Spectral domain decomposition methods for laminar bluff-body flows
Abstract
A spectral domain decomposition program is developed to solve steady and unsteady bluff-body flow problems. The program yields a divergence-free flow field inside and on the boundaries of the computational domain. Validation of the computer program is carried out by solving two benchmark problems, namely, the flow in a lid-driven regularized cavity and the flow over a backward facing step. Comparisons with previously published numerical and, where available, experimental results showed very good agreement with the present results. The ability of the method to incorporate different types of boundary conditions is illustrated by applying different outflow boundary conditions to flow over a backward facing step. The effectiveness of various widely used outflow conditions is examined by solving the flow problem in severely truncated domains. Results suggest that the flow Reynolds number may be important in the choice of an appropriate outflow condition. The application to bluff-body flows is demonstrated by solving steady and unsteady flow around a square cylinder. Strouhal numbers obtained for unsteady periodic flows at Re = 70 and 100 agree well with the published experimental and the numerical results. The effects of domain truncation and grid resolution were found to vary in importance depending on the Reynolds number. Finally, simulating the flow between two square cylinders and the flow around a flat plate placed normal to the flow highlight the flexibility of the model to incorporate more complex rectilinear geometries. Vortex shedding was observed at lower Reynolds numbers than for the corresponding single square cylinder case. For the two-cylinder case, a single vortex street was formed at small gap diameter, while coupled in-phase vortex shedding resulted at larger gap diameters. In spite of limited spatial resolution, qualitative features of the predicted flows were consistent with the available studies, and provide insight into the flow around bluff-bodies.
Degree
Ph.D.
Advisors
Lyn, Purdue University.
Subject Area
Civil engineering
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