Method for discriminating streaming flow state of high-altitude hypersonic missile

Abstract

The invention belongs to the field of missile aerodynamics, and particularly relates to a high-altitude hypersonic missile streaming flow state judgment method, which comprises the following steps: generating a spherical flow field grid, performing numerical calculation by using laminar flow, transition and turbulence models, if the transition model is close to the turbulence model, indicating that the turbulence state is basically kept, and if the transition model is close to the laminar flow model, indicating that the turbulence state is basically kept. If the results of the turbulence model and the laminar flow model are equal in difference, the transition state is basically kept; the transition Reynolds number under different flight conditions is compared with the local Reynolds number, if the local Reynolds number is larger than the transition Reynolds number, the state is a turbulent flow state, and if the local Reynolds number is far smaller than the transition Reynolds number, the state is a laminar flow state, and other states are transition states; and comparing whether the streaming flow states obtained in the two links are consistent or not, and giving a transition Reynolds number correction coefficient. According to the method, the problem of flow state discrimination of the streaming of the large-airspace hypersonic missile is solved, the flow state discrimination process of the streaming of the high-altitude hypersonic missile is combed, and reference is provided for engineering application.

Description

Technical Field

[0001] The invention belongs to the field of missile aerodynamics, relates to an aerodynamic force calculation and analysis method, and specifically relates to a method for distinguishing flow patterns around a high-altitude hypersonic missile. Background Art

[0002] Hypersonic missiles refer to missiles with a maximum flight speed greater than Mach 5, which have the characteristics of fast response speed and strong penetration capability. The flight speed of hypersonic missiles varies greatly, and the transition between different flow states such as laminar flow, transition and turbulent flow on the missile surface is common. In the laminar flow state, fluid particles do not mix with each other and the movement trajectory is orderly; in the turbulent flow state, the movement of fluid particles is irregular, and the changes of various physical quantities with time and space are random; the transition flow state is the transition process from laminar flow state to turbulent flow state. For high-altitude high-sonic flight state, the friction and heat flow obtained by different calculation models differ by several times. Therefore, it is crucial to reasonably predict when the transition process from laminar flow state to turbulent flow state occurs, and then select a suitable calculation model, which is crucial for the shape optimization design and heat protection optimization design of hypersonic missiles.

[0003] The difficulty in predicting hypersonic transition lies in the high sensitivity of parameters, huge parameter space, complexity of disturbances, nonlinear control equations, etc. In addition, due to the high cost of hypersonic wind tunnel experiments and the lack of experimental data, it also brings great challenges to experimental-numerical-theoretical coupling research. The turbulence intensity at high altitude is low, the boundary layer transition is generally a natural transition, and the nonlinear growth stage caused by disturbances lasts for a short time. Therefore, the linear stability analysis theory method is used in engineering to predict the transition, and the empirical formula of the transition Reynolds number is given based on the fitting correlation of existing data.

[0004] Considering that the friction and heat flow calculated by the turbulence model and the laminar model are quite different, the calculation results of the turbulence model used in engineering are too conservative and not conducive to optimal design; the calculation results of the laminar model are relatively radical and not conducive to safe flight. Therefore, for high-altitude high-Mach missiles in engineering, how to quickly and accurately determine the flow state by modifying the empirical formula of the transition Reynolds number needs further research. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is: how to provide a method for distinguishing the flow state of a high-altitude hypersonic missile flow around a high-altitude hypersonic missile, sort out the flow state distinguishing process of a high-altitude hypersonic missile flow around a high-altitude hypersonic missile, and provide a reference for selecting a suitable calculation flow state for a high-altitude hypersonic missile in engineering.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a method for distinguishing the flow pattern of a flow around a high-altitude hypersonic missile, and the method for distinguishing the flow pattern of a flow around a high-altitude hypersonic missile comprises the following steps:

[0009] Step 1: Generate a set of spherical flow field grids based on the shape of the hypersonic missile;

[0010] Step 2: Use laminar, transition, and turbulent models to perform numerical calculations to obtain steady-state aerodynamic characteristics, compare the axial force coefficients calculated by different flow models under the same working condition, and determine the flow pattern;

[0011] Step 3: Obtain the transition Reynolds number under different flight conditions according to the transition Reynolds number empirical formula, compare it with the local Reynolds number, and determine the flow pattern;

[0012] Step 4: Compare and analyze whether the flow pattern obtained by the empirical formula of the transition Reynolds number is consistent with the flow pattern obtained by numerical calculation, give the transition Reynolds number correction coefficient, and form a judgment process for the flow pattern of the high-altitude hypersonic missile.

