Probing density-stratified turbulence and mixing using simultaneous volumetric Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF)

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• Dr. Adrien Lefauve (DAMTP)
• Friday 18 February 2022, 12:30-13:30
• CUED, LT6.

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What are the properties of density-stratified, shear-driven turbulence? The turbulent mixing of air or water masses that have even slightly different physico-chemical composition (e.g. temperature, salinity) is crucial to many engineering and geophysical flows, from the ventilation in buildings, to the dispersion of pollutants in rivers, to the large-scale thermohaline ocean circulation regulating our climate.

Given the complexity of the problem, laboratory experiments play a crucial role to fill the gap between direct field observations and numerical modelling. The Stratified Inclined Duct (SID) is a canonical experiment designed to study the long-term behaviour of stably-stratified turbulence continuously forced by shear. This is achieved by setting up a two-layer exchange flow in a long rectangular duct connecting two large reservoirs containing different salt solutions.

I will introduce a new generation of experiments developed in the G. K. Laboratory in DAMTP to advance our understanding of these flows. These experiments rely on a new technique to measure the density field and the three-component velocity field simultaneously in three-dimensional volumes at high spatio-temporal resolutions. This technique employs a thin, pulsed vertical laser sheet that is scanned rapidly back and forth to span a three-dimensional sub-volume. We then combine successive planar measurements of stereo particle image velocimetry (sPIV) and planar laser induced fluorescence (PLIF) to re-construct three-dimensional volumes having full velocity and density data.

I will also give a few examples of advances that have been made possible by these new measurements. I will also outline what future improvements could bring to our study of stratified turbulence and mixing.

This talk is part of the Fluids Group Seminar (CUED) series.

This talk is included in these lists:

• Acoustics Lab Seminars
• CUED, LT6
• Engineering Department Acoustics/Combustion Student seminars
• Fluids Group Seminar (CUED)

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