Eddy viscosity modelling in nearly equilibrium scour holes

In this report the results of numerical experiments of two-dimensional flow computation in nearly equilibrium scour holes are presented and analysed. The numerical flow models ODYSSEE and DUCT were applied for computations on four different cases, based on a former physical model investigation (Buchko 1986). The performance of both numerical models are presented, and the computed eddy viscosity profiles are compared. Generally the computed velocity profiles seem to be in satisfactory agreement. The inflow turbulence influences the size of the eddy in DUCT differently than in ODYSSEE, however these differences are small. Besides, a few local differences can be attributed to different boundary conditions at the surface and the bed of the scour hole, in the models. The eddy viscosity profiles are in close agreement in the upstream part of the scour hole. More downstream, the eddy viscosity decreases more slowly in DUCT than in ODYSSEE. The flow model DUCT seems to be feasible for further research into scour hole formation for practical engineering.