Experimental Study On Load Characteristics Of Unsteady Hyperconcentrated Flow

Most of the rivers in our country have high sediment concentration.The physical property,kinetic characteristic and the sediment transport characteristic of the hyperconcentrated flow will no longer obey the Newton fluid motion law after the sediment concentration increases.The model test about the hyperconcentrated flow is relatively little.Therefore,this study,using hyperconcentrated flow on hydraulic structure,is of great theoretical and engineering significance.This paper takes the unsteady hyperconcentrated flow as test subject.By adjusting the sediment concentration and upstream flow condition and applying to orifice plate and flared gate piers,this paper observes the water flow pattern and collects the data of time-average pressure and fluctuating pressure.The main research results and conclusions are as follow:(1)This paper measures the time-average pressure at the bottom(middle line)of the orifice plate test section based on one self-designed model using grey plastic tube.The research results show that: the change of sediment concentration has little influence on the flow pattern;the time-average pressure and fluctuating pressure of hyperconcentrated flow has the same distributing rule as pure water flow,and the value of both increases as the sediment concentration goes high within the experimental range,and the biggest increase is 170.10%.(2)This paper measures the fluctuating pressure at the bottom(middle line)of the orifice plate test section based on one self-designed model using grey plastic tube.The research results show that: the upstream flow condition has significant influence on the fluctuating pressure,the value of it increases as the sediment concentration increases when the upstream flow condition is weak,while it decreases after the first increase as the sediment concentration increases when the upstream flow condition is strong.(3)This paper observes the form of the nappe in the air and the flow pattern in the plunge pool on one certain water project with the scale of 1:100.The research results show that: the sediment concentration has significant influence on the flow regime of both the nappe and the water in the plunge pool,the outside edge of the nappe grows more smoothly as the sediment concentration goes high,at the same time the amplitude of the swing of the nappe decreases,and the size and the number of the vortex decreases too.(4)This paper measures the time-average pressure at the bottom(middle line)of the plunge pool The research results show that: the time-average pressure of unsteady hyperconcentrated flow has the same distributing rule as pure water flow,and the value of it increases as the sediment concentration goes high within the experimental range,the biggest increase of the surface spillways is 74.14%,and that of the middle spillways is 44.27%.(5)This paper measures the fluctuating pressure at the bottom(middle line)of the plunge pool The research results show that: the fluctuating pressure of hyperconcentrated flow has the same distributing rule as pure water flow,and the change rule of the value alters as the upstream flow condition varies,the value of it increases as the sediment concentration increases when the upstream flow condition is weak,while it decreases after the first increase as the sediment concentration increases when the upstream flow condition is strong.