The near wall mixing length formulation revisited

Abstract

1. IntroductionThe calculation of transport phenomena in bound-ary layers, pipe or duct flows can be easily accom-plished by a simple, zero order, mixing lengthformulation. The application of this model in simpleengineering flows, i.e., flows without recirculation orasymmetry, is still widely extended because of its sim-plicity and its ability to match experimental results atthe same degree than more elaborated models. Most ofthe mixing-length formulations for near-wall flows usea damping factor to decrease rapidly the characteristiclength as the wall is approached. The most populardamping factor is the one suggested by van Driest [1],which has been modified extensively to accommodatedi•erent wall conditions [2–6].A yet unresolved and apparently intrinsic shortcom-ing of the mixing length model is that it cannot predictproperly the turbulent viscosity profile –n