Methods, apparatus, media, and systems for computing locally compressible flow in low-speed flow fields

Abstract

The application discloses a kind of method, equipment, medium and system for calculating local compressible flow in low-speed flow field, belong to the field of computational fluid dynamics, 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 velocity determination;When the speed in the grid is less than the set value one, the incompressible pressure correction equation is solved;When the speed is between the set value one and the set value two, the compressible pressure correction equation is solved, 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 solved.The present application can obtain more accurate low-speed flow field and local compressible flow field, and is suitable for calculating local 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:

[0006] A method for calculating local compressible flow in low-speed flow field, comprising the following steps:

[0007] 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.

[0008] Further, the set value one is 0.3Mpa, and the set value two is 0.4Mpa.

[0009] 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 include:

[0010] Step S1, creating a flow field calculation grid on a computer;

[0011] Step S2, input the computational grid into the solver module of the computer;

[0012] Step S3, the computer processes the grid;

[0013] Step S4, the flow field is solved for the processed grid, and different algorithms are used to process the grid velocity; the flow is as follows:

[0014] Step S4.1, the initial pressure and initial velocity are given or the flow field is updated by the calculation result of step S3;

[0015] Step S4.2, the momentum equation is solved to obtain a new velocity;

[0016] Step S4.3, the pressure correction equation is solved:

[0017] The grid velocity is determined, and if the velocity is less than a set value one, the mass flux generated by the density correction part is recorded as 0, and the interface correction flux expression is:

[0018] ;

[0019] denotes the density before correction, denotes the velocity correction amount, and S denotes the area of the e surface;

[0020] If the grid velocity is between a set value one and a set value two, a difference factor A is proposed, so that the mass flux generated by the density correction part is expressed as: ;

[0021] so that the interface correction flux expression is:

[0022] ;

[0023] The set value includes 0.3, and the difference factor A expression is:

[0024] ;

[0025] wherein V is the grid Mach number, URF is the relaxation factor, which is set according to the calculation, and “*” represents multiplication;

[0026] If the grid velocity is greater than the set value two, the interface flux expression is:

[0027] ;

[0028] wherein, denotes the velocity before correction, denotes the density correction amount;

[0029] Step S4.4, solving energy, turbulence scalar equation;

[0030] Step S5, judging whether the calculation converges according to the residual error, if not, repeating to step S4.1, and iteratively solving until the residual error reaches the convergence requirement;

[0031] Step S6, post-processing the calculation result.

[0032] An apparatus for calculating local compressible flow in low-speed flow field, comprising a processor and a memory, wherein the memory stores a computer program which, when loaded by the processor, executes the method according to any one of the above.

[0033] A computer readable storage medium, wherein the computer readable storage medium stores a computer program which, when loaded by a processor, executes the method according to any one of the above.

[0034] A system for calculating local compressible flow in low-speed flow field, comprising the apparatus according to the above.

[0035] The beneficial effects of the present application include:

[0036] In the pressure correction equation of the Simple algorithm, the present application adopts grid velocity as the basis for judgment and adopts the corresponding calculation method. 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 local compressible flow in low-speed flow field, and can effectively solve the convergence difficulty encountered when using the SIMPLE algorithm in the calculation of low-speed flow field, and can obtain a more accurate low-speed flow field and local compressible flow field.

[0037] Compared with the traditional compressible pressure correction equation solving method, the present application has the advantages that different calculation methods are adopted for different speed domains, which can ensure the calculation effect of large-scale 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 local incompressible flow field. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0039] Figure 1 The step flow chart of the method of the embodiment of the present application. DETAILED DESCRIPTION

[0040] All features disclosed in this specification, and / or all methods or processes disclosed in this specification may be combined in any combination, and / or substituted, unless specific excluded, in order to produce additional or modified examples.

[0041] Terminology

[0042] Simple algorithm: is the abbreviation of Semi Implicit Methed for Pressure Linked Equations, namely semi-implicit calculation method based on pressure coupling equation.

[0043] 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.

[0044] Grid: the spatial and temporal distribution evolution law of physical quantity (velocity, pressure, etc.) is embodied by the derivative relationship of partial differential equation, and the numerical discrete method is to convert these derivative relationships into algebraic relationships. In the computer solution of partial differential equation, the numerical discrete method is adopted. Discrete is to divide the continuous physical quantity into small units, and the small unit is the grid.

[0045] In view of the problems in the background, the specific implementation process of the present application is as follows:

[0046] 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 judgment. When the velocity in the grid 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.

