“射流松动泥沙”的机理及工程应用试验研究——射流引起的非均匀流全河段水面比降及垂线流速分布

Study on the Mechanism of “Scouring Sediment by Water Jets” and on Its Engineering Application ——Variations of Mean Velocities in Vertical and Surface Gradients Created by Water Jets

泥沙清淤技术及其基础研究需要不断发展，通过自制射流发生装置，在水槽中对射流引起的非均匀流水面比降及垂线流速分布全河段变化特点进行了系统试验研究。由于射流的存在，水面比降及垂线流速分布发生较大变化。水面比降射流段上游的比无射流的小，射流段及其下游比无射流的大，而全河段水面比降比无射流时增大。垂线流速分布在射流段及其下游附近发生根本的变化，有射流时，水面附近的流速比底部流速小，垂线平均流速一般小于无射流。上述这些特点与水槽流量和射流量有关，一般而言，水槽流量越大，射流量越大，这些变化越显著。

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.