Study On The Characteristics Parameters Of Shallow Water Flow Considering With Rainfall And Infiltration

In recent years,more and more attention has been paid to the study of thin laminar flow on slope,especially the flow of rainwater on slope,slope inflow and infiltration,and hydraulic characteristics of pavement,which provide a basis for discussing hydraulic erosion and pollutant transport on slope and pavement.Although some progress has been made in related research,the difference in measurement equipment,the limitation of measurement accuracy and the lack of a large number of accurate test data,and the slope thin laminar flow is very different from the traditional open channel flow,resulting in many differences in the research conclusions,and it is urgent to study the slope thin-layer water flow based on high-precision test methods.In this paper,the fixed-bed slope plexiglass tank is used to measure and analyze the hydraulic characteristic values of the downslope surface under different working conditions by particle image velocimetry(PIV).Five slopes were selected for 5°,10°,15°,20°,and 25°,and the six bed roughness were Plexiglass(theoretical roughness of 0.008mm)and five artificial roughening beds(0.5～1.0 mm,1.0～1.5 mm,1.5～2.0 mm,2.0～4.0 mm,4.0～5.0 mm)and four single-width flow rates of 0.0137 m~2/s,0.0274 m~2/s,0.0418 m~2/s,0.0560 m~2/s,the difference between Fluent simulation and test results,as well as the relationship between hydraulic characteristics,was analyzed,and the relationship between flow rate and single-width flow was corrected.At the same time,considering the two important influencing factors of rainfall and infiltration of slope flow,based on three slopes of 1°,15°and 25°,four single-width flow rates of 0.0137 m~2/s,0.0274 m~2/s,0.0418 m~2/s,0.0560 m~2/s,four rain intensities(0.50 mm/s,0.25mm/s,0.05 mm/s,no rainfall),three infiltration rates(0 cm/s,0.4851 cm/s,2.1449 cm/s)Trial and error were carried out.The perpendicular flow velocity distribution,the relationship between velocity and single width flow,and the vertical and flow direction turbulence intensity under the infiltration condition of permeable brick were analyzed.The changes of flow direction turbulence intensity distribution under different rain strength were explored,and the resistance characteristics under different rain intensity were analyzed.According to the variation relationship of velocity-flow on slope thin layer flow under different slopes and different infiltration volumes,and the change of resistance coefficient of infiltration on slope thin laminar flow.The applicability of the linear superposition method of flow velocity,flow rate and resistance under the comprehensive action of rainfall infiltration is studied.Here are conclusions:(1)It is concluded that the relationship between flow rate,flow,slope and roughness,and the drag coefficient gradually increases along the path with the increase of bed roughness,and the drag coefficient gradually decreases with the increase of slope.(2)Compared with the nullah,the vertical flow velocity of the slope thin-layer water is divided into three areas,with y/h<0.15～0.20 as the underflow area,which is mainly affected by the bed resistance,and the water flow velocity at y/h≥0.80 is affected by the water surface.The maximum flow velocity of slope surface was concentrated at the relative water depth of0.65～0.80,and it was positively correlated with the increase of water depth.In the thin laminar flow of slope surface,the flow direction turbulence intensity gradually decreases along the relative water depth,and the peak of the vertical turbulence intensity is mainly concentrated at the relative water depth of 0.30～0.40,and gradually decreases along the vertical direction.(3)The rain intensity increases,and the intensity of flow direction turbulence increases significantly.At a slope of 1°～15°,there is a critical slope that affects the change of resistance.When the slope is less than the critical value,the increase of rain intensity will lead to the increase of the resistance of the slope flow,and when the slope is greater than the critical value,the increase of the rain intensity will lead to the decrease of the resistance of the slope flow.(4)With the increase of infiltration,the overall loss of flow velocity of slope flow is large,and infiltration will reduce the resistance of slope flow,which is helpful to improve soil erosion and reduce soil erosion.(5)There is no linear superposition between infiltration resistance,rainfall resistance and total resistance,and the total resistance is less than the sum of the resistances of each component.