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Título: Flow of liquid-solid mixtures down inclined chutes
Autores: Malekzadeh, Mohammad Jafar e
Fecha: 1993
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Mechanical.
Descripción: The ability to model and predict debris flows, mudflows and sediment transport is currently hindered by a poor understanding of the fundamental aspects of solid-liquid flows. The present work attempts to further our knowledge through experimental studies of flows of highly concentrated, solid-liquid suspensions down inclines.
Preliminary experiments, measuring grain velocities for two sizes of sand and two surface inclination angles were performed in a tank of stationary water. When sub-aqueous debris flows were developed by releasing Ottawa sand from a hopper onto a rough bed, various phenomena were observed: nonuniform flows, static dead-flow regions, uniform flows and roll waves. Uniform flow was possible for a range of bed inclination angles larger than the angle of internal friction of the sand. The flow became unstable and roll waves developed at higher slopes and lower depths of flow.
Following these exploratory experiments, more detailed, controlled experiments were carried out using a non-intrusive method of velocimetry. The flowing mixture was made up of glass particles and a liquid having the same index of refraction. By passing planes of laser light through the free surface of flows at various distances from the glass sidewalls of the channel and recording video images, it was possible to identify the particles and determine the three-dimensional velocity and concentration profiles. Experiments were performed for various bed inclination angles.
Further experiments were performed with the aim of correlating the data in the form of a generalized Vedernikov formula for debris flows that relates velocity, flow depth, concentration and bed inclination angle. Various liquid-solid mixtures were used, and the variations of the average velocity with depth and sloped inclination angle were studied for different discharge-rates and solids fractions. Very different behavior was observed for the macro-viscous and transitional regimes, as defined by Bagnold. Such correlation was obtained for the macro-viscous regime; the nondimensional parameters that appear in the model involve the particle diameter, density and concentration and fluid viscosity and density. The model was compared with about 200 sets of data and good agreement was obtained.
Idioma: en