Method, device, medium and system for calculating local compressible flow in low-speed flow field

Abstract

The invention discloses a method, equipment, medium and system for calculating local compressible flow in a low-speed flow field, and belongs to the field of fluid power calculation, and the method comprises the following steps: in the process of calculating the local compressible flow in the low-speed flow field, different algorithms are adopted for processing through grid speed judgment; when the speed in the grid is smaller than a first set value, an incompressible pressure correction equation is adopted for solving; when the speed is between a set value I and a set value II, solving by adopting a compressible pressure correction equation, and calculating an interface density correction calculation result through a linear interpolation method; and when the grid speed is greater than a set value 2, solving by adopting a compressible pressure correction equation. According to the method, the accurate low-speed flow field and the local compressible flow field can be obtained, and the method is suitable for calculating the local part in the incompressible flow field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of computational fluid dynamics, and more particularly, to a method, device, medium and system for calculating local compressible flow in low-speed flow field. BACKGROUND

[0002] Simple (Semi Implicit Methed for Pressure Linked Equations) algorithm is a semi-implicit algorithm based on pressure coupling, which is commonly used to solve low-speed flow field.

[0003] At present, the calculation scheme for solving the pressure correction equation of the compressible flow using the Simple algorithm has the following technical problems: when the compressible flow is calculated in the full flow field, most of the area is a low-speed flow field, and only a small amount of area is distributed with the compressible flow, the calculation convergence is difficult, resulting in poor calculation effect, and accurate simulation effect cannot be achieved. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art, and provides a method, device, medium and system for calculating local compressible flow in low-speed flow field, which can obtain more accurate low-speed flow field and local compressible flow field, and is suitable for calculating local incompressible flow field.

[0005] The purpose of the present application is achieved by the following scheme: A method for calculating local compressible flow in low-speed flow field, comprising the following steps: In the process of calculating local compressible flow in low-speed flow field, different algorithms are used to process by grid speed determination; when the speed in the grid is less than the set value one, the incompressible pressure correction equation is used to solve; when the speed is between the set value one and the set value two, the compressible pressure correction equation is used to solve, and the interface density correction calculation result is calculated by linear interpolation method; when the grid speed is greater than the set value two, the compressible pressure correction equation is used to solve.

[0006] Further, the set value one is 0.3Mpa, and the set value two is 0.4Mpa.

[0007] Further, the different algorithms are used to process by grid speed determination; when the speed in the grid is less than the set value one, the incompressible pressure correction equation is used to solve; when the speed is between the set value one and the set value two, the compressible pressure correction equation is used to solve, and the interface density correction calculation result is calculated by linear interpolation method; when the grid speed is greater than the set value two, the compressible pressure correction equation is used to solve, and the specific steps are as follows: Step S1, creating a flow field calculation grid on a computer; Step S2, inputting the calculation grid into the solver module of the computer; Step S3, computer processing grid; Step S4, solving flow field on the processed grid, different algorithms are used to deal with the flow field solution by grid velocity judgment; the flow is as follows: Step S4.1, given the initial pressure and initial velocity or the calculation result of step S3 to update the flow field; Step S4.2, solving the momentum equation to obtain new velocity; Step S4.3, solving the pressure correction equation: Judging the grid velocity, if the velocity is less than the set value one, the mass flux generated by the density correction part is recorded as 0, and the interface correction flux expression is: ; The density before correction is represented by The velocity correction amount is represented by S, and the area of the e face is represented by S; If the grid velocity is between the set value one and the set value two, a difference factor A is proposed, so that the mass flux generated by the density correction part is expressed as: ; So that the interface correction flux expression is: ; The value of the set value includes 0.3, and the difference factor A expression is: ; Wherein, V is the grid Mach number, URF is the relaxation factor, which is set according to the calculation situation, and "*" represents multiplication; If the grid velocity is greater than the set value two, the interface flux expression is: ; Wherein, The velocity before correction is represented by The density correction amount is represented by Step S4.4, solving energy, turbulence scalar equation; Step S5, judging whether the calculation result is converged according to the residual, if not, repeating to step S4.1, and iteratively solving until the residual meets the convergence requirement; Step S6, post-processing the calculation result.

[0008] An apparatus for calculating local compressible flow in low-speed flow field, comprising a processor and a memory, the memory stores a computer program, when the computer program is loaded by the processor, the method as claimed in any one of the above is executed.

