LES of flow in a low pressure turbine cascade with oncoming wakes - The effect of wake strength and frequency

Three-dimensional large eddy simulations of flow in a low-pressure turbine cascade consisting of modern highly loaded turbine blades have been performed. The effects of the variation of frequency and strength of the impinging wakes on the suction side boundary layer transition are studied. Weak impinging wakes with a low frequency only manage to mildly trigger unstable modes, leading to a natural transition scenario. With increasing strength and/or frequency, the trigering becomes more intense and a by-pass transition scenario is obtained. In none of the simulations the boundary layer is found to become fully turbulent.