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۱Numerical Simulation of Jet Flow Hydrodynamics at Erosion Tunnel beneath Offshore Pipelines
اطلاعات انتشار: دومین کنگره ملی مهندسی عمران، سال
تعداد صفحات: ۸
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.<\div>

۲Numerical Study of Gap to Diameter Ratio Effects in Steady Current under Offshore Pipelines
اطلاعات انتشار: دومین کنگره ملی مهندسی عمران، سال
تعداد صفحات: ۸
The performance of a standard turbulence model in simulation of hydrodynamics of a steady current around a circular cylinder above a wall is examined. Mechanism of vortex shedding and effect of different gap to diameter ratios (0.1, 0.35 and 0.5) on the bed shear stress are also demonstrated. The flow field is computed with solving the Reynolds Averaged Navier–Stokes equations (RANS);whereas the 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 the numerical solutions, the flow field and its induced vortex shedding are studied. It is found that a turbulence model can well predict the flow hydrodynamics with accounting vortex shedding around a pipeline near seabed; consequently, it can be easily applied for simulation of scour under offshore pipelines.<\div>
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