The Experimental Study On The Structure Of Near-bottom Flow And Bedload Transport

The sediment movement on the bed is associated with the flow structure near the bed.Therefore,the detailed study on the diversity of the flow structure in temporal and spatial scales under various water and boundary conditions,plays a direct and effective role in revealing the complicated and random transport characteristics of the near-bed sediment movement,which is also of important academic significance.By conducting serious of flume experiments,based on the ADV velocity system and high-speed camera technology,the flow velocities and turbulence characteristic values are collected.Meanwhile,the bed load transport amounts of each strip are also measured accurately.By comparing the structure diversity among the close-set test points in lateral direction,the velocity distribution characteristics in temporal and spatial scales as well as the velocity structure mutation close two side walls are analyzed.Based on the strip-measurement method for the transporting sediment,the transport characteristic of the bed load in lateral spatial scale is analyzed in detail.Besides,by synchronizing the velocity test point and the transport sediment strip in temporal and spatial scales,the association between them is investigated preliminarily.It's found that the flow velocity distribution and turbulence structure both play important role in bed load transporting,and the effect of the turbulent intensity is particularly noticeable.The paper tries to use the tank test to study the traverse rule which the near bottom region water sand state of motion and the lateral distribution of bed load transport.Using the water channel with precision variable slope flume to perform an experiment,the velocity of experimental section was measured by ADV;dynamic record of the bedload sediment transport was collected by SMTM.From the time sediment transport process and the corresponding instantaneous velocity to analyze the effect of bottom flow structure to bedload transport.Analyzing different groups' treatment results with different flow intensity found that sediment transport reduce from the middle belt to both sides belts gradually,in general like skewness distribution;at the area near the bottom of water,we found that the transverse velocity and turbulence intensity have a great influence on the eccentricity of the sediment distribution,The distribution of the bedload sediment transport rate and the flow velocity is the main reasons of the bed surface.Transverse distribution of bedload sediment transport rate is one of the key issues to be further research in movement mechanics.The transport mechanism,influencing factors and research on calculation for non-uniform bed-load sediment are still need a further exploration.