Modeling of Flow Around a Cylinder Over a Scoured Bed

The hydrodynamics around a static horizontal cylinder and five static scoured bed profiles subjected to steady flow were simulated using a CFD model, FLOW-3D. Both a two-equation k-ϵ model and a Smagorinsky LES turbulence closure scheme were evaluated. The mean horizontal and vertical velocity estimates of both turbulence models show reasonable agreement with the data. Wake characteristics such as the reattachment point and vortex shedding were examined. The reattachment point for the k-ϵ closure scheme was consistent with the observations. However, the vortex shedding induced by the LES closure scheme resulted in a considerably larger and unsteady reattachment point. In all profiles, the size and strength of the eddies formed by the LES closure scheme were found to be grid dependent. The k-ϵ model was found to be grid dependent for the vortex shedding process.

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