Hybrid solving method for computational fluid mechanics software structure solver

Abstract

The invention provides a hybrid solving method for a computational fluid mechanics software structure solver, which comprises the following steps of: judging whether some model equations adopt a loose coupling processing method or not, appointing that the number of conservations is equal to tight coupling conservations, and then carrying out loop iteration solving on grid blocks one by one, the tight coupling equation set and the loose coupling equation set are solved in sequence, and then the loose coupling conservation quantity and the tight coupling conservation quantity are combined until iterative solution of all the grid blocks is completed. According to the method disclosed by the invention, tight coupling and loose coupling architectures are simultaneously realized under a data structure, and the solution precision, the solution efficiency and the software expansibility can be simultaneously considered by software.

Description

Technical Field

[0001] The invention belongs to the technical field of computational fluid dynamics, and in particular relates to a hybrid solving method for a computational fluid dynamics software structure solver. Background Art

[0002] The design and development of aircrafts have a comprehensive demand for computational fluid dynamics software (Computational Fluid Dynamics). Aircrafts go through all aerodynamic physics problems from taking off from the ground to high altitude and high speed, including laminar flow, turbulence, transition, engine combustion, high temperature gas effect, dynamic characteristics, multi-body separation, etc. The core of CFD software is to obtain the development form of fluid flow under given boundary and initial field conditions by solving the Navier-Stokes equations. In order to solve the aerodynamic physics problems involved in aircrafts, it is also necessary to add various physical models based on the existing Navier-Stokes equations, such as turbulence models, transition models, chemical non-equilibrium models, thermal non-equilibrium models, overlapping grid processing models, etc.

[0003] In current CFD software, Navier-Stokes equations and other model equations can adopt a tightly coupled solution architecture or a loosely coupled solution architecture. Taking the turbulence model as an example, if a tightly coupled solution strategy is adopted, the turbulence model equation and the Navier-Stokes equation are solved together in each iteration step; if a loosely coupled solution strategy is adopted, the turbulence model equation and the Navier-Stokes main equation are solved separately. After the turbulence model equation is solved, the turbulent viscosity coefficient is transferred to the main equation, and then the main equation is solved. After the main equation is solved, the flow field information related to the conservation quantity is passed to the turbulence model for the next iteration step. The tightly coupled strategy has high solution accuracy and high solution efficiency, but the software is difficult to expand, maintainable and robust; the loosely coupled strategy is adopted, the software is easy to expand and maintain, but the solution accuracy and solution efficiency are correspondingly reduced. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] According to one aspect of the present invention, a hybrid solution method for a computational fluid dynamics software structure solver is provided, the method comprising:

[0006] (1) Input condition parameters;

[0007] (2) Allocate variable storage space according to the requirement of tightly coupling all physical model equations with the mainstream NS equations;

[0008] (3) Enter the solution phase and determine whether some model equations adopt the loose coupling processing method. If so, specify the number of conserved quantities to be equal to the tightly coupled conserved quantities and execute step (4); if not, execute step (4);

[0009] (4) Solve the time step;

[0010] (5) Select a grid block;

[0011] (6) Calculate the inviscid flux of the mainstream NS equation; calculate the inviscid flux of the tightly coupled physical model equation; calculate the Reynolds stress based on the viscosity coefficient of the previous time step; calculate the viscous flux of the mainstream NS equation; calculate the viscous flux of the tightly coupled physical model; solve the source term of the tightly coupled physical model;

[0012] (7) Conduct time-advancing solutions;

[0013] (8) Complete the tightly coupled equations and obtain the tightly coupled conservation results;

[0014] (9) Determine whether some model equations adopt the loose coupling processing method. If so, start solving each loosely coupled physical model equation separately to obtain the loosely coupled conservation result and execute step (10); if not, execute step (10);

[0015] (10) Merge the loosely coupled conservation quantities and the tightly coupled conservation quantities, place the loosely coupled conservation quantity array value in the tightly coupled conservation quantity array space, and obtain the conservation quantities of all equations; update the conservation quantities of all equations of the entire flow field; restore the number of conservation quantities to the sum of the loosely coupled conservation quantities and the tightly coupled conservation quantities;

[0016] (11) Determine whether all grid blocks have been solved. If so, execute step (12); if not, select the next grid block in sequence and return to step (6) until all grid blocks have been solved.

[0017] (12) Unified update of gas variables and boundary information;

[0018] (13) Determine whether it has converged. If not, proceed to the next time step and return to step (4); if so, output the calculation results and complete the solution.

[0019] According to another aspect of the present invention, a computer program product is provided, comprising a computer program or instructions, which implement the steps of the hybrid solution method as described above when executed by a processor.

[0020] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the hybrid solution method described above are implemented.

