Experimental Analysis And Numerical Simulation Of Floating Debris Before Sluice Influence Flow Structure

Many sluices in southern China are affected by floats for a long time in operation process, thick cover layer together with the river channel boundary form a closed water boundary, causing flow section wetted perimeter increases, decreasing effective water section. The change of the flow boundary is bound to effect flow structure and flow capacity, especially, the resistance of cover layer, seriously threat to sluice flood discharge.This article will study with vegetation rivers flow problems both at home and abroad on the basis of the combination theory of hydraulics and lock out flow theory, using physical model test and numerical simulation method to quantitative analysis of flow velocity and water level along the change of situation when floating cover before sluice, based on various operating conditions, summary flow ability change rule of the sluice. The main conclusions of this paper are:Physical model test, the brake orifice outflow in the same condition, water’s height before gate of decorate cover layer would have significantly lower than before, the flow rate of the under layer is no longer half a logarithmic distribution, but approximate accord type of fish maw ")" form, the upstream water’s height has the obvious rise when weir flow, the longer of cover layer lead higher flow resistance, the upstream water’s height rise more obvious. With floating debris, the comprehensive coefficient M1 of orifice outflow is increases, flow rate correction coefficient Ks>1; The comprehensive flow coefficientM2 of weir flow is less than decorate situation, flow rate correction coefficient Ks’<1. According to the measured flow data of weir flow, fitting out a flow rate correction coefficient Ks’ expression, that relative to the upstream and downstream water’ height hs/H1 and covering length L1.Taking advantages of numerical calculation to detailed and intuitive analysis of the cover layer impact to three dimensional flow field, finding that no matter orifice outflow or weir flow situation, the upstream water flow through overlay segment will bypass the surface layer, and be forced to dive lower part, almost no fluid through the area of coverage. Cover layer will improve the flow ability of sluices when orifice outflow; Cover layer will weaken the flow ability of sluices when weir flow, and the weakened as the growth of the coating increase. The numerical calculation of velocity distribution and flow ability agree well with experimental values.