Experimental Study on Particle Pick-Up Rate of Vertical Vortices

There are numerous situations in nature and industrial flow in which particles are transported by a vortex-flowing fluid, such as near hydraulic structures such as bridge piers and abutments, spur dikes, vanes, intakes, root wads, and settling tanks. To explore vortex transport of particles, an experimental study and empirical model were performed in which particles were introduced into a vortex contained within a test section. The vortex was induced by tangential jets located in the test section just above the point of sediment introduction. Quantities varied in the experiments were particle diameter and vertical axial velocity. Dimensional analysis was performed and resulted in a relationship of normalized particle discharge as a function of particle Froude number. It was found that at low particle Froude numbers, there was no particle transport due to the absence of sufficient turbulence to entrain the particles. Also, above a critical value, particle transport increased quickly due to sufficient entraining turbulence and relatively high vertical velocity with little particle collision. However, at intermediate values, the transport decreased due to heavy particle–particle collisions. At high values, the transport increased exponentially again.