2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/18694Certain (non polymeric) fluids show an anomalously low friction when flowing against well chosen solid walls. We discuss here one possible explanation, postulating that a gaseous film of small thickness h is present between fluid and wall. When h is smaller than the mean free path l of the gas (Knudsen regime) the Navier length b is expected to be independent of h and very large (microns).5 pages, 2 EPS figures. Submitted to LangmuirSoft Condensed Mattertext