swirlFanVelocity

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>;
    useRealRadius   <bool>;

    // 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:

• swirlFanVelocity

API:

• Foam::swirlFanVelocityFvPatchField

History: Introduced in version v1806