Experimental Study On The Characteristics Of Reynolds Stress In Open Channel Flow

It is always in development and change in natural stream flow. The river flow and river channel form the unification of contradiction. The stream acts on the river bed, and the river bed works changes. In turn, the changes of the bed influence the stream structure. These two facts are always interdependent, interplay and mutual restraint, and thus are continuously in existence in the process of motion and development. The lateral erosion is the transverse deformation, which is a part of the fluvial processes.The research on the distribution of the Reynolds Stress is very important to the study of the lateral erosion. Especially in recent years, the Xiaolangdi reservoir and Sanxia reservoir are completed and put to use. The bank scour in the downstream of the reservoir is becoming a cause for concern. Whether explain the fluvial processes or solving the practical subject productions, it is necessary to study the Reynolds stress distribution in open channel flow.Based on the result of researchers before, initially aiming to study on the lateral erosion in the downstream of the reservoir, by means of data analysis in conjunction with the simplified experimental flume, the paper is studying on the lateral erosion in the downstream of the reservoir and the Reynolds Stress distribution in open channel flow.The paper first tells about the lateral erosion in the downstream of the reservoir by means of data analysis. Based on the result of researchers before and the field data, the lateral erosion in the downstream of the reservoir has been dealt with in the paper. The effect of lateral boundary condition, river regime and bed material on lateral erosion were analyzed. Some conclusions could be drawn: The lateral erosion do exist in the downstream of the reservoir. The lateral erosion was slight firstly and then gradually enhanced, sometimes the lateral erosion in the downstream of the reservoir may result in a bigger width than before the reservoir; In the reaches where the lateral boundary conditions are strong, the lateral erosion has been weak and it has been strong in the reaches where the lateral boundary conditions are weak; In the reaches where the bed material is coarse and the material in the bank is fine, the lateral erosion has been strong; and in the reaches where the bed material is fine and the erosive resistance of bank is strong, the lateral erosion has been weak; In the bifurcated reaches, the lateral erosion mainly happened in the main channel; In the wandering reaches, the character of wandering was controlled firstly and the effect of lateral erosion has been submerged; In the meandering reaches, the phenomena of the cut-bank and throw away the elbow were prevalent.In the experimental flume, MicroADV has been to measure the velocity, the turbulence intensity and the Reynolds stress. And the distribution of the Reynolds stress has been assayed and studied in the pure water flow and sediment-laden flow. Some conclusions could be drawn: the plain Reynolds stress is nearly linear larger from the water surface to the boundary. And it acquires themaximum number in the near boundary and it is gradually diminishing. The vertical Reynolds stress is also gradually ascending from the water surface down. And it acquires the maximum number in the main region and it is gradually diminishing then. The distribution of the plain Reynolds stress and the vertical Reynolds stress is uniform in the pure water flow and sediment-laden flow. The plain Reynolds stress in sediment-laden flow is larger than in the pure water flow in the near bottom region and the main current And it is not marked change in the near water surface after die sediment was took into the pure water. The vertical Reynolds stress is not also marked change after the sediment was taken into the pure water.To compare the distribution of the plain Reynolds stress with the distribution of the vertical Reynolds stress, some conclusions could be drawn. In the same relative deep in the water, the plain Reynolds stress is larger than the vertical Reynolds stress in the near bottom region. And they cut across each other in the main water region. Then the vertical Reynolds stress is larger than the plain Reynolds stress. As the Reynolds number becomes larger, the vertical Reynolds stress gradually becomes larger than the plain Reynolds stress. The vertical Reynolds stress is gradually diminishing from the boundary to in the middle of the flume.Based on these, the influences of the intensity of flow on the distribution of the Reynolds stress are made further study. Some conclusions could be drawn. Within the test, the plain Reynolds stress is larger as the sediment concentration and the intensity of flow become increase. The vertical Reynolds stress is not marked change when the sediment concentration and the intensity of flow increase. These are larger as the Reynolds number becomes larger.