Regensburg 2010 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Granular Matter/ Contact Dynamics II

DY 13.5: Vortrag

Mittwoch, 24. März 2010, 10:45–11:00, H47

Fluidization of wet granulates under shear — Seyed H. Ebrahimnazhad Rahbari, Juergen Vollmer, Stephan Herminghaus, and •Martin Brinkmann — MPI for Dynamics and Self-Organization, 37073 Göttingen

It is a common experience that small amounts of a wetting liquid like water render sand a stiff and moldable material. The cohesive forces between the sand grains are caused by capillary bridges at the points of contact. Due to the finite strength of these bridges wet sand undergoes a transition from a solid to a fluidized state under an externally applied shear force. The transition between these two dynamic states is studied in a MD-type simulation of a two-dimensional assembly of bidisperse frictionless disks under the action of a cosine force profile. In addition to soft core repulsion the disks interact through a hysteretic and short ranged attractive force modeling the effect of the capillary bridges. In this model the transition between the fluidized and the solid state is discontinuous and hysteretic. As the system size is increased the opening of the hysteresis loop becomes smaller. The parameter dependence of the critical force for solidification is modeled by combining theoretical predictions based on free volume arguments with a detailed numerical exploration of the transition.