[0021] The technical solution of the present invention is applied to provide a hybrid solution method for the structure solver of computational fluid dynamics software. The method first determines whether some model equations adopt the loose coupling processing method, specifies the number of conservation quantities to be equal to the tightly coupled conservation quantities, and then performs cyclic iterative solution for each grid block, successively solves the tightly coupled equation group and the loosely coupled equation group, and then merges the loosely coupled conservation quantities and the tightly coupled conservation quantities until the iterative solution of all grid blocks is completed. The method of the present invention realizes the tightly coupled and loosely coupled architectures at the same time under a data structure, and can realize that the software takes into account the solution accuracy, solution efficiency and software extensibility at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A flow chart of a hybrid solution method for a computational fluid dynamics software structure solver provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values.

[0027] like Figure 1 As shown, according to a specific embodiment of the present invention, a hybrid solution method for a computational fluid dynamics software structure solver is provided, the method comprising:

[0028] (1) Input condition parameters;

[0029] (2) Allocate variable storage space according to the requirement of tightly coupling all physical model equations with the mainstream NS equations;

[0030] (3) Enter the solution phase and determine whether some model equations adopt the loose coupling processing method. If so, specify the number of conserved quantities to be equal to the tightly coupled conserved quantities and execute step (4); if not, execute step (4);

[0031] (4) Solve the time step;

[0032] (5) Select a grid block;

[0033] (6) Calculate the inviscid flux of the mainstream NS equation; calculate the inviscid flux of the tightly coupled physical model equation; calculate the Reynolds stress based on the viscosity coefficient of the previous time step; calculate the viscous flux of the mainstream NS equation; calculate the viscous flux of the tightly coupled physical model; solve the source term of the tightly coupled physical model;

[0034] (7) Conduct time-advancing solutions;

[0035] (8) Complete the tightly coupled equations and obtain the tightly coupled conservation results;

[0036] (9) Determine whether some model equations adopt the loose coupling processing method. If so, start solving each loosely coupled physical model equation separately to obtain the loosely coupled conservation result and execute step (10); if not, execute step (10);

[0037] (10) Merge the loosely coupled conservation quantities and the tightly coupled conservation quantities, place the loosely coupled conservation quantity array value in the tightly coupled conservation quantity array space, and obtain the conservation quantities of all equations; update the conservation quantities of all equations of the entire flow field; restore the number of conservation quantities to the sum of the loosely coupled conservation quantities and the tightly coupled conservation quantities;

[0038] (11) Determine whether all grid blocks have been solved. If so, execute step (12); if not, select the next grid block in sequence and return to step (6) until all grid blocks have been solved.

[0039] (12) Unified update of gas variables and boundary information;

[0040] (13) Determine whether it has converged. If not, proceed to the next time step and return to step (4); if so, output the calculation results and complete the solution.

[0041] By applying this configuration mode, a hybrid solution method for the structural solver of computational fluid dynamics software is provided. The method first determines whether some model equations adopt the loose coupling processing method, specifies the number of conservation quantities to be equal to the tightly coupled conservation quantities, and then performs cyclic iterative solution for each grid block, successively solves the tightly coupled equation group and the loosely coupled equation group, and then merges the loosely coupled conservation quantities and the tightly coupled conservation quantities until the iterative solution of all grid blocks is completed. The method of the present invention realizes the tightly coupled and loosely coupled architectures at the same time under a data structure, and can realize that the software takes into account the solution accuracy, solution efficiency and software extensibility at the same time.

[0042] The hybrid architecture solution method combining tight coupling and loose coupling has three operating modes in actual operation, including full tight coupling mode, full loose coupling mode, and partial tight coupling and partial loose coupling mode. The full tight coupling mode is that the mainstream NS equations are combined with other physical model equations into a large set of equations and solved together. First, the inviscid flux, viscous flux, and source term of each equation are solved to obtain the right-hand side of the equation, and then the overall solution is time-advanced iteration. The full loose coupling mode is that the mainstream NS equations and other physical model equations are solved completely separately. After each iteration step is solved, the influence of the mainstream NS equations and other physical model equations is transferred when the conservation variables are updated. The partial tight coupling and partial loose coupling mode is that some physical models are coupled with the NS equations for solution, and some physical models are decoupled from the NS equations for solution.

[0043] One of the core difficulties of the hybrid solution method is how to achieve both tightly coupled and loosely coupled architectures under one data structure.

