zu Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen

Abstract

In this thesis, the stability and the dynamics of wet granular materials under shear are explored. Inspired by the Green’s function approach, a theoretical model for yielding of a wet pile on an inclined plane is presented. It enables one to predict the critical inclination angle at which the pile fluidizes. The theory is based on the balance of forces acting on each particle at the vicinity of the fluidization and has two major consequences. First, the theory shows that yielding of a wet pile does depend on the gravitational acceleration, whereas a dry pile fluidizes for any arbitrary small non-zero gravitational acceleration when the inclination angle exceeds a certain value depending on the geometry. Second, the theory shows that a wet pile yields in the bottom layer where the pile touches a non-slip boundary. There is excellent agreement between the theory and extensive MD-type simulations where one calculates forces between each individual pair of particles. The dynamics of driven wet particles is studied in two different ways. First, we explore dynamics of wet particles in a channel driven by gravity. Second, we apply a spatially sinusoidal driving force. In both cases we find discontinuous hysteretic solid-fluid transitions, i.e. solid-to-fluid and fluid-to-solid transitions and encountered at different forcing of the system. We calculate phase diagrams separating solid and fluid states and thresholds for the solid-to-fluid and the fluid-to-solid transitions. Beside that, we study the spatial and temporal distributions of drift velocity, granular temperature, area fraction, stress tensor, interparticle force etc. i Kurzzusammenfassung In dieser Arbeit wird die Stabilität und Dynamik feuchter granularer Medien unter der Einwirkung von Scherkräften untersucht. In Anlehung an den Greenschen Formalismums wir