Sound source calculation method, calculation device, and computer-readable storage medium

Abstract

The present invention relates to a sound source prediction method, a computing device, and a computer-readable storage medium. Among them, the sound source calculation method includes step a. Simulating the unsteady flow of the turbomachine in the channel to obtain the calculation result of the unsteady flow field; step b. According to the calculation result of step a, selecting a plurality of calculation cross-sections at a plurality of axial positions of the channel, with a first axial spacing between the plurality of calculation cross-sections, so that the sound pressure levels of the plurality of calculation cross-sections are within the error band; extracting the calculation input data of the plurality of calculation cross-sections, where the calculation input data includes average mainstream flow parameters, array coordinates, and array values under each harmonic; step c. According to the calculation input data of the channel extracted in step b, performing modal decomposition to obtain the acoustic modal data of the channel; step d. According to the acoustic modal data of the channel in step c, obtaining the sound pressure level information of each propagable mode.

Description

Technical Field

[0001] The present invention belongs to the field of acoustics, and particularly relates to a sound source prediction method, a computing device, and a computer-readable storage medium. Background Art

[0002] For a high bypass ratio turbofan engine, the fan / compressor noise contributes the most to its total sound pressure level and is the most prominent. Even in the supersonic case, the rotor / stator interference noise is still an important part of the discrete noise of the fan / compressor. Studying the propagation law of the rotor / stator interference noise and its prediction is of great significance for both the acoustic design of the engine and the noise reduction design of the engine nacelle.

[0003] According to the basic theory of acoustics, sound waves in the air are weak compression waves composed of alternating micro-compression disturbance waves and micro-expansion disturbance waves, and aerodynamic noise is the pressure disturbance in the flow field region, which propagates as sound waves through the elastic and inertial effects of the gas to the space far from the flow region.

[0004] Theoretically, as long as the algorithm has sufficient time and space accuracy, the calculation results will contain both aerodynamic and aeroacoustic information. However, because of the large difference in energy and scale between the sound variables and the flow variables that generate sound, in most cases, the disturbance level of the sound wave is 3 - 5 orders of magnitude smaller than its average flow quantity, and at the same time, the propagation of sound often has a large spatial scale. Therefore, on the premise of ensuring the simulation accuracy, obtaining the flow field and the aeroacoustic field simultaneously by solving the Navier-Stokes equations in the whole field has very high requirements for both computer hardware and numerical calculation methods, which is difficult to achieve in current engineering.

[0005] To solve the contradiction between calculation accuracy and calculation resource limitations, in recent years, in the research of aeroacoustics, a hybrid flow field / acoustic field calculation method has been developed. In this method, the computational domain is divided into a sound source generation region and an acoustic field propagation region.

[0006] In the aeroacoustic source domain, that is, in the adjacent regions such as the turbomachinery and jet in the engine, the unsteady components of the flow variables such as pressure, velocity, and density have the same order of magnitude as the steady (time-averaged) components of the flow field. Therefore, the governing equations are non-linear, time-dependent, and rotational. Therefore, the unsteady flow field here needs to be calculated by the CFD method. Since the pulsations in the CFD unsteady results include both acoustic pulsations and non-acoustic pulsations and cannot be directly used as the sound source information, accurately extracting the sound wave information from the CFD results is a key issue, which can be used for sound source evaluation and as the sound source input for subsequent sound propagation calculations. Summary of the Invention

[0007] An object of the present invention is to provide a sound source calculation method.

[0008] Another object of the present invention is to provide a computing device.

[0009] Still another object of the present invention is to provide a computer-readable storage medium.

[0010] A sound source calculation method according to an aspect of the present invention is used for calculating the sound source of an impeller machine in a channel, and includes: Step a. Simulating the unsteady flow of the impeller machine in the channel to obtain the calculation result of the unsteady flow field; Step b. According to the calculation result of Step a, selecting multiple calculation cross-sections at multiple axial positions of the channel, with a first axial spacing between the multiple calculation cross-sections, such that the sound pressure levels of the multiple calculation cross-sections are within an error band; extracting the calculation input data of the multiple calculation cross-sections, where the calculation input data includes average mainstream flow parameters, array coordinates, and array values under each harmonic; Step c. According to the calculation input data of the channel extracted in Step b, performing modal decomposition to obtain the acoustic modal data of the channel; Step d. According to the acoustic modal data of the channel in Step c, obtaining the sound pressure level information of each propagable mode.

