Author(s): Y. Lu; P. Liu; K. M. Lam
Keywords: Settling velocity; Turbulence; PIV
Abstract: Particle settling in a turbulent flow remains an unsettled problem as the averaged settling velocity of the heavy particles has been reported tobe eitherincreased or decreased by the turbulence. This paper reports an experimental investigation the settling velocities of sub-millimeter heavy particles in water under the effect of grid-generated turbulence of. Instantaneous movements of the water phase and the heavy particles are measured with time-resolved particle-image velocimetry (PIV) and particle tracking velocimetry (PTV), respectively. The averaged settling velocity of the heavy particles is found to increase with the grid oscillating frequency, probably due to the fast tracking effect. At 0.4 Hz oscillation, the settling velocity becomes about 40%higher than that in still water. The increasing trend reverses for further increase in the grid oscillating frequency.