Regensburg 2013 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 33: Poster II

DY 33.26: Poster

Donnerstag, 14. März 2013, 17:00–19:00, Poster C

Pattern formation in agitated wet granular matter — Lorenz Butzhammer, Ingo Rehberg, and •Kai Huang — Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany

Pattern formation of a thin layer of vertically agitated wet granular matter is investigated experimentally. Due to the strong cohesion arising from the capillary bridges formed between adjacent particles, agitated wet granular matter exhibits a different scenario compared with cohesionless dry particles. Rotating spirals with three arms, which correspond to the kinks between regions with different colliding phases with the vibrating plate, have been found to be the dominating pattern. This preferred number of arms arise from period tripling of the agitated granular layer, which breaks the symmetry and drives the rotation of spiral arms. From both top view snapshots and the laser profilometry method, the rotation frequency of the spiral arms is characterized with image processing procedures. Both methods reveal a finite rotation frequency at a threshold excitation acceleration, which increases linearly with the peak vibration acceleration with a slope strongly dependent on the vibration frequency. As the vibration frequency decreases, a transition from period tripling to doubling bifurcation is observed, which gives rise to `frozen' spiral arms. The phase diagram of the patterns will be presented and its dependence on various parameters will be discussed.