Author(s): Mahesh Patel; Anurag Sharma; Bimlesh Kumar
Linked Author(s):
Keywords: Downward seepage; Shields stress; Turbulent flow; Sheet layers
Abstract: Alluvial channels are often encountered with surrounding ground water table (GWT) in which channels lose considerable amount of water through their bed and banks if GWT is lower than the flow level in channel. To address this phenomenon, experiments were carried out on a 20 m long plexiglassed tilting flume in the conditions of no seepage (mobile bed channel) and with seepage. It has been observed that during the no seepage condition, particles were in the motion condition but no signature of bed-features was seen even after several hours (10h) of the run. However, after the application of seepage, movement of sediment particles significantly increased and these sand particles deposited at the adjacent section in the form of thin sheet layers without increasing the inflow discharge. Also, these sheet layers prograded towards the flow direction and formed a thick sheet layer after 24 h of the seepage run. For understanding this process of developing sheet layers, turbulent flow properties (time-mean velocities and Reynolds shear stresses) have been obtained in no seepage and conditions. We found that time-mean velocities and Reynolds shear stresses were increased significantly after implying the downward seepage, suggesting larger sediment transport in the form of sheet layers. These layers further influenced the turbulent flow properties as time mean velocities increased because of reduction in flow depth in the presence of sheet layer.
Year: 2020