Erosion of loose beds by submerged circular impinging vertical turbulent jets

Abstract

This paper presents the results of a laboratory study on the erosion of sand beds by submerged circular impinging vertical turbulent jets of water for the erosion parameter E_c less than 5. The variation of the maximum scour depth with impinging distance was studied and this revealed two major flow regimes referred to as the Strongly Deflected and the Weakly Deflected Jet Regimes. The conditions under which they exist were established. The asymptotic eroded bed profiles were found to be similar except at very low values of the erosion parameter when made non-dimensional using the maximum scour depth as the length scale. Another length scale was introduced to achieve similarity for all values of the erosion parameter. Using results from this study and the literature, semi-empirical equations have been developed for the characteristic lengths of the erosion profiles in the asymptotic state. Equations that may be used for different values of the relative density difference δρ/ρ are proposed for the maximum scour depth and the scour hole radius using data from this study and from the literature which includes data on air jets impinging on loose beds of sand and polystyrene.