[AR] Re: Concussion Wind tunnel
- From: "Monroe L. King Jr." <monroe@xxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 04 Sep 2014 06:33:39 -0700
I guess to learn anything about it in the real world I need to
photograph a explosive shockwave and see what there really is there to
work with.
One problem would be calibration even if it did work well enough to get
any data I'd need a real wind tunnel to calibrate the results.
I believe I could do that with a steel "reed" that bends a measurable
amount at differing velocities. Photograph the reed in the same frame as
the model and the deflection of the reed would indicate the velocity in
that frame.
All purely speculation any number of factors might render that a no go.
I know for a fact I can not afford a tank large enough for a proper
wind tunnel. But there are a lot of caves and wells here in Texas.
Perhaps I could get lucky and find one nearby I could pull a vacuum on?
A Roots type blower (automotive supercharger) could pull a pretty good
vacuum on a large volume pretty fast.
Monroe
> -------- Original Message --------
> Subject: [AR] Re: Concussion Wind tunnel
> From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
> Date: Thu, September 04, 2014 5:38 am
> To: arocket@xxxxxxxxxxxxx
>
>
> 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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