[0013] In the step 1, in the spherical flow field grid, the distance between the far field boundary and the missile head is not less than 10 times the missile length.

[0014] In the step 1, the spherical flow field grid is divided using ICEM, PointWise or Gambit software.

[0015] In the step 1, the type of the spherical flow field grid is an unstructured grid.

[0016] In the step 2, numerical calculations are performed using laminar, transition, and turbulence models to obtain steady-state aerodynamic characteristics, wherein the control equation used in the numerical calculation process is the NS equation.

[0017] In the step 2, the flow fields of the three models of laminar flow, transitional flow and turbulent flow are obtained by using Fluent, CFD++ or CFX computing software and a steady time marching algorithm.

[0018] In the step 2, if the transition model result is close to the turbulence model result, it means that the turbulent state is basically maintained; if the transition model result is close to the laminar model result, it means that the laminar state is basically maintained; if the gap between the transition model result and the turbulence model result and the gap between the transition model result and the laminar model result is equivalent, it means that the transition state is basically maintained.

[0019] In the step three, the transition Reynolds number of the different flight conditions is calculated using the transition Reynolds number empirical formula. If the transition Reynolds number is less than the local Reynolds number, it is a turbulent state. If the transition Reynolds number is much larger than the local Reynolds number, it is a laminar state. The others are transition states.

[0020] In the step 3, the transition Reynolds number under different flight conditions is obtained according to the transition Reynolds number empirical formula, and the transition Reynolds number is calculated using the transition Reynolds number empirical formula:

[0021]

[0022] In the formula, Re z is the empirical transition Reynolds number and Ma is the Mach number.

[0023] In step 3, the formula for calculating the Reynolds number of the whole projectile is:

[0024] Re L =ρvL / μ

[0025] In the formula, Re L is the global Reynolds number, ρ, v and μ represent the flow density, velocity and viscosity coefficient respectively, and L is the elastic length; when L = 1, Re L is the local Reynolds number.

[0026] (III) Beneficial effects

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) An innovative flow pattern identification method is proposed. This method uses the transition empirical formula as the criterion and compares it with the local Reynolds number and the global Reynolds number to reasonably determine the flow pattern, making the flow simulation process closer to the actual flight situation.

[0029] (2) When correcting the empirical formula for the transition Reynolds number, a semi-numerical and semi-empirical method was adopted, and the specific operation is simple and reliable, which provides great convenience for engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of the method for distinguishing the flow pattern around a high-altitude hypersonic missile.

[0031] Figure 2 It is the spatial grid diagram of the flow field.

[0032] Figure 3 Schematic diagram of the normal force coefficient under different calculation models.

[0033] Figure 4 Schematic diagram of the axial force coefficient under different Mach numbers and calculation models.

[0034] Figure 5 Schematic diagram of transition, local and global Reynolds numbers under different flight conditions. DETAILED DESCRIPTION

[0035] In order to make the purpose, content, and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0036] In order to solve the above technical problems, the present invention provides a method for distinguishing the flow pattern of a flow around a high-altitude hypersonic missile, and the method for distinguishing the flow pattern of a flow around a high-altitude hypersonic missile comprises the following steps:

[0037] Step 1: Generate a set of spherical flow field grids based on the shape of the hypersonic missile;

[0038] Step 2: Use laminar, transition, and turbulent models to perform numerical calculations to obtain steady-state aerodynamic characteristics, compare the axial force coefficients calculated by different flow models under the same working condition, and determine the flow pattern;

[0039] Step 3: Obtain the transition Reynolds number under different flight conditions according to the transition Reynolds number empirical formula, compare it with the local Reynolds number, and determine the flow pattern;

[0040] Step 4: Compare and analyze whether the flow pattern obtained by the empirical formula of the transition Reynolds number is consistent with the flow pattern obtained by numerical calculation, give the transition Reynolds number correction coefficient, and form a judgment process for the flow pattern of the high-altitude hypersonic missile.

[0041] In the step 1, in the spherical flow field grid, the distance between the far field boundary and the missile head is not less than 10 times the missile length.

[0042] In the step 1, the spherical flow field grid is divided using ICEM, PointWise or Gambit software.

[0043] In the step 1, the type of the spherical flow field grid is an unstructured grid.

[0044] In the step 2, numerical calculations are performed using laminar, transition, and turbulence models to obtain steady-state aerodynamic characteristics, wherein the control equation used in the numerical calculation process is the NS equation.

