CN-121997845-A - Method for decomposing coupling momentum potential theory and pressure fluctuation and application thereof

CN121997845ACN 121997845 ACN121997845 ACN 121997845ACN-121997845-A

Abstract

The invention provides a coupling momentum theory and pressure fluctuation decomposition method and application thereof, belonging to the field of fluid mechanics and aero-acoustic. The method comprises the steps of firstly obtaining flow field data, carrying out Helmholtz decomposition on a momentum density field based on a momentum potential theory to obtain momentum densities of fluid dynamics, acoustics and entropy components, then taking the momentum densities of the components as independent source items, respectively constructing independent Poisson equations describing fluid dynamics pressure, acoustics pressure and entropy pressure, and finally solving the equations to obtain a pressure fluctuation field of each physical component. The invention establishes the physical mapping of the momentum mode and the pressure mode, gets rid of the dependence of the prior art on a filtering threshold value or a propagation speed criterion, realizes the automatic and physical consistency separation of the acoustic pressure (true sound) and the hydrodynamic pressure (false sound) in the complex turbulence, and is suitable for the noise mechanism research, the source positioning and the noise reduction design.

Inventors

ZHAO XINYI
XU YIXIAN
WANG JUNCHENG
WANG XINYI
LIAO WENMIN

Assignees

浙江理工大学

Dates

Publication Date: 20260508
Application Date: 20260410

Claims (10)

1. A method of coupling momentum theory and pressure fluctuation decomposition, comprising the steps of: Acquiring transient flow field data of a target flow field, wherein the transient flow field data at least comprises density, velocity vector and pressure; based on a momentum potential theory, carrying out modal decomposition on a momentum density vector field of the target flow field, and separating to obtain the momentum density of a hydrodynamic component, the momentum density of an acoustic component and the momentum density of an entropy component; Based on a divergence form of a flow field momentum equation, respectively constructing a pressure poisson equation for independently describing hydrodynamic pressure fluctuation, acoustic pressure fluctuation and entropy pressure fluctuation, wherein a source term of the pressure poisson equation is correspondingly constructed by the momentum density of the hydrodynamic component, the momentum density of the acoustic component and the momentum density of the entropy component; and solving the pressure poisson equation to obtain a hydrodynamic pressure wave field, an acoustic pressure wave field and an entropy pressure wave field respectively.
2. The method according to claim 1, characterized by the step of modal decomposition of the momentum density vector field based on momentum potential theory, in particular comprising: Calculating a momentum density vector field of the target flow field; carrying out Reynolds decomposition on the density of the flow field, and solving a density poisson equation by taking the time derivative of the pulsation density as a source term to obtain the total pulsation scalar potential; Carrying out Reynolds decomposition on flow field pressure, and solving a pressure Poisson equation by taking a function of a time derivative of pulsating pressure and average sound velocity as a source term to obtain acoustic scalar potential; based on the helmholtz decomposition theorem, the momentum density of the hydrodynamic component and the momentum density of the acoustic component are calculated by using the total pulsed scalar potential and the acoustic scalar potential.
3. The method of claim 2, wherein the step of modal decomposition further comprises: Subtracting the acoustic scalar potential from the total pulsating scalar potential according to a thermodynamic relationship, and calculating to obtain an entropy scalar potential; And calculating the momentum density of the entropy component by using the gradient of the entropy scalar potential.
4. A method according to claim 3, wherein the momentum density of each component is determined according to the following equation: the momentum density of the hydrodynamic component comprises an average amount And the amount of pulsation In which the amount of pulsation Subtracting the average from the momentum density vector field The acoustic momentum density and the entropy momentum density are obtained; The momentum density of the acoustic component is the negative gradient of the acoustic scalar potential ; The momentum density of the entropy component is the negative gradient of the entropy scalar potential 。
5. The method of claim 1, wherein the source term of the pressure poisson equation consists of a first order linear source term generated by the corresponding momentum density component or a higher order nonlinear term generated due to self-interaction of the corresponding momentum density component and coupling with other components; the first-order linear source term is reserved as a dominant mechanism when constructing the pressure poisson equation.
6. The method of claim 5, wherein the construction of the pressure poisson equation satisfies the relationship: Source term function of hydrodynamic pressure fluctuation Momentum density at least with hydrodynamic component Correlation; source term function of acoustic pressure fluctuations At least with the momentum density of the acoustic component Time derivative of acoustic scalar potential Correlation; Source term function of entropy pressure fluctuation Momentum density at least with entropy component Time derivative of entropy scalar potential And (5) correlation.
7. The noise source decomposition method according to claim 6, wherein the specific form of the poisson's equation is: Hydrodynamic pressure poisson equation: ; Acoustic pressure poisson equation: ; entropy pressure poisson equation: ; Wherein, the 、、 Hydrodynamic pressure fluctuation, acoustic pressure fluctuation and entropy pressure fluctuation to be solved respectively; 、、 is a high order nonlinear term; is the flow field density.
8. The method of claim 1, wherein the step of solving the poisson's equation of pressure comprises: Setting boundary conditions according to physical characteristics of a flow field boundary; For solid wall boundaries, setting acoustic pressure fluctuations and entropy pressure fluctuations to zero; for far field boundaries, the normal gradients of hydrodynamic pressure fluctuations, acoustic pressure fluctuations, and entropy pressure fluctuations are set to zero to simulate no reflected outflow conditions.
9. The method as recited in claim 1, further comprising: outputting the acoustic pressure wave field and analyzing the spatial distribution, wave packet structure or spectral characteristics of the noise source based on the acoustic pressure wave field to identify dominant noise generation mechanisms.
10. A readable storage medium, characterized in that the readable storage medium has stored therein a computer program comprising program code for controlling a process to perform a process, the process comprising the method according to any one of claims 1 to 9.

