Effect of Jet Injection on Flow Structure in Local Pier Scour
Somayeh Soltani-Gerdefaramarzi *
Department of Agricalture and Natural Resources Engineering, Ardakan University, Iran
Hossein Afzalimehr
Department of Water Engineering, Isfahan University of Technology, Iran
Yee-Meng Chiew
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore
Jacques Gallichand
Département Des Sols et de Génie Agroalimentaire, Université Laval, St-Foy, QC, Canada
*Author to whom correspondence should be addressed.
Abstract
This study investigates experimentally the effect of jet injection on the flow structure around a pier-scour hole. Experiments are conducted with 1-jet, 3-jets and without jet injection under clear-water scour conditions. The results show that the jet(s) alter(s) the turbulent characteristics and vertical component of the velocity, causing a reduction of the strength of the down flow. A quadrant analysis for the Reynolds shear stress values reveals that the sweeps and ejections have the main contributions on the Reynolds shear stress production in the near-bed flow. The third-order correlations of velocity fluctuations show an obvious distinction for the jet injection experiments in comparison to that without injections, especially inside the scour hole.
Keywords: Jet injection, pier scour, quadrant analysis, Reynolds shear stress, third-order correlations