Experimental Analysis On Hydraulic Characteristics Of Thin-layer Water Flow On Slope

The hydraulic characteristics of the thin-layered flow on the slope are different from that of the open channel flow,and the analysis results based on the basic theories of traditional open channel hydraulics have large errors.The research on the hydraulic characteristics of the thin-layer water flow on the slope has been paid more and more attention.But there are few high-precision measurement results.In this paper,the variable slope flume is used as the test model,and the thin-layer water flow hydraulic characteristics test is carried out based on the particle imaging velocity field instrument(PIV),which provides technical support for the theoretical analysis.Orthogonal experiments are carried out for five slopes,five flow rates,and two roughnesses to measure the vertical velocity of the characteristic section,analyze the vertical distribution characteristics,and determine the layer turbulence discrimination;calculate the average Reynolds number and Fr of the vertical line of the corresponding characteristic section According to the German number,the relationship between the hydraulic parameters is qualitatively analyzed;the changes of the turbulent kinetic energy k and the turbulent energy dissipation rate?are analyzed,and the following main conclusions are drawn:(1)Carry out systematic research and analysis on the velocity characteristics in all directions in the area to be measured.It is concluded that when the water depth of the area to be measured is below 30 mm,the vertical velocity distribution curve is parabolic and laminar,which is fitted by a quadratic function,The resultant value is the highest;when the water depth is greater than 30 mm,the vertical velocity distribution curve shows exponential logarithmic curve as turbulent flow.Fitting with exponential logarithmic function shows the highest fitting value,which is basically consistent with the Reynolds number discriminant layer turbulence.(2)Considering the sidewall effect,the average vertical velocity can better reflect the characteristics of the flow field change than the average velocity of the section;it is recommended that the average vertical velocity corresponding to the Reynolds number is used for the thin-layer water flow on the slope to determine the flow pattern;the greater the inflow,the more the flow velocity The larger the turbulent kinetic energy,the higher the turbulent kinetic energy dissipation rate.(3)Based on the inlet water flow rate of 0.91 m~3/h?18.98m~3/h,5 kinds of slopes(1°,2°,3°,4°,5°),two kinds of roughness(absolute roughness k_sis 0 and 5 mm)The test results show that both Reynolds number Re and Froude number Fr are positively correlated with the flow rate,and the flow velocity is negatively correlated with roughness.The Reynolds number Re decreases with the increase of roughness,and the flow velocity and energy slope are negatively correlated.It is positively correlated.With the increase of the energy slope,the flow velocity shows an increasing trend.When there is no roughness,the water flow velocity gradually increases with the increase of the energy slope,and when there is roughness,the water flow velocity also gradually increases with the increase of the energy slope,but the increase is small.