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Title: Laboratory images of breaking internal waves

Description: This video shows four examples of breaking internal wave events on an underwater ridge. The lower, white layer is saltwater dyed with laser fluorescent dye and the dark layer above is a less dense, isopropyl alcohol solution. The crest of the ridge is visible at the bottom of the frame. The video clips are shown in real time. The nature of the breaking varies with the characteristics of the wave and the geometry of the topography.

In the first clip, a wave steepens as the wave passes over the crest of the ridge and eventually breaks backward. In the second clip, the period of the incident wave is increased from the first clip to generate a stronger wave-ridge interaction: the front face of the wave plunges forward while the trailing side of the wave crest is sheared backward at same time. In the third clip, the height of the interface above the ridge is reduced from the previous cases and the wave crest plunges forward in a convective instability. A pocket of fresh water is entrained in the lower layer and continues to mix as secondary instabilities form and the wave propagates downstream. The fourth wave is forced at a much lower frequency and the resulting long wave breaks through a combination of shear and convective instabilities. Kelvin-Helmholtz billows develop as the incoming wave draws salty fluid downslope. At the left of the frame, the wave face steepens locally and dense fluid plunges downward, and eventually the billows are advected downslope into a churning mass of mixing fluid.

Credits: Erin L. Hult, Cary D. Troy, and Jeffrey R. Koseff

References:

Web Page: http://pof.aip.org/pof/gallery/2006-Koseff.jsp#video

Contributed By: Tausif Billah

 
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