Description

Method for decomposing coupling momentum potential theory and pressure fluctuation and application thereof Technical Field The invention relates to the technical fields of hydrodynamics, aeroacoustics and Computational Fluid Dynamics (CFD), in particular to a method and application of coupled momentum theory and pressure fluctuation decomposition. Background In the engineering fields of aerospace, high-speed trains, wind power generation and the like, pneumatic noise generated by compressible turbulence is a key environmental protection and structural safety problem. Pressure fluctuations are the core physical quantities characterizing flow field dynamics and acoustic radiation characteristics, and consist of one fluid dynamic pressure (i.e. "pseudo-sound") that convects with fluid movement but does not radiate outward, and one acoustic pressure (i.e. "true sound") that propagates toward the far field at sonic velocity. The accurate stripping of acoustic components from near-field complex pressure signals is a prerequisite for revealing noise mechanisms and locating sound sources. When the prior art is used for pressure fluctuation decomposition, the following three technical routes mainly exist: 1. The wave number-frequency domain-based filtering method is to set a threshold value in the frequency domain by utilizing the characteristics that sound waves propagate at sound velocity and vortex waves propagate at convection velocity (namely, a technical route A in a picture 2). However, in high-speed jet or transonic flow, the convective velocity of the fluid is very close to the speed of sound, resulting in aliasing of the spectral features of the two in the wavenumber domain, failure of the physical criteria based on phase velocity, and ineffective separation. 2. The data-driven mode decomposition method comprises the steps of extracting a flow field mode by utilizing algorithms such as POD, SPOD or DMD, and then manually screening an acoustic mode (namely a technical route B in a picture 2). The mode extracted by the method is usually a mixture of hydrodynamic and acoustic components, the physical meaning is not pure, and the screening process is seriously dependent on subjective experience or far-field auxiliary data and lacks objectivity. 3. Traditional physical decomposition methods (such as the momentum theory, MPT), while MPT can strictly decompose the momentum density field into swirled (vortex), acoustic and entropy components based on helmholtz decomposition, the current research remains only at the velocity or momentum level. This theory has not previously been directly used to obtain independent acoustic pressure fields due to the lack of an explicit mathematical physical framework to map the momentum decomposition results to the pressure field. In view of the above, the prior art lacks an automated decomposition scheme that can directly act on pressure fields, is independent of empirical thresholds, and is physically strictly self-consistent. Disclosure of Invention The embodiment of the invention provides a coupling momentum potential theory and pressure fluctuation decomposition method and application thereof, and aims to solve the problems that the prior pressure decomposition technology is limited by criterion failure (filtering method) when the convection speed is close to the sound velocity, or is limited by mode physical meaning mixing and depends on subjective screening (data driving method), and pure acoustic pressure components cannot be automatically and objectively separated in complex compressible turbulence. The core technology of the invention mainly provides a method for coupling momentum theory and pressure fluctuation decomposition, which is characterized in that the momentum density is subjected to Helmholtz decomposition by utilizing the momentum theory (MPT), and fluid dynamics, acoustics and entropy momentum density components obtained by decomposition are respectively used as independent source items, and corresponding Poisson equations are constructed and solved, so that the automatic and accurate decoupling of a pressure wave field on a physical mechanism is realized. In a first aspect, the present invention provides a method of coupled momentum theory and pressure fluctuation resolution, the method comprising the steps of: Acquiring transient flow field data of a target flow field, wherein the transient flow field data at least comprises density, velocity vector and pressure; Based on a momentum potential theory, carrying out modal decomposition on a momentum density vector field of a target flow field, and separating to obtain the momentum density of a hydrodynamic component, the momentum density of an acoustic component and the momentum density of an entropy component; based on a divergence form of a flow field momentum equation, respectively constructing a pressure poisson equation for independently describing hydrodynamic pressure fluctuation, acoustic pressure fluc