REDUCTION OF SCOUR BELOW SUBMERGED IMPINGING JETS BY SCREENS

This paper presents the results of a laboratory study of the reduction of erosion of sand beds below submerged impinging circular and plane jets by screens. In this method, a screen is placed on the sand bed to reduce the impact of the jet on the bed. Dimensional arguments and mu ltiple regression analysis are used to predict the characteristic leng ths of the eroded bed in the asymptotic state. In the case of impingin g circular jets, equations for the reductions or increases of the leng th scales due to the presence of the screens are defined and evaluated and approximate equations are also given. The dynamic scour depth red uction in these experiments ranged from 47% to 84%. The reduction or i ncrease in scour hole radius could range between a reduction of 16% an d an increase of 75%. The experimental study was not as extensive in t he case of impinging plane jets. It was found, however, that the scree n helped to reduce the dynamic scour depth.