[0011] In one or more embodiments of the sound source calculation method, in Step b, the step of selecting multiple cross-sections at multiple axial positions of the channel includes:

[0012] Step b1: Estimating sound source information

[0013] Calculating the order m of the circumferential mode through the following formula:

[0014] m = sB - kv

[0015] where B is the number of rotor blades of the impeller machine, v is the number of stator blades of the impeller machine, s is the harmonic order, generally taking the first three orders, and k generally takes -10 to 10.

[0016] The cut-off condition of the mode is where where M is the axial Mach number, C0 is the speed of sound, Ω is the rotational speed (rad / s), and k m,n is the eigenvalue of the Helmholtz equation;

[0017] Step b2: Accuracy analysis

[0018] Selecting high-order modes, given the phase and amplitude, obtaining the sound field calculation data of multiple axial spacings, and selecting the axial spacing within the error band of the sound pressure level as the first axial spacing.

[0019] In one or more embodiments of the sound source calculation method, in Step c, the modal decomposition includes calculating the order m of the circumferential mode through the following formula:

[0020] m = sB - kv,

[0021] where B is the number of rotor blades of the turbomachine, v is the number of stator blades of the turbomachine, s is the harmonic order, generally taking the first three orders, and k generally takes values from -10 to 10.

[0022] In one or more embodiments of the sound source calculation method, in step c, the cut-off condition of the mode is where where M is the axial Mach number, C0 is the speed of sound, Ω is the rotational speed (rad / s), and k m,n is the eigenvalue of the Helmholtz equation.

[0023] In one or more embodiments of the sound source calculation method, in step c, the circumferential mode is obtained according to the array values and array coordinates extracted in step b, in combination with the theoretical solution of the circumferential mode shape function.

[0024] In one or more embodiments of the sound source calculation method, in step c, the circumferential mode is first calculated, and then in combination with the theoretical solutions of the radial mode shape function and the axial mode shape function, the radial mode is obtained.

[0025] In one or more embodiments of the sound source calculation method, the least squares method is used to construct a cost function for the array coordinates of the multiple cross-sections and the array values at each harmonic order. When the cost function is minimized, the radial mode is obtained by solving, that is where C represents the cost function, and P represents the radial mode; the resulting matrix is: coefficient * radial mode = source term, where the source term is composed of the circumferential mode, the radial mode, and the axial mode shape function, and the coefficient is composed of the axial mode shape function and the radial mode shape function.

[0026] According to a computing device in one aspect of the present invention, in step d, according to the acoustic mode data of the channel obtained in step c, substitute it into the sound pressure level formula:

[0027] SPL = 20 * log(P mn / (2 * 10 -5 ))

[0028] where P mn represents the amplitude of the propagable mode, and the sound pressure level information of each propagable mode can be obtained.

[0029] According to a computer-readable storage medium in one aspect of the present invention, on which a computer program is stored, and when the program is executed by a processor, it implements the sound source calculation method as described in any one of the above.

[0030] A sound source calculation device according to an aspect of the present invention is characterized by comprising: a computer-readable storage medium for storing instructions executable by a processor; and a processor for executing the instructions to implement the sound source calculation method described in any one of the above.

[0031] The advantageous effects of the present invention include but are not limited to that by selecting the first axial spacing, the finally solved result is accurate, which is used for sound source near-field flow field sound field extraction, filtering near-field disturbance waves, obtaining accurate sound source results, reducing the sound source calculation domain, reducing the unsteady flow field calculation amount, and at the same time, the sound source can be used for sound propagation calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other features, properties and advantages of the present invention will become more apparent from the following description in conjunction with the drawings and embodiments, where:

[0033] Figure 1 is a non-steady flow field calculation result diagram obtained by the sound source calculation method of an embodiment.

[0034] Figure 2 is a schematic diagram of the calculation input data for extracting the channel by the sound source calculation method of an embodiment.

[0035] Figure 3 is a sound field calculation data diagram of multiple axial spacings of the sound source calculation method of an embodiment.

[0036] Figure 4 is a flowchart of the sound source calculation method of an embodiment

[0037] Figure 5 is a flowchart of the modal decomposition process of the sound source calculation method of an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following discloses various embodiments or examples for implementing the subject technical solutions described above. To simplify the disclosure content, specific examples of each element and arrangement are described below. Of course, these are only examples and do not limit the protection scope of the present invention.

[0039] At the same time, this application uses specific terms to describe the embodiments of this application. Such as "an embodiment", "one embodiment", and / or "some embodiments" mean a certain feature, structure or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this application can be combined appropriately.