[0044] If a loosely coupled architecture is used, the mainstream NS equations have five conservation quantities: There are multiple conservation quantities in the component equations, and 1 to 2 conservation quantities in the turbulence equations. Conserved quantities in the model equations for the interaction between turbulence and chemical reactions Conserved quantities in the transition model equations They can be set to different arrays without interfering with each other, and the influence quantity is transmitted after each step is solved. The loosely coupled conservation quantity array form is as follows:

[0045]

[0046] Among them, ρ is density, u1, u2, u3 are velocity components, E is total energy, Y n is the mass fraction of the component, θ1 and θ2 are both turbulent transport, Re θ and r are transition model variables, γ1 and γ2 are pulsating quantities of the turbulence and chemical reaction interaction model, and J is the Jacobian matrix.

[0047] If a tightly coupled architecture is used, the five conservation quantities of the mainstream NS equations Multiple conservation quantities of the component equations and 1-2 conservation quantities of the turbulence equations Four conservation laws of the transition model equation Conserved quantities in the model equations for the interaction between turbulence and chemical reactions They need to be combined into a total array. The tightly coupled conserved quantity array is as follows:

[0048]

[0049] or

[0050]

[0051] In the present invention, the main core method of the hybrid architecture is to first assume that all equations are solved in a tightly coupled form, and when allocating the conserved quantity space, the conserved quantity array is allocated in the form of a completely tightly coupled architecture.

[0052] During the solution process, the grid blocks are looped one by one, and the number of conserved quantities contained in the conserved quantity array q is dynamically adjusted during the solution process, but the actual size of the space occupied by the array remains unchanged.

[0053] When solving tightly coupled equations, only the conservation quantities of the tightly coupled physical model equations contained in the array are processed. The loosely coupled physical model equations have conservation quantities ρθ1, ρθ2, ρRe θ , the value of ρr remains unchanged.

[0054] When solving the loosely coupled physical model equations, only the conservation quantities ρθ1, ρθ2, ρRe contained in the array q are processed. θAfter solving the equation, the loosely coupled conservation quantity and the tightly coupled conservation quantity are combined, and the conservation quantity becomes

[0055] After completing the current iterative calculation, continue to update the subsequent boundary information, gas variables, etc. according to the fully tightly coupled architecture.

[0056] Through the above process, the calculation efficiency and accuracy can be guaranteed, and the scalability and maintainability of the software can be greatly improved.

[0057] According to another aspect of the present invention, a computer program product is provided, comprising a computer program or instructions, which implement the steps of the hybrid solution method as described above when executed by a processor.

[0058] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the hybrid solution method described above are implemented.

[0059] In order to further understand the present invention, the following Figure 1 The hybrid solution method for the computational fluid dynamics software structure solver of the present invention is described in detail.

[0060] This embodiment provides a hybrid solution method for a computational fluid dynamics software structure solver, which specifically includes the following steps.

[0061] (1) Input grid, gas model, flow parameters, physical property parameters, chemical reaction mechanism and other conditions.

[0062] (2) According to the requirement of solving all physical model equations tightly coupled with the mainstream NS equations, storage space for all conserved quantities, gas variables, geometric quantities, etc. is allocated. Taking the transition calculation considering the high-temperature gas effect as an example, the conserved quantities That is, the conservation quantities of the physical model equations and the conservation quantities of the mainstream NS equations are uniformly allocated q_all(num_q), num_q=num_q_all (the total number of all conservation quantities), num_q_all=num_qj (the number of tightly coupled conservation quantities)+num_qs (the number of loosely coupled conservation quantities). If a fully tightly coupled architecture is adopted, num_qs=0.

[0063] (3) Start iterative solution and solve the equation: Among them, t is the time term, is the inviscid flux, including F~ iz Mainstream NS equations inviscid flux, Tightly coupled model inviscid flux and Loosely coupled model inviscid flux, ξ i are the curve coordinates, is the viscous flux, including D~ z Mainstream NS equations viscosity flux, Tightly coupled model viscous flux and Loosely coupled model viscous flux, is the source term, including Tightly coupled model source terms and Loosely coupled model source terms.

[0064] Determine whether some model equations adopt the loose coupling processing method, that is, determine whether num_qs is not equal to 0. If so, specify the number of conserved quantities to be equal to the tightly coupled conserved quantity num_q=num_qj, and execute step (4); if not, execute step (4).

[0065] (4) Solve the time step.

[0066] (5) Select a grid block.

[0067] (6) Calculate the inviscid flux F of the mainstream NS equation iz ; Calculate the inviscid flux F of the tightly coupled physical model equation ij . Calculate the Reynolds stress using the viscosity coefficient of the previous time step; calculate the viscosity flux of the mainstream NS equation Computing Viscous Fluxes for Tightly Coupled Physics Models Solving Source Terms for Tightly Coupled Physics Models

[0068] (7) Carry out time-advancing solution.

[0069] (8) Complete the tightly coupled equations and obtain the tightly coupled conservation result q_all(num_q).

