Jerry,
The transition from a laminar to a turbulent boundary layer occurs with no
change in density (that is, it is an incompressible phenomena), thus there
is essentially no change in refractive index to make it visible. Shocks,
however, by definition do involve a change in density and refractive index,
and thus with the right lighting, can be visible. That said, a shock can
cause boundary layer transition, and the thickening of a boundary layer
after transition can influence a shock location, so there is a bit of the
chicken and the egg to the question. Here, however, what is happening is a
normal shock. The B727 uses an old technology (NACA) airfoil and has a
pronounced yehudi (training edge extension) that combine to produce a
limited region of transonic flow over the wing upper surface at cruise Mach
numbers (even though that is normally undesirable). And this shock occurs
not where the flow goes supersonic, but where it slows from supersonic to
subsonic (the flow "shocks" down [in velocity]).
Gary Edwards
----- Original Message -----
From: "W. J. Liles" <wliles@xxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Tuesday, September 17, 2002 7:13 PM
Subject: Re: [OM] OT Low Flying, was an OM weekend
> Scnozz
>
> The ripple is either the boundary between laminar and turbulent flow
> over the wing or the shock front where the local airflow goes
> supersonic.
>
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|