Study On The Turbulence Characteristics And Friction Characteristics Of The River Channel With Deposits

In the Alpine Gorge area,the mountains along the banks of the river are affected by geological disasters such as collapses and debris flows.The mountain medium loosely enters the channel gradually,and it will be fixed in the channel in the form of deposition with time,thus changing the boundary conditions of the original channel.Deposits often occupy a large proportion of the river width,which complicates the flow structure of the nearby flow field and has a significant impact on the adjustment of the upstream and downstream flow structure and the law of water and sediment transport.This adjustment will have an impact on the sediment movement near the deposits,leading to major changes in the evolution of the river channel,threatening the safety and stability of the upstream and downstream buildings and people.Therefore,the changes in the friction and turbulence characteristics of the deposited rivers will have a clearer understanding of the flow structure and water-sand transport under its influence.At the same time,the research results can provide theoretical support for the process of sediment initiation,transport development and river bed evolution.In this paper,through the ADV flume experiment combined with the classic theoretical calculation method,the effects of different flow rates,intake widths and lateral slopes on the friction and turbulence characteristics of the flow are studied:(1)Choose 6 commonly used friction velocity calculation methods to infer the friction velocity under each group.After comparative analysis of the results,it is found that the threedimensional turbulent kinetic energy method is the most accurate under the conditions of uniform flow or nonuniform flow(deposition channel),followed by the Reynolds stress method.(2)The data analysis and research of the uniform flow trough experiment show that the accuracy of the friction velocity value will affect the accuracy of the parameters of the flow distribution(Carmen constant K,integration constant A).The three-way turbulence intensity coefficient does not change with the change of friction velocity under the same set of times,the D coefficient decreases with the increase of friction velocity,and there is a certain ratio relationship between the D coefficients in all directions.The change rules of the secondary drag coefficients of each group are similar,and decrease with the increase of Reynolds number;the drag coefficient decreases with the increase of the stratosphere,and the smaller the difference between the darg coefficients.In the same flow layer,the drag coefficient decreases with the increase of incoming flow,and the decrease rate slows with the increase of incoming flow.(3)Analyze the influence of the pile shape on the bed shear stress.Under different flows,the change of the bed shear stress of the accumulation section is similar to the change of the bed shear stress on the curve.With the increase of the incoming flow,the bed shear stress at the stagnation zone of the water flow and the narrow section of the deposit also increases.Due to the narrowing effect of the deposit,the high shear stress area is located downstream.As the advancement width increases,the peak shear stress and high shear stress range of the bed surface also gradually increase.Under the influence of different lateral slopes,the change range and peak size of the bed surface shear stress vary little with the increase of the lateral slope.(4)In the backwater area of the deposit,by introducing the backwater parameter ?,to quantitatively analyze the relationship between the friction velocity and the scale of the deposit,it is found that it fits well exponentially.With the increase of the incoming flow and the increase of the occupied width,the Carmen constant is contrary to the change of the rough height,and as the lateral slope increases,the correlation between the two changes is not strong.In the backwater state,the friction velocity and the rough height change have obvious consistency.(5)Analyze the pulsation probability distribution law of turbulent flow velocity in the measurement area.In each group,the variation range of vertical pulsation flow rate basically does not change with the change of flow rate and deposit size,while the variation range of vertical and vertical pulsation flow rate increases significantly.As the advance width increases,the skewness and kurtosis change of the three-way pulsation probability distribution are the same.Under different incoming flow and lateral slope changes,the skewness and kurtosis change of the vertical and horizontal pulsation probability distribution are similar,but the vertical direction is opposite.