Re: Sighted a shock wave above airliner wing

Date:         12 Oct 98 00:02:10 
From:         "J. W. Dawson" <hatcat@frontiernet.net>
Organization: Frontier Internet Rochester N.Y. (716)-777-SURF
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Phil Dunn wrote in message ...
>Do you think this could be condensation instead of shock wave?
>
>I have flown lots of supersonic formation and you don't see shock waves.
>You can feel them though.
>
>But as the pressure gets very low, you can see transient condensation of
>water and this appears like shock wave.
>
>Much like the stuff you see coming off the wing with high lift
>configuration entering high humidity area.
>
>And shock wave formation will kill lift aft of it pretty suddenly, no?

I have to admit, I was a bit puzzled about it myself.

But no, not condensation. What I saw looked like - this doesn't describe it
very well but I can't think of a better description - more like a ripple
would appear in glass, with a definite edge to it. And it wasn't in the
glass of the window, either. But there was no whiteness or gray fuzziness
that you would get from condensation.

Now, as to lift effects... well, I don't claim to be an expert on
aerodynamics but I understand what you're stating and it's got me scratching
my head, too. But is local supersonic flow that uncommon? I seem to have
read that it isn't all that unusual but to what extent and what shock
configuration you might get is beyond my limited knowledge.

Regards,

Jerome (HatCat)