Wind power boosting rotor external field vibration sound radiation simulation method

Abstract

The invention relates to a wind power boosting rotor outfield vibration sound radiation simulation method, which comprises the following steps: based on fluid simulation software Star-ccm +, taking a wind power boosting rotor outer cylinder contour as a rigid wall surface, setting an inlet condition as a wind speed and an outlet condition speed as 0, and calculating outer cylinder contour pulsating pressure; based on structural finite element software Abaqus, a finite element model is established according to the outer cylinder structure of the wind power boosting rotor, pulsating pressure serves as load input, constraint conditions are added, and the vibration displacement of the outer cylinder is calculated; based on acoustic finite element software Actran, node position information of the structural finite element model is imported, an external field acoustic domain is established, and external cylinder external field vibration sound radiation is calculated by taking external cylinder vibration displacement as load input; according to the method, calculation is carried out based on a frequency domain, the real sound wave transmission condition and the actual sound pressure cannot be reflected, and certain limitation exists. Therefore, by adopting the vibration sound radiation time domain simulation analysis method, the vibration sound radiation condition in the time domain can be obtained, and the change of the actual sound pressure along with the time can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of wind-assisted rotors, and in particular to a method for simulating external field vibration and acoustic radiation of a wind-assisted rotor. Background Art

[0002] The wind-assisted propulsion rotor uses wind energy to propel the ship to sail. It is an innovative energy-saving technology with independent structure, simple installation and good prospects. Foreign applications show that the energy saving effect of wind-assisted propulsion rotors used in bulk carriers and large oil tankers can reach 5%-30%, which is an important technical means to solve the three stages of EEDI. When a ship equipped with a wind-assisted propulsion rotor is in a crosswind or oblique wind state, adjusting the speed and direction of the rotor can make the ship generate thrust in the forward direction, thereby using wind energy to achieve a propulsion effect. Compared with wind-assisted propulsion technologies such as kites and sails, wind-assisted propulsion rotors have strong adaptability to wind speed and wind direction, relatively small volume and wind-receiving area, safer and more conducive to ship layout. In addition, wind-assisted propulsion rotors and energy-saving and emission-reduction measures such as hydrodynamic energy saving and alternative fuels can be used in combination to further enhance the energy-saving and emission-reduction effects, and are also suitable for new ships and operating ships.

[0003] Research has found that during the operation of the wind-assisted rotor, due to the high-speed rotation of the outer cylinder, the flexibility of the system itself, and the friction and impact of the internal equipment, the structural vibration will occur and generate huge noise, especially after the wind-assisted rotor is on board, the vibration response will be greater. The dynamic load generated by the vibration of the wind-assisted rotor is positively correlated with the weight. Therefore, once the large wind-assisted rotor still has such a large amount of vibration, the dynamic load generated by the vibration will inevitably pose a threat to the structural safety. Therefore, it is necessary to simulate and predict the noise of the wind-assisted rotor during operation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for simulating the external field vibration and acoustic radiation of a wind-assisted rotor, which can simulate the noise of the wind-assisted rotor during operation, in view of the deficiencies in the prior art.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution: a method for simulating external field vibration and acoustic radiation of a wind-assisted rotor, comprising the following steps: (1) Use the fluid simulation software Star-ccm+ to establish the external contour model of the wind-assisted rotor and set the fluid domain, where the inlet condition is the wind speed, the outlet condition is the pressure outlet, and the other surfaces are set as no-slip walls. The external contour of the wind-assisted rotor is set as the wall and the relative rotation rate of the wall is given; (2) The mesh of the outer contour of the wind-assisted rotor is encrypted, the separated flow fluid model is selected, the gas density is set to constant, and the K-Omega turbulence model is used to perform unsteady calculations to obtain the pulsating pressure data at the mesh points of the outer cylinder of the wind-assisted rotor. (3) Through the grid mapping technology, the pulsating pressure data output by Star-ccm+ is mapped into a structural grid form and exported as a node file and a load file. The grid mapping technology includes dividing the outer cylinder contour into small areas, and mapping the fluid grid in each area to a single grid point; (4) In the Abaqus finite element analysis software, a finite element model is constructed based on the geometric model of the wind turbine rotor. Through the secondary development function, the reference points established by the node file and the load file are cyclically read and bound to the outer cylinder contour geometric model to realize the loading of pulsating pressure; (5) In Abaqus, the dynamic implicit analysis method was used and the maximum incremental step size was set to 0.1 s to ensure the stability and accuracy of the subsequent acoustic simulation calculations. Dynamic analysis was carried out to obtain the normal vibration response of the outer cylinder of the wind-assisted rotor. (6) Import the calculation results of Abaqus into the acoustic finite element software Actran to obtain the acoustic structural model, obtain the outer envelope surface of the acoustic model based on the acoustic structural model, and generate the external acoustic field based on the outer envelope surface; (7) In Actran, set the acoustic boundary condition to Infinite, simulate the sound wave without reflection at the boundary, set the appropriate interpolation order, and import the normal vibration response calculated by Abaqus as the acoustic excitation boundary condition; The setting of the Infinite boundary condition is intended to simulate the free propagation of sound waves in an infinite sound field and avoid the deviation of sound pressure calculation caused by boundary reflection; (8) Carry out time-domain acoustic vibration and acoustic radiation analysis in Actran to calculate the sound pressure at each point in the external acoustic domain. This can not only obtain the overall transmission and change trend of the sound pressure, but also the sound pressure change and actual sound pressure at the focus position; Time domain acoustic analysis can accurately reflect the actual situation of sound wave transmission and the actual sound pressure, and provide detailed information on vibration sound radiation in the time domain and the change of sound pressure over time.

