Numerical simulation of oscillatory flow and current around a circular cylinder

The proposed paper aims to present a parametrical analysis via CFD (Computational Fluid Dynamics) of the drag amplification factor of a cylinder in a current superposed to an in-line oscillatory velocity. Numerical simulations based on a two-dimensional discrete vortex method with viscous diffusion have been carried out in order to obtain the drag amplification factor against U-0/U-1 (the relation between the uniform velocity U-0 and the oscillatory-velocity amplitude U-1) for various values of KCI (the Keulegan-Carpenter number). This work is related with fundamental research regarding hydrodynamics aspects of marine risers. The results obtained in this paper can be applied in the analysis. of marine risers concerning vortex shedding and flow-induced vibration. The parametrical analysis provides a better comprehension of the drag amplification phenomena when a circular cylinder is submersed in current with a superposed oscillatory flow. The amplification coefficient obtained can be used in a parametric form in the analysis of the force coefficients present in mooring systems. The results obtained via CFD ate in good agreement with those provided by a theoretical curve for the range of values of U-1/U-0 > 1.0 in which this curve applies. For values of U-1/U-0 < 1.0 the numerical simulations are compared to a second theoretical equation and they show some dependence on KC effect not predict for this equation. The attraction of applying numerical methods to such problem is that the flow can be studied in closer detail. The study of the drag amplification factor has relevant significance in the analysis of marine risers. In this sense, fundamental knowledge can be achieved performing a parametrical analysis of the phenomena in a relative fast way via CFD.