[0047] 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:

[0048] Step S1, creating a complete set of flow field calculation grid;

[0049] Step S2, inputting the grid into the solver;

[0050] Step S3, processing the grid;

[0051] Step S4, solving the flow field for the processed grid, and the flow field solving is processed by different algorithms through grid velocity judgment, and the flow is as follows:

[0052] Step S4.1, given initial pressure and initial velocity or update flow field with the result of last step;

[0053] Step S4.2, solve momentum equation to get new velocity;

[0054] Step S4.3, solve pressure correction equation:

[0055] If the grid velocity is less than 0.3Ma, the mass flux generated by the density correction part is recorded as 0, and the interface correction flux expression is:

[0056]

[0057] wherein, denotes the velocity before correction, and denotes the density correction amount; denotes the velocity correction amount, and S denotes the area of the e face;

[0058] 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:

[0059] So that the interface correction flux expression is:

[0060]

[0061] The difference factor A expression is:

[0062]

[0063] Wherein, V is the grid Mach number, URF is the relaxation factor, which can be set according to the calculation, and "*" represents multiplication;

[0064] If the grid velocity is greater than 0.4Ma, the interface flux expression is:

[0065]

[0066] Wherein, denotes the velocity before correction, denotes the density correction amount;

[0067] Step S4.4, solve energy, turbulence and other scalar equations;

[0068] Step S5, determine whether the calculation result is converged according to the residual, if not, repeat to step S4.1, and iteratively solve until the residual meets the convergence requirement;

[0069] Step S6, post-process the calculation result.

[0070] ​​​​Further in optional implementation, there is also provided a device for calculating locally compressible flow in low-speed flow field, comprising a processor and a memory, wherein the memory stores a computer program which, when loaded by the processor, executes the method as described in any of the above embodiments.

[0071] Further in optional implementation, there is also provided a computer readable storage medium, wherein 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.

[0072] Further in optional implementation, there is also provided a system for calculating locally compressible flow in low-speed flow field, comprising the device as described in the above embodiments.

[0073] The units described in the embodiments of the present application can be implemented by software or hardware, and the units described can be arranged in a processor. In some cases, the names of the units do not constitute a limitation on the units themselves.

[0074] According to an aspect of the embodiments of the present application, there is provided a computer program product or a computer program, which comprises computer instructions stored in a computer readable storage medium. A processor of a 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 implementation manners.

[0075] 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 can exist separately 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 of computing locally compressible flow in low speed flow fields, characterized by, Comprising the following steps: In the process of calculating the local compressible flow in low-speed flow field, different algorithms are used to handle through grid velocity judgment; when the velocity in the grid is less than a set value, the incompressible pressure correction equation is used to solve; when the velocity 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 through linear interpolation method; when the grid velocity is greater than the set value two, the compressible pressure correction equation is used to solve; specifically comprising: 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, the computer processes the grid; Step S4, solving the flow field for the processed grid, the flow field solving is handled by different algorithms through grid velocity judgment; the process is as follows: Step S4.1, giving the initial pressure and initial velocity or updating the flow field with the calculation result of step S3; 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 the set value one, the mass flux generated by the density correction part is 0, and the interface correction flux expression is: ； denotes the density before correction, denotes the speed correction amount, S denotes the e-plane area; If the grid speed is between set value one and set value two, a difference factor A is proposed such that the mass flux expression generated by the density correction part is: ; Then the interface correction flux expression is: ； The value of the set value includes 0.3, then the difference factor A expression is: ； Wherein, V is the grid Mach number, URF is the relaxation factor, which is set by the calculation, "*" represents multiplication; If the grid velocity is greater than the set value two, the interface flux expression is: ； wherein denotes the speed before correction, denotes the density correction amount; Step S4.4, solving the energy and turbulence scalar equation; 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.

2. The method of computing locally compressible flow in low-speed flow fields of claim 1, wherein, The set value one is 0.3Ma, and the set value two is 0.4Ma.

3. An apparatus for computing locally compressible flow in low speed flow fields, characterized by, Including a processor and a memory, the memory stores a computer program, when the computer program is loaded by the processor and executes the method as claimed in any one of claims 1-2.

4. A computer-readable storage medium, characterized in that, The computer program is stored in a readable storage medium, and the computer program is loaded by a processor and executes the method as claimed in any one of claims 1-2.

5. A system for computing locally compressible flow in low speed flow fields, characterized by, Including the device of claim 3.

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