|Cooperation:||Dr. Christoffer Norberg|
|Sponsors:||The Ministry of Culture and Higher Education of Iran|
|Publications:||[1-8], see references below|
|Start of project:||spring 1994|
|End of project:||December 1998|
The subject of flow past slender bluff bodies is of relevance to technical problems associated with energy conservation, structural design and acoustic emissions. In this work, calculations of unsteady 2D- and 3D-flow around rectangular cylinders, which are a type of slender bluff bodies, are carried out. Some useful physical quantities such as the dominating wake frequency (Strouhal number), mean and RMS values of lift, drag and moment, various surface pressure were calculated for different Reynolds number.
In 2D-calculations, flow around rectangular cylinders were performed. An incompressible SIMPLEC code is used employing non-staggered grid arrangement. The QUICK and Van Leer schemes are used for the convective terms. The time discretization is implicit and a second-order Crank-Nicolson scheme is employed. The influence of Reynolds number(Re=45-500), body side ratio (B/A=1-4) and angle of incidence (alpha=0-90) is investigated. Effect of the various numerical parameters such as time step, domain size, blockage, grid distribution and spatial resolution in both far- and near-body regions is investigated. At outlet of the computational domain, a convective Sommerfeld boundary condition is compared with a traditional Neumann condition. The onset of vortex shedding is investigated by using the Stuart-Landau equation, at various angles of incidence for a square cylinder.
In 3D-calculations, direct numerical simulation (DNS) of unsteady flow around a square cylinder at zero incidence for moderate-Reynolds numbers (Re=150 - 500) and large eddy simulation (LES) at Re=22000 are performed. A non-staggered grid arrangement, incompressible, finite-volume code is used employing an implicit fractional step method with a multi-grid pressure Poisson solver. A second-order central scheme is used for the convective and diffusion terms. The influence of the aspect ratio, finer grid and time step on the results are investigated for DNS. By DNS simulations, the study of transition from 2D- to 3D-flow, the wake structure, A- and B-mode of secondary vortices and a comparison of 2D and 3D results with experimental results are carried out. Also some dissimilarities with the flow around a circular cylinder are investigated.
In LES simulations, three different Subgrid-scale models, the Smagorinsky, dynamic and dynamic one-equation models for Re=22000, are applied and their results are compared with experimental results.
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This page, Vortex Shedding - flow around rectangular cylinders, should be part of a frames system at www.tfd.chalmers.se/~lada/projects/proind.html