Study of Tip-Clearance Flow and Rotor-Stator Interaction using LES

In liquid handling systems like pumps, low pressure fluctuations downstream of the rotor can induce cavitation which can sometimes lead to undesirable acoustic noise. It has been hypothesized that both the ``cutting'' of the stator wakes by the rotor, and the tip-leakage flow are together responsible for these low pressure fluctuations. In order to analyze the temporal dynamics of this flow and determine the underlying mechanism for these low pressure fluctuations, a large-eddy simulation (LES) solver has been developed. The presence of the tip-gap can significantly increase the complexity of the grid topology and this has been avoided by using a novel approach which combines an immersed-boundary technique with a structured grid, generalized curvilinear coordinate solver. The solver is being used to simulate and analyze in detail, the tip-clearance flow including the three-dimensional structure of the flow in the tip-gap and the dynamics of the vortical structures that are formed due to the interaction of the tip-leakage flow and the endwall turbulent boundary layer.