Resistance Research Of Changjiang River Model

River model test is an important research method of flood-control, waterway regulation etc. Resistance of river bed is one of the key points of what river model have to simulation. For simulating resistance accurately, we should know the condition of the river model, in which it can meet the law of resistance similitude. This paper is based on resistance problem of Changjiang river model. By experimental and numerical study, this paper offered new resistance adjustment method for the Changjiang river model, enriched roughness technique of fixed bed model, and brought forward some experimental productions on a new-type model sand's resistance characteristic.(1) By experiments on rectangular cross-section flume adding Y-shaped roughness elements and gravels, we knew the each connection between flow resistance and roughness density, relative height and flow intensity, educed a formula calculating the flow resistance, and analyzed the velocity profile.(2) By experiment on V-shaped flume had no roughness elements and adding Y-shaped roughness elements, it results the connection between flow resistance and roughness, water depth and flow intensity. Based upon the velocity profile on vertical line and transect, it's obvious that flow intensity and adding artificial roughness have deep relationship with velocity distribution.(3) By flume experiments, the resistance characteristic is compared between the V-shaped cross-section channel and rectangular cross-section channel after adding artificial roughness. The research results show that: when flow entered in the turbulent regions, the Reynolds number of the V-shaped channel is smaller than that of rectangular cross-section flume. When the Reynolds number is small, the resistance coefficient of the V-shaped channel is smaller than that of rectangular channel. With the Reynolds number increasing, both resistance coefficients trends to the same value.(4) The two-dimensional flow around Y-shaped roughness element has been simulated By CFD model, the calculation results show that: with the Reynolds number increasing, the drag and lift coefficients can be divided into three fields: laminar, transitional and turbulent field. It preliminarily shows up the micro-mechanism of increasing resistance by adding artificial roughness.(5) A experimental study is described for the variation of compound plastics sand waves. The results show that: under a certain depth of water, with the flow intensity increasing the sand waves goes through three stages: ripples, dune, and plane movable bed. Wave height and length firstly increases and then decreases with flow strength increasing. The metric of sand waves increased with increasing of median grain size of the plastic sand. When the sand waves fully developed, the bed roughness can increase from 0.013(plane bed) to more than 0.03.(6) By date collection, the Shields number as function of sand Shields number is compared among two kinds of model sand and natural sand.