An Experimental Study on the Interaction Between Settling Particles and Near-Wall Hairpin Vortices in Turbulent Liquid-Solid Open-Channel Flow

Simultaneous visualization is carried out for settling fine copper particles and fluorescent tracer particles in turbulent water flow in an open channel. PIV and PTV techniques are applied to the images of the scattered light from the copper particles and those of the fluorescent light of the tracer particles, respectively. In order to mine the hairpin vortices from the images, the motion of tracer particles around the hairpin vortices has been predicted by using the database obtained by direct numerical simulation (DNS) for turbulent channel flow. It is found that the lift-up of hairpin vortices is attenuated by the depositing copper particles. The clusters of copper particles are found to be sustained in convergence-dominant regions of main flow.