Scour Caused by 2D Horizontal Jets

An analysis is presented of the 309 known laboratory data for local scour depth developed by two-dimensional (2D) horizontal jets, which leads to development of a new comprehensive prediction equation. The new equation comprises a number of mutually independent multiplying factors, which account for the effects on local scour depth of the characteristics of the applied jet flow and the bed sediment, as well as the extent of a downstream protective apron. When unitized in terms of the jet thickness, the equation shows that the maximum possible dimensionless local scour depth is equal to three times the jet Froude number expressed in terms of jet velocity and jet thickness. The equation is compared to most of the existing predictive equations by applying each equation to the existing data, the comparison indicating that the new method has superior performance. Indeed, many of the existing predictive equations are shown to perform poorly when judged against the known laboratory data. The known existing equations are listed in the paper.