[krembil]

Hello,

I am running simpleFoam. The report of the forces on aerodynamic bike is:

# Time forces(pressure,viscous,porous) moment(pressure,viscous,porous) localForces(pressure,viscous,porous) localMoments(pressure,viscous,porous)
1176 ((1.88755 -16.4704 0.0649157),(8.30496 -0.0435128 -0.000451409),(0 0 0)) ((0.0149643 -0.595882 -164.082),(9.27736e-05 0.00486565 -3.26585),(0 0 0))
1176 ((1.88755 -16.4704 0.0649157),(8.30496 -0.0435128 -0.000451409),(0 0 0)) ((0.0149643 -0.595882 -164.082),(9.27736e-05 0.00486565 -3.26585),(0 0 0))

As one can see, y component of the pressure force (-16.4704) is high, it should be less than 1. I have the same simulation run in Fluent.
I am not sure why this number is so high. The simulation runs without any problems, residuals are low, the mesh is OK.

The force file is:

forces
{
type forces;
functionObjectLibs ("libforces.so");
outputControl timeStep;
outputInterval 1;

patches ( "BIKE"
"BOTTOM" );
pName p;
UName U;
rhoName rhoInf; // Indicates incompressible
log true;
rhoInf 1.205; // Redundant for incompressible
dragDir (1 0 0);
liftDir (0 0 1);

I have also tried with liftDir (0 1 0) and still get the same numbers.
The BOTTOM patch is just the lower part of the bike with finer mesh.

Thanks in advance!

[MichaelD]

Hi, sorry for the late reply, just in case you haven't solved this yet:


It's the lift force that's supposed to be less than 1, not the lift coefficient right?

I'm not very experienced in OpenFOAM or c++, but I haven't seen syntax like

patches     ( "BIKE"
                  "BOTTOM" );

before. So maybe what's happening it's only calculating the forces for one of the patches?

I'd either try something like

patches( "(BIKE|BOTTOM)");

or create a group like they do in the motorcycle tutorial.