  In this work, we numerically study the elastic contact between isotropic and
anisotropic, rigid, randomly rough surfaces and linearly elastic counterfaces
as well as the subsequent Reynolds flow through the gap between the two
contacting solids. We find the percolation threshold to depend on the
fluid-flow direction when the Peklenik number indicates anisotropy unless the
system size clearly exceeds the roll-off wave length parallel to the easy flow
direction. A critical contact area near 0.415 is confirmed. Heuristically
corrected effective-medium treatments satisfactorily provide Reynolds
fluid-flow conductances, e.g., for isotropic roughness, we identify accurate
closed-form expressions, which only depend on the mean gap and the relative
contact area.
