Turbulence approach for predicting scour at abutments.

This study proposes a scour equation for abutments that is based on a combination of Newton's second law and a turbulence model comprised of a pair of isotropic vortices. A control volume of the scour hole is considered on which the sum of forces equals nil. The effect of abutments on local scour is usually modelled by an empirical K-factor for which there is no physical description available. Here, we deduce a relation between abutment shape and the maximum scour depth by using engineering tools from turbulence science. We pay attention to the scour effects of several types of abutments, such as submerged, non-submerged, permeable and impermeable and the impact of bed protection. We consider the highly nonlinear combination of constriction and local scour. The unknowns in the proposed scour equation are calibrated and validated with several scour tests. [ABSTRACT FROM AUTHOR]