoustic far-field spherical radiation noise spectrum model P for forming underwater vehicle structure s (ω)；
The stage of rapidly deducing and forecasting the radiation sound pressure of the field point comprises the following steps:
s3, using the acoustic far-field spherical radiation noise spectrum model P s Using grid nodes of (omega) and acoustic far-field spherical surface as input to calculate sound pressure spectrum of any field pointp(r,θ,φ,ω) Obtaining the azimuth pointing factor of any field point by adopting an interpolation technologyB(θ,φ,ω) ，(r, θ,φ,ω) Is a representation of the location of the field point in a spherical coordinate system,ris the distance between the field point and the origin of the coordinate system of the underwater vehicle along with the ship,θ、φrespectively, the longitude angle of the spherical coordinate systemAnd a latitude angle;
s4, calculating distance attenuation factorC(r) Incorporating said azimuth orientation factorB(θ,φ,ω) From said acoustic far-field spherical radiation noise spectrum model P s (ω) deduces the radiated noise at any field point.
Preferably, in step S1), the structure of the underwater vehicle is discretized into finite elements to form a structure finite element model, the interface between the underwater vehicle and the seawater is a fluid-solid coupling surface, and a finite element mesh on the fluid-solid coupling surface is a fluid boundary element model; the acoustic far-field spherical surface is a spherical surface which has the radius N times of the maximum size of the underwater vehicle and surrounds the underwater vehicle, and N is a natural number more than 1; and dividing the acoustic far-field spherical surface into grids to form an acoustic far-field spherical grid model, and recording coordinates and serial numbers of grid nodes.
Preferably, in step S2, the fluid-solid coupling dynamic equation of the submersible vehicle structure is as follows:
Figure 789715DEST_PATH_IMAGE001
（E1）
in the formula (E1), the compound is,jis an imaginary part unit, omega is the pulsation circular frequency of the fluid-solid coupling system, U is the displacement column vector of the structure finite element node, F m Is a unit mechanical excitation force column vector, F, acting on the underwater vehicle p Exciting force column vectors which are given by equivalence and act on the freedom degree of the structure nodes are acted on the sound pressure of the fluid-solid coupling surface of the underwater vehicle, M is a structure mass matrix, C is a damping matrix, K is a rigidity matrix, L is a freedom degree conversion matrix used for extracting the normal displacement vibration data of the fluid-solid coupling surface, and G is a conversion matrix used for converting the sound pressure of the fluid-solid coupling surface into omega fluid to act on the exciting force of the freedom degree of the structure nodes; the matrixes E and D are respectively fluid influence coefficient matrixes of vibration and sound pressure on field point sound pressure; u shape n Is the vibration displacement column vector on the coupling surface and P is the sound pressure column vector.
Preferably, the sound pressure column vector P with the acoustic far-field spherical grid node as the field point in step S2) s The expression of (a) is:
P s =E s P-D s U n （E3）
in the formula (E3), E s And D s The method comprises the following steps of respectively arranging the row vectors of fluid influence coefficients given by vibration and sound pressure to different grid nodes of an acoustic far-field spherical surface according to rows to form a matrix;
the sound pressure column vector P taking the acoustic far-field spherical grid node as a field point s For a single frequency calculation, P is calculated for all single frequencies of the frequency band to be analyzed s And integrating to obtain an acoustic far-field spherical radiation noise spectrum model P s (ω)。
Preferably, the sound pressure spectrum of the arbitrary field point in step S3)p(r,θ,φ,ω) The expression of (c) is:
p(r,θ,φ,ω)=αB(θ,φ,ω)C(r,ω) （E4）
in the formula (E4), the compound represented by the formula,αis the amplitude factor of the exciting force of the underwater vehicle,B(θ,φ,ω) Is an azimuth directional factor used for reflecting the change of the radiation sound pressure of the underwater vehicle on the acoustic far-field spherical surface under the action of unit exciting force along with the azimuth,C(r,ω) The distance attenuation factor is used for reflecting the attenuation rule of the radiation sound pressure of the underwater vehicle along with the distance.
Preferably, the azimuth pointing factor of the arbitrary field point in step S3B(θ,φ,ω) The expression of (a) is:
Figure 238014DEST_PATH_IMAGE002
（E5）
in the formula (E5), the compound represented by the formula,A(θ,φ) Is the sound pressure variation along with the azimuth at the unit distance caused by the exciting force of the underwater vehicle with the unit amplitude,r s is the spherical radius of the acoustic far field,eis a natural logarithm base, and the number of the logarithm bases,cis the speed of sound.
