Conditional Sampling Measurements in the Developing Region of The 3-D Turbulent Jet from a Square Nozzle

Abstract

Developing region of the 3-D turbulent free jet issuing from a 60mm×60mm square nozzle was investigated experimentally both by conventional and conditional sampling techniques. As opposed to the turbulent corner boundary layer, contours of the mean velocity and those of the fluctuating velocity components obtained by conventional averaging do not show any significant difference in distorsion between them. Nearly the same contours were observed in the conditionally averaged quantities, although some characteristic differences exist in the inner and in the outer intermittent region of the mixing layer. It is found that turbulent zone-averaged eddy viscosity takes practically a constant value over the mixing layer and that turbulence production occurs essentially when the flow is turbulent. From the results of conditionally averaged secondary flow field, a possible entrainment mechanism is proposed.