Large-Eddy Simulation of Rotor Tip-Clearance Flows: Computational Challenges and Accomplishments

The tip-leakage flow dynamics in axial turbomachines has been studied using large-eddy simulation (LES) with particular emphasis on understanding the underlying mechanisms for viscous losses, low-pressure fluctuations, and tip-leakage vortex oscillations. Such an understanding is essential to predicting and eventually controlling cavitation, noise, and vibration in liquid handling systems such as pumps and ducted propellers, and improving their performance. An overview of the computational challenges and major accomplishments of this Challenge Project is presented. These include: (i) improvements of parallel performance, optimization, and portability of the LES code, (ii) LES of the tip-leakage flow in a linear cascade, (iii) detailed analysis of flow statistics, vortex dynamics, and pressure fluctuations, (iv) exploration of tip-leakage flow control strategies by modifying the tip-gap size and end-wall shape, and (v) extension of the flow solver for multiphase simulations of cavitating flow in a rotating twisted blade.