Preferably, any interpolation technique is used in step S3 to obtainAzimuthal orientation factor of a field pointB(θ,φ,ω) The method comprises the following steps:
s31, the vector of the field point pointed to by the origin of coordinates is given by the coordinates of the field point in the ship-associated coordinate system and is recorded as
r=(x,y,z) （E7）
The distance of the field point from the origin is:
Figure 551839DEST_PATH_IMAGE003
（E8）
calculating the distance between each grid point on the acoustic far-field spherical surface and the field point, and using standard numerical value comparison program, screening the 3 acoustic far-field spherical grid nodes nearest to the field point, and recording their positions as radial representation(x i s , y i s ,z i s )，i=1,2,3, the distances of the three points from the origin are all the radii of the acoustic far-field spherer s ；
S32, mapping the three acoustic far-field spherical grid points to radius ofrThe position relation of the mapping points and the field points is utilized to establish an interpolation relation, and the coordinates of the three mapping points are expressed as
Figure 478207DEST_PATH_IMAGE004
（E9）
S33, establishing three interpolation weight coefficients by using the mapping point coordinates, wherein the three interpolation weight coefficients are expressed as:
Figure 558158DEST_PATH_IMAGE005
（E10）
in formula (E10):Ais the area of a triangle with three mapping points as vertices, expressed as:
Figure 911779DEST_PATH_IMAGE006
（E11）
in the formula (E11), r 12 Is the vector from the mapping point No. 1 to the mapping point No. 2, r 13 The vector formed by the mapping point 1 pointing to the mapping point 3 is calculated by the coordinates of the mapping points:
Figure 444392DEST_PATH_IMAGE007
（E12）
in the formula (E10), the compound represented by the formula (E10),u、vis the field point at r 12 And r 13 Coordinate values in the stretched generalized planar coordinate system, passing through r 1X Are respectively associated with r 12 And r 13 The inner product of (a) is given, expressed as:
Figure 174450DEST_PATH_IMAGE008
（E13）
in the formula (E13), r 1X Is the radius from the 1 mapping point to the 2 mapping point, expressed as:
r X1 =(x-x 1 ,y-y 1 ,z-z 1 ,) （E14）
in the formula (E10), the compound represented by the formula (E10),a i 、b i 、c i from r 12 And r 13 Given modulo, note:
Figure 374488DEST_PATH_IMAGE009
，
Figure 899010DEST_PATH_IMAGE010
then, thena i 、b i 、c i Respectively calculated as:
Figure 918918DEST_PATH_IMAGE011
（E15）
s34, calculating the azimuth orientation factor by using the obtained three interpolation weight coefficients, wherein the expression is as follows:
Figure 187089DEST_PATH_IMAGE012
（E16）
in the formula (E16), the compound represented by the formula,P i s (ω)，iand =1,2,3, which is the radiation sound pressure spectrum of the acoustic far-field spherical grid node, and is directly extracted from the calculation result of the formula (E4).
Preferably, the distance attenuation factor in step S4C(r) The calculating method comprises the following steps:
Figure 976053DEST_PATH_IMAGE013
（E6）。
preferably, the method is used for radiated noise field isobologram prediction.
The invention further provides a computer-readable storage medium storing a computer program, which is characterized in that the computer program, when executed by a processor, implements the above-mentioned fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure.
The invention provides a rapid deduction method for real-time simulation of radiation noise of a submersible vehicle structure, which comprises the following steps: firstly, a fluid boundary element technology is coupled by using a structural finite element in advance to carry out relatively accurate fluid-solid coupling vibration prediction on the underwater vehicle, then a radiation sound pressure field on an acoustic far-field spherical surface surrounding the underwater vehicle is predicted, and an acoustic far-field spherical surface radiation noise spectrum model is established. The acoustic far-field spherical radiation noise spectrum model is implanted into a dynamic simulation system and is used for developing the radiation noise dynamic simulation of the underwater vehicle in the navigation state. In the dynamic simulation of the radiation noise of the underwater vehicle, the azimuth directing factor prediction and the distance attenuation factor prediction are carried out by respectively utilizing an interpolation rule and an underwater sound attenuation rule according to the separation characteristics of azimuth and distance of a radiation noise field of the underwater vehicle, then an excitation force amplitude factor is given in real time by combining a steering control simulation prediction program to quickly obtain a radiation noise spectrum at any azimuth and any distance relative to the underwater vehicle, and the process is called as a deduction process. The beneficial effects include:
1. the method completes the fluid-solid coupling surface vibration and sound pressure distribution prediction which must be completed by radiation noise prediction in advance independently of the radiation noise dynamic simulation process, and forms an acoustic far-field spherical radiation noise spectrum model which has less data volume and is easy to implant into a dynamic simulation system;
2. the underwater acoustic propagation law is used as a deduction basis, an acoustic far-field spherical radiation noise spectrum model is used as input, azimuth direction factor prediction and distance attenuation factor prediction are carried out by respectively utilizing an interpolation technology and an underwater acoustic attenuation law according to the separation characteristic of azimuth and distance of a submarine radiated noise field, so that the problem of the calculation efficiency of predicting the radiated noise by using large-scale fluid-solid vibration and boundary sound pressure data numerical integration in the traditional structural finite element coupling fluid boundary element technology can be effectively solved, the used model data volume is small, the prediction process is simple, and the underwater acoustic radiation noise prediction method is particularly suitable for being implanted into a yacht control dynamic simulation system;
3. the dynamic simulation process is separated from the fluid-solid coupling surface vibration and sound pressure distribution forecasting process which must be carried out in step, so that the technical precision advantage of structural finite element coupling fluid boundary elements is inherited; an acoustic far-field spherical radiation noise spectrum model which has less data volume and is more suitable for being implanted into a dynamic simulator is formed, and the problem of storage capacity of a structural finite element coupling fluid boundary element technology is solved; by adopting a deduction technology, the radiation noise of the underwater vehicle is forecasted at a higher calculation speed, so that the radiation noise is forecasted at a higher speed on the premise that the forecasting precision is fully guaranteed, and the requirement of dynamic simulation of the radiation noise of the underwater vehicle in a navigation state is met;
4. the method can be used for realizing the dynamic simulation of the radiation noise of the navigation state of the underwater vehicle and supporting the inspection and evaluation of the design and control effect of the navigation radiation noise in the research and development of the low-noise underwater vehicle.
