PNNL

Abstract

Observations of entrainment into natural gravity-driven flows on sloping surfaces are described. It is shown that the laboratory-based entrainment law of Ellison & Turner (1959), which is often used for modeling of atmospheric and oceanic flows, underestimates the entrainment rates substantially, arguably due to the fact that the laboratory flows have been conducted at Reynolds numbers (Re ¡ã 10 3) below what is required for mixing transition (Re ¡ã 10 4) whereas the natural flows occur at much higher Reynolds numbers (Re ¡ã 10 7). New entrainment law of the form E ¡ã Ri-3/4 is proposed for the atmospheric Richardson number range 0.15