 The open source CFD toolbox
Force coefficients

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

Fields

• force coefficients: forceCoeff
• moment coefficients: momentCoeff

Storing of integrated values for further post-processing:

• total moment coefficient: Cm
• total drag coefficient: Cd
• total lift coefficient: Cl
• total front lift coefficient: Cl(f)
• total rear lift coefficient: Cl(r)

# Further information

Related:

Source code:

Example usage:

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