On 16 Apr 2007 19:26:17 -0700, Kev wrote:

On Apr 16, 3:59 pm, Tom L. wrote:
The big question is "why does the wake turbulence descend?"
Is the air volume inside the vortices denser than surrounding air?

Found it, Tom. Ref:

http://www.airpower.maxwell.af.mil/a...ug/carten.html

"Cruise altitude vortices usually level off at about 1000 feet below
the altitude of the aircraft as their density comes into equilibrium
with that of the surrounding air. Decay processes then take over. "

Regards, Kev


Great! Thanks for the effort.

Now I have a new question -- where is this extra air coming from, and
how?
The vortices grab some additional air molecules and then take them
down. Theere is now a volume of air with missing molecules (if I'm
allowed to speak in K-grade language). These molecules have to be
replaced, and the only source is lower -- in the more dense air that
is in addition getting the extra particles. So there must exist an
additional upward moving air flow outside the vortices.

The pictures showing jets right on top of clouds do seem to indicate
this. The vortices seem to suck in clouds from below and then spin
them.
So there is this secondary air movement starting at 1000' below an
aircraft, moving upwards on both sides of the aircraft and filling the
low density areas left by the vortices and wing downwash.
Interesting.

- Tom