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kriz June 10, 2010 13:03

Basic question to buoyantBoussinesqPisoFoam

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?

ovie June 11, 2010 19:50

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.

panda60 June 12, 2010 03:35

How about your boundary condition for pressure ?
If fixed value, then should not be a uniform value.

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