Master thesis and internship[BR]- Master's thesis : Boundary layer stability and shock interactions in a high-speed low pressure turbine cascade[BR]- Integration Internship : The von Karman Institute

Abstract

A DNS numerical test case used the discontinuous Galerkin method and the Walloon super-computer Zenobe to study transonic aerodynamics of a linear low pressure turbine cascade, mimicking geared turbofan conditions during cruise. Separation, transition, and losses were examined at Mach 0.7, 0.9, and 0.95, with a constant Reynolds number of 70 · 10³ based on the true chord. The objective was to understand blade behavior without inlet turbulence, comparing results to experimental data. The pressure distribution was slightly overestimated. Separation occurs over the suction side (SS) at 58% and 69% of blade length for the first two Mach numbers. Skin friction is low in the Mach 0.95 case, but separation does not take place for this case. The shock was considered as influencing factor. Shock appears at Mach 0.9 or higher, with a choked passage at 0.95. Separation bubbles with turbulent reattachment are formed on the pressure side (PS) between 0% and 50% of the SS. Separation on the SS was identified as laminar separation long bubble, while reversed transition develops on the PS after reattachment. Wake losses increase with higher Mach numbers, and turbulence is more prominent at lower Mach numbers. The turbulent decay is more important at low Mach. Vortex shedding frequencies were computed at 43 kHz, 52 kHz, and 59 kHz, and compared with Roshko corre- lation. This investigation provided insights into the aerodynamic characteristics of the linear low pressure turbine cascade, addressing separation, transition, losses, and wake behavior.