[0070] (9) Determine whether some model equations adopt the loose coupling processing method, that is, determine whether num_qs is not equal to 0. If so, the loosely coupled physical model equations are solved separately, including gradient calculation, viscous flux calculation, inviscid flux calculation, source term solution, and time advancement iteration, etc., to obtain the loosely coupled conservation result qs (num_qs), and execute step (10); if not, execute step (10).

[0071] (10) Combine the loosely coupled conservation quantities and the tightly coupled conservation quantities, place the qs array values ​​in the q array space, and obtain the conservation quantities of all equations q_all (num_q+num_qs);

[0072] Update the conservation quantities of all equations of the entire flow field;

[0073] Restore the number of conserved quantities to num_q=num_qj+num_qs.

[0074] (11) Determine whether all grid blocks have been solved; if so, execute step (12); if not, select the next grid block in sequence and return to step (6) until all grid blocks have been solved.

[0075] (12) Update gas variables and boundary information uniformly.

[0076] (13) Determine whether it has converged. If not, proceed to the next time step and return to step (4); if so, output the calculation results and complete the solution.

[0077] In summary, the present invention provides a hybrid solution method for a computational fluid dynamics software structure solver, which first determines whether some model equations use a loosely coupled processing method, specifies the number of conservation quantities to be equal to the tightly coupled conservation quantities, and then performs cyclic iterative solutions for each grid block, successively solving the tightly coupled equation group and the loosely coupled equation group, and then merging the loosely coupled conservation quantities and the tightly coupled conservation quantities until the iterative solutions of all grid blocks are completed. The method of the present invention realizes both tightly coupled and loosely coupled architectures under a data structure, and can realize that the software takes into account the solution accuracy, solution efficiency and software extensibility at the same time.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hybrid solution method for a structural solver of computational fluid dynamics software, characterized in that: The hybrid solution method for the computational fluid dynamics software structure solver includes: (1) Input condition parameters; (2) Allocate variable storage space according to the requirement of tightly coupling all physical model equations with the mainstream NS equations; (3) Enter the solution phase and determine whether some model equations adopt the loose coupling processing method. If so, specify the number of conserved quantities to be equal to the tightly coupled conserved quantities and execute step (4); if not, execute step (4); (4) Solve the time step; (5) Select a grid block; (6) Calculate the inviscid flux of the mainstream NS equation; calculate the inviscid flux of the tightly coupled physical model equation; calculate the Reynolds stress based on the viscosity coefficient of the previous time step; calculate the viscous flux of the mainstream NS equation; calculate the viscous flux of the tightly coupled physical model; solve the source term of the tightly coupled physical model; (7) Conduct time-advancing solutions; (8) Complete the tightly coupled equations and obtain the tightly coupled conservation results; (9) Determine whether some model equations adopt the loose coupling processing method. If so, start solving each loosely coupled physical model equation separately to obtain the loosely coupled conservation result and execute step (10); if not, execute step (10); (10) Merge the loosely coupled conservation quantities and the tightly coupled conservation quantities, place the loosely coupled conservation quantity array value in the tightly coupled conservation quantity array space, and obtain the conservation quantities of all equations; update the conservation quantities of all equations of the entire flow field; restore the number of conservation quantities to the sum of the loosely coupled conservation quantities and the tightly coupled conservation quantities; (11) Determine whether all grid blocks have been solved. If so, execute step (12); if not, select the next grid block in sequence and return to step (6) until all grid blocks have been solved. (12) Unified update of gas variables and boundary information; (13) Determine whether it has converged. If not, proceed to the next time step and return to step (4); if so, output the calculation results and complete the solution.

2. The hybrid solution method for the computational fluid dynamics software structure solver according to claim 1, characterized in that: The condition parameters in step (1) include: grid, gas model, incoming flow parameters, physical property parameters and chemical reaction mechanism.

3. The hybrid solution method for the computational fluid dynamics software structure solver according to claim 1, characterized in that: Calculating the viscous flux of the tightly coupled physical model in step (6) includes calculating the viscous flux of the turbulence model equation, the energy equation and the component equation.

4. The hybrid solution method for the computational fluid dynamics software structure solver according to claim 3, characterized in that: Solving the source terms of the tightly coupled physical model in step (6) includes solving the source terms of the turbulence model, the component equation, the turbulent chemical reaction interaction model and the ignition model.

5. The hybrid solution method for the computational fluid dynamics software structure solver according to claim 4, characterized in that: In step (9), each loosely coupled physical model equation is solved individually, including gradient calculation, viscous flux calculation, inviscid flux calculation, source term solution, and time advancement iteration.

6. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the steps of the hybrid solution method according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the hybrid solution method according to any one of claims 1 to 5 are implemented.

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