Ocean flow captured in a box: experiments on geostrophy

Abstract

The ocean is far from being understood. In an attempt to add to the understanding of geostrophic flow (balance with the Coriolis force) and its interaction with time-dependent wave phenomena, this study treats a model (experimental set-up) for geostrophic currents, with which experiments on flow through a rectangular box on a rotating platform have been performed. A dataset studying the effect of tilt of the box and its eccentricity with respect to the position of the rotation axis has been produced, measuring the differential pressure between two points perpendicular to the flow direction within the box and the established flow as a function of table's rotation frequency and pump steering voltage.The mean-time differential pressure was not affected by eccentricity. The tilt of the box influenced the observed differential pressure such that it is suggested there exists a relation between the differential pressure and the wave attractor that could form in a tilted box. Rotation influences the through flow in the tubes that connect the box with pump and flowsensor. The relationship found between flow, differential pressure and Coriolis parameter was consistent within equal parameter settings, but did not follow the expected geostrophic relation. This leads to the suggestions much more physics is involved in the system we try to fathom than can be understood through the (quasi-) geostrophic equations.