Experimental Study on the Propagation and Stability of Tidal Vortices

Abstract

Laboratory studies of tidal vortex formation and propagation through an idealized inlet configuration are presented for various water depths over flat bathymetry. Using surface particle image velocimetry, starting-jet vortices were tracked and vortex diameter was calculated over the course of four consecutive tidal cycles. It was determined that the ratio of tidal excursion to frictional length scale is a critical parameter for determining whether the flow is advection or friction dominated, and plays a role in characterizing the vortex structure. To investigate tidal vortex stability, the tendency of instabilities to stop growing, the authors applied a variation of the shallow wake parameter equation using the vortex diameter as the length scale. Flow characterizations were further analyzed using the aspect ratio δ and vortex Reynolds number Rv to evaluate δ2Rv, giving the degree of three-dimensional structure and two-dimensional confinement in the vortices.