# Forces from simpleFoam

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June 26, 2014, 07:47
Forces from simpleFoam
#1
New Member

Sture Smidt
Join Date: Mar 2013
Posts: 25
Rep Power: 5
Hi,

This may have been covered before but:
-What is the reference density used by simpleFoam? I am analyzing a sphere in air at 10 m/s, but the stagnation pressure is 20% off. This may indicate that the density is treated as unity (1.0).

Are the simpleFoam results based on a density of unity?
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 June 26, 2014, 09:34 #2 Senior Member   Alexey Matveichev Join Date: Aug 2011 Location: Nancy, France Posts: 1,423 Rep Power: 25 Hi, there's no density in simpleFoam cause equations are divided by constant density and you're using kinematic viscosity. Surely miss in stagnation pressure can mean error in simpleFoam, but it equally (actually more likely) can be the error in your case setup.

 June 28, 2014, 18:00 #3 Senior Member   Joachim Herb Join Date: Sep 2010 Posts: 387 Rep Power: 11 Is your medium air (with density 1.2xx kg/m³)? In simpleFOAM the pressure used is p/rho, so this might explain the 20 % difference you see?

 August 7, 2014, 14:41 Forces from simpleFoam #4 New Member   Sture Smidt Join Date: Mar 2013 Posts: 25 Rep Power: 5 How about forces from simpleFoam extracted with functionObjects? Are they normalized with the density like F=f/rho? SS

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