It is now possible to use waveVelocity and waveAlpha boundary conditions
in cases in which the waves generate localised flow reversals along the
boundary. This means waves can be speficied at arbitrary directions and
with zero mean flow. Previously and integral approach, similar to
flowRateOutlet, was used, which was only correct when the direction of
wave propagation was aligned with the boundary normal.
This improvement has been achieved by reformulating the waveVelocity and
waveAlpha boundary conditions in terms of a new fixedValueInletOutlet
boundary condition type. This condition enforces a fixed value in all
cases except that of advection terms in the presence of outflow. In this
configuration a gradient condition is applied that will relax towards
the desired fixed value.
The wavePressure boundary condition has been removed, as it is no longer
necessary or advisable to locally switch between velocity and pressure
formulations along a wave boundary. Wave boundaries should now have the
general fixedFluxPressure or fixedFluxExtrapolatedPressure conditions
applied to the pressure field.
Two new tutorial cases have been created to demonstrate the new
functionality. The multiphase/interFoam/laminar/wave3D case demonstrates
wave generation with zero mean flow and at arbitrary angles to the
boundaries, and incompressible/pimpleFoam/RAS/waveSubSurface
demonstrates usage for sub-surface problems.
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