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

Related:

Source code:

API:

Example usage: