DNS of fully turbulent flow in a LPT passage

This work addresses the pattern of turbulent kinetic energy generated by distortion and the effect of external disturbances on boundary layer transition. This is investigated with direct numerical simulation of grid turbulence convected through a linear turbine blade cascade. Comparisons are made with results from earlier computations of flow through the same cascade with a turbulence free inflow and an inflow with migrating wakes. The distribution of turbulence in the passage strongly depends on the mean flow field and can partly be explained by the travel time needed for the inlet turbulence to drift to a certain location. This results in a local amplification of turbulence near the leading edge stagnation region and in the passage on the pressure side near the trailing edge. The penetration of disturbances into the blade boundary layers induces bypass transition. In particular, the transition pattern on the suction side of the blade differs significantly for the three types of inflow.