Boundary-condition patch geometry has to match the dimensionality

s_apply_boundary_patches (src/pre_process/m_boundary_conditions.fpp) dispatches by dimensionality:

if (p > 0) then                                  ! 3D
    if      (patch_bc(i)%geometry == 2) call s_circle_bc(i, bc_type)
    else if (patch_bc(i)%geometry == 3) call s_rectangle_bc(i, bc_type)
else if (n > 0) then                             ! 2D
    if      (patch_bc(i)%geometry == 1) call s_line_segment_bc(i, bc_type)

There is no else. A geometry belonging to the other dimensionality falls straight through: the patch is never applied, nothing is printed, and the face silently keeps whatever bc_[xyz] gave it.

That is quiet in the worst way. A nozzle cut into a no-slip wall with a 3D geometry in a 2D case simply stays a solid wall — the run completes, writes output, and the jet has a velocity of exactly zero for all time with no indication anything was ignored.

Running it

./mfc.sh validate examples/2D_bc_patch_geometry/case.py                  # geometry 1, valid in 2D
GEOMETRY=3 ./mfc.sh validate examples/2D_bc_patch_geometry/case.py       # a 3D geometry in a 2D case

	before	after
GEOMETRY=1	passes	passes
GEOMETRY=3	passes, then does nothing at run time	patch_bc(1)%geometry must be 1 (line segment) in 2D; geometry 3 is never applied

The 3D direction is symmetric: geometry 1 in a 3D case is equally ignored, and is now equally refused.

A second trap in the same corner

The case carries a second initial-condition patch a few cells thick at the inlet, and it is load-bearing: the Dirichlet buffer is filled by pre_process from the initial condition at the boundary face. A domain initialised at rest stores rest in that buffer, and the "inflow" then delivers zero for all time — again with no warning. This is not what the validator change addresses; it is noted here because the two failures look identical from the outside, and knowing that saves working out which one is in play.

Scope

Validator only; no source change and no golden files. All 182 example cases still validate.