Study On Hydrodynamic Characteristics Of Sheet Flow On Lower Slope Surface

Slope runoff is one of main motive force factors of soil erosion. Study on hydrodynamiccharacteristics regularity of slope flow is basic to make clear mechanism of soil erosion.Because of the particularity of flow pattern of slope flow, the variation of hydrodynamicparameters with flow discharge、slope gradient and surface roughness still has lots ofproblems. To provide the theory basis for soil erosion correlational research, a series ofexperiments on shallow flow on slope surface were performed at the indoor experiment offixed bed. The study selected6kinds flow discharge (0.04、0.08、0.12、0.16、0.2、0.24L/s)、15kinds of slope gradient (0～5°,one kind of slope gradient every other20′)and5differentkinds of rough bed(one kind of organic glass slippery surface and4different kinds of sanddiameter bed:0.5～1.25，1.25～2.5，2.5～5，5～10mm) and analysed the variation ofReynolds number、Froude number、flow velocity、water depth、resistance coefficient andstream power with flow discharge、slope gradient and surface roughness. Main researchresults included:(1) Experimental study under the condition of organic glass slippery surfaceReynolds number, Froude number, flow velocity, water depth and stream power tendedto increase and resistance coefficient tended to decrease while flow discharge increased in thecondition of the same slope gradient. Reynolds number, Froude number, flow velocity,resistance coefficient and stream power tended to increase and water depth tended to decreaseif slope gradient increased in the condition of the same flow discharge. The relationship ofthese parameters with flow discharge and slope gradient could be well described by powerfunctions, and express as y=kqasb(y—hydrodynamic parameters; q—flow discharge; s—slopegradient; k, a, b—coefficient). Flow discharge had greater influence on Reynolds number,Froude number, flow velocity, water depth and resistance coefficient than slope gradient. Theopposite that slope gradient had greater influence on stream power than flow discharge. Therelationship between Reynolds number and Froude number could be well described by powerfunctions in the condition of the same flow discharge and the different slope gradient.(2) Experimental study under the condition of the different roughness surfaceReynolds number, flow velocity and stream power tended to decrease and water depthand resistance coefficient tended to increase if the roughness increased in the condition of the same slope gradient and flow discharge. There was significant correlation of these parameterswith slope gradient and flow discharge. The relationship could be well described by powerfunctions, and express as y=kqasbdc(y—hydrodynamic parameters; q—flow discharge;s—slope gradient; d—roughness; k, a, b, c—coefficient). Flow discharge had the biggestinfluence on Reynolds number, flow velocity, water depth and resistance coefficient. Theroughness was the second and the slope gradient was the third. The opposite that slopegradient had the biggest influence on stream power. Flow discharge was the second, and theroughness was the third. The relationship of resistance coefficient and Reynolds number couldbe also well described by power functions. It could be described as f=K/Rea(f—resistancecoefficient; Re—Reynolds number; K, a—coefficient).