Turbulent Generation of Internal Gravity Waves

Figure 1	Figure 2
Experiments performed by Kathleen Dohan, Dept. Math. and Stat. Sciences, U. Alberta

"Mixing box" experiments are performed in which an oscillating grid creates turbulence in a salt-stratified fluid. (See Figure 1, above.) Over time the mixing region deepens entraining successively more dense fluid.

The experiments are performed in a box with a large aspect ratio. As a result, a large scale circulation develops within the turbulent mixing region.

Beneath the mixing region, large ampitude internal gravity waves are excited.

In the image of the vertical time series (Figure 2, above), a vertical slice of a digitised image of the experiment is recorded over time. The deepening of the mixing region and the structures therein are visualised with pearlescent dye. The internal waves are visualised by illuminating horizontal dye lines.

Vertical and horizontal time series images are used to characterise the eddy length and time scales in the turbulent mixing region and are used to measure the energy associated with the waves.

Preliminary data suggests the waves are of such large amplitude that the dynamics of the turbulent mixing region are significantly affected by the motion of the underlying waves

More details are available.

Department of Physics

Department of Earth and Atmospheric Sciences