Structural grid heat flow calculation method for complex flow

Abstract

The invention provides a structural grid heat flow calculation method for complex flow. The structural grid heat flow calculation method comprises the following steps: step 1, obtaining a temperature value TC at the center of a first layer of grid in the normal direction of a wall surface; 2, solving the volume V of a first layer of grid in the normal direction of the wall surface, and the areas Si and Si + 1 of two surfaces vertical to the normal direction, thereby obtaining the distance d from the grid center to the wall surface; and 3, according to the temperature obtained in the step 1 and the distance obtained in the step 2, adopting a Fourier formula to obtain typical appearance heat flow distribution. The method comprises the following steps: solving a cell volume V and two surface areas Si and Si + 1 perpendicular to the normal direction of a wall surface to obtain a distance from a cell center to the wall surface, and combining a Fourier formula with a temperature value TC at the cell center of a first layer of grids in the normal direction of the wall surface to obtain typical appearance heat flow distribution; compared with a control volume method and a finite element method, the method is high in calculation efficiency and simple in program implementation; compared with a traditional Fourier formula direct solving method, the method has the advantages of being good in universality, high in calculation precision and the like.

Description

Technical Field

[0001] The invention relates to the technical field of computational fluid dynamics, and in particular to a structural grid thermal flow calculation method for complex flow. Background Art

[0002] Due to the existence of complex phenomena such as shock waves, shock wave boundary layer interference, separation and reattachment in hypersonic flight, the aerodynamic thermal effect cannot be ignored.

[0003] In engineering, it is required to simulate aerodynamic heat as accurately as possible to provide a basis for the design of thermal protection systems. Considering the simulation accuracy, structural grids with good body fit and high calculation accuracy are generally used for simulation. After obtaining the simulation results, the heat flow post-processing calculation has high requirements for the accuracy of the temperature gradient. Currently, there are several methods such as direct solution using Fourier formula, control volume method and finite element method. The calculation formulas of control volume method and finite element method are relatively complex. The direct solution method using Fourier formula is commonly used in engineering.

[0004] The direct solution method using Fourier formula needs to obtain the distance from the first layer of grid in the normal direction of the wall to the wall. For complex shapes, it is cumbersome to directly calculate the distance formula. Solvers such as CFL3D use the unit cell volume / wall bottom area method to calculate the distance, which makes full use of the characteristics of the structured grid and has the characteristics of simple calculation and strong applicability, but there is a certain deviation for irregular hexahedrons. The present invention provides a new method for calculating the wall distance, thereby improving the accuracy of heat flow calculation. Summary of the invention

[0005] The purpose of the present invention is to provide a structural grid heat flow calculation method for complex flow, which can provide a new method for calculating wall distance and improve the accuracy of heat flow calculation;

[0006] The present invention provides a structural grid heat flow calculation method for complex flow, comprising the following steps: Step 1: Obtaining the temperature value T at the center of the first layer of grid normal to the wall surface C ; Step 2: Solve the first layer of mesh volume V in the normal direction of the wall, and the area S of the two surfaces perpendicular to the normal direction i and S i+1 , thereby obtaining the distance d from the grid center to the wall; Step three: According to the temperature obtained in step one and the distance obtained in step two, use Fourier formula to obtain the typical external heat flux distribution.

[0007] Furthermore, in step 1, the temperature value T at the center of the first layer of grid normal to the wall is obtained by using a computational fluid dynamics solver based on the grid center structure grid. C .

[0008] Furthermore, the computational fluid dynamics solver is a general computational fluid dynamics calculation software.

[0009] Furthermore, the computational fluid dynamics solver is a dedicated computational fluid dynamics solver.

[0010] Furthermore, in step 2, the distance d from the center of the grid to the wall is:

[0011] Furthermore, in step three, the Fourier formula is: Among them, q w is the wall heat flux, κ w is the thermal conductivity, where the negative sign represents the heat transfer in the direction of decreasing temperature. Represents the derivative of temperature along the wall normal.

[0012] Further, Among them, T w is the wall temperature.

[0013] Further, in step three, the typical shape is a hypersonic aerodynamic thermal benchmark model.

[0014] Furthermore, the hypersonic aerodynamic thermal benchmark model includes a flat plate or a spun body.

[0015] Furthermore, the hypersonic aerodynamic thermal benchmark model includes a waverider body or a lifting body.

