The forceCoeffs
function object generates aerodynamic force and moment
coefficient data for surfaces and porous regions, with optional:
- inclusion of porous drag
- local co-ordinate system
- data binning
Usage🔗
Basic operation of the forceCoeffs
function object comprises:
forceCoeffs1
{
type forceCoeffs;
libs ("libforces.so");
patches (<list of patch names>);
}
For more complete control, the full set of input entries includes:
forceCoeffs1
{
// Mandatory entries
type forceCoeffs;
libs ("libforces.so");
patches (<list of patch names>);
// Optional entries
// Field names
p p;
U U;
rho rho;
// Reference pressure [Pa]
pRef 0;
// Include porosity effects?
porosity no;
// Store and write volume field representations of forces and moments
writeFields yes;
// Centre of rotation for moment calculations
CofR (0 0 0);
// Lift direction
liftDir (0 0 1);
// Drag direction
dragDir (1 0 0);
// Pitch axis
pitchAxis (0 1 0);
// Freestream velocity magnitude [m/s]
magUInf 30;
// Reference length [m]
lRef 1;
// Reference area [m2]
Aref 1.75;
// Spatial data binning
// - extents given by the bounds of the input geometry
binData
{
nBin 20;
direction (1 0 0);
cumulative yes;
}
}
Default behaviour assumes that the case is compressible. For incompressible cases, i.e. solved using the kinematic pressure:
\[p_k = \frac{p}{\rho} \qquad [\mathrm{m}^2 \mathrm{s}^{-2}]\]the rho
entry can be used to set the freestream density:
rho rhoInf;
rhoInf 100000;
Sample output🔗
Text reporting:
- Coefficient data divided into total, pressure, viscous and porous contributions
forceCoeffs forceCoeffs1 write:
Coefficient Total Pressure Viscous Internal
Cd: 0.420059 0.406413 0.0136462 0
Cd(f): 0.215934 0.208904 0.00703002 0
Cd(r): 0.204125 0.197509 0.00661615 0
Cl: 0.0530861 0.0530808 5.34317e-06 0
Cl(f): 0.195825 0.189931 0.00589387 0
Cl(r): -0.142739 -0.13685 -0.00588852 0
CmPitch: 0.169282 0.163391 0.00589119 0
CmRoll: 0.00590429 0.00569735 0.000206938 0
CmYaw: 0.000571337 0.000892135 -0.000320798 0
Cs: -0.0133976 -0.0131692 -0.000228412 0
Cs(f): -0.00612746 -0.00569246 -0.000435004 0
Cs(r): -0.00727014 -0.00747673 0.000206593 0
Stored properties🔗
Reduced data🔗
The following data are stored by the function object, and can be used by other function objects:
-
Cm
: total moment coefficient -
Cd
: total drag coefficient -
Cl
: total lift coefficient -
Cl(f)
: total front lift coefficient -
Cl(r)
: total rear lift coefficient
Fields🔗
-
forceCoeff
: force coefficients -
momentCoeff
: moment coefficients
Further information🔗
Related:
- forces function object
Source code:
API:
Example usage:
- sonicFoam
nacaAirfoil
tutorial: $FOAM_TUTORIALS/compressible/sonicFoam/RAS/nacaAirfoil