# Basic question to buoyantBoussinesqPisoFoam

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 June 10, 2010, 13:03 Basic question to buoyantBoussinesqPisoFoam #1 New Member   Christoph Join Date: Apr 2010 Posts: 19 Rep Power: 9 Hi! I have a (simple) question, using buoyantBoussinesqPisoFoam. Before getting into calculations with convection, I am trying to resolve the principal behaviour of the OF solver. I have set up a room, 5m in height, constant temperature, with a gravitational body force of 10 m/s^2. Am I correct assuming that the "pressure" p in OF is pressure divided by density, i.e. p=pressure/density? Having a graviational body force acceleration of 10 m/s^2, I was expecting a pressure difference of 50 Pa from 0 to 5m. paraFoam however shows me a pressure difference of about 100 [Pa]? [m^2/s^2]? from the floor to the ceiling. - What is the variable p in OF? pressure [Pa] or pressure/density [m^2/s^2]? - Having no fluid flow, only gravitational body forces, why does the pressure not decrease with rho*g*height, i.e. 50Pa at 5m height and g=10 m/s^2? http://www.bilder-space.de/show_img....&size=original Last edited by kriz; June 10, 2010 at 13:18. Reason: added picture

 June 11, 2010, 19:50 #2 Member   Ovie Doro Join Date: Jul 2009 Posts: 99 Rep Power: 10 Hi Kriz, I think you are right about the pressure in bouyantBousinessqFoam. The pressure is normalized by density as you described. With respect to pressure variation, If I recall correctly, I am not sure the hydrostatic pressure variation for a gas (air in your case) ought to be significant under the conditions you describe in your simulation.

 June 12, 2010, 03:35 #3 Senior Member   Jiang Join Date: Oct 2009 Location: Japan Posts: 186 Rep Power: 10 How about your boundary condition for pressure ? If fixed value, then should not be a uniform value.

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