The two-dimensional, viscous, unsteady, and incompressible flow by a circular cylinder in oscillatory motion is investigated by solving the Navier-Stokes equations. A CFD (Computational Fluid Dynamics) code based on a multi-block FDM/FVM hybrid method has been developed and extensively tested against other CFD and flow visualization results. The multi-block hybrid method uses rectangular grid- structured FDM (Finite Difference Method) at far field and body-fitted-coordinate-structured FVM (Finite Volume Method) in the near field. The FVM code is able to reproduce with high accuracy the flow characteristics around arbitrary 2D bodies for various experimental conditions. The FDM code used in the outer domain is developed so that it can include arbitrary rigid and free-surface boundaries. The numerical computations successfully captured many important flow features for various types of flow conditions. In particular, the flow simulations for an oscillating cylinder are able to reproduce, through advanced computer graphics software, various interesting features observed in the physical experiments for a variety of K-C numbers. The developed computer program is proved to be robust and efficient to be able to simulate more complicated flow problems including both seabed and free surface.
The oil companies or offshore industries rely in most cases on subsea pipelines or risers to transport gas and oil from ocean grounds to land or surface platforms. Therefore, they have to ensure that these offshore structures are resistant and stable while undergoing the hydrodynamic forces induced by currents and waves. In this regards, it is very important to accurately predict the hydrodynamic forces (inertia, drag and lift) and better understand the nonlinear unsteady viscous flow phenomena around a circular cylinder, along with an accurate calculation of relevant parameters, such as the Strouhal number related to the frequency of the vortex shedding.