[0040] In the following embodiments, the sound source calculation of the impeller machinery in the channel takes the fan noise of a turbofan engine as an example, and is approximately a hard-wall circular pipe for hydrodynamic simulation calculation.

[0041] Reference Figures 1 to 4 As shown, the sound source calculation method of the impeller machinery in the channel includes:

[0042] Step a. Simulate the unsteady flow of the impeller machinery in the channel to obtain the calculation results of the unsteady flow field;

[0043] First, construct a calculation model of the channel 100 and the blade profile of the impeller machinery 200. Since multiple-plane data extraction is required in subsequent steps and a certain axial space is needed, it is reserved when constructing the model. Use the CFD method for unsteady calculation according to the model. As Figure 1 shown, obtain the sound pressure under each harmonic.

[0044] Step b. According to the calculation results of step a, select multiple calculation cross-sections 10 at multiple axial positions in the channel 100. There is a first axial spacing L1 between the multiple calculation cross-sections 10, so that the sound pressure levels of the multiple calculation cross-sections 10 are within the error band. It can be understood that the number of calculation cross-sections 10 is not limited to Figure 2 the three shown in the figure, and can also be more. After the selection of the calculation cross-sections 10, extract the calculation input data of the multiple calculation cross-sections 10. The calculation input data includes average mainstream flow parameters, array coordinates, and array values under each harmonic. Taking the techplot software as an example for illustration, for the process of extracting average mainstream flow parameters, the flow field result file can be imported into tecplot, converted from a 3D view to a 2D view, with the abscissa being the axial direction and the ordinate being the radial direction, and select the mainstream flow parameters at the required axial positions. The array coordinates and array values under each harmonic are array data. The flow field result file can be imported into the tecplot software, and the coordinates, pressure data, etc. corresponding to the specified array grid can be extracted in the selected domain, and the data is output and written into an editable.dat file. The above introduction taking techplot as an example is only to more clearly and intuitively illustrate the embodiment, rather than the present invention relying on techplot to be carried out. The beneficial effect of selecting the first axial spacing L1 is that the final sound source calculation result can be accurate. The principle is that the inventor found that the position of multiple planes from the sound source has no influence on the sound pressure level, and the selection of the spacing between multiple cross-sections has a greater influence on the sound pressure level. As Figure 3 shown in the error band B area, that is, the middle dotted line represents the standard value, and the upper and lower two dotted lines represent the upper and lower limits of the allowable error. It can be understood that some spacings seem close, but the sound pressure levels are very different. For example Figure 3As shown, the abscissas of numerical points 2 and 3 are close to that of numerical point 1, but the ordinates are quite different. Only the spacing value of numerical point 1 meets the requirement that the sound pressure level is within the error band. For example, the same is true for numerical points 4 and 5. The spacing value of numerical point 5 meets the requirement that the sound pressure level is within the error band, while numerical point 5 is significantly deviated. The inventor found that the principle lies in that the cost function is a function related to the axis coordinates, and there is singularity when solving the cost function. The significantly deviated numerical points are the singular solutions. The cost function C is as follows:

[0045]

[0046] where i is the number of axial sections, j is the radial mode order, n is the radial mode order, P is the radial mode amplitude, α is the integral function of the radial mode shape function and the axial mode shape function, and q is the integral function of the unsteady pressure and the radial mode shape function.

[0047] The first axial spacing L1 that meets the requirements can be calculated by the estimation method. The specific steps can be:

[0048] Step b1: Estimate the sound source information

[0049] Calculate the order m of the circumferential mode through the following formula:

[0050] m = sB - kv

[0051] where B is the number of rotor blades of the turbomachine, v is the number of stator blades of the turbomachine, s is the harmonic order, generally taking the first three orders, and k generally takes -10 to 10.

[0052] The cut-off condition of the mode is where where M is the axial Mach number, C0 is the speed of sound, Ω is the rotational speed (rad / s), and k m,n is the eigenvalue of the Helmholtz equation;

[0053] Step b2: Precision analysis

[0054] Select high-order modes, given the phase and amplitude, and obtain the sound field calculation data of multiple axial spacings by propagating in channel 100. Select the axial spacing within the error band of the sound pressure level as the first axial spacing L1. For example Figure 3 As shown, select the axial spacing within error band B as the first axial spacing L1.

[0055] Step c. According to the calculation input data of multiple cross-sections 10 obtained by extraction in step b, average the mainstream flow parameters, array coordinates, and array values, and perform modal decomposition to obtain the acoustic modal data of the channel.

