[AR] Re: Concussion Wind tunnel
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 4 Sep 2014 08:38:54 -0400
On Wed, Sep 03, 2014 at 10:57:15PM -0700, David Weinshenker wrote:
>Ben Brockert wrote:
>> There are times when wind tunnels give much better data than FEA, but
>> for modeling something that is rotationally symmetric through a small
>> range of operable flight angles the data from FEA is going to be a lot
>> more accurate than something like trying to use an explosion as a very
>> transient wind tunnel.
>
>Don't many supersonic tunnels inherently operate in a "very transient"
>mode? I thought that was a common characteristic of such systems...
More like "transient" than "very transient". The idea is something
like "we compressed a lot of air on one end, and pulled a vacuum on
the other end, and got supersonic flow for a fraction of a second
after breaking the separating membrane", not "we were trying to get
data from a shock wave whose thickness is measured in microns".
(Shock waves are closely followed by expansion waves, after which the
gas slows back down. With really huge explosions -- as in, nuclear --
there can be a serious distance between the two, but for anything an
experimenter in the same room can survive, the distance will be
microscopic. See
https://www.youtube.com/watch?v=Qn5vysBkWdM#t=75
then imagine that on a much, much, much smaller scale.)
--
Norman Yarvin http://yarchive.net/blog
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