Rotating flow past disks and cylindrical depressions

The flow of a rotating fluid over isolated three-dimensional topographic features has been investigated. Laboratory experiments have been conducted with a rotating water channel to determine the characteristics of the flow over and around truncated cylindrical disks and depressions located on the upper and lower bounding surfaces of the channel. The geometry of the rotating channel allowed the beta effect to be modelled and cases of beta-plane westward, beta-plane eastward and f-plane flows were studied. Flow patterns revealed by the use of an electrolytic precipitation technique are presented, and the flow behaviour is quantified in terms of a characteristic speed of the flow through a circular cylinder circumscribing the topography in the vicinity of the channel midplane. Case studies are presented for a range of values of Rossby number, Ekman number, beta parameter, and cylinder height-to-radius ratio. The vorticity equation and associated boundary conditions are discussed for the cases studied in the laboratory and appropriate numerical solutions are obtained. The laboratory and numerical experiments demonstrate the character of the horizontal steering of fluid by the topographic features as a function of the system parameters. Comparisons between laboratory and numerical experiments are presented and shown to be in good agreement.