Julie Albagnac
David Laupsien
Dominique Anne-Archard
Institut de Mécanique des Fluides de Toulouse
Toulouse, FRANCE
Image by J. Albagnac, D. Laupsien and D. Anne-Archard, IMFT, France
Are vortex rings always the same (from a topological and/or dynamical point of view)? no!
It is now well known that both topology and dynamics of such a vortical structure strongly depend on the generation conditions. The present study focuses on the effect of the fluid nature itself. Indeed, despite the same generation conditions (same piston-cylinder apparatus + same stroke ratio ending to the same relative position to the cylinder exit) and the same inertial effect (same generalized Reynolds number), Figures 1 and 2 highlight the strong influence of the fluid nature on annular vortex behavior. Figure 1 shows obvious different topologies for Newtonian (left) and viscoelastic (right) vortex rings. Figure 2 presents a time evolution of a vortex ring in a Newtonian (top) and viscoelastic (bottom) fluid. Newtonian vortex ring furls, propagates by auto-induced effect and diffuses (increase of its diameter) while propagating. Non-Newtonian viscoelastic vortex ring, instead, first furls and expends as it is propagating away then stops, unfurls and goes back, contracting in the radial direction.
These images may be freely reproduced with the accompanying credit: "Image by J. Albagnac, D. Laupsien and D. Anne-Archard, IMFT, France"
Julie Albagnac
Institut de Mécanique des Fluides de Toulouse
Toulouse, FRANCE
julie.albagnac@imft.fr