gapPressureFvPatchVectorField

Description

The gapPressure boundary condition applies the gap pressure to the selected patch. It is derived from the tractionDisplacement boundary condition and shares its general mechanism (including the spring-dashpot system). However, with gapPressure, the user does not need to specify the traction vector or pressure directly.

Warning

This BC is specifically designed to work in conjunction with a gapGasModel that dynamically provides the gap pressure at every iteration.

Options

The gapPressure fvPatchField can be selected in the patch subdictionary inside the boundaryField subdictionary of the displacement field.

Parameters in the patch subdictionary for gapPressure:

planeStrain	Activates the plane strain approximation for the normal stress at the boundary. When enabled, the normal strain is assumed constant across the last layer of cells. Default: `false`.
fixedSpring	Activates a fixed spring-dashpot system for additional stability. Default: `false`.
fixedSpringModulus	Spring modulus in N/m. Required when `fixedSpring` is set to `true`.
dashpotModulus	Dashpot modulus in N/m. Required when `fixedSpring` is set to `true`.
relax	Relaxation factor for gradient updates. Default: `1.0`.
value	Initial displacement value (not stress).

Usage

To apply the gapPressure boundary condition to a given patch, you need to specify its typename in the patch definition in the boundary condition file (e.g., 0/D or 0/DD for simulations involving incremental mechanical solvers).

Example: Applying gapPressure to the fuelInner patch:

fuelInner
{
    type            gapPressure;

    // Activate plane strain approximation for the normal stress at the
    // boundary. It is false by default.
    planeStrain     false;

    // Relaxation factor for the gradient update
    relax           1.0;

    // Initial displacement value
    value           $internalField;
}