Mixed hp-FEM for incompressible fluid flow on anisotropic meshes are analyzed. A discrete inf-sup condition is proved with a constant independent of the meshwidth and the aspect ratio. For each polynomial degree $k\geq 2$, velocity-pressure subspace pairs are presented which are stable on quadrilateral mesh-patches, independently of the element aspect ratio implying in particular divergence stability on the so-called Shishkin-meshes. ...

Divergence stability of mixed hp-FEM for incompressible fluid flow for a general class of possibly highly irregular meshes is shown. The meshes may be refined anisotropically and contain hanging nodes on geometric patches. The inf-sup constant is independent of the aspect ratio of the elements and the dependence on the polynomial degree is given explicitly. Numerical estimates of inf-sup constants confirm our results.