Author(s): Kiyoshi Kawanishi; Hitoshi Masuoka; Peter Nielsen
Linked Author(s): Kiyoshi Kawanishi
Keywords: Turbulent flows; Suspended particles; Vertical velocity
Abstract: Experiments using sinking particles, diesel droplets and bubbles have been conducted in previous studies. They clarified two mechanisms that particles follow them through velocity changes: one is “Vortex trapping”, another is “Trajectory biasing”. The purpose of this study is to clarify the quantitative relation between turbulence parameters, the mean and variance of vertical velocity of particles. Experiments were carried out with a turbulence tank and an open channel. Types of particles in these experiments were polystyrene, polypropylene, polyamide, and bubbles. Motion of particles was continuously measured by a 3D tracking system comprised of two digital video cameras. In turbulence tank experiment, though in strong turbulence mean vertical velocities of particle were more accelerated than those in still water, in moderate turbulence, mean vertical velocities of particle depend on Stokes number were accelerating or decelerating. In open channel experiment, mean vertical velocities of particles turned in accelerated from decelerated at weaker turbulence than in turbulence tank. Velocity variances were dependent on Stokes number in addition to diameter and density of particle.
Year: 2010