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Rockwell Lecture Series — Flow Behavior of Aspherical Particles
Science and Engineering Complex, Room 204

Speaker: Jennifer Sinclair Curtis, Distinguished Professor, Department of Chemical Engineering, The University of California, Davis

Most industrial and geophysical particulate flows involve aspherical particles, and particle shape has been observed to significantly affect flow behavior. For example, NASA is interested in simulating the descent of a spacecraft approaching the Lunar or Martian surface along a specified trajectory which involves gas jet-soil particle surface interaction through the landing and engine shutdown. In order to predict the erosion of the Lunar or Martian soil (regolith), a description for the flow behavior for the regolith is needed. For Lunar and Martian soils, the particles are highly aspherical and irregular, and these properties of the soil greatly affect the rate of crater growth and the trajectories of the liberated particles. This presentation will discuss the development of closure models for a particle-phase continuum treatment via the discrete element method that incorporates features of particle asphericity - from simple particle shapes to ones that are more irregular. For highly irregular particles, mechanical interlocking, due to particle asperities or the bulk particle shape, can lead to orders of magnitude change in flowability. In most of our studies, aspherical grains are described using linked and overlapping spheres. With this linked approach, particle flexibility can also be described with a bonded particle model employing virtual bonds between constituent spheres. Such virtual bonds incorporate normal and shear forces, as well as bending and torsional moments, and allow for particle breakage.

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