基于大涡模拟的低压涡轮平面叶栅非定常流动机理研究

In order to deeply understand the spatio- temporal evolution of unsteady flow in a high-load low pressure turbine cascade, a large eddy simulation program of compressible Navier-Stokes equations based on dynamic Smagorinsky model was developed. The Mach number was 0.4 and Reynolds number at the outlet was 0.6×10⁵ (based on isentropic expansion process). The distribution of time- averaged wall-static pressure coefficient and total pressure loss coefficient agreed well with experiment and direct numerical simulation results. The numerical results show that the transition process of the fluid in suction side boundary layer is close to natural transition at low Reynolds number. In the transient flow field, the boundary layer near the rear part of the suction side subjected to intermittent separation and reattachment. More than one separation bubble existed on the cascade surface. The separation zone was just the accumulation area of low-energy fluid rather than the region of aerodynamic loss source.