Drawings
FIG. 1 is a flow chart of a fast deduction method for real-time simulation of low-frequency radiation noise of a submersible structure according to the present invention;
FIG. 2 is a schematic view of a fluid boundary meta-model of a submersible;
FIG. 3 is a schematic diagram of an acoustic far-field spherical mesh model;
FIG. 4 is a schematic diagram of a steel ribbed cylindrical shell model for simulating a submersible vehicle according to one embodiment;
FIG. 5 is a schematic diagram of a finite element model of a steel ribbed cylindrical shell structure for simulating a submersible vehicle in the first embodiment;
FIG. 6 is a schematic diagram of a boundary element model of a steel ribbed cylindrical shell for simulating an underwater vehicle in the first embodiment;
FIG. 7 is a schematic diagram of an acoustic far field spherical grid according to a first embodiment;
FIG. 8 is a schematic view of a model of the underwater vehicle to be used for developing dynamic simulation of radiation noise in a sailing state according to the second embodiment;
FIG. 9 is a schematic view showing the relationship between the navigation path of the underwater vehicle and the site position during dynamic simulation of the navigation radiation noise of the underwater vehicle in the second embodiment;
FIG. 10 is a schematic view of the embodiment two in which the radiated noise of the underwater vehicle in the sailing state and the control simulation of the operation boat are performed simultaneously and output;
FIG. 11 is a schematic diagram showing the comparison of radiation noise for navigating at an optimal route in consideration of and without consideration of noise radiation factors of the underwater vehicle in the third embodiment;
FIG. 12 is a schematic view of a 36m long ribbed cylindrical shell model used for simulating a submersible vehicle in the fourth embodiment;
FIG. 13 is a sound field area mesh for sound field isobologram prediction in the fourth embodiment;
fig. 14 is an isobologram of a radiated noise field predicted by using a deduction technique in the fourth embodiment.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The invention provides a rapid deduction method for real-time simulation of low-frequency radiation noise of a structure of a submersible vehicle, which is characterized in that an acoustic far-field spherical radiation noise spectrum model is established before dynamic simulation, and the prediction process of a vibration spectrum and a sound pressure spectrum on a fluid-solid coupling surface with the longest calculation time and the largest data storage requirement is completed in advance; then further reducing the data storage scale according to the principle that the acoustic far-field spherical grid is sparser than the underwater vehicle fluid-solid coupling surface grid, and forming an acoustic far-field spherical radiation noise spectrum model which is easy to implant into a dynamic simulation system; and then, according to the radiation noise field rule of the sound source of the underwater vehicle in water, the radiation noise of any field point is given by using a deduction technology.
As shown in fig. 1, the fast deduction method for real-time simulation of low-frequency radiation noise of a structure of a submersible vehicle provided by the invention includes two stages of establishing an acoustic far-field spherical radiation noise spectrum model and fast deducting and forecasting field point radiation sound pressure.
The fluid-solid coupling surface vibration and sound pressure distribution forecasting which must be completed by the radiation noise forecasting is completed in advance independent of the dynamic simulation process of the radiation noise of the navigation state of the underwater vehicle, and an acoustic far-field spherical radiation noise spectrum model which has less data volume and is easy to implant into a dynamic simulation system is formed. The stage of establishing the acoustic far-field spherical radiation noise spectrum model comprises the following steps:
s1, establishing a submersible vehicle structure finite element model and a fluid boundary element model, establishing an acoustic far-field spherical radiation noise spectrum model, dividing a frequency band to be analyzed into a series of discrete frequencies, wherein the acoustic far-field spherical radiation noise spectrum model is used for representing a sound pressure spectrum of a grid node on an acoustic far-field spherical surface;
s2, aiming at each frequency omega in the frequency band to be analyzed, solving the fluid-solid coupling dynamic equation of the underwater vehicle structure to obtain a vibration displacement column vector U on a coupling surface n Predicting a sound pressure spectrum P with acoustic far-field spherical grid nodes as field points according to the sound pressure column vector P s Integrating the sound pressure spectrum P at each frequency omega s Acoustic far-field spherical radiation noise spectrum model P for forming underwater vehicle structure s (ω)。
In the dynamic simulation of the radiation noise of the navigation state of the underwater vehicle, a deduction technology is adopted at the stage of rapidly deducing and forecasting the radiation sound pressure of a field point: an acoustic far-field spherical radiation noise spectrum model is used as input, azimuth directional factor prediction and distance attenuation factor prediction are carried out by utilizing an interpolation means and a hydroacoustic attenuation rule respectively according to the separation characteristics of azimuth and distance of a radiation noise field of the underwater vehicle, and then an excitation force amplitude factor is given in real time by combining a steering control simulation prediction program to give radiation noise of any field point caused by the underwater vehicle. The stage of rapidly deducing and forecasting the radiation sound pressure of the field point comprises the following steps:
s3, using the acoustic far-field spherical radiation noise spectrum model P s Using grid nodes of (omega) and acoustic far-field spherical surface as input to calculate sound pressure spectrum of any field pointp(r,θ,Ф,ω) Obtaining the azimuth orientation factor of any field point by adopting an interpolation technologyB(θ,Ф,ω) (ii) a An azimuth pointing factor is given by an interpolation means, a distance attenuation factor is formed according to a spherical expansion rule of sound pressure along with distance, an excitation force amplitude factor is given in real time by a yacht control simulation forecasting program, and radiation noise of any field point is given by the product of the three factors;
s4, calculating distance attenuation factorC(r) Incorporating said azimuth orientation factorB(θ,Ф,ω) From said acoustic far-field spherical radiation noise spectrum model P s (ω) deduces the radiated noise at any field point. The deduction technology is used for effectively reducing the calculation scale in the prediction of the radiation noise at any field point, so that the millisecond-level real-time prediction of the radiation noise in the instantaneous state of the underwater vehicle can be realized, and the requirement that the prediction speed of the radiation noise in the navigation state of the underwater vehicle is matched with the control simulation speed of the yacht is met.
In the simulation of the radiation noise of the navigation state of the underwater vehicle, after the position and the attitude (namely the state) of the underwater vehicle are given by a boat control simulation system in real time, the radiation noise of a certain determined position in space caused by the underwater vehicle at the moment needs to be determined. The coordinates of the determined position relative to the coordinate system of the vehicle with the vessel can be given by coordinate transformation. Since the state of the underwater vehicle changes in real time, the determined position (hereinafter "site") changes in real time in the ship-based coordinate system. Therefore, the simulation problem of the radiated noise of the navigation state is as follows: and (3) forecasting the radiation noise of a dynamic change field point caused by the underwater vehicle in real time.