[0056] Similar to step b, the order m of the circumferential mode is:

[0057] m = sB - kv

[0058] where B is the number of rotor blades of the turbomachine, v is the number of stator blades of the turbomachine, s is the harmonic order, generally taking the first three orders, and k generally takes values from -10 to 10.

[0059] The cut-off condition of the mode is where where M is the axial Mach number, C0 is the speed of sound, Ω is the rotational speed (rad / s), and k m,n is the eigenvalue of the Helmholtz equation

[0060] The circumferential mode can be obtained through circumferential arrays, i.e., array coordinates and array numerical calculations. The circumferential mode can be represented by the combination of array data and the mode shape function. For the approximately hard-wall circular tube of channel 100, the shape function has a theoretical solution, and the circumferential mode can be obtained by obtaining the array data.

[0061] For the radial mode, since the circumferential mode can be expressed as the combination of the radial mode, the radial mode shape function, and the axial mode shape function. For the hard-wall circular tube, the radial and axial shape functions have theoretical solutions. Given the known circumferential mode, the radial mode can be obtained. Among them, the forward and backward propagation modes are distinguished by the axial wave number.

[0062] Using the least squares method to construct a cost function for the array data of multiple cross-sections. The cost function is related to the radial mode. When the cost function is minimized, the radial mode is obtained by solving, expressed as where C represents the cost function and P represents the radial mode. The obtained matrix is: coefficient * radial mode = source term, where the source term is composed of the circumferential mode, the radial and axial mode shape functions, and the coefficient is composed of the axial and radial mode shape functions. Finally, the matrix is solved to obtain the radial mode.

[0063] Step d. According to the acoustic mode data of the channel in step c, obtaining the sound pressure level information of each propagable mode may include

[0064] Step d1. Through step c, the propagable acoustic mode information, i.e., the mode of order (m, n), can be obtained, where m represents the circumferential mode order and n represents the radial mode order.

[0065] Step d2. According to the sound pressure level formula SPL = 20 * log(P mn / (2 * 10 -5 )), where P mn represents the amplitude of the propagable mode, the sound pressure level information of each propagable mode can be obtained.

[0066] In some embodiments, there may finally be a step of precision analysis to verify the calculation results. The standard for precision definition can be that the cost function error is less than 1%, or of course other appropriate standards, as long as the purpose of verification can be achieved. If the precision does not meet the requirements, it is necessary to reselect the cross-sectional data to carry out the analysis.

[0067] According to another aspect of this case, this case also provides a computer-readable storage medium.

[0068] The above computer-readable storage medium provided by the present disclosure stores computer instructions thereon. When the computer instructions are executed by a processor, the program can be executed by the processor to implement the steps executed by the program in the sound source calculation method introduced in the above embodiments.

[0069] It can be understood that the sound source calculation device corresponding to the embodiments of the above calculation method can be a computer, a server, a smart mobile device, a virtual reality device, an augmented reality device, etc. The sound source calculation device may include a processor and a computer-readable storage medium. The processor can execute the instructions stored in the computer-readable storage medium to implement the sound source calculation method. In some embodiments, the processor may include at least one hardware processor, for example, a microcontroller, a microprocessor, a reduced instruction set computer (RISC), an application specific integrated circuit (ASIC), an application specific instruction set processor (ASIP), a central processing unit (CPU), a graphics processing unit (GPU), a physics processing unit (PPU), a single-chip microcomputer, a digital signal processor (DSP), a field programmable gate array (FPGA), an advanced reduced instruction set system (ARM), a programmable logic device (PLD), any circuit or processor capable of executing at least one function, etc., or any combination thereof.

[0070] The computer-readable storage medium can store computer-readable instructions and / or data. The computer-readable storage medium may include memory and storage.

[0071] The memory can store computer-readable instructions and / or data in a volatile manner. For example, it can store program instructions for modal decomposition, program instructions for precision analysis, etc. The memory can be a volatile read-write memory, such as a random access memory (Random Access Memory, RAM). The memory may include, for example, a dynamic RAM (DRAM), a double data rate synchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristor RAM (T-RAM), a zero capacitor RAM (Z-RAM), etc.

[0072] The memory can store computer-readable instructions and / or data non-volatilely. For example, it can store program instructions for modal decomposition, program instructions for precision analysis, etc. The memory can include mass storage, removable storage, read-only memory (ROM), etc., or any combination thereof. Exemplary mass storage can include magnetic disks, optical disks, solid-state drives, etc. Exemplary removable storage can include flash drives, floppy disks, optical disks, memory cards, compact disks, magnetic tapes, etc. Exemplary ROM can include mask ROM (MROM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), CD-ROM, digital versatile disc ROM, etc. In some embodiments, the memory can be implemented on a cloud platform. By way of example only, the cloud platform can include private cloud, public cloud, hybrid cloud, distributed cloud, cross-cloud, multi-cloud, etc., or any combination thereof.

