Numerical Simulation of Jet Flow Hydrodynamics at Erosion Tunnel beneath Offshore Pipelines

Hydrodynamics of flow in erosion tunnel caused by local scour below offshore pipelines is studied using a standard turbulence model in simulation of a steady current flow around a pipeline above seabed. The flow field is computed with solving the Reynolds Averaged Navier-Stokes equations (RANS); whereas seabed under pipeline is treated as a plane boundary and a no-slip boundary condition on pipe surface, is considered. The governing equations are solved using finite volume method in a Cartesian coordinate system. Based on numerical solutions, flow characteristics and effect of lee-wake vortices forming behind the pipeline in erosion tunnel are studied. It is found that mean flow velocity in the erosion tunnel is an appropriate parameter in calculation of Shields parameter and it can be applied in calculation of sheet-flow transport rate in determination of scour potential along seabed.

Keywords:

Reynolds Averaged Navier Stokes Equations , turbulence model , erosion tunnel and local scour