The structure of the underwater vehicle is firstly dispersed into finite elements to form a structure finite element model. The dimensions of the finite elements are required to meet the density requirement of 6 units at the vibration wavelength of a structure, and each structural finite element contains information of the material, the plate thickness and the like of the structure. The interface of the underwater vehicle and the seawater is called a fluid-solid coupling surface, and a finite element mesh on the fluid-solid coupling surface is used as a fluid boundary element model, as shown in fig. 2. In order to establish a far-field spherical radiation noise spectrum model, a spherical surface surrounding the underwater vehicle is also established, and the spherical surface is called an acoustic far-field spherical surface. The radius of the acoustic far-field sphere is taken as N times the maximum dimension of the underwater vehicle, where N is taken as 5. And dividing the acoustic far-field spherical surface into grids to form an acoustic far-field spherical grid model, wherein the grid scale is selected according to 1/6 of the sound wavelength under the quasi-forecast frequency, and as shown in figure 3, the coordinates and the serial numbers of grid nodes are recorded.
The frequency band to be analyzed needs to be divided into a series of single frequencies for each instantaneous radiation noise forecast of the underwater vehicle, the forecast is carried out aiming at each single frequency, and then the results are integrated into a radiation noise spectrum. Therefore, in the subsequent prediction, the prediction is completed for one single frequency, and then the results are integrated.
In the first stage, the process of the acoustic far-field spherical radiation noise spectrum model is as follows:
and establishing a fluid-solid coupling dynamic equation according to the structure finite element and the fluid boundary element of the underwater vehicle, and obtaining vibration and sound pressure on a fluid-solid coupling surface by resolving the fluid-solid coupling dynamic equation. The fluid-solid coupling power equation is shown as (E1):
Figure 937056DEST_PATH_IMAGE014
（E1）
in the formula (E1), the compound represented by the formula (I),jis an imaginary part unit, and the pulsation circular frequency omega of the fluid-solid coupling system is an input parameter. Other known quantities also include: f m The system comprises a unit mechanical excitation force column matrix, a structural mass matrix M, a damping matrix C, a rigidity matrix K, a freedom degree conversion matrix L and a conversion matrix G, wherein the unit mechanical excitation force column matrix, the structural mass matrix M, the damping matrix C and the rigidity matrix K are used for extracting normal displacement vibration data of a fluid-solid coupling surface; the coefficient matrices E and D relating to the fluid dynamics, which are frequency dependent. Matrix or column vector F m M, C, K, L, G are limited by commerceThe element program is automatically generated according to the specific position of the exciting force applied to the structure and the information of the material, the plate thickness, the geometry and the like of the structure; matrices E and D are automatically generated by the commercial boundary element program from the geometry of the fluid-solid coupling surfaces, the fluid acoustic parameters, and the frequency input parameters. Solving the matrix equation set will eliminate the exciting force column vector F of the equivalent structure node degree of freedom acting on the underwater vehicle fluid-solid coupling surface p And structural finite element node displacement column vectors U are obtained finally, and vibration displacement column vectors U on the fluid-solid coupling surface are obtained n And a sound pressure column vector P.
By using vibration displacement column vector U on fluid-solid coupling surface n And the sound pressure column vector P can forecast the radiation sound pressure of any field point in the seawater, and the expression is in the form of matrix product:
p(r)=E’P-D’U n （E2）
in the formula (E2), r is the position coordinates of the field point, which is an input parameter; e 'and D' are the fluid influence coefficient row vectors of vibration and sound pressure on each fluid-solid coupling surface to the field point sound pressure, which are given by a commercial boundary element program, and the row number is the boundary element grid number.p(r) is the magnitude of the complex sound pressure at the field point r.
When the number of finite elements and boundary elements on the fluid-solid coupling surface is large, the matrix dimension in the formulas (E1) and (E2) is large, so that the solving scale is very large and is used for calculationp(r) U to be stored n And P data volume is also large, the dynamic simulation of the navigation radiation noise of the underwater vehicle cannot be directly carried out by using the steps, so that the sound pressure with the grid nodes on the acoustic far-field spherical surface as field points is only calculated by using the formula (E2) and is used for subsequent real-time prediction. This process can be represented by formula (E3):
P s =E s P-D s U n （E3）
in the formula (E3), E s And D s The method is a matrix formed by arranging the row vectors of fluid influence coefficients given by different nodes of an acoustic far-field spherical grid in rows; p s The acoustic far-field spherical grid nodes are taken asThe sound pressures given for the field points are arranged in a row giving a column vector.
s The results are forecasted by aiming at one single frequency, the same analysis is carried out on all single frequencies of the analysis frequency band, and the results can be integrated to give an acoustic far-field spherical radiation noise spectrum model P s (ω)。
In the second stage, a far-field spherical radiation noise spectrum model and acoustic far-field spherical grid node coordinates are used as input, and radiation noise of any field point is deduced and predicted.
The law of the radiated noise field of the underwater vehicle in seawater shows that the underwater vehicle has the separability of azimuth and distance, namely, the sound pressure spectrum of any field pointp(r,θ,φ,ω) Is expressed by the formula:
p(r,θ,φ,ω)=αB(θ,φ,ω)C(r,ω) （E4）
in the formula (E4), (E)r,θ,φ,ω) Is a representation of the location of the field point in a spherical coordinate system,ris the distance between the field point and the origin of the coordinate system of the underwater vehicle along with the ship,θ,φthe longitude angle and the latitude angle of the spherical coordinate system are respectively,αis the exciting force amplitude factor of the underwater vehicle, is given in real time by the steering control simulation forecasting program,B(θ,φ,ω) Is an azimuth pointing factor used for reflecting the change of the radiation sound pressure of the underwater vehicle on the acoustic far-field spherical surface under the action of unit exciting force along with the azimuth,C(r,ω) The distance attenuation factor is used for reflecting the attenuation rule of the radiation sound pressure of the underwater vehicle along with the distance, and the distance attenuation factor is specifically expressed as follows:
Figure 709840DEST_PATH_IMAGE015
（E5）
Figure 516122DEST_PATH_IMAGE016
（E6）
in the formulae (E5) and (E6),A(θ,φ,)is the sound pressure variation along with the azimuth at the unit distance caused by the exciting force of the underwater vehicle at the unit amplitude,r s is the spherical radius of the acoustic far field,eis a natural logarithm base, and the number of the logarithm bases,cis the speed of sound.