[0016] The technical solution of the present invention is to solve the unit cell volume V and the two surface areas S perpendicular to the wall normal. i , S i+1 , to obtain the distance from the grid center to the wall, and use the Fourier formula combined with the temperature value T at the center of the first layer of grid normal to the wall C , obtain the heat flux distribution of typical shapes; compared with the control volume method and the finite element method, it has high calculation efficiency and simpler program implementation; compared with the traditional direct solution method using Fourier formula, it has the characteristics of good versatility and high calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 Schematic diagram of the distance d from the grid center to the wall in step 2;

[0019] Figure 2 A computational grid diagram provided for an embodiment of the present invention;

[0020] Figure 3 A comparison chart of heat flow calculation and experiment provided in an embodiment of the present invention; DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of 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.

[0022] The method of the present invention specifically comprises the following steps:

[0023] Step 1: Use the computational fluid dynamics solver based on the grid center structure grid to obtain the temperature value T at the center of the first grid layer of the wall normal to the typical research shape C ;

[0024] The computational fluid dynamics solver is a general computational fluid dynamics calculation software such as CFL3D or a self-developed special computational fluid dynamics solver; the typical research shape is a hypersonic aerodynamic thermal benchmark model such as a flat plate, a rotating body, a waverider, a lifting body, etc. In this embodiment, the computational fluid dynamics solver selected is a self-developed three-dimensional complex flow computational fluid dynamics solver, and the research shape selects a hollow cylindrical skirt shape;

[0025] Step 2: Calculate the distance d from the center of the grid to the wall;

[0026] First, solve the unit cell volume V and the two surface areas S perpendicular to the wall normal i , S i+1 , and then the distance from the center of the grid to the wall is obtained by the following formula (such as Figure 1 shown):

[0027]

[0028] Solving for unit cell volume and surface area is a routine technique and can be found in a mathematics handbook.

[0029] Step 3: Use Fourier's law to calculate the heat flow and obtain the heat flow rate distribution of the typical shape;

[0030] According to the temperature obtained in step 1 and the distance obtained in step 2, the heat flux distribution of the typical shape is obtained by using Fourier formula;

[0031] The Fourier formula is:

[0032]

[0033] Among them, q w is the wall heat flux, κ wis the thermal conductivity coefficient. The negative sign in the program represents that heat is transferred in the direction of decreasing temperature. The subscript w represents a constant value at the wall. Represents the derivative of temperature along the wall normal.

[0034]

[0035] Example 1

[0036] In this embodiment, for a hollow cylindrical skirt (such as Figure 2 The test was carried out as shown in the figure, with the incoming flow Mach number being 11.27, the incoming flow static pressure being 87.165Pa, the incoming flow static temperature being 128.9K, and the wall temperature being 297.2K.

[0037] Figure 3 A comparison between the calculated results of the dimensionless heat flux st and the experimental results is given, thereby verifying the effectiveness of the present invention.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A structural grid heat flow calculation method for complex flow, characterized in that: The steps include: Step 1: Obtain the temperature value T at the center of the first layer of grid normal to the wall C ; Step 2: Solve the first layer of mesh volume V in the normal direction of the wall, and the area S of the two faces perpendicular to the normal direction i and S i+1 , thereby obtaining the distance d from the grid center to the wall; Step 3: Based on the temperature obtained in step 1 and the distance obtained in step 2, use the Fourier formula to obtain the typical heat flux distribution.

2. The structural grid heat flow calculation method for complex flow according to claim 1, characterized in that: In step 1, the temperature value T at the center of the first layer of grid normal to the wall is obtained by using a computational fluid dynamics solver based on the grid center structure grid. C .

3. The structural grid heat flow calculation method for complex flow according to claim 2, characterized in that: Computational fluid dynamics solver is a general computational fluid dynamics calculation software.

4. The structural grid heat flow calculation method for complex flow according to claim 2, characterized in that: The computational fluid dynamics solver is a dedicated computational fluid dynamics solver.

5. The structural grid heat flow calculation method for complex flow according to claim 1, characterized in that: In step 2, the distance d from the center of the grid to the wall is:

6. The structural grid heat flow calculation method for complex flow according to claim 1, characterized in that: In step three, the Fourier formula is: Among them, q w is the wall heat flux, κ w is the thermal conductivity, where the negative sign represents the heat transfer in the direction of decreasing temperature. Represents the derivative of temperature along the wall normal.

7. The structural grid heat flow calculation method for complex flow according to claim 6, characterized in that: Among them, T w is the wall temperature.

8. The structural grid heat flow calculation method for complex flow according to claim 1, characterized in that: In step three, the typical shape is a hypersonic aerodynamic thermal benchmark model.

9. The structural grid heat flow calculation method for complex flow according to claim 8, characterized in that: Hypersonic aerodynamic thermal benchmark models include flat plates or spun bodies.

10. The structural grid heat flow calculation method for complex flow according to claim 8, characterized in that: Hypersonic aerodynamic thermal benchmark models include waverider bodies or lifting bodies.

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