Experimental Study of Flow Field and Movement of Sediment over a Ramp

Binit Kumar,Subhojit Kadia,Zulfequar Ahmad

doi:10.32732/jcec.2019.8.2.79

Binit Kumar, Subhojit Kadia + Show 1 more

Open Access

https://doi.org/10.32732/jcec.2019.8.2.79

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Abstract

Applications of hydraulic structures in low dams and diversion structures in countries like India, where sediment is a serious concern, demands a good expanse of research on the flow field and movement of sediment. The present study was focused on the non-uniformity in the velocity distribution along the flow direction and the movement of sediment over a ramp. The velocity distribution of the flow near and over the ramp was studied with the help of Acoustic Doppler Velocimeter. Experiments were conducted to study the mechanics and kinematics of movement of sediment particles. The movement of sediment particles over the smooth ramp was studied with the help of high-speed camera system. The particle velocity, acceleration, applied force and the angle of velocity vector were processed and analyzed from the captured images using digital image analysis techniques. The path of the movement of sediment particle was tracked. The vector results of the flow pattern indicated a very high amount of increase of the uplift velocity (y – component of the instantaneous flow velocity) component over a ramp. The sediment had very little movement for about 3.8 seconds at the beginning of the ramp and accelerated as it moved along the ramp in the downstream side. The path of the sediment movement over the ramp was found to be inclined by 25.6 to 35.7 degree to the horizontal axis which was almost parallel to the ramp (29.055 degree).

Highlights

The movement of sediment particles on a river bed and over the hydraulic structures depends on two parameters i.e. critical tractive shear stress and bed shear stress
The flow pattern near and over a ramp was studied experimentally using ADV to understand the movement of sediment over a ramp
A reverse flow was observed over the ramp, near its boundary that may be due to the flow separation in that region

Summary

Introduction

The movement of sediment particles on a river bed and over the hydraulic structures depends on two parameters i.e. critical tractive shear stress and bed shear stress. Abbott and Francis [9] studied the trajectories of solitary grains in water stream by the help of thousands of photographs taken during the movement of particles They observed the positions, velocities and the acceleration of the grains at different positions. The author had presented the three modes of transport i.e. rolling, saltation and suspension of the particles and its proportion at different stages of flow. Ramesh et al [14] carried out the experimental studies using high-speed cameras and observed the movement of sediment particles for a transitionally rough bed. This will be very helpful in maintaining the continuity of sediment over the structures and protecting the structures from the scouring

Experimental set-up

Experimental conditions

Results and discussions

Conclusions

Notations as