2015 APS/DFD Milton van Dyke Award winning poster presented at the DFD Gallery of Fluid Motion:
Variable Density Vortex Ring Dynamics in Sharply Stratified Ambient Fluids (P0050)
Vortex rings are commonly found in nature when a flow is impulsively started from a round orifice, for instance dolphins are known to create and play with vortex rings by blowing air when underwater. They are also observed in the atmosphere, for instance, above volcanoes when hot air, full of ash from the crater is suddenly released. The dynamics of settling vortex rings in a stratified environments such the ocean and the atmosphere is therefore of great interest, particularly when addressing mixing of the stratified layers that constitute the stratification. In the case of a homogeneous ambient, vortex rings are known to have a very stable structure and the mechanisms leading to breakup and mixing have yet to be to be understood. Here we considered a vortex ring with a heavy core (green), settling in a fluid whose density increases with depth (stratified flow). The above images show the interplay between entrainment due to the rotating motion of the vortex and the density difference between the core and the ambient that is being wrapped during the entrainment process. This mechanism leads to an instability, also known as Rayleigh-Taylor that tears the vortex into braids, leading to a jelly fish pattern.
APS Physics (American Physical Society)
Gallery of Fluid Motion
Presented by the APS Division of Fluid Dynamics
http://gfm.aps.org/meetings/dfd-2015/55f8d658b8ac311c710000bb
68th Annual Meeting of the APS Division of Fluid Dynamics (November 22, 2015 — November 24, 2015)
AUTHORS
DOI: http://dx.doi.org/10.1103/APS.DFD.2015.GFM.P0050