## Description🔗

The swirlFanVelocity is a boundary condition that provides a jump condition for velocity across a cyclic pressure jump condition and applies a transformation to the velocity.

The velocity jump is specified with a swirl component as follows:

$u_{tan} = \frac{\Delta_P}{r_{eff} f_{eff} \omega_{rpm} \frac{\pi}{30}}$

where:

Property Description
$$u_{tan}$$ Tangential component of velocity
$$\Delta_P$$ Pressure drop across the cyclic
$$r_{eff}$$ Effective radius
$$f_{eff}$$ Fan efficiency coefficient
$$\omega_{rpm}$$ RPM of the fan

Alternatively an inner and outer radii can be used instead of $$r_{eff}$$. The $$u_{tan}$$ is as follows for $$r > r_{inner}$$ and $$r < r_{outer}$$:

$u_{tan} = \frac{\Delta_P}{r f_{eff} \frac{\omega_{rpm}}{\pi 30}}$

with $$r = x_{f} - x_{origin}$$, and $$f$$ is the face center.

The radial velocity is zero in the this model.

## Usage🔗

The condition requires entries in both the boundary and field files.

### Boundary file🔗

<patchName>
{
type            patch;
...
}


### Field file🔗

<patchName>
{
// Mandatory entries
type            swirlFanVelocity;
rpm             <Function1<scalar>>;

// Optional entries
phi             <word>;
p               <word>;
rho             <word>;
origin          <vector>;
fanEff          <scalar>;
rEff            <scalar>;
rInner          <scalar>;
rOuter          <scalar>;

// Inherited entries
patchType       cyclic;
...
}


where:

Property Description Type Required Default
type Type name: swirlFanVelocity word yes -
rpm RPM of the fan Function1<scalar> yes -
phi Name of flux field word no phi
p Name of pressure field word no p
rho Name of density field word no rho
origin Fan centre vector no Zero
fanEff Fan efficiency scalar no 1
rEff Effective radius scalar no 0
rInner Inner radius scalar no 0
rOuter Outer radius scalar no 0
useRealRadius Flag to use inner/outer radii bool no false

The inherited entries are elaborated in:

• Foam::fixedJumpFvPatchField
• Foam::Function1

• Negative rpm will reverse the input tangential direction.
• This boundary condition needs to be used with a pressure-jump (e.g. fan) condition with a non-zero dp, otherwise no swirl will be applied (dp=0).
• Please ensure physical and complementary set-ups for the pressure-jump and swirlFanVelocity boundary conditions.

## Further information🔗

Tutorial:

• N/A

Source code:

API:

History:

• Introduced in version v1806