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From: Clemens Winkler <ClemensWinkler@gmx.net>
Newsgroups: comp.soft-sys.matlab
Subject: Re: SimHydraulics: "Hydraulic Fluid" question
Date: Tue, 12 Aug 2008 10:03:40 -0700 (PDT)
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On 12 Aug., 18:49, Simo Kauth <ka...@hrz.tu-chemnitz.de> wrote:

> Unfortunately I don't have the Dubbel here right now, nor would I call
> me an expert on fluid dynamics. But I would guess that the mentioned
> formula is rather an approximation, which might come close to reality in
> most cases. Or under common operation pressures. In a real hydraulic
> system, there will always be some gas dissolved in the fluid, which is
> then probably dominating the scene.

Thanks for your commments.

I would have thought that, too. But the strange thing is, that I
calculated the change in the bulk modulus with the SimHydraulics
formula with alpha = 0.01 (default value in the block is 0.005) for a
given fluid and get changes for the bulk modulus at about 0.002 * 10^9
Pa. for a pressure of >200 * 10^5 Pa. The book "Dubbel" talks about
changes of 0.x * 10^9 Pa over a pressure range from 0...250 * 10^5 Pa.
So from this point it is vice versa, the gas doesn't have much
influence over the change in pressure.

Maybe someone else have more information about this?
Thanks! Clemens