[0006] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the above-mentioned method for simulating the external field vibration and acoustic radiation of a wind-assisted rotor, in step (3), the grid mapping method includes dividing the outer cylinder contour of the wind-assisted rotor into small areas, and mapping the fluid grid in each area into a grid point to reduce the number of grids and optimize computing resources and efficiency.

[0007] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In the above-mentioned method for simulating external field vibration and acoustic radiation of a wind-assisted rotor, in step (4), the specific steps are as follows: (4.1) Establish a finite element model based on the wind turbine rotor geometry model; (4.2) Based on the node file obtained in step (3), traverse the node file and read it line by line. Each time a line of coordinates is read, a reference point is created in abaqus to obtain a set of structural loading grids. All reference points are bound to the outer cylinder contour geometry model so that the load can be transmitted to the outer cylinder structure. (4.3) Based on the load file obtained in step (3), traverse the load file and read it line by line. For each line of load changing with time, a load amplitude curve is created; (4.4) Based on the reference point of step (4.2) and the load amplitude curve of step (4.3), batch create loads, the load action area is the reference point, the load size is 1, the load amplitude is the load amplitude curve, and finally complete the loading of pulsating pressure.

[0008] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In the above-mentioned method for simulating the external field vibration and acoustic radiation of a wind-assisted rotor, in step (7), the setting of the non-reflecting boundary Infinite boundary condition is used to simulate the propagation process of sound waves in an infinite sound field to avoid the sound pressure calculation result being too large due to the reflection of sound waves on the boundary. The setting of this value is closely related to the size of the acoustic domain. When the acoustic domain is small, a larger interpolation order Interpolation Order needs to be set. Conversely, when the acoustic domain is large, a smaller interpolation order InterpolationOrder is set.

[0009] The technical problem to be solved by the present invention can also be achieved by the following technical scheme. In the above-mentioned method for simulating the external field vibration and acoustic radiation of a wind-assisted rotor, in step (8), the time domain acoustic analysis can reflect the actual sound wave transmission situation and the actual sound pressure size, and obtain the vibration and acoustic radiation situation in the time domain and the actual sound pressure change with time.

