Session AM - Chaos and Fractals.
ORAL session, Sunday morning, November 23
Saratoga, SMH
The effect of viscoelasticity on fluid mixing is investigated by measuring stretching fields [2] in a time-periodic flow. The stretching fields label the stable and unstable manifolds, and control the mixing dynamics. The presence of polymer in the fluid produces qualitative changes in the stretching fields, compared to their viscosity-matched Newtonian counterparts at the same Reynolds number (Re). Surprisingly, higher concentrations of lines of intense stretching as well as stronger folding of these lines are observed in the viscoelastic fluid. The stable and unstable manifolds cross more frequently, indicating that chaotic mixing will be enhanced. We also compare probability distributions of stretching in the viscoelastic and Newtonian cases. The total stretching over the entire flow is larger in the polymer solution, especially at the highest Re studied. These dynamic enhancements produced by viscoelasticity grow with Re.
[1]Work supported by the NSF-DMR under Grant No. 0072203 to Haverford College.
[2] Voth, G.A., G. Haller and J.P. Gollub, 2002, Phys. Rev. Letters 88, 254501