Browsing by Author "Lazarus, John Henry"

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    Evaluation parameters for computer aided design of irrigation systems
    (1987) Todes, M A; Lazarus, John Henry
    The research has entailed the formulation and coding of computer models for the design of pressurized irrigation systems. Particular emphasis has been given to the provision of routines for the evaluation of the expected performance from a designed system. Two separate sets of models have been developed, one for the block or in-field system and one for file mainline netWork. The thesis is presented in three seelions asfollows : * Basic theory, in which the general background to the research is covered. * The models, which includes detailed descriptions of both the design models and the computer programs. * Applications, in which several test casesof both sets of models are reported.
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    Hydraulic conveyance of solid capsules
    (1972) Lazarus, John Henry; Kilner, F A
    The hydraulics of two phase flow of capsule - liquid mixtures is investigated experimentally and analytically. The technology of hydraulic transportation of solid capsules in pipes is advanced to the point of practical feasibility by the development and successful operation of experimental equipment in the laboratory. This involves the innovation of aspects of the technology concerned, such as novel booster pumps, injectors and metering equipment. The effect of independent variables such as capsule geometry, density, roughness and concentration as well as mean water velocity and pipe inclination are investigated. It is shown to what extent these variables affect the dependent variables. A theoretical analysis is presented for the determination of dependent variables, such as capsule velocity, excess energy and power dissipation. Flow conditions around static capsules are shown to be amenable to analysis, supplemented by experimentally determined coefficients. Energy dissipation at the inlet and outlet of static concentric and eccentric capsules is investigated for the first time, and empirical formulations are presented, which are simple and consistent with all the data. A correlation involving a pseudo hydraulic mean radius for analysing the friction head loss in eccentric annuli is presented. There have been numerous investigations concerned with friction head losses in concentric annuli. However, the correlation presented in this thesis is simpler than those given by other investigators and incorporates a wide range of experimental data satisfactorily. A theoretical analysis for flow in annuli of varying eccentricity is also presented in a novel manner and agreement with experiment is evidenced. A study is presented of incipient conditions of capsule motion which indicates a form of empirical equation for excess energy dissipation when capsules are moving.
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    The range of applicability of models for the flow of high concentration backfill slurries in pipelines
    (1992) Goosen, Peter Edward; Lazarus, John Henry
    Two models recently developed at the University of Cape Town are intended to model the flow of high concentration backfill slurries. These models are the Cooke model for dense phase flow of cyclone classified tailings and the Paterson model for stabilised flow of high concentration full plant tailings. These two materials (cyclone classified tailings and full plant tailings) form the extremes, in terms of particle size distribution, of tailings materials used as backfill in South African gold mines. The purpose of this dissertation is to investigate the possibility of applying these models in the region, in terms of particle size distribution, between full plant tailings and cyclone classified tailings. Measured pressure gradient data has been collected for materials with particle size distributions ranging from full plant tailings to cyclone classified tailings. The calculated model predictions are then compared with the measured data in order to determine the range of applicability of the models. Three intermediate materials were made up by mixing full plant tailings and cyclone classified tailings in ratios of 1 to 2, 1 to 1 and 2 to 1. These, together with the cyclone classified tailings and two full plant tailings materials, provided the range of materials in terms of particle size distribution. The six materials are characterised in terms of relevant solid and particle properties. Measured pressure gradient data is then presented covering two pipe diameters (40 mm and 80 mm nominal bore), a range of solids concentrations (35% to 52% by volume) and a range of flow velocities (0.5 to 4.5 m/s). The models of Cooke and Paterson are reviewed. Model predictions are then calculated for comparison with the measured data. The range, in terms of solids concentration and particle size distribution, over which each model is in acceptable agreement with the measured data is then presented and reported as the range of applicability of the model.