采用γ-Re_(θt)模型的转捩流动计算分析

Transitional Flow Simulation Based on γ-Re_(θt) Transition Model

为了在黏性流动数值模拟中实现边界层转捩的自动预测,将γ-Reθt转捩模型引入到三维非结构混合网格的雷诺平均Navier-Stokes方程求解程序(HUNS3D)。该转捩模型由两个依赖当地变量定义的关于间歇因子和当地化转捩起始动量厚度雷诺数的输运方程组成,其数值求解算法与流场求解程序中湍流模型的求解方法相同。为了考察和验证HUNS3D程序中γ-Reθt转捩模型对航空工程中的常见附面层自由转捩问题的预测精度,对低速平板流动、Aerospatial-A翼型、NLR 7301超临界翼型和NASA Trap wing高升力构型等典型外形的自由转捩流动进行了计算,并将计算结果与相关试验结果进行了对比分析。算例结果表明:γ-Reθt转捩模型对于转捩位置具有很好的敏感性,能比较准确地预测自然转捩和分离转捩,可以有效提高HUNS3D程序对实际流动的模拟能力和预测精度。

In order to predict the boundary layer transition automatically in viscous flow simulation, γ-Reθt transition model is implemented in a hybrid unstructured Reynolds averaged Navier-Stokes flow solver which was originally developed by the authors and named as HUNS3D. The transition model is built on two locally defined transport equations. The first equation is for intermittency and the second for the transition onset criterion based on momentum-thickness Reynolds number. The nu- merical algorithms for solving the transition model equations are the same as those for solving turbulence model equations. To validate and assess the ability and the accuracy of the HUNS3D^s γ-Reθt transition model in predicting the boundary layer transition in typical aeronautical engineering cases, a series of free transitional flows around typical configurations, including flat plate, AerospatiaI-A airfoil, NLR 7301 supercritical airfoil and NASA Trap wing high lift configuration, are simulated and the computed results are compared with corresponding experimental data, which demonstrate that the γ-Reθt transition mod-el is very sensitive to the transition onset location and it predicts the natural transition and separation-induced transition accu- rately. With this transition model, the performance of the HUNS3D code in simulating the engineeringly realistic flow can be greatly enhanced.