English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The head-on collision of two vortex rings can produce diverse phenomena: atiara of secondary rings, vortex sheets which flatten and interact iteratively,or the violent disintegration of the rings into a turbulent cloud. The outcomeof the interaction is determined by the nature of the instability affecting twoimpinging vortex rings. Here, we carry out a systematic study to determine thedominant instability as a function of the parameters of the problem. To thisend, we numerically simulate the head on collision of vortex rings withcirculation Reynolds numbers between $1000$ and $3500$ and varying slendernessratios $\Lambda=a/R$ ranging from $\Lambda=0.1$ to $0.35$, with $a$ the coreradius and $R$ the ring radius. By studying the temporal evolution of theenergy and viscous dissipation, we elucidate the role azimuthal instabilitiesplay in determining what the outcomes of the collision are. We then comparethese collisions to the head-on impact of a vortex ring on a free-slip and ano-slip wall. The free-slip wall imposes a mirror symmetry, which impedescertain instabilities and at sufficiently large Reynolds numbers leads to theformation of a half-tiara of vortices. Impact against a no-slip wall results inthe process where a secondary vortex ring is formed after the ejection of theresulting boundary layer. When the Reynolds number is above a certainthreshold, which increases with $\Lambda$, the vortices disintegrate throughazimuthal instabilities, resulting in a turbulent cloud.

Instability and disintegration of vortex rings during head-on collisions and wall interactions