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How does one vary Mach number and dynamic pressure independently in a wind tunnel

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Old   August 3, 2009, 12:23
Default How does one vary Mach number and dynamic pressure independently in a wind tunnel
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JaneD
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Hello all,

I am newbie to fluid dynamics. How does one vary Mach number and dynamic pressure independently in a wind tunnel. i want to repeat the same in CFD.

Thanks,
Jane
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Old   August 3, 2009, 13:00
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Brendan Sloan
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Quote:
Originally Posted by my_cfd View Post
Hello all,

I am newbie to fluid dynamics. How does one vary Mach number and dynamic pressure independently in a wind tunnel. i want to repeat the same in CFD.

Thanks,
Jane
Pt/P = {1+ [((gamma-1)/2)*Mach^2]} ^(gamma/[gammma-1])

Pt = Total pressure
P = Static pressure
gamma = ratio of specific heats (1.4 for air)
Mach = Mach number


Change your static pressure, and you can adjust your total pressure & mach number semi-independantly of each other.


If your doing this in a wind-tunnel, you obviously need a pressurised tunnel.


Beware of Reynolds effects while doing this however. Matching compressibility effects with Reynolds effects on a scaled tunnel model is not possible*.

*at least, not that I'm aware.
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