SIMULATION OF VORTEX SHEDDING PAST A SQUARE CYLINDER NEAR A WALL

Calculations are reported for the flow past a square cylinder at Re = 22,000 placed at various distances from an adjacent wall, including th e limiting case without wall influence. Experiments have indicated tha t unsteady vortex shedding is suppressed when the wall is relatively c lose to the cylinder. Two-dimensional (2-D) unsteady equations are sol ved which allow any periodic shedding motion to be resolved; the super imposed turbulent fluctuations are simulated with two versions of the k-epsilon turbulence model: the standard k-epsilon model and the modif ication attributable to Kato and Launder (1993), which eliminates the excessive turbulent kinetic energy production in stagnation regions pr oduced by the standard model. Wall functions are used with both versio ns. The standard model was found to damp the shedding motion unrealist ically so that shedding was suppressed at considerably larger gap widt hs than observed experimentally. The Kato-Launder modification yields reasonable predictions over the full range of gap widths; for G(W)/D = 0.75 a quantitative comparison is presented with the authors' phase-r esolved experiments, which shows fairly good accord.