uniformFixedValueTube

Syntax

Defined in the boundary condition of the pressure field 0/p.

fvPatchField uniformFixedValueTube;

 outlet
 {
     type        uniformFixedValueTube;
     tubeOutletPressure  0;
     tubeLength          1;
     tubeDiameter        0.2;
     lambda              0.24;
 }

Examples

Variant with constant tubeOutletPressure:

outlet
{
    type        uniformFixedValueTube;
    tubeOutletPressure  0;
    tubeLength          1;
    tubeDiameter        0.2;
    lambda              0.24;
}

Variant with tubeOutletPressure varying with time:

outlet
{
    type        uniformFixedValueTube;
    tubeOutletPressure  table
    (
        (0.0  0.0)
        (0.1  0.5)
    );
    tubeLength          1;
    tubeDiameter        0.2;
    lambda              0.24;
}

Description

The uniformFixedValueTube pressure boundary condition models an outlet with an additional attached tube. The pressure at the end of the attached tube is specified and the pressure loss along the tube is calculated and used to compute the pressure at the patch. Pressure loss along the tube is computed as

\Delta p = (\lambda \frac{L_\mathrm{tube}}{D_\mathrm{tube}} + C_\mathrm{addLoss}) \frac{\rho}{2} U_\mathrm{bulk}^2

with U_\mathrm{bulk} = \int_P \vec{n} \cdot \vec{u}\,\mathrm{d}P the patch averaged normal velocity and \rho the density field at the patch.

This boundary condition reads the following keywords:

  • fluxFieldName = The name of the surface flux (default: “phi”)

  • densityFieldName = The name of the density field (default: “rho”)

  • tubeOutletPressure = The pressure at the attached tube’s outlet. This field allows entry of a Function1 object, e.g. a table to set a pressure value varying with time.

  • tubeLength = The attached tube’s length.

  • tubeDiameter = The attached tube’s diameter.

  • lambda = The attached tube’s friction factor depending on Reynolds number and surface roughness. See for https://en.wikipedia.org/wiki/Moody_chart more details.

  • additionalLossCoeff = Coefficient C_\mathrm{addLoss} to model additional losses in the pipe, e.g. due to bends or components in the tube. (default: 0)

  • relax = Additional relaxation factor used during calculation of the patch averaged velocity U_\mathrm{bulk} resulting in U_\mathrm{bulk} = U_\mathrm{bulk} f_\mathrm{relax} + U_\mathrm{bulk}^\mathrm{old} (1 - f_\mathrm{relax}) (default: 0.9)

Restrictions

None.