Large-Eddy Simulation of Compressible Transitional Cascade Flows with and without Incoming Free-Stream Turbulence

Large-eddy simulation of compressible transitional flows in a low-pressure turbine cascade is performed by 6th-order compact difference and lOth-order filtering method. Numerical results without free-stream turbulence and those with about 5% free-stream turbulence are compared. In these simulations, separated flows in the turbine cascade accompanied by laminar-turbulent transition are realized, and the present results closely agree with past experimental measurements in terms of the static pressure distribution around the blade. In the case where no free-stream turbulence is taken into account, the unsteady pressure field essentially differs from that with strong free-stream turbulence. In the case of no free-stream turbulence, pressure waves that propagate from the blade's wake region have appreciable effects on the separated-boundary layer near the trailing edge and on the neighboring blade.