Study on the Mechanism of "Scouring Sediment by Water Jets" and on Its Engineering Application
-Variations of Mean Velocities in Vertical and SurfaceGradients  Created by Water Jets
Huang Suiliang
(Beijing Normal University, Beijing 100875)

Abstract: It is necessary to develop technologies of silt clearence and to carry out its fundamental research. Through the water jet device made by ourself, the flow structure and the deformation of riverbeds of non-uniform flow caused by water jets, the mechanism of "Scouring Sediment by Wate Jets"and optimum parameters of water jets in engineering application have been studied in an experimental flume. The characteristics of water surface gradients and of velocity distribution along the depth of non-uniform flow created by water jets in the flume are presented in this paper. Because of existing water jets, water surface gradients and distrbutions of velocities along the depth vary greatly compared with those in the uniform flow. Water surface gradients of existing water jets are less than those of non-existing water jets in the upstream of water jet tubes, in the reach of water jet tubes and its downstream reach water surface gradients of existing water jets are larger than those of non-existing water jets, while as a whole in the flume mean water surface gradient of existing water jets. The above characteristics is dependent on the discharge in the flume and the discharge of water jets. Generally speaking, the larger the discharge in the flume and the larger the discharge of water jets, the more remarkable the differences of water surface gradients and distributions of velocities along the depth between existing water jets and non-existing water jets. Turbulent structures and deformation of riverbeds caused by water jets will be studied in another paper.
Keywords: water jets, non-uniform flow, watersurface gradients, distributions of velocities along the depth.