[0010] Compared with the prior art, the beneficial technical effect of the present invention is that the method is based on the frequency domain to carry out calculations, and cannot reflect the actual sound wave transmission situation and the actual sound pressure size, and has certain limitations. Therefore, the present invention adopts a vibration sound radiation time domain simulation analysis method, which can obtain the vibration sound radiation situation in the time domain and obtain the actual sound pressure change over time; in addition, the method realizes the accurate simulation of the external field vibration sound radiation of the wind-assisted rotor by combining the fluid simulation software Star-ccm+, the finite element analysis software Abaqus and the acoustic finite element software Actran, especially by encrypting the external contour grid, selecting the separated flow fluid model and using the K-Omega turbulence model to perform unsteady calculations, it can accurately obtain the pulsating pressure data on the grid points of the outer cylinder of the wind-assisted rotor, thereby improving the simulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a simulation flow chart of the external field vibration and acoustic radiation simulation method of the wind-assisted rotor of the present invention; Figure 2 It is a fluid simulation diagram of the external field vibration and acoustic radiation simulation method of the wind-assisted rotor of the present invention; Figure 3 It is a velocity distribution diagram in the fluid domain of the external field vibration and acoustic radiation simulation method of the wind-assisted rotor of the present invention; Figure 4 A network mapping flow chart of the wind-assisted rotor external field vibration and acoustic radiation simulation method of the present invention; Figure 5 It is a load loading flow chart of the external field vibration and acoustic radiation simulation method of the wind-assisted rotor of the present invention; Figure 6 It is a schematic diagram of the normal vibration response of the outer cylinder of a wind-assisted rotor in the method for simulating the external field vibration and acoustic radiation of a wind-assisted rotor of the present invention; Figure 7 It is a schematic diagram of the acoustic simulation process of the wind-assisted rotor external field vibration acoustic radiation simulation method of the present invention. DETAILED DESCRIPTION

[0012] The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so as to facilitate further understanding of the present invention by those skilled in the art, and do not constitute a limitation on the rights thereof.

[0013] Example 1, reference Figure 1-7 , a method for simulating the external vibration and acoustic radiation of a wind-assisted rotor. The main idea of ​​this method is: (1) Based on the fluid simulation software Star-ccm+, the outer cylinder contour of the wind-assisted rotor is taken as a rigid wall surface, the inlet condition is set as wind speed, and the outlet condition speed is set as 0, and the pulsating pressure of the outer cylinder contour is calculated; (2) Based on the structural finite element software Abaqus, a finite element model was established according to the wind turbine rotor outer cylinder structure. The pulsating pressure was used as the load input and constraints were added to calculate the vibration displacement of the outer cylinder. (3) Based on the acoustic finite element software Actran, the node position information of the structural finite element model is imported to establish the external field acoustic domain. The vibration displacement of the outer cylinder is used as the load input to calculate the external field vibration acoustic radiation of the outer cylinder.

[0014] In addition, the external field we mentioned means the external sound field. For example, for a hollow sphere, its interior is the internal sound field, and its exterior is the external sound field. If you calculate the internal sound field, the steps are the same, just establish the internal fluid domain. The only difference is that when calculating the internal sound field, the reflection of the sound wave on the wall of the structure must be considered. Therefore, the inside and outside are the inside and outside in space, because we are concerned about the sound heard outside when the rotor is running, that is, the noise radiated outward by the rotor, that is, here is to solve the external field vibration; Also, the fluid domain is a rectangle.

[0015] The specific process is as follows: 1. About fluid simulation: 1. According to the geometric model of the wind turbine rotor, establish its external contour model in starccm+, and establish a rectangular fluid domain outside; 2. Set the inlet, outlet and wall conditions respectively: 2.1 The inlet condition is velocity inlet, and the initial velocity of the fluid is given; 2.2 The outlet condition is pressure outlet; 2.3 The remaining surfaces of the fluid domain are set as no-slip walls. It should be noted that no-slip walls mean that the velocity of the fluid at the wall is zero; 2.4 The outer contour of the wind-assisted rotor is set as the wall, and the relative rotation rate of the wall is given to simulate its rotation in the fluid domain. It should be noted that the given relative rotation rate of the wall is loaded according to the actual speed of the wind-assisted rotor; 3. Encrypt the mesh of the outer contour of the wind turbine rotor to ensure the accuracy of the calculation results. It should be noted that the encryption process actually means that the mesh size of the area close to the structure is set smaller, because finite element calculation is mesh calculation. One mesh and ten meshes in the same area are definitely different. One mesh is one value, but ten meshes can show the changes in this small area. The result will be more accurate and less likely to miss some peaks. Because we are mainly concerned about the flow field changes around the structure, we need to encrypt it, and there is no need to pay attention to the mesh farther away, so the size can be slightly larger to optimize the calculation efficiency. The specific value can be selected according to the use requirements; 4. Select separated flow fluid, set the gas to constant density, use K-Omega turbulence model, and carry out unsteady calculation. It should be noted that the unsteady calculation is based on time. According to whether the physical quantities of fluid flow (such as velocity, pressure, temperature, etc.) change with time, the flow can be divided into two categories: unsteady flow and unsteady flow. If the physical quantities of the fluid do not change with time, it is unsteady flow; if the physical quantities of the fluid change with time, it is called unsteady flow; 5. Set the output conditions to output the pulsating pressure at the grid points on the contour of the outer cylinder of the wind-assisted rotor.