An interpolation method is adopted to calculate the azimuth pointing factor with any field position as input, and the main steps are as follows:
(a) The vector of the field point pointed to by the origin of coordinates is given by the coordinates of the field point under the ship-associated coordinate system and is recorded as:
r=(x,y,z) （E7）
the distance of the field point from the origin is then:
Figure 425172DEST_PATH_IMAGE017
（E8）。
(b) Calculating the distance between each grid point on the acoustic far-field spherical surface and the field point, and using standard numerical value comparison program, screening the 3 acoustic far-field spherical grid nodes nearest to the field point, and recording their positions as radial representation(x i s ,y i s ,z i s )，i=1,2,3, the distances of the three points from the origin are all the radii of the acoustic far-field spherer s 。
(c) The three acoustic far-field spherical grid points are mapped to the radius ofrThe interpolation relation is established by utilizing the position relation of the mapping points and the field points. The coordinates of the three mapping points are expressed as:
Figure 291497DEST_PATH_IMAGE018
（E9）
(d) Utilizing the mapping point coordinates to establish three interpolation weight coefficients expressed as:
Figure 285998DEST_PATH_IMAGE019
（E10）
in formula (E10):Ais the area of a triangle with three mapping points as vertices, expressed as:
Figure 895971DEST_PATH_IMAGE020
（E11）
in the formula (E11), r 12 Is the radius of the 1 mapping point to the 2 mapping point, r 13 Is the radius formed by the 1 mapping point pointing to the 3 mapping point, and is calculated by the coordinates of the mapping points:
Figure 659527DEST_PATH_IMAGE021
（E12）
in the formula (E10), the compound represented by the formula,u、vis the field point at r 12 And r 13 The coordinate value in the stretched generalized plane coordinate system can pass through r 1X Are respectively associated with r 12 And r 13 The inner product of (a) is given, expressed as:
Figure 962333DEST_PATH_IMAGE022
（E13）
in the formula (E13), r 1X Is the radius from the 1 mapping point to the 2 mapping point, expressed as:
r X1 =(x-x 1 ,y-y 1 ,z-z 1 ,) （E14）
in the formula (E10), the compound represented by the formula,a i 、b i 、c i from r 12 And r 13 Given modulo, note:
Figure 175621DEST_PATH_IMAGE023
，
Figure 589284DEST_PATH_IMAGE024
then, thena i 、b i 、c i Respectively meterThe calculation is as follows:
Figure 472927DEST_PATH_IMAGE025
（E15）
(e) And calculating the azimuth orientation factor by using the obtained three interpolation weight coefficients, wherein the expression is as follows:
Figure 946633DEST_PATH_IMAGE026
（E16）
in the formula (E16), the compound represented by the formula,P i s (ω)，iand (c) =1,2,3, which are radiation sound pressure spectrums of 3 acoustic far-field spherical grid nodes screened out in the step (b) caused by unit exciting force of the underwater vehicle, and can be directly extracted from the calculation result of the formula (E3).
Distance attenuation factorC(r) Can be calculated directly by using (E6), among themrHas been given by (E8) in the calculation of the azimuth pointing factor.
Amplitude of excitation force in boat-handling control simulationαGiven in real time, the formula (E4) can be directly substituted at each instantaneous radiated noise prediction. Thus, the formula (E4) can be used for forecasting the radiation noise spectrum of any field point caused by the underwater vehicle.
Example one
In order to verify the correctness of the radiation noise rapid deduction technology, an algorithm program is written, the radiation noise of a steel ribbed cylindrical shell under the action of an exciting force is forecasted, and the forecasting process of the radiation noise of the underwater vehicle at a certain instant is simulated. The relevant parameters of the cylindrical shell are shown in table 1, and the structural form is shown in fig. 4. In prediction, the density of the fluid outside the cylindrical shell is 1000kg/m 3 The speed of sound is 1450m/s. The excitation force with the amplitude of 1N vertically and outwards acts on the middle rib, and the excitation frequency covers the frequency band of quasi 20Hz to 100 Hz.
Figure 650147DEST_PATH_IMAGE027
Fig. 5 to 7 are respectively a structural finite element model, a boundary element model and an acoustic far-field spherical grid of the cylindrical shell. In order to ensure that the structural finite element mesh density of the cylindrical shell can meet the precision requirement of cylindrical shell vibration and radiation noise prediction, the finite element size is 350mm, and finally the whole finite element model comprises 9508 finite elements, wherein the number of the finite elements or boundary elements on the fluid-solid coupling surface is 8948. The radius of the acoustic far-field spherical surface is 9.5m, the highest frequency to be predicted is 100Hz, the sound wave length of the frequency is the shortest and is 14.5 m, so the size of the acoustic far-field hemispherical grid is 2.4 m, and the number of nodes of the final acoustic far-field spherical grid is 146.
