Flow Measurements Near a Reynolds Ridge

Abstract

The Reynolds ridge is a well-known phenomenon first observed
\nin 1854 by Henry David Thoreau. It was then rediscovered
\nby Langton in 1872, but Reynolds was the first to recognize
\nthat the surface tension difference was the physical mechanism
\nbehind its formation and saw the equality between the case of
\na spreading film and that of a stagnant film met by oncoming
\nflow. However, it wasn't until McCutchen in 1970 that the
\nprediction of a boundary layer forming beneath the film was
\nintroduced as the cause of the surface deformation rise ahead
\nof the film due to the retardation of the flow. The first quantitative
\ntheory of the ridge was formed by Harper and Dixon
\n(1974), who stated that the surface tension gradient balances
\nthe viscous shear stress generated in the boundary layer. Experimental
\nstudies of the ridge so far include Schlieren visualizations
\nby Sellin (1968) as well as by Scott (1982) who measured
\nthe surface slope across the ridge and found good comparisons
\nbetween the theoretical results of Harper and Dixon. Finally, it
\nwas Scott who recognized that even at very low levels of surface
\ncontamination the Reynolds ridge is found to exist.