Conditional measurements in a heated axisymmetric turbulent mixing layer

CONDITIONAL measurements of axial velocity u and temperature θ fluctuations are obtained in the mixing layer of a slightly heated round jet, which exhausts into still ambient air. The trimodal shape of the probability density function of temperature is used to distinguish between the turbulent and nonturbulent parts of the flow. A distinction is also made between the nonturbulent "cold" ambient fluid and the nonturbulent "hot" fluid of the potential core. Both velocity and temperature fluctuations associated with either "hot" or "cold" fluid are very nearly Gaussian. Fluid from the "hot" or "cold" side of the mixing layer is found on the opposite side of the mixing layer well beyond the central mixing region, consistent with the notion of bulk transport of nonturbulent fluid by a large-scale motion comparable to the width of the flow.