Considering that the lubricant film thickness is very small in typical conditions, the choice of the position of S between γl and Pðγl Þ should not noticeably affect the results. Only in the inlet and outlet zones, the film thickness may be relatively large. However,
the hydrodynamic pressure buildup is mostly concentrated in the zones where the film thickness is small. The related effects are studied in Section 4.1 where it is shown that indeed the results do not significantly depend on the choice of the position of S, while
the computational scheme appears more robust for S ¼ Pðγl Þ.