Computational methodology for large-eddy simulation of tip-clearance flows

A large-eddy-simulation-based flow solver that combines an immersed-boundary technique with a curvilinear structured grid has been developed to study the temporal and spatial dynamics of an incompressible rotor-tip-clearance flow. The overall objective of these simulations is to determine the underlying mechanisms for low-pressure fluctuations downstream of the rotor near the end wall. Salient features of the numerical methodology, including the mesh topology, the immersed boundary method, the treatment of numerical instability for nondissipalive schemes on highly skewed meshes, and the parallelization of the code for shared memory computer platforms, are discussed. The computational approach is shown to be capable of capturing the evolution of the highly complicated flowfield characterized by the interaction of distinct blade-associated vortical structures with the turbulent end-wall boundary layer. Simulation results are compared with experiments, and qualitative as well as quantitative agreement is observed.