Masters Degrees (Civil Engineering)

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Browsing Masters Degrees (Civil Engineering) by browse.metadata.advisor "Basson, Gerrit"

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    EVALUATION OF VORTEX SETTLING BASIN (VSB) PERFORMANCE IN GRIT REMOVAL FROM SEWER LINES
    (Stellenbosch : Stellenbosch University, 2022-12) Nguza, Tanduxolo Clive; Basson, Gerrit; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: This study was motivated by the prevalence of sewer spillages and sediment deposition in sewers. The objective of this study was to validate the CFD (Computer Fluid Dynamics) modelling of the sewer VSB (Vortex Settling Basin) design by Basson (2020) referred to as VSB 1 and to investigate two modified VSB design configurations (referred to as VSB 2 and VSB 3) including hydraulic aspects of the VSBs that could not be modelled in CFD. The flow patterns and flow velocity contours in the VSB cylinder were observed in VSB 1 and 3 as predominantly radial flow patterns; and axial flow patterns in the CFD VSB and VSB 2. The observed VSB cylinder flow velocities decreased with increasing depth into the VSB cylinder. The observed head losses increased with an increase in flow rate for all three VSB models. The sediment entered the VSB cylinder in the flow as bed load; and settled into the VSB cylinder against the outer sides for the CFD modelled VSB, for VSB 1 and 2. Sediment settled along the centreline of the dominant radial flow pattern in the VSB 2. The highest sediment trapping efficiency of 98.76% was observed for the VSB 1 for Fr=0.575 at PWWF. The observed CFD modelling sediment trapping efficiency of 100% for Fr=0.696 at PWWF was higher than sediment trapping efficiencies of 94.71% and 97.22% for VSB 1 and 2 respectively. The observed maximum sediment storage was 0.093m3 at Fr=0.575 for PWWF in VSB 2. The CFD modelling sediment storage capacity of 6.95m3 at Fr=0.696 for PWWF was lower than the observed VSB model sediment storage capacities of 10.2m3 and 10.4m3 for VSB 1 and 2 respectively at prototype sediment storage volumes. The VSB’s floating debris conveyance efficiency of plastic bottles, plastic bags filled with garbage, and rags, posed no risk of obstructing the flow or causing blockages, even at high concentrations. The VSB 1 and 2 conveyed a log length of 0.58m and 0.79m respectively. Bernoulli’s equation was applied to calculate the water levels through the VSB bypass, and the design was effective in conveying flow in the event of a blockage. The CFD modelling of the VSB by Basson (2020) was partially validated due to practical constraints in sediment sizes, densities and grading that resulted in differences in sediment trapping efficiency and sediment storage capacity. The physical modelling of the VSBs successfully characterised their hydraulic behaviour in terms of flow patterns, water levels, flow velocities, sediment, floating debris and the VSB bypass hydraulic performance in the event of a blockage. The results from this study could be used as guidelines in sewer VSB design considerations.
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    Quantifying river losses on the Sundays River between Darlington Dam and Korhaans Drift Weir through hydrodynamic modelling
    (Stellenbosch : Stellenbosch University, 2022-11) Nel, Aldré; Basson, Gerrit; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: The Sundays River, downstream of Darlington Dam in the Eastern Cape of South Africa, forms part of an inter-basin transfer scheme operated by the Lower Sundays River Water User Association (LSRWUA) to supply bulk water to the Sundays River Valley Municipality (SRVM), the Nelson Mandela Bay Metro (NMBM) as well as the predominantly citrus irrigators in the Sundays River Valley. An increase in agricultural development, population growth and persistent drought necessitates an increase in efficiency in managing water resources. This study aimed to quantify transfer losses over the 2021/2022 water year along the Sundays River between Darlington Dam and Korhaans Drift Weir where raw water is diverted into a formal canal scheme for supply purposes.