Turbulent diffusion of momentum and heat from a smooth, plane boundary with zero pressure gradient

Abstract

Results of an experimental investigation of the turbulent diffusion of momentum and heat from a smooth, plane boundary with zero pressure gradient are presented. A 10 ft long, 6 ft wide heated boundary maintained at a uniform temperature, formed part of the floor of the 6-ft square test section of a recirculating, low velocity wind tunnel. The velocities have been measured with hot-wire anemometers and the Reynolds stress distribution in the boundary layer has been computed from the measurements of the crossed-hot-wire anemometers. The temperatures have been measured with thermocouples, and the transferred heat has been determined from the electrical input to the heated boundary. Data on the pertinent variables have been collected along the centerline of the boundary and at four cross-sections of the boundary layer. The distribution of the mean velocity, for both neutral stability and various lapse rates, was found to be described more accurately by a "modified logarithmic law'' The distribution of the mean temperature in the thermal boundary layer was found to be similar to that of the mean velocity when momentum and thermal boundary layers are of the same thickness. The local drag coefficient was found to increase considerably with increasing negative Richardson numbers. Also Karman's modification of the Reynolds analogy between momentum and heat transfer was found to be in good agreement with the experimental results.