This boundary condition provides a cyclic condition for p_rgh. It applies
corrections to the value and gradient on both sides of the cyclic to
account for the non-cylicity of the gravitational force.
This condition is only needed when the cyclic patches have a transformation
and a normal component in the direction of gravity. If the cyclic patches
are orthogonal to the direction gravity, then a normal cyclic boundary
condition can be used instead.
Care must be taken when using this boundary condition that the simulation
is actually cyclic. The following constraints apply:
- Both cyclic patches must be oriented in the same way with respect to
gravity. In practice this means that applicability is limited to cyclics
with translational transformations.
- The model cannot have any dependence on the absolute value of the
pressure field. The absolute value of the pressure, in reality, varies
between each repetition of the geometry; it is not actually formally
cyclic. Only the gradient of the pressure field can be truly cyclic. This
model is therefore only valid if the absolute value of the pressure is
arbitrary, and only the gradient has an effect on the solution. This is
the case for incompressible multiphase solutions or incompressible
Boussinesq-like models of density variation. It is not true if (for
example) a compressible thermodynamic model is being used.
Specification is as follows. A "patchType" entry must be provided to
indicate that this condition overrides the underlying cyclic constraint,
and a "rhoInf" entry is needed (by the owner patch only) to specify the
density of the far-field environment. For example:
cyclicA
{
type prghCyclicPressure;
patchType cyclic;
rhoInf 1; // [kg/m^3]
}
cyclicB
{
type prghCyclicPressure;
patchType cyclic;
}
A tutorial, incompressibleVoF/trayedPipe, has been added to demonstrate
usage of this boundary condition.
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