[0045] In the step 2, the flow fields of the three models of laminar flow, transitional flow and turbulent flow are obtained by using Fluent, CFD++ or CFX computing software and a steady time marching algorithm.

[0046] In the step 2, if the transition model result is close to the turbulence model result, it means that the turbulent state is basically maintained; if the transition model result is close to the laminar model result, it means that the laminar state is basically maintained; if the gap between the transition model result and the turbulence model result and the gap between the transition model result and the laminar model result is equivalent, it means that the transition state is basically maintained.

[0047] In the step three, the transition Reynolds number of the different flight conditions is calculated using the transition Reynolds number empirical formula. If the transition Reynolds number is less than the local Reynolds number, it is a turbulent state. If the transition Reynolds number is much larger than the local Reynolds number, it is a laminar state. The others are transition states.

[0048] In the step 3, the transition Reynolds number under different flight conditions is obtained according to the transition Reynolds number empirical formula, and the transition Reynolds number is calculated using the transition Reynolds number empirical formula:

[0049]

[0050] In the formula, Re z is the empirical transition Reynolds number and Ma is the Mach number.

[0051] In step 3, the formula for calculating the Reynolds number of the whole projectile is:

[0052] Re L =ρvL / μ

[0053] In the formula, Re L is the global Reynolds number, ρ, v and μ represent the flow density, velocity and viscosity coefficient respectively, and L is the elastic length; when L = 1, Re L is the local Reynolds number.

[0054] Example 1

[0055] like Figure 1 As shown, the specific implementation steps of the method for distinguishing the flow pattern of the high-altitude hypersonic missile flow around this embodiment are as follows:

[0056] Based on the shape of a missile, a set of spherical flow field grids is generated. The distance between the far field boundary of the flow field grid and the missile head is not less than 10 times the missile length, such as Figure 2 The height of the first layer of grid near the missile wall should satisfy the dimensionless wall distance y as much as possible. + ~1. The missile head and wings are respectively set with density boxes of approximately the same size as the wall grid. The meshing can be done using software such as ICEM, PointWise or Gambit, and the mesh type is unstructured.

[0057] Through calculation software such as Fluent, CFD++ or CFX, the steady time advancement algorithm is used to combine the laminar flow, transition and turbulence calculation models to perform numerical simulation of the flow field and calculate the aerodynamic characteristics under steady state, where the control equation is the NS equation:

[0058]

[0059] Where W, F and G are the conservative, inviscid and viscous fluxes respectively, and H is the source term. Compare the axial force coefficients calculated by different flow models under the same working condition to determine the flow pattern. If the transition model results are close to the turbulence model results, it means that the turbulent state is basically maintained. If they are close to the laminar model results, it means that the laminar state is basically maintained. If the difference between the turbulence model results and the laminar model results is comparable, it means that the transition state is basically maintained.

[0060] The transition Reynolds number under different flight conditions is obtained according to the transition Reynolds number empirical formula. The transition Reynolds number is calculated using the transition Reynolds number empirical formula:

[0061]

[0062] Where Re z is the empirical transition Reynolds number, Ma is the Mach number. The formula for calculating the Reynolds number of the entire missile is:

[0063] Re L =ρvL / μ

[0064] Where Re L is the global Reynolds number, ρ, v and μ represent the flow density, velocity and viscosity coefficient respectively, and L is the elastic length. When L = 1, Re L If the transition Reynolds number is less than the local Reynolds number, it is a turbulent state. If the transition Reynolds number is much larger than the local Reynolds number, it is a laminar state. The others are transition states.

[0065] The method for distinguishing the flow pattern of a high-altitude hypersonic missile flow around the present invention is used to distinguish the flow pattern of a missile flow around the missile. For high-altitude high Mach conditions, such as Ma≥6 flight conditions, the normal force coefficient is as follows: Figure 3 As shown in Figure 2, the normal force coefficients under different calculation models are basically the same, and the calculation results are reliable. Figure 4 As shown in the figure, when the Mach number Ma=6, the differences between the calculation results of the laminar and turbulent models and the transition model are basically the same, and the transition model is recommended for calculation; when the Mach number Ma=8 and 10, the differences between the calculation results of the laminar model and the transition model are small, and the laminar model is recommended for calculation.