[0009] A computer readable storage medium having stored therein a computer program which, when loaded by a processor, performs the method of any one of the above.

[0010] A system for computing locally compressible flow in low speed flow field, comprising the device as described above.

[0011] The beneficial effects of the present application include: In the pressure correction equation of the Simple algorithm, the grid velocity is used as the basis for judgment, and the corresponding calculation method is used. When the grid velocity is between 0.3Ma and 0.4Ma, a linear difference factor A is proposed to optimize the calculation in the transition region between compressible and incompressible. The present application is applied to the calculation of locally compressible flow in low speed flow field, which can effectively solve the convergence difficulty encountered in the calculation of low speed flow field using the SIMPLE algorithm, and can obtain more accurate low speed flow field and locally compressible flow field.

[0012] Compared with the traditional compressible pressure correction equation solving method, the advantage of the present application is that different calculation methods are used for different speed domains, which can ensure the calculation effect of large range low speed flow field and the accurate simulation of a small amount of compressible flow field. Therefore, the method established by the present application is suitable for calculating locally in incompressible flow field. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0014] Figure 1 The step flow chart of the method of the embodiment of the present application. DETAILED DESCRIPTION

[0015] All features disclosed in all examples in the present specification, or all steps in the methods or processes impliedly disclosed, can be combined and / or extended, replaced, in any way, except for mutually exclusive features and / or steps.

[0016] TERMS EXPLANATION Simple algorithm: is the abbreviation of Semi Implicit Methed for Pressure Linked Equations, that is, the semi-implicit calculation method based on pressure coupled equation.

[0017] Pressure correction equation: in order to meet the mass conservation in the flow field, the equation of pressure correction value is derived in the Simple algorithm.

[0018] Grid: the partial differential equation embodies the spatial and temporal distribution evolution law of physical quantities (velocity, pressure, etc.) through derivative relationship, and the numerical discrete method is to convert these derivative relationships into algebraic relationships. In the computer solution of partial differential equations, the numerical discrete method needs to be used. Discrete is to divide the continuous physical quantity into small units, and the small unit is the grid.

[0019] In view of the problems in the background, the specific implementation process of the present application is as follows: The present application adopts the combination of compressible simple algorithm and incompressible simple algorithm to solve the local compressible flow in low-speed flow field. Different algorithms are used for processing through grid velocity determination. When the grid velocity is less than 0.3Ma, the incompressible pressure correction equation is used for solving; when the velocity is between 0.3 and 0.4Ma, the compressible pressure correction equation is used for solving, and the interface density correction calculation result is calculated through linear interpolation method; when the grid velocity is greater than 0.4Ma, the compressible pressure correction equation is used for solving.

[0020] More specifically, in one embodiment, a method for calculating local compressible flow in low-speed flow field is provided, and the specific implementation steps are as follows: Step S1, creating a complete set of flow field calculation grid; Step S2, inputting the grid into the solver; Step S3, processing the grid; Step S4, solving the flow field for the processed grid, and the flow field solving is processed by different algorithms through grid velocity determination, and the flow is as follows: Step S4.1, giving initial pressure and initial velocity or updating the flow field with the calculation result of the last step; Step S4.2, solving the momentum equation to obtain new velocity; Step S4.3, solving the pressure correction equation: Determine the grid velocity, if the velocity is less than 0.3Ma, the mass flux generated by the density correction part is 0, and the interface correction flux expression is:

[0021] The density before correction is represented by rho0, The velocity correction amount is represented by deltaU, and S represents the area of the e surface; If the grid velocity is between 0.3Ma and 0.4Ma, a difference factor A is proposed, so that the mass flux generated by the density correction part is expressed as: ​Thus, the interface correction flux expression is: ; The difference factor A expression is: ; Wherein, V is the grid Mach number, URF is the relaxation factor, which can be set according to the calculation, and "*" represents multiplication; If the grid velocity is greater than 0.4Ma, the interface flux expression is: ; Wherein, Indicates the velocity before correction, Indicates the density correction amount; Step S4.4, solving energy, turbulence and other scalar equations; Step S5, determining whether the calculation result is converged according to the residual, if not, repeating to step S4.1, and iteratively solving until the residual meets the convergence requirement; Step S6, post-processing the calculation result.

