Chimera RANS simulations of pier scour and contraction scour in cohesive soils

The research is part of the development of SRICOS-EFA for predicting the scour depth around a pier as well as the contraction scour due to the contracted section in the channel. The Chimera RANS incorporated with the scour rate equation in cohesive soils is used to simulate the scour process around a complex single pier and around an abutment. The computational domain is first divided into a number of smaller grid blocks that allow complex configurations and flow conditions to be modeled efficiently through the judicious selection of different block topology, flow solvers and boundary conditions.; The scour rate equation is experimentally obtained from Erosion Function Apparatus (EFA). Two types of soils are used to validate the Chimera RANS method compared to experiments done in the flume. The effect of turbulence in the scour rate is also investigated to improve the capability of the Chimera RANS method to predict the scour profile, especially behind the pier.; The Chimera RANS method has proven to be an accurate method to predict bed shear stress around a pier and an abutment. The overall predictions of scour depth history are in good agreement with experimental data for both pier scour and abutment scour. The comparison of scour depth history with the experimental data of contraction scour is also performed. There are some discrepancies between the numerical and experimental results for contraction scour.; Equations of maximum bed shear stress are proposed for three different applications: around a pier, around an abutment, and along the centerline of a channel at the contracted section. Also, the equation of maximum bed shear stress around a pier when the abutment exists is proposed.