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Direct numerical simulations of vortex rings at ReΓ = 7500

Published online by Cambridge University Press:  22 May 2007

MICHAEL BERGDORF
Affiliation:
Computational Science & Engineering Laboratory, ETH Zurich, Switzerland
PETROS KOUMOUTSAKOS
Affiliation:
Computational Science & Engineering Laboratory, ETH Zurich, Switzerland
ANTHONY LEONARD
Affiliation:
Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, USA

Abstract

We present direct numerical simulations of the turbulent decay of vortex rings with ReΓ = 7500. We analyse the vortex dynamics during the nonlinear stage of the instability along with the structure of the vortex wake during the turbulent stage. These simulations enable the quantification of vorticity dynamics and their correlation with structures from dye visualization and the observations of circulation decay that have been reported in related experimental works. Movies are available with the online version of the paper.

Type
Papers
Copyright
Copyright © Cambridge University Press 2007

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References

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Bergdorf et al. supplementary movie

Movie 1. Spanwise and streamwise-vorticity crosscuts for ring A (Re_Γ = 7500, size of the Gaussian core: R/2.42, with R being the vortex ring radius). Green and red colours denote positive and negative values, respectively. The left-hand panels display the decay of the translation velocity and circulation of the ring.

Download Bergdorf et al. supplementary movie(Video)
Video 8.9 MB

Bergdorf et al. supplementary movie

Movie 1. Spanwise and streamwise-vorticity crosscuts for ring A (Re_Γ = 7500, size of the Gaussian core: R/2.42, with R being the vortex ring radius). Green and red colours denote positive and negative values, respectively. The left-hand panels display the decay of the translation velocity and circulation of the ring.

Download Bergdorf et al. supplementary movie(Video)
Video 2.8 MB

Bergdorf et al. supplementary movie

Movie 2. Visualization of the vortex lines of ring B (Re_Γ = 7500, size of the Gaussian core: R/3.52, with R being the vortex ring radius) at t = 120.53. Hairpin vortices are apparent in the wake region of the ring.

Download Bergdorf et al. supplementary movie(Video)
Video 5.1 MB

Bergdorf et al. supplementary movie

Movie 2. Visualization of the vortex lines of ring B (Re_Γ = 7500, size of the Gaussian core: R/3.52, with R being the vortex ring radius) at t = 120.53. Hairpin vortices are apparent in the wake region of the ring.

Download Bergdorf et al. supplementary movie(Video)
Video 1.7 MB