基于IDDES框架的γ-Reθ转捩模型

针对高超声速流动的γ-Re_θ转捩模型在模拟强制转捩时存在捕获边界层内扰动不足的缺点，将RANS（Reynolds Averaged Navier-Stokes）框架改为IDDES（Improved Delayed Detached Eddy Simulation）框架，既能像基于RANS框架的转捩模型一样模拟复杂构型的自然转捩，又能发挥IDDES能够捕获更多脉动信息的优点，较为准确地模拟粗糙颗粒诱导强制转捩。通过对一系列简单构型的自然转捩及来流马赫数为6条件下平板上单个粗糙颗粒诱导强制转捩的模拟表明，模型既能体现γ-Re_θ转捩模型的优点，在自然转捩模拟中具有较强的鲁棒性，能够反映雷诺数等因素对转捩位置的影响规律；也能体现IDDES方法的优点，能够捕捉粗糙颗粒诱导的扰动及涡结构，从而较为准确地刻画出强制转捩的整个流程。

γ-Reθ transition model based on IDDES frame

The improved γ-Re_θ transition model for hypersonic flow has the disability of capturing the disturbances in forced transition. To solve the problem, the RANS (Reynolds Averaged Navier-Stokes) framework is modified to IDDES (Improved Delayed Detached Eddy Simulation)frameworks. The new method can not only simulate the natural transition in the γ-Re_θ model but also simulate the forced transition process precisely by capturing more details in disturbances in the IDDES methods. The results of a series of natural transition of simple geometry cases and the roughness induced transition in a Mach number 6 flat plate show that the new method has the advantages of both the γ-Re_θ model and the IDDES methods. When simulating the natural transition, the influence rules on transition of important parameters such as Reynolds number and leading edge radius could be correctly reflected. When simulating the forced transition, the formation, development, and breakdown processes of the streamwise vortexes induced by the roughness element could be also captured.