Berlin 2005 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 34: Poster

DY 34.94: Poster

Montag, 7. März 2005, 15:30–18:00, Poster TU D

Kolmogorov-Sinai Entropy of Wet Granular Gas — •Axel Fingerle, Vasily Zaburdaev, and Stephan Herminghaus — MPI for Dynamics and Self-Organisation, Bunsenstraße 10, 37073 Göttingen

Wet granular matter is a fast developing and modern branch of Soft Matter Physics. There is a growing number of experimental and numerical works, but the theoretical background is far behind that. We try to treat the wet granulate as a complex dynamical system and to use powerful tools available in this area. Such is for example the Lyapunov spectrum. A positive Lyapunov exponent indicates chaotic behavior. We aim to calculate the Kolmogorov-Sinai (KS) entropy [1], which in our case is the sum of positive Lyapunov exponents. We apply a technique similar to [2] developed for a gas of hard spheres. The main peculiarity of our system is the hysteretic nature of the interaction due to the liquid bridge formed upon each collision of two particles. By averaging binary collisions using the distributions of the N-particle system for velocities and free paths, we obtain an analytic expression for the KS entropy. The distribution functions of the velocities and impact parameter in real granular systems are also discussed.

[1] J.-P. Eckmann and D. Ruelle, Rev. Mod. Phys. 57, 617 (1985).

[2] H. van Beijeren, J.R. Dorfman, H.A. Posch, and Ch. Dellago, Phys. Rev. E 56, 5272 (1997).