2D Numerical Simulation Of The Overland Flow Fields And Laboratory Experiment Study On Fixed Bed Slope

The water depth on the slope surface is very small.Affected by the natural conditions of the surface and the disturbance of rainfall,the hydraulic characteristics of the slope are complex and the existing experimental results are not identical.The research on hydraulic characteristics of slope flow has long been a concern of academia and engineering.This paper intends to use model tests and numerical simulations for the hydraulic characteristics of slope flow affected by a single raindrop,and to establish a numerical simulation model,a discrete method,and further hydraulic characteristics.The VOF calculation model was used to perform free surface tracking on raindrops and slope flows,and the standard turbulence model was used to simulate the changes in the characteristics of water and gas flow during raindrop drop and the various hydraulic characteristics of the landslide flow and the slope flow.The main research contents are as follows:(1)The effects of different raindrops and rainfall height conditions,single rain drop velocity,volume change,the impact on water velocity,and the effect of water layer thickness on the impact force.(2)Based on the flow test of indoor fixed bed slope surface,the change law of flow hydraulics parameters(velocities,Reynolds number,Froude number,and drag coefficient)at different water depths,different gradients and different bed surface roughness are analyzed;(3)Numerical simulation of slope flow velocity in the fixed-bed test under water release conditions was carried out to analyze the Reynolds number,Froude number and drag coefficient,and compared with the test results;(4)Validation of numerical simulation results based on experimental results of fixed-bed slope surface flow mechanics parameters changed the theatricality Reynolds number.According to the simulation and test results,the following conclusions are drawn:(1)Under the same water layer thickness,the greater the final speed,the greater the impact force,the increase of the water layer thickness,and the reduction of the impact force;With the increase of the height,the diameter of raindrops entering the water becomes smaller;at the same height,as the diameter of the raindrop increases,the diameter of the raindrop increases.(2)Under the same gradient,with the increase of roughness,the average flow velocity decreases rapidly and then slowly decreases.Finally,it reaches a plateau,and the Reynolds number increases with the increase of roughness,increases slowly after a sudden decrease,and finally reaches a plateau;Under the condition of roughness,the average flow velocity increases with the increase of slope;under different slope conditions,the Reynolds number is proportional to the slope;under the same flow conditions with the same bed surface and with the increase of slope,the Fronde number shows an increasing trend.The drag coefficient and slope are also in a positive relationship;the same slope,different roughness,and the Fronde number decreases as the drag coefficient increases.(3)The value of the lower critical Reynolds number measured in the test is about 400.(4)When the rainfall intensity and slope are 15 o,there are two kinds of flow states with the increase of rainfall intensity;The Reynolds number and Fronde number increase with the increase of rainfall,and the drag coefficient decreases.When the single-width flow is the same,the correction coefficient increases first and then decreases with the increase of rainfall.When the rainfall is different,the flow rate and the Fronde number show an increasing trend.