Weakly Interacting Two Parallel Plane Jets

Abstract

The mean velocity field of unventilated two parallel plane jets for large nozzle spacing ratios has been studied using a two-component laser Doppler anemometer. Results show that by comparison with small s/w (less than 5), the interactions between the inner shear layer and the recirculation zone for large s/w are weaker. The initial peaks of turbulence intensities and Reynolds shear stress corresponding to the nozzle inner and outer edges tend to persist downstream from the location of the vortex centre without being overwhelmed by the influences caused by the recirculating flow in the recirculation zone. The lateral turbulence intensities and Reynolds shear stress in the outer shear layer spread and decay more rapidly than in the inner shear layer. The attraction of the two individual jets towards each other is clearly illustrated by the mean velocity vector field and supported by static pressure measurements. Comparisons of the results of the unventilated jets with those of ventilated jets in the literature indicate there is no recirculation zone in the ventilated jets and the unventilated jets combine to develop into a single free jet much earlier than ventilated jets.