Experiment On Groynes Induced Flow Circulations And Associating Sediment Deposition

Groyne is a hydraulic structure frequently used in river engineering projects.It narrows river to optimize shipping condition.It also generates flow circulation and makes the velocity distribution and sediment transport processes very complex.Practical engineering has made full use of groyne on account of its lower cost.But if designed improperly,groynes may cause waterlogging and have a significant effect on the local water environment and shipping.Existing research on flow and sediment in groyne fields is primarily based on mathematical model simulations.Field study and physical model based experimental studies are limited.Studies on a groyne system of complex condition are still scarce.In this study,we built a physical model of a wide channel in a large-scale flume to simulate the flow and suspended load process in continuous groyne fields.The velocity on the whole flow field was measured using the particle tracking velocimetry(PTV)with the integration of multi-vidicons.The weight and size of sediment were acquired by the way of meshing.The discharge and water depth hydrograph were recorded by a electromagnetic flowmeter(EMF)and pressure sensor array to analyze characteristics of the circulation zone and transport of suspended sediment load.It was found from the experimental results that:(1)in a circulation zone there are three sub-regions: the negative-velocity region,the positive-velocity region and the main flow region.Small secondary circumfluence occurs in front of barrier,and its size shows a positive correlation with the velocity outside;(2)the discharge of the negative flow can reach 50% of the main flow,verifying with velocity on the boundary between the positive and negative regions,whose position remains unaffected by water depth;(3)the distributions of the weight and size of deposited sediment load is similar to velocity distribution.More sediment particles are deposited on the main flow region upstream.In the circulation zone and jetty head,there are few deposition.The experiment results in a set of reliable data that can be used for further study of flow and sediment processes due to groyne-induced circulations and for detailed verification of numerical models.