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The effect of orifice edge geometry on the discharge of non-Newtonian liquids from a tank
Author(s)
Mampouya, Ninelle Samia
Date Issued
2026
Type
master thesis
Publisher
Cape Peninsula University of Technology
Abstract
The discharge coefficient can be challenging to predict. This is due to many factors, including rheological characteristics of the flow liquid and orifice geometry. Indeed, predicting the orifice discharge can be difficult but can be accomplished experimentally. Flow rates were measured for square bevel back cut angle, chamfer-, quadrant- and short square-edged orifices from the bottom of the tank. The discharge coefficient was determined and related to the Reynolds number for water, different concentrations of glycerine and CMC solutions, and bentonite and kaolin suspensions. The calibrated average Cd values for: square bevel back cut angle edge was 0.6; chamfer-edged 0.88, quadrant-edged 0.84, and short square-edged 0.58 in the turbulent flow regions. The highest Re values for square-edged orifices (short square-edged and square-edged orifice with bevel back cut angle) were 14000 to 23000 whereas for chamfer and quadrant the Re was 14000 to 25000 for all water tests. The rheological parameters of the slurrie liquids were obtained and utilised in the determination of Re values for the different concentrations of the liquids discharged. The Re values for liquids tested; highly viscous Newtonian, Power Law, Herschel Bulkley and Bingham, were 18, 66, 300, and 340. It was determined that Cd as a function of the Re in the laminar flows were 0.00823𝑅𝑒0.39, 0.0787𝑅𝑒0.40 , 0.0904𝑅𝑒0.39 , and 0.0923𝑅𝑒0.38 for highly viscous Newtonian liquids and 0.0009 Re0.77 , 0.0128 Re0.71, 0.0276 Re 0.57 and 0.0188Re0.63 for square bevel back cut angle, short square, chamfer- and quadrant-edged orifices, respectively. The results obtained for all the orifice geometry explored showed that the Cd increased as the Re increased, but from Re of 1000, the Cd increased significantly before decreasing and becoming constant. This study adds to the empirical data that already exists in the discharge of non-Newtonian liquids from tanks for different edge geometry and confirms that the efficiency of flow in discharging operations is dependent on the edge effect of the orifice flow meter. This will be useful in engineering designs and processes.
Additional information
Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2026
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Mampouya, NS_214194582 (1).pdf
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