Effect of Transition on Self-Sustained Shock Oscillations in Highly Loaded Transonic Rotors

Abstract

Recent trends in numerical studies suggest the possible need for scale-resolving simulations for resolving shock oscillations on transonic compressors, the sources of which are unclear. The effect of promoting transition on the suction side upstream of self-sustained shock oscillations from a laminar shock/boundary-layer interaction (altitude conditions) in transonic compressors is studied using implicit large-eddy simulation, as well as experiments in a transonic cascade. The experiment is performed at conditions leading to different shock structures, and the shock behavior is captured with high-speed schlieren imaging. The Rolls-Royce HYDRA in-house code is employed for the numerical simulations. Trends in the change of oscillation behavior are discussed. The work addresses the fundamentally different behavior between an idealized quasi-2D LES case and an experimental cascade. This suggests that a simplification of the shock oscillation problem to a more canonical form is needed in order to investigate the oscillation mechanism itself experimentally and validate the CFD of the mechanism before returning to more complex cases. The reader is referred to youtu.be/CNRz7IYl1Pk for a condensed summary of the work with flow visualization.