Hi LilBeng,
with
SymbolicLFI(force * v, definedon=grid_mesh.Boundaries('bottom'))you apply a force with the density “force”.
If you want to have a point load
SymbolicLFI(force * v, definedon=grid_mesh.BBoundaries('some_point'))you could use an approximation of the Dirac Delta distribution
SymbolicLFI(approx_delta_eps * v, definedon=grid_mesh.Boundaries('bottom'), bonus_intorder=8)For a gravity force you would write
SymbolicLFI(9.81 * v)without dividing through the area.
NGSolve does not use units internally. If you define a rectangle with L=2, W=1 then the resulting displacement has the same “unit” as L.
I would recommend using SI units ( L=2m), non-dimensionalize the equation or compute the resulting units on paper before.
I hope this answers your questions.
Best
Michael