obtaining p from p_rgh

toboto · June 21, 2017, 13:59

Dear All,

In almost all multiphase solvers we solve for p_rgh (static or thermodynamic pressure - hydrostatic pressure) instead of p.

Then, we can obtain p by using:

Code:

p = p_rgh + rho*gh;

In most multiphase solvers the density is variable along the depth. So, instead of that, we should do something like:

$p=p\_rgh+g\int_{0}^{h}\rho(z).dz$

So, is that some kind of simplification in OpenFOAM, a bug or am I missing something?

jherb · June 21, 2017, 16:36

This is just the way, p_rgh is defined/used within OpenFOAM. It is not a physical quantity, just used internally.

toboto · June 29, 2017, 04:40

Thanks Joachim for your help

June 21, 2017, 13:59	obtaining p from p_rgh	#1
toboto New Member toboto Join Date: Jun 2016 Posts: 20 Rep Power: 10	Dear All, In almost all multiphase solvers we solve for p_rgh (static or thermodynamic pressure - hydrostatic pressure) instead of p. Then, we can obtain p by using: Code: p = p_rgh + rho*gh; In most multiphase solvers the density is variable along the depth. So, instead of that, we should do something like: $p=p\_rgh+g\int_{0}^{h}\rho(z).dz$ So, is that some kind of simplification in OpenFOAM, a bug or am I missing something?

June 21, 2017, 16:36		#2
jherb Senior Member Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 22	This is just the way, p_rgh is defined/used within OpenFOAM. It is not a physical quantity, just used internally. Tobi and toboto like this.

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June 29, 2017, 04:40		#3
toboto New Member toboto Join Date: Jun 2016 Posts: 20 Rep Power: 10	Thanks Joachim for your help