# Calculating Density in ParaView

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 July 4, 2020, 13:06 Calculating Density in ParaView #1 New Member   Ahsan Join Date: Nov 2019 Location: Bologna, Italy Posts: 27 Rep Power: 6 Dear Users, Can someone please help with how to get the density in ParaView? I am using interMixingFoam solver of OpenFOAM, and the parameters I get after the run are p, p_rgh, U, alpha.water, alpha.air, alpha.other, nut, nuTilda... but there is no rho for the density... I want to have a density profile since my density in the domain changes as two fluids mix together. Can I get it somehow? Is there a way to achieve that? I tried to use the calculator filter with (p-p_rgh)/(9.81*coordsZ) but this gives huge values at the bottom of the domain, probably due to a "zero" in the denominator... can someone please help me with this issue...? Thanks a lot in advance Have a good day!!!

 July 20, 2020, 19:43 #2 Senior Member   Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 21 You should be able to write rho with a writeObjects function object: https://www.openfoam.com/documentati...teObjects.html dlahaye and mahsankhan like this.

May 27, 2021, 08:50
Alternate and faster solution
#3
New Member

Ahsan
Join Date: Nov 2019
Location: Bologna, Italy
Posts: 27
Rep Power: 6
Quote:
 Originally Posted by jherb You should be able to write rho with a writeObjects function object: https://www.openfoam.com/documentati...teObjects.html

However, what you suggested would need the simulation to start over again. There exist another option:
Once you have run the OpenFOAM simulation, just open it in ParaView and apply the calculator filter like this (-p+p_rgh)/(9.81*(CoordZ)) and this will give you the density for the whole domain.

May 28, 2021, 10:13
#4
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Join Date: Apr 2020
Location: UK
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Quote:
 Originally Posted by mahsankhan Thank you for your reply. However, what you suggested would need the simulation to start over again.
No - you misunderstood jherb - just run the solver with the -postProcess flag and the writeObjects func, and it will spit out the field for you without running any more of the simulation. Eg.:

Code:
`someFoamSolver -postProcess -latestTime -func "writeObjects(h, rho)"`

 Tags density, filter, openfoam, paraview, pressure