有/无尾迹作用下低压涡轮叶栅分离边界层转捩的大涡模拟

采用经过大量算例验证的可压缩大涡模拟求解器对雷诺数为60154、马赫数为0.402的低压涡轮叶栅T106D-EIZ进行了细致模拟，计算了定常来流和周期性尾迹来流两种工况.对计算结果的分析表明:定常来流工况下，叶片吸力面后部出现大尺寸的层流分离泡，分离剪切层的转捩过程受Kelvin-Helmholtz （K-H）不稳定性控制；尾迹来流工况下，由于来流尾迹的周期性扫掠，时均分离泡尺寸变小，叶栅总压损失降低.对相位平均和瞬态流场的分析表明，尾迹引起的逆射流使分离点后移，形成卷起涡结构，逆射流掠过卷起涡的过程中与其发生强烈的相互作用，产生大量气动损失，而后卷起涡破碎，流动转捩为湍流. 

Large-eddy simulation of separated boundary layer transition in low-pressure turbine cascade with and without wakes

A well validated large-eddy simulation (LES) solver for compressible flows was employed to simulate the low pressure turbine (LPT) cascade T106D-EIZ where the Reynolds number and Mach number were 60154 and 0.402,respectively. Two cases with steady inflow and periodic wakes inflow were calculated and analyzed. The results of steady inflow case show that large separation bubble appears at the rear part of the blade suction surface and transition process of the separated shear layer is dominated by Kelvin-Helmholtz (K-H) instability. In the wakes inflow case, due to the periodic sweeping of inflow wakes, the size of time mean separation bubble significantly reduces and the total pressure loss of the cascade also decreases. The analysis of phase averaged and instantaneous flowfield reveals that the negative jet of wake-induced forces the separation point to move forward and then the roll-up vortex emerges. The strong interactions of sweeping negative jet and roll-up vortex result in large aerodynamic losses. Then roll-up vortex quickly breakdowns and boundary layer transitions to turbulence.