高超声速钝楔边界层转捩大涡模拟

 以五阶迎风和八阶对称格式混合差分格式求解三维可压缩滤波Navier-Stokes方程，对来流Mach数为6.0、半锥角5°的高超声速空间发展钝楔边界层转捩至完全湍流进行了大涡模拟。时间推进采用紧致存储三阶Runge-Kutta方法，亚格子尺度模型为Driest因子修正的Smagorinsky涡黏性模型。通过定常流场入口边界附近吹／吸引入不稳定扰动斜波的方法数值模拟得到了层流失稳转捩直至完全湍流的空间发展全过程。对扰动的线性、非线性增长以及湍流斑的形成和发展进行了分析，给出了转捩及完全湍流下的速度相关量统计并与实验、DNS结果进行了对比分析，计算结果与理论及实验吻合。

Large Eddy Simulation of Transition in a Hypersonic Blunt-wedge Boundary Layer

The transition mechanism of a hypersonic boundary layer in the conditions of high Mach number and high Reynolds number is investigated, and the evolution of instable structures is analyzed.The numerical method is large eddy simulation (LES).The spatial transition coherent structure of a hypersonic blunt-wedge boundary layer at a free-stream Mach number of Ma_∞=6.0 based on free stream velocity and a Reynolds number of Re=2.0×10⁶/inch is studied with a hybrid method of a fifth order upwind compact difference and a eighth-order symmetric compact difference for the three-dimensional compressible Favre-filtered Navier-Stokes equations.The compact storage third-order explicit Runge-Kutta method is applied for time-integration.The sub-grid scales are formulated according to the modified Smagorinsky eddy-viscosity model.Based on the linear stability theory,a particular perturbation of blowing and suction is int roduced close to wall as unstable disturbances on the inflow boundary.The obtained flow process is divided into three stages:the linear and weakly no nlinear growth of disturbance,transition,and full turbulence.The result presents that LES can simulate hypersonic blunt-wedget ransition well.