We are measuring the amount of mixing that occurs when two fluids of different density exchange in opposite directions through a constriction or over a sill. Such exchange flows commonly occur through ocean straits and over bottom sills. The constrictions control the rate of transport of water into or out of estuaries and marginal seas and between abyssal ocean basins. This process may contribute to the overall amount of mixing required to maintain the stratification of the oceans and the present global rate of overturning.

Analytical methods are frequently used to estimate exchange flows through these constrictions; we have focused on extending the simple analytical solutions to more realistic cases. Exchange flows involve strong velocity and density gradients between the two layers flowing in different directions, and this flow can become "critical" (i.e. reach the speed of gravity waves on the density interface) so that there is a hydraulic control point in the strait or above the sill.

Relevant Papers:

Prastowo, T. J., Griffiths, R. W., Hughes, G. O. and Hogg, A. McC. (2006) Mixing due to exchange flows through a horizontal constriction. J. Fluid Mech