Effect of a discontinuous topography on the self- organization of confined quasi-two-dimensional flow

Abstract

The effect of a discontinuous topography on the self-organization process in quasi two-dimensional flows is studied experimentally. Experiments are performed in a rotating tank, in which the flow is quasi two-dimensional. Different tank sizes and bottom topographies were used to study their effect on the evolution of the flow. A step topography with different heights and a ridge topography were used to divide the domain in two equally sized subdomains. The effect of a discontinuous topography was studied by considering the time evolution of the ratio of enstrophy and energy, which is a measure of the size of the vortex structures. This ratio shows a power-law behaviour .... The power-law coefficient for the case when a step or ridge is present is the same as the power-law coefficient for a tank with a flat bottom and half the size. This shows us that the step acts as a virtual wall on the evolution of the characteristic scale of the vortex structures. The evolution of the velocity directly above the step was studied as well. In the initial stage, vortices are strong enough to cross the step, which can be seen by a horizontal velocity which is normal to the step. After several rotation periods, the velocity normal to the step becomes very small and vortices are no longer crossing the step. Also a relatively high velocity parallel to the step is seen in the case of a step topography, however, in the case of a ridge topography, this parallel velocity is absent.

Date of Award	30 Apr 2010
Original language	English
Supervisor	Ruben R. Trieling (Supervisor 1), G.J.F. van Heijst (Supervisor 2) & M. Tenreiro (External coach)