Simultaneous Measurements of Particle Settling Velocity and Oscillatng-Grid Turbulence

Abstract

Turbulence influence on the settling behavior of solid particles has attracted significant research efforts in the past decades, but remains challenging due to limitations in experimental techniques, especially in simultaneous two-phase measurements. In this study, a digital PIV system with enhanced shadow processing function was employed to conduct simultaneous velocity measurements of individual solid particles driven by gravity and the ambient fluid in a confined turbulent environment. The experiments were conducted in a water tank with turbulence generated by a grid oscillating in the vertical direction. Several types of grains, varying in shape and size, were tested with different oscillating frequencies. Settling behavior of solid particles subjected to ambient turbulent flow was analyzed in three aspects, i.e. settling velocity, relative settling velocity and settling velocity fluctuation, with respect to the simultaneous turbulent flow conditions. A small dynamic observation frame was first adopted for detailed flow sampling and the effect of secondary flow was also discussed.