Unsteady aerodynamic force prediction on a square cylinder using κ-ε turbulence models

In designing structurally safe large-scale civil structures, the dynamic structural behavior in response to unsteady wind loadings should be investigated. Since a typical civil structure is a blunt body, flow separates, reattaches, and forms an unsteady vortex in the wake region behind the structure. Conventional k-epsilon turbulence models have failed in predicting unsteady turbulent flows around blunt bodies, unless careful modifications suited to the specific cases were made. Systematic investigation of numerical effects on the computation of turbulent flows over a square cylinder has been made. It has been found that some conventional k-epsilon models may give reasonable predictions when proper numerical parameters are incorporated. Critical numerical aspects are found to be the near-wall grid spacing and the choice of convection schemes, while the temporal accuracy effect is not so important. A numerical prediction is compared in detail not only with experimental measurements but also with the results from a sophisticated turbulence simulation.