Journal of Fluid Mechanics

Vortex ring bubbles

T. S.  Lundgren a1 and N. N.  Mansour a2
a1 Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, MN 55455, USA
a2 NASA Ames Research Center, Moffett Field, CA 94035, USA

Article author query
lundgren ts   [Google Scholar] 
mansour nn   [Google Scholar] 


Toroidal bubbles with circulation are studied numerically and by means of a physically motivated model equation. Two series of computations are performed by a boundary-integral method. One set shows the starting motion of an initially spherical bubble as a gravitationally driven liquid jet penetrates through the bubble from below causing a toroidal geometry to develop. The jet becomes broader as surface tension increases and fails to penetrate if surface tension is too large. The dimensionless circulation that develops is not very dependent on the surface tension. The second series of computations starts from a toroidal geometry, with circulation determined from the earlier series, and follows the motion of the rising and spreading vortex ring. Some modifications to the boundary-integral formulation were devised to handle the multiply connected geometry. The computations uncovered some unexpected rapid oscillations of the ring radius. These oscillations and the spreading of the ring are explained by the model equation which provides a more general description of vortex ring bubbles than previously available.

(Published Online April 26 2006)
(Received February 27 1990)