Can the turbulent-nonturbulent interface be associated with a transport barrier?
ORAL
Abstract
In this study, we explore the interface between turbulent and non-turbulent regions in jet flows. We employ simultaneous Particle Image Velocimetry (PIV) and Laser-Induced Fluorescence (LIF) measurements to capture the interface dynamics. Our primary objective is to track the mechanisms of large-scale engulfments and small-scale nibblings that shape the interface. This is achieved using a traversing camera system that moves along with the jet's streamwise evolution, covering a range from 10D to 60D downstream of the nozzle. We quantify the diffusive transport of linear momentum and the advective transport of passive particles. The small-scale nibbling structures at the interface, which were previously only visible in scalar LIF images, are now brought to light by diffusive transport barriers. Our findings reveal that the interface does not act as a barrier to passive particles. However, it shows a strong correlation with the diffusive transport of momentum. These significant insights contribute to our understanding of the mixing process between turbulent and non-turbulent flows.
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Publication: Westerweel, J., Fukushima, C., Pedersen, J. M. & Hunt, J. C. R. 2005 Mechanics of the turbulent/nonturbulent interface of a jet. Phys. Rev. Lett. 95, 174501.<br><br>Eisma, J., Westerweel, J. & van de Water, W. 2021 Do coherent structures organize scalar mixing in a turbulent boundary layer? J. Fluid Mech. 929.<br><br>Haller, G. 2023 Transport Barriers and Coherent Structures in Flow Data. Cambridge University Press.<br><br>Haller, G., Katsanoulis, S., Holzner, M., Frohnapfel, B. & Gatti, D. 2020 Objective barriers to the transport of dynamically active vector fields. J. FluidMech. 905.
