Novel Menter SST-like turbulence model and calculation method thereof
By combining the new Menter SST turbulence model with Kok TNT model, the existing turbulence model is solved inadequate accuracy in simulating complex flow of scramjet engines, and higher simulation accuracy and robustness are achieved, especially in strong inverse Performance in pressure gradient flow.
Patent Information
- Application Number
- CN202411687045.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-25
- Publication Date
- 2024-12-27
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing turbulence models, such as Menter BSL and Menter SST two-eq models, are difficult to accurately simulate the complex jet, shear layer, wall turbulence and separation flow inside the scramjet engine, resulting in insufficient simulation accuracy and cannot meet the needs of engineering applications.
Develop a new Menter SST turbulence model. By combining the Kok TNT model, using specific control equations and calculation methods to calculate the mixed function, model constant, turbulent kinetic energy and turbulence frequency, improving the shear layer, mixed layer and wall turbulence. Simulation capability, especially in strong reverse pressure gradient flow.
Without increasing the calculation amount, the numerical simulation accuracy and robustness of aerospace engines are improved, and the prediction ability of complex flow conditions is significantly improved, which is of practical engineering value.
Smart Images
Figure CN119203851A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of aerodynamics and computational fluid dynamics, and specifically relates to a novel Menter SST-like turbulence model and a calculation method thereof. Background Art
[0002] In the process of scramjet engine design and numerical evaluation, how to correctly simulate complex turbulence is one of the key technical issues that need to be solved. Although direct numerical simulation and large eddy simulation have a solid theoretical basis and wide applicability, the unbearable massive calculations make them not yet valuable for engineering applications. Turbulence models based on the RANS framework are still the most effective and practical choice for solving engineering turbulence problems.
[0003] So far, many turbulence models have been developed, the most famous of which is A series of turbulence models, A series of turbulence models, as well as the Menter BSL two-equation model and the Menter SST two-equation model. Among them, The series turbulence model is particularly suitable for simulations involving wall turbulence, but its disadvantage is that it is sensitive to free flow. The series of turbulence models are particularly suitable for shear layer simulation, but the disadvantage is that they are not good at simulating wall turbulence, especially not suitable for strong adverse pressure gradient flow simulation; Menter BSL two-equation model and Menter SST two-equation model are both based on Model (Wilcox 1988) and The model is a hybrid that combines the advantages of both types of models and is considered to be the most widely used model in engineering applications. However, since the scramjet engine often involves jets, shear layers, wall turbulence, separated flows, etc., the flow is extremely complex. Even the Menter BSL two-equation model and the Menter SST two-equation model cannot accurately simulate all working conditions and engine configurations. It is necessary to develop a more robust turbulence model to improve the accuracy of engine simulation.
[0004] Currently, there is an urgent need to develop a new Menter SST-like turbulence model and its calculation method. Summary of the invention
[0005] One technical problem to be solved by the present invention is to provide a novel Menter SST-like turbulence model. Another technical problem to be solved by the present invention is to provide a calculation method for a novel Menter SST-like turbulence model.
[0006] The governing equations of the novel Menter SST-like turbulence model of the present invention are as follows: ; in, is the density, is the turbulent kinetic energy, is the turbulence frequency, is the turbulent kinetic energy generation term; for Direction speed, for Direction coordinates; For time, is the turbulent viscosity coefficient, is the laminar viscosity coefficient, is the turbulent dynamic viscosity coefficient; and are model constants; is a mixed function, calculated by the following formula: Mixing functions for: ; in, and To calculate the mixing function Intermediate variables used in the process, is the distance from the grid cell to the nearest solid wall; is the kinematic viscosity coefficient; The calculation method of each model constant is: ,in, , ; ; ,in, , ; ,in, , ; ,in, , ; ; is the von Karman constant, ; Viscosity coefficient The calculation method is: ; in, and To calculate the viscosity coefficient Intermediate variables used in the process; ; is the vorticity, ; ; is the speed in the i direction, is the i-direction coordinate.
[0007] The calculation method of the novel Menter SST-like turbulence model of the present invention comprises the following steps: S10. Calculate the viscosity coefficient of the flow field ; Carry out CFD calculation of the flow field, and calculate the viscosity coefficient of the flow field based on the Nth step flow field calculation results of all CFD grid cells, combined with the new MenterSST-like turbulence model ; Where N is the number of steps to start turbulence calculation; S20. Calculate the mixing function ; S30. Calculation of model constants ; According to the mixed function and model parameters, calculate the model constants , include and ; S40. Calculation of turbulent kinetic energy and turbulence frequency ; According to the model constant and the new Menter-like SST turbulence model to calculate the turbulent kinetic energy of all grid cells in the flow field at step N+1 and turbulence frequency ; S50. Complete iterative calculation; Based on the convergence criterion of the flow field calculation, decide whether to continue the iteration or stop the calculation.