[0073] As described above, by using the sound source calculation method, calculation device, and computer-readable storage medium introduced in the above embodiments, the beneficial effects include that by selecting the first axial spacing, the finally solved result is accurate, which is used for sound source near-field flow field sound field extraction, filtering near-field disturbance waves, obtaining accurate sound source results, reducing the sound source calculation domain, reducing the unsteady flow field calculation amount, and at the same time, the sound source can be used for sound propagation calculation.

[0074] Although the present invention is disclosed as above in the foregoing embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, all modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention fall within the protection scope defined by the claims of the present invention.

Claims

1. A sound source calculation method for calculating the sound source of an impeller machine in a channel, characterized in that Including: Step a. Simulate the unsteady flow of the impeller machinery in the channel to obtain the calculation results of the unsteady flow field; Step b. According to the calculation results of step a, select multiple calculation cross-sections at multiple axial positions in the channel. There is a first axial spacing between the multiple calculation cross-sections, so that the sound pressure levels of the multiple calculation cross-sections are within the error band; Extract the calculation input data of the multiple calculation cross-sections. The calculation input data includes average mainstream flow parameters, array coordinates, and array values under each harmonic; In step b, the step of selecting multiple cross-sections at multiple axial positions in the channel includes: Step b1: Estimate the sound source information Calculate the order m of the circumferential mode through the following formula: where B is the number of rotor blades of the turbomachine, and v is the number of stator blades of the turbomachine, is the harmonic order, and generally the first three orders are taken, generally taken from -10 to 10, The cut-off condition of the mode is , where , where M is the axial Mach number, C0 is the speed of sound, is the rotational speed, with the unit of rad / s, m,n is the eigenvalue of the Helmholtz equation; Step b2: Precision analysis Select high-order modes, given the phase and amplitude, obtain the sound field calculation data at multiple axial spacings, and select the axial spacing within the error band of the sound pressure level as the first axial spacing; Step c. According to the calculation input data of the channel extracted in step b, perform modal decomposition to obtain the acoustic modal data of the channel; Step d. According to the acoustic modal data of the channel in step c, obtain the sound pressure level information of each propagable mode.

2. The sound source calculation method according to claim 1, wherein In step c, the modal decomposition includes calculating the order m of the circumferential mode through the following formula: ， where B is the number of rotor blades of the turbomachine, and v is the number of stator blades of the turbomachine. is the harmonic order, generally taking the first three orders. generally taking values from -10 to 10.

3. The sound source calculation method according to claim 2, characterized in that In the step c, the cut-off condition of the mode is , where , where M is the axial Mach number, C0 is the speed of sound, is the rotational speed, with the unit of rad / s, m,n is the eigenvalue of the Helmholtz equation.

4. The sound source calculation method according to claim 3, characterized in that In step c, the circumferential mode is obtained according to the array values and array coordinates extracted in step b, combined with the theoretical solution of the circumferential mode shape function.

5. The sound source calculation method according to claim 1, characterized in that, In step c, first calculate the circumferential mode, and then combine the theoretical solutions of the radial mode shape function and the axial mode shape function to obtain the radial mode.

6. The sound source calculation method according to claim 5, characterized in that Construct a cost function for the array coordinates of the multiple cross-sections and the array values under each harmonic using the least squares method. When the cost function is minimized, solve for the radial mode, that is , where C represents the cost function and P represents the radial mode; the resulting matrix is: coefficient * radial mode = source term, where the source term is composed of the circumferential mode, radial mode, and axial mode shape functions, and the coefficient is composed of the axial mode shape function and the radial mode shape function.

7. The sound source calculation method according to claim 1, characterized in that In step d, according to the acoustic modal data of the channel obtained in step c, substitute it into the sound pressure level formula: ， Among them represents the amplitude of the propagable mode, and the sound pressure level information of each propagable mode can be obtained.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, This program is executed by a processor to implement the sound source calculation method according to any one of claims 1-7.

9. A sound source calculation device, characterized in that, Including: A computer-readable storage medium for storing instructions executable by a processor; A processor for executing the instructions to implement the sound source calculation method according to any one of claims 1 to 7.

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