[0016] 2. Network mapping, refer to Figure 4 : 1. Based on the star-ccm+ simulation software, the node pressure on the outer cylinder contour of the wind turbine rotor is output into a csv file: 1.1 Each moment is output into a csv file, a total of 300 files, with a time interval of 0.2s, a total of 60s; 1.2 In each csv file, the first column of data is the current pulsating pressure, the second, third, and fourth columns are x, y, and z coordinates, and each csv file has 25834 nodes; Since there are too many fluid grids, if they are all imported into the structural model for loading and calculation, huge computing resources will be required, which will seriously affect the computing efficiency. Therefore, it is necessary to perform grid mapping, reduce the number of grid points of the fluid grid through the grid mapping method, and output it into a set of structural grids; 2. Simplified principle of grid mapping: 2.1 The outer cylinder profile of the wind turbine rotor is composed of a cylinder body and a top cover. The fluid grids of the cylinder body and the top cover are mapped respectively. 2.2 The specific grid mapping operation is to divide the outer cylinder contour into small areas, and the fluid grid in each area is mapped to 1 grid point, so as to achieve the purpose of reducing the number of grids. It should be noted that here; 2.3 Since the outer cylinder of the wind-assisted propulsion rotor is a cylinder, the cylindrical coordinate system is used for grid mapping. The origin of the coordinate is the center of the bottom of the outer cylinder, and the height direction of the outer cylinder is the Z axis; 3. Grid mapping process: 3.1 According to the parameters of the wind-assisted rotor, determine the parameters of the cylinder and the top cover; 3.2 Independently set the number of cylinders distributed along the axis and circumference / the number of top covers distributed along the radial and circumference; 3.3 Divide the cylinder and the top cover along the axial, circumferential and radial directions to determine the loading area of ​​the cylinder / top cover and the cylindrical coordinates of the central loading point of each loading area; 3.4 Carry out coordinate system transformation, transform the cylindrical coordinate system into a rectangular coordinate system, and obtain the area of ​​each loading area and the rectangular coordinates of the central loading point; 3.5 Based on the outer cylinder contour pulsating pressure calculated by star-ccm+ (i.e. the above-mentioned csv file), the coordinates of the fluid grid points and the pulsating pressure at each point changing with time can be known; 3.6 Traverse the fluid grid coordinate points, determine the loading area where the coordinate point is located based on the loading area obtained in 3.3, count and accumulate the pulsating pressure, so as to obtain the number of fluid grid points in each area and the sum of the pulsating pressure, and finally obtain the average pressure of each area; 3.7 Based on the loading area in 3.4 and the average pressure in each area in 3.6, the loading load in each area can be obtained; 3.8 Based on the loading point coordinates of 3.4 and the loading point loads of 3.7, the structural grid after the fluid grid is mapped can be obtained (including grid coordinates and the loads of each grid point that change with time); 4. Load output: 4.1 Output the structural mesh obtained above into two files: node file and load file; 4.11 Node file: Each row is a different grid point, and the columns are x, y, and z coordinates; 4.12 Load file: Each row is a different grid point, and the column is the load variation along time; 5. Load loading, refer to Figure 5 : 5.1 Based on Abaqus large-scale finite element analysis software, secondary development operations are carried out to cyclically read node files and load files, and batch load the pulsating pressure onto the outer cylinder contour geometry model. The specific process is as follows: 5.11 Based on the wind-assisted rotor model, establish the wind-assisted rotor geometry model (including the outer cylinder contour geometry model) in the abaqus software; 5.12 Based on the node file obtained in the previous step, traverse the node file and read it line by line. Each time a line of coordinates is read, a reference point is created in abaqus to obtain a set of structural loading grids, and all reference points are bound to the outer cylinder contour geometry model, so that the load can be transmitted to the outer cylinder structure; It should be noted that in order to transmit the load to the outer cylinder structure, the load needs to input the values ​​of three directions, CF1, CF2, and CF3, and then give an amplitude curve. The final load is CF×amplitude. For example, CF is (0, 0, 2), which is the load in the z direction. The amplitude change curve is 2 times the size. The time change is the output of the fluid. The step length of the fluid output determines the step length of the load, and the total calculation time of the fluid determines the duration of the load. It should be noted that the reference point is the name of the abaqus software, not a proper noun. Its actual meaning is to create a spatial geometric point based on its xyz coordinates; In addition, the binding mentioned above is actually an operation of the abaqus software, which is a general name for structural finite element calculation. Its meaning is to control the six degrees of freedom of the nodes of the two bound parties at the contact point to be consistent, and no relative displacement and rotation occur (the six degrees of freedom are U1, U2, U3, UR1, UR2, UR3, which are displacement and rotation in the xyz direction). It will also set a distance tolerance, so that when there are some cases involving surface binding, even if the geometric positions do not necessarily coincide, they can be automatically corrected to the corresponding positions according to this tolerance. In this way, loading the load on the above-mentioned spatial geometric points is equivalent to directly loading it on the corresponding position of the structure; 5.13 Based on the load file obtained in the previous step, traverse the load file and read it line by line. Each time a line of load that changes with time is read, a load amplitude curve is created. It should be noted that the creation of the load amplitude curve is based on the software's own functions and secondary development. When it is loaded, a load value and its change curve need to be entered. This change curve has two columns, the first column is time, and the second column is load size. Both need to be entered manually. If only the software is used, the load must be entered manually one by one. This workload is unimaginable. However, based on secondary development, the program can be used to read the input in batches. The specific program content can be selected according to the usage requirements. 5.14 Based on the reference point of 5.12 and the load amplitude curve of 5.13, batch create loads, the load action area is the reference point, the load size is 1, the load amplitude is the load amplitude curve, and finally complete the pulsating pressure loading work.

