COMPUTATIONAL ANALYSIS OF FLOW CHARACTERISTICS AROUND HYBRID SPUR DYKES

Abstract

Spur dykes are river training structures commonly installed for erosion control and bank protection purpose. The installation of groyne however results in highly turbulent flow resulting in high local scour in the vicinity of the tip of groyne. Several research works have shown that impermeable groynes are more effective in river training but results in high local scour, permeable groynes results in lower local scouring but are not effective as river training structure. In this dissertation work an attempt is made to combine impermeable and permeable groynes and analyze the performance of resulting hybrid groynes as an alternative groyne with minimization of local scouring phenomenon. In general, the flow structure around a hybrid spur dyke has the combined effect of a permeable and an impermeable spur dykes. Flow around the hybrid groyne is analyzed by numerical modelling using CFD code ANSYS FLUENT. The Realizable K-e model is used for turbulence modelling. The groynes are tested for their performance at various flow depth and Froude number. Performance of these hybrid spurs is compared with impermeable and permeable spur based on the tip velocity, maximum velocity, and separation length. The bandall structure with permeable base is found to provide separation length comparable to impermeable groynes and at the same time shows considerable reduction in velocity and bed shear amplification.