三维非平衡多温流动的物理模拟与数值研究
Physical Modeling and Numerical Studies of Three-dimensional Non-equilibrium Multi-temperature Flows
摘要：
对于越来越稀薄的流场，Navier-Stokes（NS）方程失去了部分准确性，由于单一的温度近似。为了克服这一障碍，本文提出了一种基于Bhatnagar-Gross-Krook（BGK）方程和Landau-Teller-Jeans松弛模型耦合的连续多温度模型，用于二维高超声速非平衡多温度流场计算。近年来，发展了一种两阶段四阶气体动力学格式（GKS），该格式在时间和空间上都达到了四阶精度，具有较高的计算效率和鲁棒性。为了准确、高效地模拟多温非平衡流动，在两阶段四阶框架下，采用四阶Simpson插值规则对新出现的源项进行插值，实现了高阶三维多温GKS。通过对衰减均匀各向同性湍流、低密度喷管流、稀薄高超声速平板绕流和IV型激波-激波干扰的数值模拟，验证了多温度模型的正确性。统一气体动力学方案（UGKS）的结果，和直接模拟蒙特卡罗（DSMC）的解决方案，以及在某些情况下进行验证。计算结果不仅证实了该格式的高阶精度和较强的鲁棒性，而且与UGKS和DSMC相比，计算效率有了显著提高，特别是在近连续流区。
英文摘要：
For increasingly rarefied flowfields, the Navier-Stokes (NS) equations lose accuracy partially due to the single temperature approximation. To overcome this barrier, a continuum multi-temperature model based on the Bhatnagar-Gross-Krook (BGK) equation coupled with the Landau-Teller-Jeans relaxation model has been proposed for two-dimensional hypersonic non-equilibrium multi-temperature flow computation. In recent study, a two-stage fourth-order gas-kinetic scheme (GKS) has been developed for equilibrium flows, which achieves a fourth-order accuracy in space and time as well as high efficiency and robustness. In this paper, targeting for accurate and efficient simulation of multi-temperature non-equilibrium flows, a high-order three-dimensional multi-temperature GKS is implemented under the two-stage fourth-order framework, with the fourth-order Simpson interpolation rule for the newly emerged source term. Simulations on decaying homogeneous isotropic turbulence, low-density nozzle flow, rarefied hypersonic flow over a flat plate, and type IV shock-shock interaction are used to validate the multi-temperature model through the comparison with experimental measurements. The unified gas kinetic scheme (UGKS) results, and the Direct simulation Monte Carlo (DSMC) solutions will be used as well in some cases for validation. Computational results not only confirm the high-order accuracy and quite robustness of this scheme, but also show the significant improvement on computational efficiency compared with UGKS and DSMC, especially in the near continuum flow regime.
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