Could someone tell, please, has someone constructed finite difference mixed derivatives on quadrilateral (non-orthogonal) grids, already? Without using aconformal mapping to an orthogonal grid. I mean we have the mixed differential operator and try to represent it through a difference relation.I searched with the help of Google Scholar, but found nothing.I tried to constuct it myself, but have problems with the symmetry of mixed second difference derivative: $$ f_{xy} = f_{yx} $$
Finite difference mixed derivatives on quadrilateral (non-orthogonal) grids
finite difference