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From: Simo Kauth <kauth@hrz.tu-chemnitz.de>
Newsgroups: comp.soft-sys.matlab
Subject: Re: SimHydraulics: "Hydraulic Fluid" question
Date: Tue, 12 Aug 2008 17:44:33 +0200
Organization: Chemnitz University of Technology
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The bulk modulus already tells you, how the fluid reacts on a change in 
pressure:
http://en.wikipedia.org/wiki/Bulk_modulus
So: Yes, there is still a dependency on the pressure

Your formula only adapts the bulk modulus so that it copes with 
dissolved gasses.

I hope this helped...

Clemens Winkler schrieb:
> Hello,
> 
> the SimHydraulics toolbox provides the "Hydraulic Fluid" block, as
> described here:http://www.mathworks.com/access/helpdesk/help/toolbox/
> physmod/hydro/ref/hydraulicfluid.html
> 
> The mentioned formula calculates a new bulk modulus against the
> "Relative gas content at atmospheric pressure" (alpha).
> 
> But let us assume, that we have pure liquid, so alpha = 0. Now there's
> no dependency of the pressure at all, because all terms with pressure
> vanish, due to alpha = 0.
> 
> What I do not understand is: shouldn't there still be a dependency,
> even if there's no gas in my liquid? The formula provides only a
> pressure-dependency for the unsolved gas in the liquid. What about the
> liquid itself?
> 
> Can anyone help me to understand that?
> Thanks a lot!
> Clemens