Morphodynamics of a sediment bed in a fluid-filled cylinder during spin-down: an experimental study

This paper presents a detailed experimental study of the evolution of a sediment bed under the action of the boundary layers formed under a spin-down flow in a rotating fluid-filled cylindrical tank. Both complete and partial spin-down are considered, i.e., with the tank coming to a complete stop or being only partially decelerated. Two nondimensional numbers, the Reynolds (Re) and Rossby (Ro) numbers, govern the flow. During the spin-down, the bed morphology changes, exhibiting distinct characteristic patterns. The changes are measured using a light attenuation technique (LAT). Background rotation suppresses the emergence of instabilities and turbulence, making the patterns more regular and smoother. In spite of the differences and complexity in the patterns, radially inward transport is explained by the total radial force exerted by the flow as computed using classical expressions for the structure of laminar boundary layers.