Access to the Sea Fund

Measuring the Three-Dimensional Structure of Stratified Turbulence

Andone Claire Lavery and W. Rockwell Geyer

Mixing in stratified flows is fundamentally important for understanding and quantifying the transport processes in the ocean. Recent field experiments conducted by the PIs in the Connecticut River estuary outflow, a highly-stratified, strongly-sheared estuarine environment, have  challenged the long-standing paradigm that mixing occurs in the cores of shear instabilities. These provocative results were obtained by the unique combination of high-frequency, high-resolution broadband acoustic backscattering methods combined with a novel approach for in situ measurements of turbulence. However, these measurements did not resolve the three-dimensional structure or temporal evolution of shear instabilities. Yet these are critical components to the complete understanding of the transition to turbulence within shear instabilities in stratified flows at very high Reynolds number.

We propose to develop and use a combination of advanced acoustic techniques and ship- mounted, in situ turbulence measurements to quantify the three-dimensional structure of stratified turbulence in an estuarine outflow.  Specifically, we would like to use Access to the Sea funding to develop and deploy two acoustic backscattering systems, involving a broadband acoustic backscattering array and a multibeam system, which resolve the three-dimensional structure of shear instabilities and stratified turbulence. In addition to addressing this important fluid dynamics problem, the methods have application to the quantification of a variety of physical and biological processes in the ocean.

Last updated: June 21, 2012