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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Institut für ComputerphysikStart date: 2004End date: 2009Author: search.filters.author.Fonseca Fonseca, Frank Rodolfo

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    Sedimentation of oblate ellipsoids
    (2004) Fonseca Fonseca, Frank Rodolfo; Herrmann, Hans (Prof. Dr.)
    The tree leaves flutter to the ground in autumn, exhibiting a complex motion and refusing to follow the shortest path. The way in which objects fall to the ground has been studied since antiquity. Objects were thought to return to their natural'' places by the ancient Greeks. During Renaissance, Galileo Galilei dropped two metal balls from the leaning Tower of Pisa and showed that they fall at the same rate despite having different masses. Newton showed, that the bodies fall on earth driven by a constant acceleration and he also observed the complex motion of objects falling in both air and water. But despite gravity's undeniable attraction, not all falling objects travel downwards in straight trajectories. The consideration of fluid surrounding the objects, introduces a very complicated and nonlinear interaction between the object and the fluid. The first pioneering effort was made by Maxwell, who was the first to consider the fluid-object interaction and proposed a odel for a falling paper strip. In the beginning, theoreticians made few assumptions a) constrained motion in 2-d was taken into account b) vortices in fluid were ignored c) considered a fluid with zero viscosity Based on these assumptions, Gustav Kirchhof showed that the problem reduces to a simplified set of equations that can be solved for simple particle geometries. This method also appears in the Horace lamb's classic treatise on hydrodynamics, (Lamb). A deeper understanding of the motion of falling objects in a fluid is of great technical importance, and has been investigated in a variety of contexts, including meteorology (Kajikawa), aircraft stability (Mises), power generation (Lugt), chemical engineering (Marchildon), and also in the study of stability of submarines and the centrifugation of cells by biological techniques.