Figure 336344DEST_PATH_IMAGE028
Table 2 compares the resource and time requirements for forecasting a site using and without the deduction technique, where the sound pressure spectrum calculation takes 9 frequency points in the 20-100Hz band. As can be seen from table 2: the deduction technology is used, extra time is spent on acquiring a far-field spherical radiation noise spectrum model in the first stage, but the time spent does not occupy real-time simulation time of the second stage; the advantage of using the deduction technology is embodied in the real-time simulation process of the second stage, and at this time, the deduction technology uses a far-field spherical radiation noise spectrum model with smaller data volume as input, and uses an interpolation technology and a formula to forecast the sound pressure spectrum of a field point. If the deduction technology is not used, the vibration displacement column vector U on the fluid-solid coupling surface needs to be used n And the sound pressure column vector P is used as an input forecast field point sound pressure spectrum, and the input data volume and the calculation amount are much larger. As the number of finite elements and boundary elements on the fluid-solid coupling surface grows, the advantages in memory and computation time using the deduction technique will be more significant.
Example two
The underwater vehicle to be used for carrying out the dynamic simulation of the radiation noise in the sailing state is shown in fig. 8, and the ship length of the underwater vehicle is 40 meters, and the diameter of the underwater vehicle is 1.8 meters. The dynamic simulation of the navigation state radiation noise of the underwater vehicle is needed, and the relationship between the navigation path of the underwater vehicle and the site position during the dynamic simulation is shown in fig. 9: the position and the posture of the underwater vehicle in the process of navigation are given in real time by using a boat-handling control simulation program, a certain determined position is set in space, the radiation noise spectrum of the point caused by the underwater vehicle is calculated in real time, and a sonar station is simulated to detect the radiation noise of the underwater vehicle. Therefore, the boat control simulation system gives coordinates, namely field points, of the sonar station relative to a coordinate system of the body of the underwater vehicle through coordinate transformation in real time in the boat control simulation; and simultaneously, the rotating speed of the propeller is used for providing the magnitude of the exciting force of the propeller, and a radiation noise forecasting program is used for forecasting the radiation noise spectrum of the field point caused by the exciting force of the propeller of the underwater vehicle in navigation. Firstly, vibration spectrum and sound pressure spectrum calculation on a fluid-solid coupling surface is completed by using a structural finite element coupling fluid boundary element technology, and 100 frequency points are selected in a frequency band of 10Hz to 100Hz for representing spectrum characteristics. The structure of the underwater vehicle is divided into 342552 finite elements, wherein the number of finite elements or boundary elements on the fluid-solid coupling surface is up to 119712, and the occupation amount of a storage space for storing vibration spectrum and sound pressure spectrum data is 183.2MB. For the real-time forecasting requirement of dynamic simulation, an acoustic far-field spherical surface is established, the radius is 200 meters, the acoustic far-field spherical surface is divided into grids, the grid dimension is 2.4 meters, and the number of finally obtained grid nodes is 67602. The radiation noise spectrum is forecasted by taking the grid nodes as field points, a far-field spherical radiation noise spectrum model is obtained, and the data volume is 51MB. During dynamic simulation, a radiation noise spectrum model of a far-field spherical surface is used as input, and a deduction technology is adopted, so that the radiation noise spectrum of a field point where a sonar station is used can be rapidly forecasted. Fig. 10 is an output interface of applying the deduction technology to dynamic simulation of radiation noise in a navigation state, and in practical use, a sound pressure spectrum level curve at the upper right corner in the graph and an X coordinate output at the lower right corner representing the motion position of the underwater vehicle dynamically change in real time at the same time.
The result shows that the method can completely realize the matching of the radiation noise forecasting speed of the underwater vehicle and the control simulation of the yacht when the method is used for carrying out the noise spectrum forecasting time of 50 frequency points on the underwater vehicle with the length of 40 meters in millisecond level. The invention can realize the dynamic simulation of the radiation noise of the navigation state of the underwater vehicle, and on the basis, the invention can support the inspection and evaluation of the design and control effect of the navigation radiation noise in the research and development of the low-noise underwater vehicle.
EXAMPLE III
The method is used for developing the hidden autonomous navigation path planning of the underwater vehicle. When the underwater vehicle is autonomously navigated, obstacles and unfavorable hydrological environmental factors need to be avoided, and the underwater vehicle can reach a target in the shortest navigation time and path. Therefore, an objective function calculation module is implanted into a yacht control simulation program, and an airway is optimized by quantifying various factors. In order to take the noise radiation of the underwater vehicle into consideration of one of the constraint conditions and realize the concealed navigation of the underwater vehicle, the noise of a sonar station caused by the underwater vehicle is forecasted according to the real-time simulation result of the underwater vehicle boat-handling control program, and the forecast result is submitted to a target function calculation module in real time, so that the optimal path planning considering the concealed navigation is realized. By using a deduction technology, the prediction of the radiation noise spectrum can be completed in real time in the autonomous navigation simulation of the underwater vehicle, the radiation noise spectrum is used as input, the total sound level is calculated, and therefore the radiation noise spectrum is submitted to an objective function calculation module in a quantized mode for carrying out route optimization, and a more concealed navigation strategy is formed. Fig. 11 is a comparison of radiated noise for an optimal path with and without consideration of the noise radiation from the underwater vehicle, and it can be seen that in the case of a path length of 900 meters as well, if the noise radiation from the underwater vehicle is not considered, a path of 300 meters will have radiated noise exceeding the constraint threshold, which is detrimental to the stealth of the underwater vehicle.
