A quasi-3D prediction model of wall jet rock scour in plunge pools

A new computational method for predicting rock scour in plunge pools and stilling basins of high-head dams is presented. This accounts for 2D vertical diffusion and subsequent deflection of high-velocity jets at the bedrock. This forms wall jets that are being diverted by protruding rock blocks. The model computes the corresponding turbulent pressures that may eject single blocks. It is applicable along the bedrock situated outside of the area of jet impingement, both towards the dam and downstream. It is complementary to the existing rock scour prediction methods valid inside the turbulent shear layer of the jet. Simultaneous application of these methods to a series of 2D vertical jet slices produces a quasi-3D rock scour prediction model.