[0017] 3. Structural simulation: 1. Based on the Solidworks 3D model of the wind-boosting rotor, complete the 2D CAD schematic diagram of each component of the wind-boosting rotor outer cylinder; 2. Based on the 2D CAD schematic diagram and dimensioning of each component of the outer cylinder, a finite element model of the outer cylinder is established in the large-scale finite element analysis and calculation software Abaqus; 3. Use the dynamic implicit analysis method to carry out dynamic calculations, and set the maximum incremental step size to 0.1s for subsequent acoustic simulation calculations. It should be noted that the dynamic implicit analysis method here is an analysis method that needs to be set during calculations. It is generally divided into static calculations and dynamic calculations, which are further divided into dynamic explicit calculations and dynamic implicit calculations. Our problem is to use dynamic implicit because our model involves multiple load points, and the degree of freedom involved is relatively complex. Therefore, the implicit analysis calculation has better accuracy and is easier to converge. 4. Normal vibration response of the outer cylinder of the wind-assisted rotor, refer to Figure 6 , the maximum normal vibration response is at the edge of the top cover.

[0018] 4. Acoustic simulation, refer to Figure 7 : 1. Acoustic simulation model: 1.1 Outer envelope of wind-assisted rotor acoustic model: Based on the calculation results of ABAQUS, it is imported into the ACTRAN software, and the outer envelope is generated based on the model; 1.2 Acoustic domain: Based on the outer envelope surface, the external acoustic field is generated using the "radiation" method; 1.3 Acoustic domain boundary: Based on step 1.2, when generating the external acoustic field, the acoustic field boundary is generated at the same time, and the acoustic boundary conditions are given; 1.4 Field points: 12 field points are evenly set on a circle with a radius of 12.5m and a height of 2m; 2. Acoustic simulation process: 2.1 Based on the structural finite element simulation results, the structural grid node information and grid node vibration are obtained; 2.2 Import the structural grid node information into the Actran software to obtain the acoustic structure model; 2.3 Based on this model, the outer envelope of the acoustic model is generated, and the mesh node vibration information is imported into actran as the acoustic excitation boundary of the outer envelope to calculate the vibration sound radiation; 2.4 Based on the outer envelope surface formed in step 2.3, the outer acoustic domain is generated based on the "radiation" method. The outer envelope surface of the acoustic model is coupled with the acoustic domain. Based on the principle of vibration acoustic radiation, sound waves are generated at the coupling boundary through acoustic excitation (i.e. normal vibration). Based on the transmission principle of sound waves in the fluid domain (acoustic radiation principle), the sound pressure of each point in the acoustic domain can be calculated; 2.5 Generate the outer acoustic domain boundary based on the "radiation" in step 2.4. Since the acoustic domain in actual situation is an infinite area, and it is impossible to establish an infinite acoustic domain in acoustic simulation, it is necessary to set the acoustic domain boundary to simulate an infinite sound field. Otherwise, the sound wave will be reflected when it is transmitted to the boundary, resulting in a larger actual calculated sound pressure result. It should be noted that the meaning of infinity here is that the sound wave radiates all the time without reflection. Of course, this is an ideal situation. After all, the sound wave will always hit an object and reflect. However, one thing is that the sound wave will attenuate as it propagates, and the other is that the direction after reflection may not necessarily return to the sound field and affect the noise level. Therefore, as long as the structure is in an open area, this method can be used to simulate an infinite sound field. 