NUMERICAL SIMULATION OF STEADY CURRENT BELOW OFFSHORE PIPELINE NEAR PLANE BOUNDARY

This paper presents a k-e turbulence model for simulation of steady current and its induced vortex shedding caused by the presence of an offshore pipeline. performance of the model around a circular cylinder above a wall with gap to diameter ratios of 0.1, 0.35 and 0.5 under different flow regimes with reynolds numbers of 1500, 2500 and 7000 is studied. the flow field is computed with solving the reynolds averaged navier-stokes equations (rans); the seabed under pipeline is treated as a plane boundary with no-slip boundary condition on pipe surface. the governing equations are solved using finite volume method in a cartesian coordinate system. based on the numerical solutions, the flow field, vortex shedding and distribution of shear stress due to the presence of the pipeline near seabed are studied. in addition the mechanism of vortex shedding with different gap to diameter ratios is examined with focusing on the effect of vortex shedding on bed shear stress. it is found that the k-e turbulence model can well predict the flow field and its induced vortex shedding around a pipeline; hence it can be easily applied for simulation of scour below an offshore pipeline