Example four
When designing the preliminary scheme of the underwater vehicle, the equal-sound-pressure line graph of the radiation noise field needs to be forecasted aiming at the ribbed cylindrical shell structure taking the underwater vehicle as a prototype, and the distribution of the radiation noise under different excitation frequencies in space is judged. FIG. 12 is a ribbed cylindrical shell 36m long and 3.6m in diameter for isobologram prediction of radiated noise fields. In order to predict the characteristics of the noise field caused by the vibration of the cylindrical shell, the sound field area to be predicted is divided into grids, as shown in fig. 13, the total sound level at the nodes of the grids is predicted, and then the total sound level is displayed in the form of a isobologram according to the size of the total sound level. In order to enable the isobologram to represent the change rule of sound wave propagation, the grid density cannot be too thin, so that the number of grid nodes is large, and the number of the grid nodes for forming the isobologram is 10201 for a 36-meter-long cylindrical shell. If the radiation noise prediction using the region grid node as the field point is performed by directly using the vibration spectrum and the sound pressure spectrum data on the fluid-structure interaction surface one by one, there is a problem that the prediction time is too long, for example, about 36 hours are required for completing the prediction of 1 frequency point for the model of this embodiment, and if the total sound level prediction is completed on this basis, the required time is longer. Therefore, the method provided by the invention is used, the calculation time can be greatly saved by establishing a far-field spherical radiation noise spectrum model and then rapidly predicting the radiation noise spectrum taking the area grid nodes as field points by using a deduction technology on the basis of the far-field spherical radiation noise spectrum model. Fig. 14 is a radiated noise field equal sound pressure line graph predicted by the deduction technology of the present patent, which is a radiated noise field equal sound pressure line graph obtained by performing total sound level calculation after sound pressure prediction of each node of a grid is completed by using 20 frequency points, and the total time is 30 minutes.
The embodiment verifies the implementation effect of the method for the isobologram forecasting of the radiation noise field. In order to draw an isobologram of the underwater structure radiation noise field, the radiation noise needs to be calculated according to large-scale field points in the underwater structure radiation noise field, and the distribution rule of the radiation noise generated by the underwater structure vibration in the space is given. The present invention has the advantage of high efficiency and low resource requirements in single site noise prediction, and thus has stronger analysis capability on the problems.
Those not described in detail in this specification are well within the skill of the art.
Finally, it should be noted that the above detailed description is only for illustrating the technical solution of the patent and not for limiting, although the patent is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the patent can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the patent, which should be covered by the claims of the patent.

Claims (10)

1. A fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure is characterized by comprising the following steps: the method comprises two stages of establishing an acoustic far-field spherical radiation noise spectrum model and rapidly deducing and forecasting field point radiation sound pressure:
the stage of establishing the acoustic far-field spherical radiation noise spectrum model comprises the following steps:
s1, establishing a finite element and a fluid boundary element model of a submersible vehicle structure, establishing an acoustic far-field spherical radiation noise spectrum model, dividing a frequency band to be analyzed into a series of discrete frequencies, wherein the acoustic far-field spherical radiation noise spectrum model is used for representing a sound pressure spectrum of a grid node on an acoustic far-field spherical surface;
s2, aiming at each frequency omega in the frequency band to be analyzed, solving the fluid-solid coupling dynamic equation of the underwater vehicle structure to obtain a vibration displacement column vector U on a coupling surface n And the sound pressure column vector P, predicting the sound pressure spectrum P with the acoustic far-field spherical grid node as the field point s Integrating the sound pressure spectrum P at each frequency omega s Acoustic far-field spherical radiation noise spectrum model P for forming underwater vehicle structure s (ω)；
The stage of rapidly deducing and forecasting the radiation sound pressure of the field point comprises the following steps:
s3, using the acoustic far-field spherical radiation noise spectrum model P s (omega) and grid nodes of the acoustic far-field spherical surface are used as input to calculate the sound pressure spectrum of any field pointp(r,θ,φ,ω) Obtaining the azimuth pointing factor of any field point by adopting an interpolation technologyB(θ,φ,ω)，(r,θ,φ,ω) Is a representation of the location of the field point in a spherical coordinate system,ris the distance between the field point and the origin of the coordinate system of the underwater vehicle along with the ship,θ、φthe longitude angle and the latitude angle of the spherical coordinate system are respectively;
s4, calculating distance attenuation factorC(r) Incorporating said azimuth orientation factorB(θ,φ,ω) From said acoustic far-field spherical radiation noise spectrum model P s (ω) deduces the radiated noise at any field point.
2. The fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure according to claim 1, characterized by: in the step S1), dispersing the underwater vehicle structure into finite elements to form a structure finite element model, wherein the interface of the underwater vehicle and the seawater is a fluid-solid coupling surface, and a finite element grid on the fluid-solid coupling surface is a fluid boundary element model; the acoustic far-field spherical surface is a spherical surface which has the radius N times of the maximum size of the underwater vehicle and surrounds the underwater vehicle, and N is a natural number more than 1; and dividing the acoustic far-field spherical surface into grids to form an acoustic far-field spherical grid model, and recording coordinates and serial numbers of grid nodes.
3. The fast deduction method for the real-time simulation of the low-frequency radiation noise of the underwater vehicle structure as recited in claim 2, characterized in that: the fluid-solid coupling power equation of the structure of the underwater vehicle in the step 2) is as follows:
Figure 846251DEST_PATH_IMAGE001
（E1）
in the formula (E1), the compound represented by the formula (I),jin terms of the imaginary unit of the number,ωfor the pulsating circular frequency of the fluid-solid coupling system, U is a displacement column vector of a structure finite element node, F m For acting on the unit mechanically-excited force column matrix of the underwater vehicle, F p Exciting force column vectors which are given by equivalence and act on the freedom degree of the structure nodes for the sound pressure of the fluid-solid coupling surface acting on the underwater vehicle, wherein M is a structure mass matrix, C is a damping matrix, K is a rigidity matrix, L is a freedom degree conversion matrix used for extracting the normal displacement vibration data of the fluid-solid coupling surface, and G is a conversion matrix used for converting the sound pressure of the fluid-solid coupling surface into the exciting force of the freedom degree of the fluid acting on the structure nodes; matrices E and D are the row, matrix or column vectors F of the fluid influence coefficients of vibration and sound pressure on the sound pressure at the site, respectively m M, C, K, L and G are automatically generated by a commercial finite element program according to the specific position of the exciting force applied to the structure and the information of the material, the plate thickness, the geometry and the like of the structure; matrices E and D are automated by the commercial boundary element program based on the geometry of the fluid-solid coupling surfaces, the fluid acoustic parameters and the frequency input parametersAnd (4) generating.