2.6 There are three main methods for setting acoustic boundaries in actran, such as Infinite, PML, APML, Exterior, etc. The Infinite method is used here. It should be noted that the Infinite method involves a sound transmission theory. For example, a wall is air for two hundred years. When sound waves pass from the air to the wall, due to impedance (related to the density, elastic modulus, Poisson's ratio, etc. of the wall), only part of the sound waves can pass through, and the other part will be refracted back, and then part of it will be lost when it penetrates the air from the wall. The ratio of the sound wave that passes through to the original sound wave is the sound transmission coefficient of the wall. However, the principle of no reflection is to achieve the principle that the sound wave is completely absorbed and not reflected by setting this impedance, simulating its infinite propagation in the air without sound waves reflecting back. This method simulates that the sound wave does not reflect at the boundary by setting the acoustic domain boundary as a non-reflection boundary, thereby simulating the process of infinite propagation of sound waves in the acoustic domain. 2.7 In the Infinite setting of the non-reflecting boundary, the interpolation order needs to be set. The setting of this value is closely related to the size of the acoustic domain. When the acoustic domain is small, a larger interpolation order needs to be set. On the contrary, when the acoustic domain is large, a smaller interpolation order is also acceptable. It should be noted that the size of the interpolation order here is related to the size and wavelength of the acoustic field. When the thickness of the acoustic field is small and the wavelength is large, a higher interpolation order is required. When the thickness of the acoustic field is large and the wavelength is small, a smaller interpolation order is required. A convergence analysis can be performed through a finite number of tests. By taking different interpolation orders to see the convergence of the results, a suitable interpolation order that can meet both accuracy and efficiency can be obtained. 2.8 After setting the acoustic field, acoustic boundary and acoustic excitation boundary conditions, you can carry out time domain acoustic vibration and acoustic radiation analysis; It should be noted that: The commonly used frequency domain acoustic analysis process is: calculate the time domain pulsating pressure through fluid simulation software, convert the pulsating pressure from time domain to frequency domain load through Fourier transform, load the frequency domain pulsating pressure onto the structure to carry out frequency response calculation, and obtain the vibration response of the structure at each frequency point; finally, import the response into the acoustic software as acoustic excitation to carry out vibration acoustic radiation simulation calculation; however, this method is based on frequency domain calculation, which cannot reflect the actual sound wave transmission situation and the actual sound pressure size, and has certain limitations.

[0019] Therefore, the present invention adopts the vibration sound radiation time domain simulation analysis method, which can obtain the vibration sound radiation situation in the time domain and obtain the actual sound pressure change over time; In addition, the time-domain acoustic analysis is based on acoustic simulation calculations in the time domain. The acoustic excitation boundary conditions loaded by it are also the time-normal vibration responses directly calculated by the finite element software Abaqus. Vibration acoustic radiation simulation calculations are carried out through the set incremental steps. While calculating the sound pressure in the acoustic domain, the sound pressure that changes with time at the field point is calculated through the principle of acoustic radiation. It can not only obtain the overall transmission and change trend of the sound pressure, but also the sound pressure change and actual sound pressure size at the concerned position. It should be noted that, given the structural simplicity of the analysis object, that is, it is a regular cylindrical shape, its sound wave radiation pattern shows a typical annular diffusion feature, propagating evenly outward along the circumference. Therefore, by observing the propagation path and intensity distribution of the sound waves, we can intuitively identify the areas with strong sound wave radiation and how the sound waves change dynamically with the structural morphology. This type of analysis helps us accurately judge the potential acoustic weaknesses in the structure, and then guide the adoption of targeted optimization measures, such as adding vibration damping materials in areas with significant sound wave radiation to achieve improved acoustic performance.

