PIV measurements of opposing-jet ventilation flow in a reduced-scale simplified empty airplane cabin

Mixing ventilation in airplane cabins is driven by overhead supply jets, which may be directed towards each other, interact and merge before entering the passenger area. Although many studies already investigated airplane cabin mixing ventilation, detailed knowledge on the fundamental flow components (i.e. supply jets, interaction zone, merged jet and secondary flows) is rather scarce, but can be useful to obtain new insights into mixing ventilation design optimisation. This paper presents time-averaged 2D particle image velocimetry (PIV) measurements of the flow driven by isothermal opposing plane jets in a reduced-scale water-filled generic airplane cabin. Two configurations of opposing jets, i.e. ceiling jets and lateral jets, are examined with inlet Reynolds numbers ranging from 3,450 to 4,650. The analysis focuses on the mean velocity and Reynolds stresses of the whole flow field and the aforementioned fundamental flow components. Decay rates of the supply jets and decay and growth rates of the merged jet are analysed and the size of the interaction zone is assessed. The supply jet velocity decays very fast due to the interaction with the opposing jet. Within the interaction zone, the turbulence levels are high and turbulence is highly anisotropic. A comparison between the merged jet and a self-similar turbulent plane free jet is presented as well. The measurement data is also valuable for (sub-configuration) computational fluid dynamics (CFD) validation purposes.