I’ve a question about a curious phenomena that I recently saw.
Have a look at the water drops on the flaps in this image.
This photo was taken in flight, and I was curious about why the water droplets didn’t get blown off.
I presume this is to do with the boundary layer, and the airflow departing the upper surface of the wing before it reached this point. But I was really surprised by this. Could it really be that there is virtually no air flow on the supper surface of the flaps, while passing through the air? Speed would have been about 140kts at the time.
The droplets were not frozen. I could seem the vibrate all the time, but they were not flowing backwards. After maybe 30 mins they gradually disappeared, I think through evaporation. Very occasionally I could see a droplet move slightly backwards on the surface and then stop. So they definitely weren’t frozen.
It’s the first time that I’ve seen this, and was curious if this is common, and if I’m correct in thinking that it’s to do with the boundary layer separating ahead of this point?
Colm
No laminar flow over that wing .. that’s why. That’s why bugs or dirt on a Piper, Cessna (and TB :-)) wing make little difference – if they’re not on the leading edge! O a high performance sail plan that would be very different.
D’alembert’s paradox strikes again?
