2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/84806By re-interpreting a recent successful closure procedure in terms of local spatial averaging and the neglect of fluctuations about that average, it is shown how the results of that closure scheme (the ''alpha model'') may be more simply derived.To appear in Physics of Fluids (2002)Fluid Dynamicstext