4. The fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure according to claim 1, characterized by: sound pressure column vector P with acoustic far-field spherical grid node as field point in step S2) s The expression of (a) is:
P s =E s P-D s U n （E3）
in the formula (E3), E s And D s The method comprises the following steps of (1) forming matrixes by arranging row vectors of fluid influence coefficients given by different grid nodes of an acoustic far-field spherical surface by vibration and sound pressure according to rows;
the sound pressure column vector P taking the acoustic far-field spherical grid node as a field point s For a single frequency calculation, P is calculated for all single frequencies of the frequency band to be analyzed s And integrating to obtain an acoustic far-field spherical radiation noise spectrum model P s (ω)。
5. A fast deduction method for real-time simulation of low frequency radiation noise of a submersible vehicle structure according to claim 3, characterized in that: the sound pressure spectrum of the arbitrary field point in step S3p(r,θ,φ,ω) The expression of (a) is:
p(r,θ,φ,ω)=αB(θ,φ,ω)C(r,ω) （E4）
in the formula (E4), the compound represented by the formula,αis the amplitude factor of the exciting force of the underwater vehicle,B(θ,φ,ω) Is an azimuth directional factor used for reflecting the change of the radiation sound pressure of the underwater vehicle on the acoustic far-field spherical surface under the action of unit exciting force along with the azimuth,C(r,ω) The distance attenuation factor is used for reflecting the attenuation rule of the radiation sound pressure of the underwater vehicle along with the distance.
6. A low frequency for a submersible vehicle structure as claimed in claim 5The fast deduction method for the real-time simulation of the radiation noise is characterized in that: the azimuth pointing factor of the arbitrary field point in step S3B(θ,φ,ω) The expression of (c) is:
Figure 225280DEST_PATH_IMAGE002
（E5）
in the formula (E5), the reaction mixture is,A(θ,φ) Is the sound pressure variation along with the azimuth at the unit distance caused by the exciting force of the underwater vehicle with the unit amplitude,r s is the spherical radius of the acoustic far field,eis a natural logarithm base, and the number of the logarithm bases,cis the speed of sound.
7. The fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure according to claim 6, characterized by: in step S3, an interpolation technology is adopted to obtain the azimuth pointing factor of any field pointB(θ,φ,ω) The method comprises the following steps:
s31, the vector of the field point pointed to by the origin of coordinates is given by the coordinates of the field point in the ship-associated coordinate system and is recorded as
r=(x,y,z) （E7）
The distance of the field point from the origin is:
Figure 681669DEST_PATH_IMAGE003
（E8）
calculating the distance between each grid point on the acoustic far-field spherical surface and the field point, and using standard numerical value comparison program, screening the 3 acoustic far-field spherical grid nodes nearest to the field point, and recording their positions as radial representation(x i s , y i s ,z i s )，i=1,2,3, the distances of the three points from the origin are all the radii of the acoustic far-field spherer s ；
S32 combines the three soundsThe optical far-field spherical grid points are mapped to radius of the optical far-field spherical grid points according to the directions of respective radial diametersrThe interpolation relation is established by utilizing the position relation of the mapping points and the field points, and the coordinates of the three mapping points are expressed as follows:
Figure 171556DEST_PATH_IMAGE004
（E9）
s33 uses the mapping point coordinates to establish three interpolation weight coefficients, which are expressed as:
Figure 764212DEST_PATH_IMAGE005
（E10）
in formula (E10):Ais the area of a triangle with three mapping points as vertexes, expressed as:
Figure 579721DEST_PATH_IMAGE006
（E11）
in the formula (E11), r 12 Is the vector from the mapping point No. 1 to the mapping point No. 2, r 13 The vector formed by the mapping point 1 pointing to the mapping point 3 is calculated by the coordinates of the mapping points:
Figure 257827DEST_PATH_IMAGE007
（E12）
in the formula (E10), the compound represented by the formula,u、vis the field point at r 12 And r 13 Coordinate values in the stretched generalized planar coordinate system, through r 1X Are respectively associated with r 12 And r 13 The inner product of (a) is given, expressed as:
Figure 816984DEST_PATH_IMAGE008
（E13）
in the formula (E13), r 1X Is the vector from the 1 st mapping point to the 2 nd mapping point,expressed as:
r X1 =(x-x 1 ,y-y 1 ,z-z 1 ,) （E14）
in the formula (E10), the compound represented by the formula (E10),a i 、b i 、c i from r 12 And r 13 Given modulo, note:
Figure 529725DEST_PATH_IMAGE009
，
Figure 984978DEST_PATH_IMAGE010
then, thena i 、b i 、c i Respectively calculated as:
Figure 415959DEST_PATH_IMAGE011
（E15）
s34, calculating the azimuth orientation factor by using the obtained three interpolation weight coefficients, wherein the expression is as follows:
Figure 513228DEST_PATH_IMAGE012
（E16）
in the formula (E16), the compound represented by the formula,P i s (ω)，iand =1,2,3, which is the radiation sound pressure spectrum of the acoustic far-field spherical grid node, and is directly extracted from the calculation result of the formula (E4).
8. The fast deduction method for real-time simulation of low-frequency radiation noise of a submersible vehicle structure according to claim 6, characterized by: distance attenuation factor in step S4C(r) The calculation method comprises the following steps:
Figure 346055DEST_PATH_IMAGE013
（E6）。
9. the fast deduction method for the real-time simulation of the low-frequency radiation noise of the underwater vehicle structure as recited in claim 1, wherein: the method is used for radiated noise field equal sound pressure line graph forecasting.
10. A computer-readable storage medium, storing a computer program, characterized in that the computer program, when being executed by a processor, carries out the method of any one of claims 1 to 9.
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