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An experimental investigation into the behaviour of bidisperse granular avalanches

Porte, E.M. (2014) An experimental investigation into the behaviour of bidisperse granular avalanches.

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Abstract:Granular flows cover a variety of appearances in a variety of circumstances. Snow avalanches and rock slides are among the natural granular flows and granular flows appear in industry when particles are transported. Even though the size and shape of the material differ among the different types of flows, some phenomena appear in any of these flows. Among these phenomena is the formation of levees. When a flow comprises at least two sizes of particles, size segregation is clearly visible since the large particles accumulate on the side and front of the flow forming the levees. In previous attempts to study the formation of levees, at the University of Cambridge, the reproducibility proved to be critical in setting up experiments. The angle of repose and the alteration of the reservoir size were used in a first attempt to find a setup with reproducible flows. Since this study was insufficient to set up reproducible experiments, a slightly different approach is used in this investigation. Instead of studying the mutual friction between particles (angle of repose) the frictional behaviour on a specific roughness is studied. The main purpose of this investigation is to gain insight in the specific behaviour of the particles available in the laboratory in Cambridge. The basal friction is experimentally determined, according to the method of Pouliquen (1999), in order to be able to predict instabilities. Additional experiments with bidisperse mixtures of the available particles, mimicking a study of Goujon et al. (2007), are used to support the prediction of instabilities and investigate the significance of increased flow mobility on the reproducibility of experiments. The results obtained in this study are relevant for future experiments for the following reasons. Firstly, insight in the flow behaviour based on basal friction saves the researcher time in setting up any bidisperse flow experiments. Secondly, unexpected behaviour was observed in some of the flows, which would be interesting to investigate in greater detail.
Item Type:Internship Report (Master)
University of Cambridge, United Kingdom
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:research, experimental, granular, avalanches, flow
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