[0008] Furthermore, the convergence criterion is that the maximum value of the density gradient of the entire flow field or the maximum value of the total energy gradient decreases by two orders of magnitude, or the inlet and outlet flow error is less than 0.5%.
[0009] The novel Menter SST turbulence model and its calculation method of the present invention convert Kok TNT Model and The turbulence model is mixed to give full play to the advantages of both. Without increasing the amount of calculation, the simulation capabilities of shear layer, mixing layer and wall turbulence are improved, especially the simulation capabilities of flows with strong adverse pressure gradients. Ultimately, it effectively improves the accuracy and robustness of numerical simulations of aerospace engines and has practical engineering value. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1A flow chart of a calculation method of a novel Menter SST-like turbulence model of the present invention; Figure 2 This is a schematic diagram of the structure of the test model for generating a strong adverse pressure gradient flow field in Example 1; Figure 3 This is a comparison chart of the wall pressure distribution predicted by various turbulence models obtained in Example 1 and the test data results; Figure 4 Schematic diagram of the flow field of the DLR scramjet combustion chamber of Example 2; Figure 5a A comparison diagram of velocity profiles at different flow direction positions predicted by various turbulence models obtained in Example 2 and experimental data (x=67mm); Figure 5b A comparison chart of velocity profiles at different flow direction positions predicted by various turbulence models obtained in Example 2 and experimental data (x=110 mm); Figure 5c A comparison chart of velocity profiles at different flow direction positions predicted by various turbulence models obtained in Example 2 and experimental data (x=142mm); Figure 5d This is a comparison chart of velocity profiles at different flow direction positions predicted by various turbulence models obtained in Example 2 and the experimental data (x=218mm).
[0011] In the figure, the new Menter SST-like turbulence model of the present invention is represented as SST-M; the Menter SST two-equation model is represented as SST; the kok TNT turbulence model is represented as TNT; and EXP represents experimental data. DETAILED DESCRIPTION
[0012] The present invention is described in detail below with reference to the accompanying drawings and embodiments.
[0013] The governing equations of the novel Menter SST-like turbulence model of the present invention are as follows: ; in, is the density, is the turbulent kinetic energy, is the turbulence frequency, is the turbulent kinetic energy generation term; for Direction speed, for Direction coordinates; For time, is the turbulent viscosity coefficient, is the laminar viscosity coefficient, is the turbulent dynamic viscosity coefficient; and are model constants; is a mixed function, calculated by the following formula: Mixing functions for: ; in, and To calculate the mixing function Intermediate variables used in the process, is the distance from the grid cell to the nearest solid wall; is the kinematic viscosity coefficient; The calculation method of each model constant is: ,in, , ; ; ,in, , ; ,in, , ; ,in, , ; ; is the von Karman constant, ; Viscosity coefficient The calculation method is: ; in, and To calculate the viscosity coefficient Intermediate variables used in the process; ; is the vorticity, ; ; is the speed in the i direction, is the i-direction coordinate.
[0014] like Figure 1 As shown, the calculation method of the novel Menter SST-like turbulence model of the present invention comprises the following steps: S10. Calculate the viscosity coefficient of the flow field ; Carry out CFD calculation of the flow field, and calculate the viscosity coefficient of the flow field based on the Nth step flow field calculation results of all CFD grid cells, combined with the new MenterSST-like turbulence model ; Where N is the number of steps to start turbulence calculation; S20. Calculate the mixing function ; S30. Calculation of model constants ; According to the mixed function and model parameters, calculate the model constants , include and ; S40. Calculation of turbulent kinetic energy and turbulence frequency ; According to the model constant and the new Menter-like SST turbulence model to calculate the turbulent kinetic energy of all grid cells in the flow field at step N+1 and turbulence frequency ; S50. Complete iterative calculation; Based on the convergence criterion of the flow field calculation, decide whether to continue the iteration or stop the calculation.
[0015] Furthermore, the convergence criterion is that the maximum value of the density gradient of the entire flow field or the maximum value of the total energy gradient decreases by two orders of magnitude, or the inlet and outlet flow error is less than 0.5%.
