[klausb]

Hello,

I've changed the mesh and AOA setting approach of a case and can't reproduce the results.

Changes:

1: The mesh was changed from a rectangular mesh created with snappyHexMesh and a tool which helped to get the y+ = 1 right to an o-mesh with y+ = 1.

- the rectangular mesh had the following boundary patches: inlet, outlet, top, bottom, front, back, airfoil
- the o-mesh has front, back, airfoil, farfield

2: The AOA (6.24°) was initially set in the mesh, it's now set by setting the x,z components of the velocity in the U (14.6 m/s) file. The mesh was/is in the x,z plane. The directions in the forceCoeffs file to calculate x,z were adjusted accordingly.

Results:

Expected: cl = 1.14 cd = 0.0225
Current result: cl = 1.6 cd = -0.025 (negative!)

Strange U/p results visible in paraFoam (see attachment farfield_error)


U file:

FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (14.513 0 1.587); // angle of attack = 6,24° vx=v*cos(6,24°), vy=v*sin(6,24°)

boundaryField
{
front
{
type empty;
}

back
{
type empty;
}

airfoil
{
type fixedValue;
value uniform (0 0 0);
}

farfield
{
type freestream;
freestreamValue uniform (14.513 0 1.587);
}
}


forceCoeffs file:

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

patches ("airfoil");
pName p;
UName U;
rhoName rhoInf;
log true;

CofR (0.25 0 0);

rhoInf 1.225;
}


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

patches ("airfoil");
pName p;
UName U;
rhoName rhoInf;
log true;

liftDir (-0.108653 0 0.994075);
dragDir (0.994075 0 0.108653);
CofR (0.25 0 0);
pitchAxis (0 1 0);

magUInf 14.6;
rhoInf 1.225;
lRef 1;
Aref 0.1;
}


boundary file:

4
(
front //auto1
{
type empty;
nFaces 40800;
startFace 81300;
}
back //auto2
{
type empty;
nFaces 40800;
startFace 122100;
}
airfoil //auto3
{
type wall;
nFaces 300;
startFace 162900;
}
farfield //auto4
{
type patch;
nFaces 300;
startFace 163200;
}
)



What's wrong with the farfield settings?

What's wrong with the AOA settings?

Klaus