Forces from simpleFoam

sture · June 26, 2014, 07:47

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?

alexeym · June 26, 2014, 09:34

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.

jherb · June 28, 2014, 18:00

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?

sture · August 7, 2014, 14:41

How about forces from simpleFoam extracted with functionObjects? Are they normalized with the density like F=f/rho?

SS

August 7, 2014, 14:41	Forces from simpleFoam	#4
sture New Member Sture Smidt Join Date: Mar 2013 Posts: 27 Rep Power: 13	How about forces from simpleFoam extracted with functionObjects? Are they normalized with the density like F=f/rho? SS

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June 26, 2014, 09:34		#2
alexeym Senior Member Alexey Matveichev Join Date: Aug 2011 Location: Nancy, France Posts: 1,930 Rep Power: 38	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
jherb Senior Member Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 21	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?