Numerical analysis of flow past an elliptic cylinder near a moving wall

Abstract

A large eddy simulation based on the lattice Boltzmann method is used in this study to develop a computation program for fluid flow past an elliptic cylinder near a moving wall. The flow field around the elliptic cylinder as it approaches the moving wall is simulated for different axis ratios at Reynolds numbers of 200 and 400. The effects of the gap ratio, axis ratio, and Reynolds number on the flow field, force coefficient, and Strouhal number are investigated. The moving wall inhibits the normal velocity and stabilizes the flow, thereby suppressing vortex shedding. This study focuses on the mechanisms that various parameters influence the vortex shedding of flow past an elliptic cylinder near a moving wall. The calculation results show that decreasing the gap and axis ratios both suppress vortex shedding, while the increase in Reynolds number effectively alleviates the complete suppression of vortex shedding. A decreased axis ratio increases the gap ratio for vortex shedding suppression, and an increased Reynolds number significantly lowers the gap ratio for complete vortex shedding suppression. As the gap ratio decreases, owing to the interaction between the positive vortex separated from the lower side of the cylinder and the negative vortex separated from the moving wall, the strength of the positive vortex formed at the lower side of the cylinder gradually decreases downstream. This interaction is more prominent at small axis ratios. When the Reynolds number increases, the interaction between the positive vortex separated from the lower side of the cylinder and the negative vortex separated from the moving wall is noticeably weaker, and the positive vortex maintains its strength for a longer distance downstream. The computed results are in good agreement with the limited experimental data published in literature.