Construction Of OpenFOAM Solver Based On BGK Model And Its Application In Real Gas Effect Simulation

As the human activities in near-space increase,more and more concepts of the near-space vehicles have been put forward.In near-space,the aerodynamic performance of these newly developed aircrafts are quite different from the traditional ones.To simulate and predict their performance accurately and efficiently is of great interest for the field of aerospace engineering.In order to achieve this aim,a stochastic particle method based on the kinetic theory is combined with the framework of OpenFOAM in the present work.Firstly,using moment method and one-dimensional shock wave numerical simulation,the benchmark study of several common kinematic models(BGK,ES-BGK,S-BGK,Fokker-Planck,ES-FokkerPlanck,Cubic-Fokker-Planck)is investigated from theoretical analysis and numerical comparisons.Compared with the results of Boltzmann equation,it is noted that the modified BGK model is generally better than modified Fokker-Planck model for the simulation of nonequilibrium flows,in which the S-BGK model has the best accuracy.However,the ES-BGK model is more stable than the S-BGK model in the simulation of hypersonic gas flows due to the validation of H theory.Therefore,considering its advantages,the ES-BGK model for the diatomic gas is chosen to build a solver in OpenFOAM.Inspiring from the structure of the dsmc Foam,a solver named esbgk Foam which includes rotational and vibrational energy is developed in the present paper.This solver implements the ES-BGK model successfully,and its validation and grid independence are investigated with the typical cylindrical flows.Finally,using the proposed esbgk Foam solver,the cylindrical and conical flows are studied.The effects of Kn number,Ma number and vibration energy excitation on the flow fields and surface parameters are analyzed.The numerical results indicate that the vibration energy excitation has a stronger influence on the cylindrical flow than the conical flow.Furthermore,for the cylindrical and conical flows,their heat and friction coefficients satisfy the same tendency as the Ma and Kn numbers increase.Specifically,the heat coefficient increases as the Ma and Kn numbers increase,while the friction coefficient is independent with the Ma number and increases as the Kn number increases.In addition,for the conical flow,when the Kn number increases,the slopes of the heat and friction coefficients along the flow direction decrease,and their distributions tend to be more flat.