simpleFoam vs buoyantSimpleFoam
 

Dear Foamers,

I am quite new to use OF to solve external aerodynamics. I am writing here to ask for your kind help.
I try to simulate a cube placed on the ground on a face in order to understand how OF manage the force calculation with simpleFoam and with buoyantSimpleFoam.
The point is that I should get the same value of forces on the cube, but something is wrong...
I tried to compare the data in the postProcessing/forces folder with the value obtained by the integral of pressure on the cube's surfaces in paraFoam but i cant get the point.
Maybe I make some mistakes: to integrate pressure on faces I generate surface normals on the cube and the integrate the calculated variable p*normals.

The topics are these:
1. there is any differences on forceCalculation between simple and buoyant?
2. why the intergals of (p*normals) do not match with the force calculation of postProcessing folder?

I'd like to thank anyone could help me...


Here below there some values:


/*___with simpleFoam___*/

P
pressure 0;
dimensions [0 2 -2 0 0 0 0];

--> after 50k iter

forces(pressure, viscous, porous)
(-1.677823966 -0.04192667675 0.8973219913) only pressure

while with the integrateVariable on P
1.47393 -0.0309424 -0.895828


/*___withbuoyantSimpleFoam____*/

P
pressure 101325;
dimensions [1 -1 -2 0 0 0 0];

P_RGH
pressure 100000;
dimensions [1 -1 -2 0 0 0 0];

--> after 50k iter
forces(pressure, viscous, porous)
(-3.544135454 -0.2622319888 -24650.00027) only pressure

while with the integrateVariable on P_rgh
193.717 421.979 26073.8


while with the integrateVariable on P
193.71 421.967 26072.3