fanPressure

Description

The fanPressure is a pressure boundary condition to assign either a pressure inlet or outlet total pressure condition for a fan. The condition sets the static pressure from a definition of the total pressure and pressure drop as a function of volumetric flow rate across the patch.

The non-dimensional flux is calculated as follows:

$$phi = \frac{4 \dot{m}}{\rho \pi^2 d_m^3 \omega}$$

The non-dimensional flux is calculated as follows:

$$\Psi = \frac{2 \Delta P}{\rho (\pi \omega d_m)}$$

Property	Description
$d_m$	Fan mean diameter [m]
$\Delta P$	Pressure drop
$\omega$	Rotational speed [rad/s]
$\dot{m}$	Mass flow rate

The non-dimensional table should be given as $\Psi = F(\phi)$.

The condition sets the static pressure at the patch $p_p$ based on a specification of the total pressure, $p_0$, and pressure drop, $p_d$, specified as a function of the volumetric flow rate.

$$p_p = p_0 - p_d$$

Usage

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

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

<patchName>
{
    // Mandatory entries
    type            fanPressure;
    fanCurve        <Function1<scalar>>;
    direction       <word>;

    // Optional entries
    nonDimensional  <bool>;

    // Conditional entries

      // if 'nonDimensional' is true
      rpm           <Function1<scalar>>;
      dm            <Function1<scalar>>;

    // Inherited entries;
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: fan	word	yes	-
fanCurve	Dataset of pressure vs flow rate	Function1<scalar>	yes	-
direction	Direction of flow through fan	word	yes	-
nonDimensional	Flag to use non-dimensional curves	bool	no	false
rpm	Fan rpm (for non-dimensional curve)	Function1<scalar>	conditional	-
dm	Fan mean diameter (for non-dimensional curve)	Function1<scalar>	conditional	-

Options for the direction entry:

Property	Description
in	Into the fan
out	Out of the fan

The inherited entries are elaborated in:

• Foam::totalPressureFvPatchScalarField
• Foam::Function1

• For compatibility with older versions (OpenFOAM-v2006 and earlier), a missing fanCurve keyword is treated as a tableFile and makes the file keyword mandatory.

Further information

Tutorial:

• TJunctionFan

Source code:

• fanPressure

API:

• Foam::fanPressureFvPatchScalarField

History: Introduced in version 1.5