[0016] Example 1: This example is used to test the numerical prediction ability of the new Menter SST-like turbulence model proposed in the present invention for flow fields with strong adverse pressure gradients. Figure 2 As shown, the test model has an inlet height of 20 cm, the front half is a 22.9 cm long flat plate, followed by an inclined groove, which consists of a 2.54 cm deep, 6.19 cm long backward step and a 16 cm long 20° slope. The incoming flow Mach number is 2.92, the total pressure is 0.69 MPa, the total temperature is 258 K, the inlet boundary adopts the incoming flow condition, the outlet boundary adopts supersonic extrapolation, and the wall is an adiabatic no-slip wall.
[0017] Figure 3 A comparison diagram of the wall pressure distribution predicted by various turbulence models obtained in this embodiment and the experimental data results is given. It can be seen that for most areas, the prediction results of the new Menter SST-like turbulence model of the present invention are no less than those of the Menter SST two-equation model and the kok TNT turbulence model; in the shear layer reattachment area at the trailing edge of the oblique groove, the new Menter SST-like turbulence model of the present invention is significantly better than the Menter SST two-equation model and the kok TNT turbulence model, and is closer to the experimental results.
[0018] Example 2: This example is used to test the prediction effect of the new Menter SST-like turbulence model of the present invention on the development of the central mainstream area and the shear layer. The test flow field is as follows Figure 4 The flow field of the DLR scramjet combustion chamber shown. The preheated air expands into the combustion chamber through the nozzle. The combustion chamber inlet is 50mm high and 40mm wide. The support plate is 32mm long and 6mm high. Hydrogen is sprayed into the combustion chamber through 15 small holes on the bottom of the support plate. The diameter of the nozzle is 1mm, the spacing between the nozzles is 2.4mm, and the coordinate origin is located on the lower wall and 23mm away from the leading edge of the support plate.
[0019] The flow and jet conditions of this embodiment are shown in Table 1. In order to reduce the amount of calculation, two-dimensional calculation is used, and the mesh is encrypted at the combustion chamber inlet, support plate and wall surface, and the total mesh volume is about 200,000. The inlet is a supersonic inflow, and all parameters are fixed; the outlet adopts the extrapolated boundary condition; the upper and lower walls of the combustion chamber and the support plate surface are considered to be adiabatic non-slip walls.
[0020] Table 1
[0021] It can be seen that Figure 5a~Figure 5d As shown, the prediction results of the new Menter SST-like turbulence model of the present invention are significantly better than those of the Menter SST two-equation model and the Kok TNT turbulence model, are closer to the experimental results, and have excellent simulation capabilities for shear layers.
[0022] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and the embodiments, and can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional improvements and modifications can be easily realized without departing from the principles of the present invention. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.
Claims
1. A new Menter SST-like turbulence model, characterized by: The governing equations of the new Menter SST-like turbulence model are as follows: ； in, is the density, is the turbulent kinetic energy, is the turbulence frequency, is the turbulent kinetic energy generation term; for Direction speed, for Direction coordinates; For time, is the turbulent viscosity coefficient, is the laminar viscosity coefficient, is the turbulent dynamic viscosity coefficient; and are model constants; is a mixed function, calculated by the following formula: Mixing functions for: ； in, and To calculate the mixing function Intermediate variables used in the process, is the distance from the grid cell to the nearest solid wall; is the kinematic viscosity coefficient; The calculation method of each model constant is: ,in, , ; ； ,in, , ; ,in, , ; ,in, , ; ； is the von Karman constant, ; Viscosity coefficient The calculation method is: ； in, and To calculate the viscosity coefficient Intermediate variables used in the process; ; is the vorticity, ; ; is the speed in the i direction, is the i-direction coordinate.
2. A calculation method for a novel Menter SST-like turbulence model, which is used for the novel Menter SST-like turbulence model described in claim 1, characterized in that: The following steps are involved: S10. Calculate the viscosity coefficient of the flow field ; Carry out CFD calculation of the flow field, and calculate the viscosity coefficient of the flow field based on the Nth step flow field calculation results of all CFD grid cells, combined with the new Menter SST turbulence model ; Where N is the number of steps to start turbulence calculation; S20. Calculate the mixing function ; S30. Calculation of model constants ; According to the mixed function and model parameters, calculate model constants , include and ; S40. Calculation of turbulent kinetic energy and turbulence frequency ; According to the model constant and the new Menter-like SST turbulence model to calculate the turbulent kinetic energy of all grid cells in the flow field at step N+1 and turbulence frequency ; S50. Complete iterative calculation; Based on the convergence criterion of the flow field calculation, decide whether to continue the iteration or stop the calculation.
3. The calculation method of a novel Menter SST-like turbulence model according to claim 2 is characterized in that: The convergence criterion is that the maximum value of the density gradient of the entire flow field or the maximum value of the total energy gradient decreases by two orders of magnitude, or the inlet and outlet flow error is less than 0.5%.