[0022] Further in the optional implementation, another device for calculating local compressible flow in low-speed flow field is provided, comprising a processor and a memory, and the memory stores a computer program which, when loaded by the processor, executes the method as described in any of the above embodiments.

[0023] Further in the optional implementation, a computer readable storage medium is provided, and the computer readable storage medium stores a computer program which, when loaded by a processor, executes the method as described in any of the above embodiments.

[0024] Further in the optional implementation, a system for calculating local compressible flow in low-speed flow field is provided, comprising the device as described in the above embodiments.

[0025] The units described in the embodiments of the present application can be implemented in the form of software or hardware, and the described units can also be arranged in a processor. In some cases, the names of these units do not constitute a limitation on the units themselves.

[0026] According to an aspect of an embodiment of the present application, a computer program product or computer program is provided, which comprises computer instructions stored in a computer readable storage medium. The processor of the computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions, so that the computer device executes the method provided in the various optional implementations described above.

[0027] As another aspect, the embodiments of the present application also provide a computer readable medium, which can be included in the electronic device described in the above embodiments, or exist independently without being assembled into the electronic device. The computer readable medium carries one or more programs, which, when executed by the electronic device, enable the electronic device to implement the method described in the above embodiments.

Claims

1. A method for calculating local compressible flow in a low-velocity flow field, characterized in that, Includes the following steps: In calculating the local compressible flow in a low-velocity flow field, different algorithms are used based on the grid velocity. When the velocity in the grid is less than a set value one, the incompressible pressure correction equation is used to solve the problem. When the velocity is between a set value one and a set value two, the compressible pressure correction equation is used to solve the problem, and the interface density is calculated and corrected using linear interpolation. When the grid velocity is greater than a set value two, the compressible pressure correction equation is used to solve the problem.

2. The method for calculating local compressible flow in a low-velocity flow field according to claim 1, characterized in that, The first setting is 0.3 MPa, and the second setting is 0.4 MPa.

3. The method for calculating local compressible flow in a low-velocity flow field according to claim 1, characterized in that, The determination of mesh velocity employs different algorithms. When the velocity in the mesh is less than a set value one, the incompressible pressure correction equation is used for solution. When the velocity is between a set value one and a set value two, the compressible pressure correction equation is used for solution, and the interface density correction result is calculated using linear interpolation. When the mesh velocity is greater than a set value two, the compressible pressure correction equation is used for solution, specifically including the following sub-steps: Step S1: Create a flow field calculation mesh on the computer; Step S2: Input the computational mesh into the computer's solver module; Step S3: Computer processes the mesh; Step S4: Solve the flow field on the processed mesh. The flow field solution uses different algorithms based on the mesh velocity determination. The process is as follows: Step S4.1: Update the flow field by providing the initial pressure and initial velocity or the calculation results from step S3; Step S4.2: Solve the momentum equation to obtain the new velocity; Step S4.3: Solve the pressure correction equation: Determine the mesh velocity. If the velocity is less than a set value of 1, record the mass flux generated by the density correction component as 0. The expression for the interface correction flux is: ； This indicates the density before correction. This represents the velocity correction amount, and S represents the area of ​​surface e. If the grid velocity is between setpoint one and setpoint two, then an interpolation factor A is proposed, so that the mass flux generated by the density correction part is expressed as: ; This makes the interface-corrected flux expression as follows: ； If the set value includes 0.3, then the expression for the difference factor A is: ； Where V is the mesh Mach number, URF is the relaxation factor, which can be set according to the calculation situation, and "*" indicates multiplication; If the grid velocity is greater than the set value of two, the interface flux expression is: ； in, Indicates the speed before correction. Indicates the density correction amount; Step S4.4: Solve the energy and turbulence scalar equations; Step S5: Determine whether the calculation result has converged based on the residual. If it has not converged, repeat step S4.1 and iterate until the residual meets the convergence requirement. Step S6: Post-process the calculation results.

4. An apparatus for calculating local compressible flow in a low-velocity flow field, characterized in that, It includes a processor and a memory, wherein the memory stores a computer program that, when loaded by the processor, executes the method as described in any one of claims 1 to 3.

5. A computer-readable storage medium, characterized in that, A computer program is stored in a readable storage medium, the computer program being loaded by a processor and executing the method as described in any one of claims 1 to 3.

6. A system for calculating local compressible flow in a low-velocity flow field, characterized in that, Includes the device as described in claim 4.

Images