[0066] The calculation results of transition, local and global Reynolds numbers are as follows Figure 5As shown in the figure, the transition Reynolds number under Mach number Ma<6 is smaller than the local Reynolds number, indicating that the selection of the turbulence calculation model is reasonable, which is consistent with the calculation model used in this study for the above flight conditions, and preliminarily confirms the reliability of the empirical formula of the transition Reynolds number. When the Mach number Ma≥6, the transition Reynolds number begins to be greater than the local Reynolds number. Continuing to use the turbulence model may lead to a larger axial force calculation result, which is not conducive to the optimization design. In detail, when the Mach number Ma=10, the transition Reynolds number is greater than the local Reynolds number and the global Reynolds number (local Reynolds number×missile length), and the whole missile does not undergo transition. It is recommended to use the laminar flow model for calculation. When the Mach number is 6≤Ma<10, the transition Reynolds number is greater than the local Reynolds number and less than the global Reynolds number (local Reynolds number×missile length), and transition occurs in some parts of the whole missile. It is recommended to use the transition model for calculation. The above results are basically consistent with the flow pattern obtained by CFD numerical calculation.

[0067] Therefore, the present invention believes that the prediction calculation model using the transition Reynolds number method is simple to operate and the results are reliable, that is, if the transition Reynolds number is less than the local Reynolds number, it is a turbulent state. If the transition Reynolds number is greater than the local Reynolds number × the length of the projectile, it is a laminar state, and the others are transition states.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for distinguishing flow patterns around a high-altitude hypersonic missile, characterized in that: The method for distinguishing the flow pattern of the flow around a high-altitude hypersonic missile comprises the following steps: Step 1: Generate a set of spherical flow field grids based on the shape of the hypersonic missile; Step 2: Use laminar, transition, and turbulent models to perform numerical calculations to obtain steady-state aerodynamic characteristics, compare the axial force coefficients calculated by different flow models under the same working condition, and determine the flow pattern; Step 3: Obtain the transition Reynolds number under different flight conditions according to the transition Reynolds number empirical formula, compare it with the local Reynolds number, and determine the flow pattern; Step 4: Compare and analyze whether the flow pattern obtained by the empirical formula of the transition Reynolds number is consistent with the flow pattern obtained by numerical calculation, give the transition Reynolds number correction coefficient, and form a judgment process for the flow pattern of the high-altitude hypersonic missile.

2. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, characterized in that: In the step 1, in the spherical flow field grid, the distance between the far field boundary and the missile head is not less than 10 times the missile length.

3. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, characterized in that: In the step 1, the spherical flow field grid is divided using ICEM, PointWise or Gambit software.

4. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, wherein: In the step 1, the type of the spherical flow field grid is an unstructured grid.

5. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, characterized in that: In the step 2, numerical calculations are performed using laminar, transition, and turbulence models to obtain steady-state aerodynamic characteristics, wherein the control equation used in the numerical calculation process is the NS equation.

6. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 5, characterized in that: In the step 2, the flow fields of the three models of laminar flow, transitional flow and turbulent flow are obtained by using Fluent, CFD++ or CFX computing software and a steady time marching algorithm.

7. The method for distinguishing the flow pattern of a high-altitude hypersonic missile flow as claimed in claim 6, characterized in that: In the step 2, if the transition model result is close to the turbulence model result, it means that the turbulent state is basically maintained; if the transition model result is close to the laminar model result, it means that the laminar state is basically maintained; if the gap between the transition model result and the turbulence model result and the gap between the transition model result and the laminar model result is equivalent, it means that the transition state is basically maintained.

8. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, characterized in that: In the step three, the transition Reynolds number of the different flight conditions is calculated using the transition Reynolds number empirical formula. If the transition Reynolds number is less than the local Reynolds number, it is a turbulent state. If the transition Reynolds number is much larger than the local Reynolds number, it is a laminar state. The others are transition states.

9. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 8, characterized in that: In the step 3, the transition Reynolds number under different flight conditions is obtained according to the transition Reynolds number empirical formula, and the transition Reynolds number is calculated using the transition Reynolds number empirical formula: In the formula, Re z is the empirical transition Reynolds number and Ma is the Mach number.

10. The method for distinguishing flow patterns of a high-altitude hypersonic missile flow as claimed in claim 1, characterized in that: In step 3, the formula for calculating the Reynolds number of the whole projectile is: Re L =ρvL / μ In the formula, Re L is the global Reynolds number, ρ, v and μ represent the flow density, velocity and viscosity coefficient respectively, and L is the length of the elastic body; when L = 1, Re L is the local Reynolds number.

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