[FLASH-USERS] How to properly calculate sound speed
Tomasz Plewa
tplewa at fsu.edu
Tue Feb 2 08:21:12 EST 2010
Seyit -
The sound speed is one of the quantities defined by the equation of
state, and so the gamma(s) in general are as well. Constant gamma is
essentially a fairly good model applying only to relatively simple
gases. As you already implied, the value of sound speed does not depend
on physics processes per se but rather on the thermodynamic state of matter.
Also,
C^2 = gamma P/rho
Reviewing a few chapters in the thermodynamics textbook might be most useful, and you may want to take a look at
http://en.wikipedia.org/wiki/Speed_of_sound
Tomek
---
Seyit Hocuk wrote:
> Hi all,
>
> Within Flash, the speed of sound is calculated by "C = gamma P/rho" with
> a constant predefined gamma. However, if you have additional physics
> like heating, cooling, or radiative transfer effects, gamma should vary.
> Hence, the sound speed is then calculated wrong. Gamma is in fact
> "dlog(P)/dlog(rho)" and the sound speed is actually "dP/drho".
>
> How can one approximate, if not solve, the sound speed more carefully?
>
> One basic idea I had was to derive 'C' for a zone using a neighboring
> zone (P2-P1/rho2-rho1) and to take the average of 'C' for an entire
> block. That doesn't work very well.
>
> Kind regards,
> Seyit
>
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