Mixing and scalar dissipation rate in a decaying jet

The temporal development of the mixing field in a decaying jet (Re = 50,000) was quantified by measuring mole fraction and scalar dissipation rate (SDR) decaying, isothermal, turbulent gaseous jet. 2D measured using planar laser induced fluorescence acetone and, with appropriate image processing, this allowed estimation SDR two in-plane components within 16% error. instantaneous averaged distributions are reported for downstream dimensionless distances up to 7 nozzle exit diameters 35 flow timescales after end injection. With advection last uniform concentration (UEC) profile core away from exit, region weak arises at jet's trailing edge. Estimates made Lagrangian frame reference show that edge becomes leaner, injection (AEI), faster than steady state, confirming existence an ‘entrainment wave’. normalised probability density functions various stations times AEI differ lognormal distribution both low high values negative skewness positive excess kurtosis. A pseudo 3D SDR, including estimate out plane component, showed reduced departure lognormal. may be attributed disappearance strong shear layer associated absence momentum AEI. To authors’ knowledge, study provides first measurements isothermal