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

Aakash Mishra, Alain Pumir, and Rodolfo Ostilla-Mónico
Phys. Rev. Fluids 6, 104702 – Published 27 October 2021

Abstract

The head-on collision of two vortex rings can produce diverse phenomena: A tiara of secondary rings, vortex sheets which flatten and interact iteratively, or the violent disintegration of the rings into a turbulent cloud. The outcome of the interaction is determined by the nature of the instability affecting two impinging vortex rings. Here we carry out a systematic study to determine the dominant instability as a function of the parameters of the problem. To this end, we numerically simulate the head-on collision of vortex rings with circulation Reynolds numbers between 1000 and 3500 and varying slenderness ratios Λ=a/R ranging from Λ=0.1 to 0.35, with a the core radius and R the ring radius. By studying the temporal evolution of the energy and viscous dissipation, we elucidate the role azimuthal instabilities play in determining what the outcomes of the collision are. We then compare these collisions to the head-on impact of a vortex ring on a free-slip and a no-slip wall. The free-slip wall imposes a mirror symmetry, which impedes certain instabilities and at sufficiently large Reynolds numbers leads to the formation of a half-tiara of vortices. Impact against a no-slip wall results in the process where a secondary vortex ring is formed after the ejection of the resulting boundary layer. When the Reynolds number is above a certain threshold, which increases with Λ, the vortices disintegrate through azimuthal instabilities, resulting in a turbulent cloud.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
20 More
  • Received 22 July 2021
  • Accepted 13 October 2021

DOI:https://doi.org/10.1103/PhysRevFluids.6.104702

©2021 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Aakash Mishra1, Alain Pumir2,3, and Rodolfo Ostilla-Mónico1

  • 1Department of Mechanical Engineering, University of Houston, Houston, Texas 77040, USA
  • 2Université de Lyon, ENS de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, 69342 Lyon, France
  • 3Max Planck Institute for Dynamics and Self-Organization, 37077 Göttingen, Germany

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 6, Iss. 10 — October 2021

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review Fluids

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×