Observations of jets in density stratified crossflows

The results are presented of a water tunnel study undertaken to determine the characteristics of a circular jet in a density stratified crossflow. Flow visualization indicates that the salient characteristics include a stable potential core of length L in the vicinity of the jet exit. The length of the stable potential core depends on the velocity ratio α = UJ/U∞ and the non-dimensional frequency ND/U∞. As α is increases the value of L increases; L also increases for increasing values of ND/U∞ < 0.03. However, L decreases with increasing ND/U∞ for values of ND/U∞ > 0.03. Knowledge of this variability is necessary for quantifying mixing rates. Further downwind, the jet trajectory evolves to a maximum height of rise zm, and subsequently relaxes to a lower equilibrium level, ze. Values of zm and ze are in agreement with the predictions of scaling arguments. Mean density measurements indicate rapid increase of dilution for small distances from the jet exit; however, for large distances predominantly horizontal mixing processes result in much slower increase of dilution with distance.