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-   -   Density in icoFoam Densidad en icoFoam (http://www.cfd-online.com/Forums/openfoam-solving/60048-density-icofoam-densidad-en-icofoam.html)

manuel August 23, 2006 12:47

Hi, Thanks in advance . i
 
Hi,
Thanks in advance .

i try to run a nozzle model, very simple, using icofoam. After try and try, and try ;-), run without problems. I run the same model in ANSYS and the result are not equal. In ansys, i need the density, but in IcoFoam No.

what equations solved icofoam, where not is necesary the density.??

My model is a modifid cavity, whit the nu 0.01.

thanks.
________________
Hola
Gracias por adelantado.

yo estoy tratando de correr un modelo de una tobera sencilla. Despues de tratat y tratar, logre que corriera sin problemas. Yo tratto de correr el mismo ejemplo en Ansys, pero el resultado no es el mismo. Ademas en ansys es necesario la densidad pero en icofoam no.

Que ecuaciones resuelve icofoam, donde no es necesario la densidad?

Mi modelo es como el modelo cavity pero modificado, con nu de 0.01

Gracias

Manuel F. Mejia De Alba
Universidad Nacional de Colombia.

grtabor August 23, 2006 13:41

In icoFoam, the pressure being
 
In icoFoam, the pressure being solved is not the true pressure but is in fact p/rho. Thus the density cancels out throughout.

Gavin

manuel August 24, 2006 16:50

Hi Ok, the press is equal.
 
Hi

Ok, the press is equal. But, what happend whit the velocity, the graphics change, when change the density.

how i do, for make a model with the density of any value.

thanks

hjasak August 24, 2006 17:00

Multiply the pressure field wi
 
Multiply the pressure field with the value of density. If you want to feel really good about it, you can also add it an offset, e.g. 101325 Pascal for air at atmospheric conditions.

This can all be done after the simulation and there's no need to change the solver. Look at the magU utility for examples - you will be manipulating the pressure instead.

Hrv

manuel August 24, 2006 17:37

ok, with the press, i not have
 
ok, with the press, i not have problems

my doubts are with the velocity field:

this is independent of density??

thanks and sorry the insistence.

Manuel.

hjasak August 25, 2006 07:26

Velocity is fine: remember, yo
 
Velocity is fine: remember, you only have grad p in the momentum equation and that does not change for arbitrary offset of p.

Enjoy,

Hrv

manuel August 26, 2006 12:35

Hi again, and I am sorry for i
 
Hi again, and I am sorry for inconvenients for so many questions. One more, when I`m looking in the icofoam solver code, it appears a phi term (like a field Phi), that is multiply for velocity, and I`m not sure if that term is related with viscous loss term of generalized momentum equation. The problem is that changes in the kinematic viscosity produces big changes in the velocity field pattern, and not only in velocity field values.

Thanks again

manuel August 26, 2006 12:42

Hi again, and I am sorry for i
 
Hi again, and I am sorry for inconvenients for so many questions. One more, when I`m looking in the icofoam solver code, it appears a phi term (like a field Phi), that is multiply for velocity, and I`m not sure if that term is related with viscous loss term of generalized momentum equation. The problem is that changes in the kinematic viscosity produces big changes in the velocity field pattern, and not only in velocity field values.

rieuk September 22, 2010 04:10

Yeah but when you change viscosity you're changing Reynolds number so you should expect a change in flow field. Also if I'm not mistaken, Phi is a scaled flux per unit density per unit area...?


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