Sediment Transport and Morphodynamics Induced by a Translating Monopolar Vortex

Abstract

AbstractWe performed laboratory experiments to describe and quantify the transport of sediment and the changes in the bed due to a generic translating monopolar vortex. Experiments were performed inside a water‐filled, square tank with a particle bed on the bottom and a vertical plate attached perpendicular to one of the sidewalls. The tank was placed on top of a rotating table to create the vortex by changing its rotation rate. This change created a current inside the tank that separated at the edge of the vertical plate, with the shear layer rolling up into a vortex. Once the vortex was formed, the table was promptly stopped. Sediment particles are brought into suspension and captured by the vortex, forming a conical region that moves with the vortex until the sediment resettles in the bed, changing the original bed morphology. Three different measurement techniques were used to obtain information about the flow velocities, the sediment in suspension, and the net changes in the bed. Changes in the bed morphology occur along the trajectory of the vortex, where a region of erosion is followed by a region of deposition. The strength of a vortex is the main parameter governing the capture and suspension of particles with similar characteristics. A power law relationship is found between the vortex strength and the net displaced particle volume. Experiments were also performed without sediment to determine if the presence of sediment could affect the vortex dynamics. However, a definitive answer requires more experiments to obtain reliable statistics.