Visible shock wave

[Photo taken out of airplane window]

Here is a reduced GIF of a photograph taken through the window of a 747 at cruising altitude over the atlantic. Running vertically down the center of the photo is a curvy gray stripe. This stripe is the shadow of some kind of pressure phenomena occurring just above the wing. The stripe of shadow slowly moved around over many minutes. Occasionally it would wiggle, presumably as the wing cut through turbulent air. Besides this one strip of shadow, there were OTHERS (100K) in various places on the wing. They were only visible in direct sunlight.

I've heard this phenomena described as shockwaves that attach themselves to the places on wing surfaces where the airflow goes transonic. But they might also be the place where the airflow detaches from the wing surface, i.e. a transition from normal laminar flow to a turbulent "stalled" area on the wing.

Here's some email discussion about it.

And a website about shocks attached to wings


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