On the evolution of laminar vortex rings

Abstract

Using Laser Doppler Anemometry (LDA) and Digital Particle Image Velocimetry (DPIV), the physical properties of laminar vortex rings are investigated in the Reynolds-number range 830 ≤ Re ≤ 1650. The measured initial circulations of the vortex rings are found to agree well with corrected versions of the vorticity-flux (slug-flow) model proposed by Didden and Pullin. The DPIV and LDA data show excellent agreement regarding local velocities and vortex-ring circulations. The DPIV data depict the distribution of the vorticity and circulation in the core regions, where the resulting vorticity distributions are found to be self-similar Gaussian profiles. The propagation velocity of the vortex rings is well approximated by an analytical model of Saffman for large core sizes. In the asymptotic limit t → ∞, the trajectories are in excellent agreement with the exact Stokes-dipole solution of Cantwell and Rott.

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Correspondence to A. Weigand or M. Gharib.

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The support of the Office of Naval Research (ONR-URI grant N00014-92-J-1610) under the program management of Dr. Edwin Rood is gratefully acknowledged.

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Weigand, A., Gharib, M. On the evolution of laminar vortex rings. Experiments in Fluids 22, 447 (1997). https://doi.org/10.1007/s003480050071

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Keywords

  • Vorticity
  • Vortex Ring
  • Laser Doppler Anemometry
  • Digital Particle Image Velocimetry
  • Vorticity Distribution