Claims

1. A method for simulating external vibration and acoustic radiation of a wind-assisted rotor, characterized in that: The following steps are involved: (1) Use the fluid simulation software Star-ccm+ to establish the external contour model of the wind-assisted rotor and set the fluid domain, where the inlet condition is the wind speed, the outlet condition is the pressure outlet, and the other surfaces are set as no-slip walls. The external contour of the wind-assisted rotor is set as the wall and the relative rotation rate of the wall is given; (2) The mesh of the outer contour of the wind-assisted rotor is encrypted, the separated flow fluid model is selected, the gas density is set to constant, and the K-Omega turbulence model is used to perform unsteady calculations to obtain the pulsating pressure data at the mesh points of the outer cylinder of the wind-assisted rotor. (3) Through the grid mapping technology, the pulsating pressure data output by Star-ccm+ is mapped into a structural grid form and exported as a node file and a load file. The grid mapping technology includes dividing the outer cylinder contour into small areas, and mapping the fluid grid in each area to a single grid point; (4) In the Abaqus finite element analysis software, a finite element model is constructed based on the geometric model of the wind turbine rotor. Through the secondary development function, the reference points established by the node file and the load file are cyclically read and bound to the outer cylinder contour geometric model to realize the loading of pulsating pressure; (5) In Abaqus, the dynamic implicit analysis method was used, the maximum incremental step was set to 0.1 s, and dynamic analysis was carried out to obtain the normal vibration response of the outer cylinder of the wind-assisted rotor; (6) Import the calculation results of Abaqus into the acoustic finite element software Actran to obtain the acoustic structural model, obtain the outer envelope surface of the acoustic model based on the acoustic structural model, and generate the external acoustic field based on the outer envelope surface; (7) In Actran, set the acoustic boundary condition to Infinite, simulate the sound wave without reflection at the boundary, set the appropriate interpolation order, and import the normal vibration response calculated by Abaqus as the acoustic excitation boundary condition; (8) Perform time-domain acoustic vibration and acoustic radiation analysis in Actran to calculate the sound pressure at each point in the external acoustic domain. This can not only obtain the overall transmission and change trend of the sound pressure, but also the sound pressure change and actual sound pressure size at the focus position.

2. A method for simulating external field vibration and acoustic radiation of a wind-assisted rotor according to claim 1, characterized in that: In step (3), the grid mapping method includes dividing the outer cylinder contour of the wind-assisted rotor into small areas, and mapping the fluid grid in each area into a grid point to reduce the number of grids and optimize computing resources and efficiency.

3. The method for simulating external field vibration and acoustic radiation of a wind-assisted rotor according to claim 1, characterized in that: In step (4), the specific steps are as follows: (4.1) Establish a finite element model based on the wind turbine rotor geometry model; (4.2) Based on the node file obtained in step (3), traverse the node file and read it line by line. Each time a line of coordinates is read, a reference point is created in abaqus to obtain a set of structural loading grids. All reference points are bound to the outer cylinder contour geometry model so that the load can be transmitted to the outer cylinder structure. (4.3) Based on the load file obtained in step (3), traverse the load file and read it line by line. For each line of load changing with time, a load amplitude curve is created; (4.4) Based on the reference point of step (4.2) and the load amplitude curve of step (4.3), batch create loads, the load action area is the reference point, the load size is 1, the load amplitude is the load amplitude curve, and finally complete the loading of pulsating pressure.

4. The method for simulating external field vibration and acoustic radiation of a wind-assisted rotor according to claim 1, characterized in that: In step (7), the setting of the non-reflecting boundary Infinite boundary condition is used to simulate the propagation process of sound waves in an infinite sound field to avoid the sound pressure calculation result being too large due to the reflection of sound waves on the boundary. The setting of this value is closely related to the size of the acoustic domain. When the acoustic domain is small, a larger interpolation order Interpolation Order needs to be set. Conversely, when the acoustic domain is large, a smaller interpolation order Interpolation Order is set.

5. The method for simulating external field vibration and acoustic radiation of a wind-assisted rotor according to claim 1, characterized in that: In step (8), the time domain acoustic analysis can reflect the actual sound wave transmission and the actual sound pressure, and obtain the vibration sound radiation in the time domain and the actual sound pressure change over time.

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