Experimental Study On Hydraulic Characteristics Of Shallow Flow On Artificial Rough Bed

Shallow flow is formed by the rain after seepage and filling in lower places. It is the first step of runoff on earth surface and main drive of soil erosion. So it is very important and has great scientific meanings to do some research on shallow flow. The research on hydraulic characteristics of shallow flow can help us in many aspects, such as preventing soil erosion, protecting environment and so on. On the basis of consulting a large number of relative materials of home and abroad, this paper presents the new researches and the latest developments on hydraulic characteristics of shallow flow. Using the knowledge of hydraulics, soil and water erosion and so on, an indoor fixed-bed experiment of overland flow was simulated aiming to find out the relationships between hydraulic characteristics (Reynolds number, Froude number, flow velocity, water depth and resistance coefficient) and discharge, slope gradient and roughness. Hydraulic characteristics of shallow flow on slope surface were researched in the paper from the following two aspects:(1) Experimental study on hydromechanics of overland flow under the same roughness conditionA series of experiments of shallow flow on slope surface were performed on a artificial rough bed (grain size of sediment is 2mm-5mm) with 5 different gradients ( i=0.002, 0.005, 0.01, 0.02 and 0.05) through the indoor fixed-bed resistance test. The preliminary result indicates that:The Re number of overland flow increase with the increasing of discharge and slope gradient. However, the effect of discharge is greater than that of slope gradient. The average velocity and water depth increase with the increasing of discharge. Resistance coefficient decreases with the increasing of discharge.(2) Experimental study on hydromechanics of overland flow under different roughness conditionA series of experiments on overland flow hydromechanics under different roughness condition were performed on organic glass slippery surface and artificial rough bed (grain size of sediment is 0.2mm-0.5mm, 0.5mm-1mm, 1mm-2mm and 2mm-5mm) with 5 different kinds of gradient(gradient is: i=0.05,0.02,0.01,0.005,0.002 ). Through the experiment study on hydromechanics of overland flow under different roughness conditions, the relationships between hydro-dynamic parameters of fixed-bed shallow flow (Reynolds number, Froude number, resistance coefficient and flow velocity) and bed roughness was studied by means of the experiment on overland flow hydromechanics of different roughness, the preliminary result indicates that:Fixed-bed shallow flow Reynolds number and Froude number tends to decrease with the increase of grain size; Overland flow Reynolds Number and Froude number tends to diminish, water flow velocity tends to diminish, and resistance coefficient tends to increases, if bed surface roughness increases in the same condition of lope gradient and flow discharge. It shows that consumed energy for working of water flow surmounting resistance tends to increase.