Vortex Dynamics in a Rapidly Rotating Container with Axial Forcing

We have studied vortex dynamics that formed in rotating tanks due to axial forcing. A cylindrical, water-filled tank of 15cm radius is spun on a turntable; forcing is provided by a pump drawing water through 2 through-holes at tank bottom, which is fed back homogeneously at the radial boundary. Control variables include the axial forcing volumetric pump flow rate (Q), rotation frequency (ω), and fluid volume within the tank i.e. watermark height (h) on the cylinder. Cylinder rotation forms a parabolic deformation on the surface, while often distinct tendril-like vortices are observed that extend all the way to the tank bottom. Different flow regimes are observed: vortex dipoles; tripoles; and a "critical" regime whose vortex surface connects to one through-hole which resembles a bathtub whirlpool. This study focuses on determining the existence and finding the boundary between these flow types in control variable space, and finding correlation between the variables and other internal vortex dynamics. Approximately 100 experiments were conducted at differing values of Q, ω, and h, with consequent regimes observed and analyzed.