Berkeley Fluids Seminar

Monday, January 18, 2016

3110, Etcheverry Hall, 12:00-13:00

Eldad Afik (Weizmann Institute for Science)

A Lagrangian approach to elastic turbulence: Pair dispersion in a dissipative chaotic flow

Pair dispersion is the basis for understanding transport phenomena in flows. Its study at the small scales is of wide interest mainly for two reasons: (i) much of the dynamics relevant for biology and chemistry takes place at the scales dominated by viscosity; (ii) microfluidic devices are playing an important role in research and industrial technologies, often including complex fluids and flows whose dynamics still lack a universal description. We have conducted a microfluidic experiment generating `elastic turbulence’, a flow characterised in the literature as smooth in space and random in time. Using a novel 3d particle tracking method we provide a conclusive experimental evidence that the short time dynamics, which follows a power-law quadratic in time, is dominant over a significant time. This scaling, also known as the ballistic pair separation, is universal, yet it has been overlooked so far in this context. Furthermore, we realized that the leading paradigm in the community, the exponential pair separation prediction, relies on restrictive assumptions which are unlikely to be realizable for tracer particles in bounded natural and experimental scenarios known to us.

E. Afik, Scientific Reports, 5:13584, Sep 2015.
E. Afik and V. Steinberg, ArXiv e-prints 1502.02818 (2015). submitted.

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Acknowledgments

Prof. Graham Fleming (Vice Chancellor for Research, UC Berkeley)

Prof. Eliot Quataert on behalf of The Theoretical Astrophysics Center and the Astronomy Department (UC Berkeley)

Prof. Philip S. Marcus on behalf of the Mechanical Engineering Department (UC Berkeley)

Prof. Michael Manga (Earth and Planetary Science, UC Berkeley)

Prof. Evan Variano (Civil and Environmental Engineering, UC Berkeley)