| A generalized numerical method for solution of the incompressible Navier-Stokes equations for two- and three-dimensional geometries has been developed. Incompressible fluids are encountered in a variety of engineering problems including offshore marine sciences, low-speed aerodynamics, and a wide class of civil and industrial engineering applications. The focus of the research is rooted in offshore hydrodynamics with the study of how incompressible fluids interact with the structures they surround, and in turn, how these structures respond to the external fluid forces. One important instance of this flow-structure coupling arises with the prediction and suppression of vortex-induced vibrations (VIV) which is a critical concern to the offshore oil industry, particularly with the design of offshore risers and spars. Although typical amplitudes of vibration for risers undergoing VIV are small, the risers can still experience fatigue failure as a result of the persistent dynamic stresses. Most all of the current models used to predict VIV response characteristics are derived from a database of experimental results with a large scatter of predicted responses being observed. However, surprisingly little work has been done to apply the governing incompressible Navier-Stokes equations to numerically obtain flow structure solutions about cylindrical members. Hence, the goal of this research is to develop and validate a tractable numerical option for approaching VIV and other offshore hydrodynamic problems.; In terms of numerics, a pressure correction method is implemented for solution of the incompressible Navier-Stokes equations using deformable hybrid grids and an empirical turbulence model. An analytic wall function is combined with the turbulence model to increase solution efficiency and reduce the near-wall resolution required to model fully turbulent flows. The pressure correction method is loosely coupled with an elastic body structural response to obtain unsteady flow structure solutions, In addition, the entire flow-structure solution methodology has been combined with a feedback control mechanism to assess the possibility of using dynamic positioning to control certain classes of VIV motion. Solutions of the Navier-Stokes equations are obtained using an edge-based finite volume discretization on non-staggered grids and artificial dissipation is introduced into the momentum equations to suppress oscillatory solutions. |
