Conditional Statistics of Reynolds Stress in Curvilinear Cross Section Incipient Motion Channel¹

Abstract—Experiment was carried out on the curvilinear sand bed channel at threshold condition with uniform sand. Quadrant analysis has been used to investigate the contribution of bursting events to the production of Reynolds shear stress (RSS). Increased second order moment near the bed causes initiates sediment transport. Third order moment, which shows the skewness and diffusion behaviour, has been also analyzed for threshold channel. Quadrant analysis suggest that Hole region affects the contribution of bursting events to the total RSS production. Reynolds shear stress are partitioning into bursting events ejections, sweeps, inward and outward interactions, it is shown that sweep account most of stress close to rough surface. The difference between fractional contribution of sweeps and ejection (ΔS₀) to the stress is related with the third order moments of the stream wise and vertical velocity fluctuations and the relationship has been developed in between third order moments and ΔS₀.