Conditional probability densities in a turbulent heated round jet

A digital data acquisition system and a technique for determining a turbulent/nonturbulent interface from the probability density function of a passive scalar are adopted to study an axisymmetric heated-air turbulent jet with a coflowing external stream. Probability density functions of velocity and temperature fluctuations, as well as their products, are determined in the turbulent part of the flow. The probability density functions show increasing divergence from Gaussian distributions as the distance from the jet axis increases. Departures from Gaussian distributions are in general greater for inward than for outward radial motion, and cannot be explained on the basis of a cumulant discard approach assuming a Gram-Charlier distribution.