Compressible large eddy simulation of the boundary layer evolution in a low-pressure turbine cascade at different Reynolds numbers

Abstract

An in-house large eddy simulation code based on three-dimensional compressible N-S equations was used to research the evolution process of the boundary layer in the low-pressure turbine T106A cascade. Analyses of the separation and reattachment phenomenon as well as the unsteady aerodynamic characteristic on the suction surface at different Reynolds numbers were performed. A variation range of Reynolds number which is based on the exit isentropic velocity and axial chord length extends from 0.6 × 105 to 2.0 × 105. The time-averaged wall-static pressure coefficient compares well with the experimental and DNS data. The effect of Reynolds number on the flow field is mainly embodied at the rear part of the suction side. At low Reynolds number condition, the value of the total pressure loss and the width of the wake are significantly large. With the increase of Reynolds number, the wake zone becomes narrower and the wake centerline moves to the pressure side. The size of separation bubble at the leading edge grows slightly and the coherent structures are more close to the cascade surface. At the case of Re = 2.0 × 105, the two-dimensional shear layer evolves directly into small-scale vortices, whereas the rolling of spanwise vortex and hairpin vortex generation do not appear.