Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Modern Computational Fluid Dynamics modelling (CFD) are becoming common design and analysis tools in the engineering field. Nowadays, project designs involve the use of CFD techniques along with physical scale modelling to analyse the complex rapidly varied and turbulent flows which would not be easily analysed by physical modelling. In particular, the consideration and/or use of CFD modelling in the Hydraulic Engineering field remains on the increase. Apart from being used for comparison with other design techniques, CFD may in future become a standalone modelling technique in hydraulic structures design. This research aims to use CFD models to validate the simulation of the flow over two ogee dam spillways which are installed in the Hydraulic Laboratory of Stellenbosch University. To achieve this simulation of the flow which involves an interaction between water and air, the flow behaviour has been mapped by the Volume of Fluid (VOF) and the realisable "𝑘−𝜀" turbulence numerical models. The Volume of Fluid (VOF) and the realisable "𝑘−𝜀" models simulate the free surface of two-phase flow and the flow turbulence, respectively. Firstly, the study embarks with details on the actual design approaches of a typical ogee dam spillway. It subsequently presents the geometry and dimensions of the physical models, the testing procedure and the experimental test results achieved from this modelling exercise. For CFD modelling, a commercially available Computational Fluid Dynamics (CFD) package, Ansys-Fluent, was used. To model the physical model, the use of Reynolds-averaged Navier-Stokes equations in combination with the realisable k-ε eddy-viscosity closure model was adopted. The process of CFD model development and the underlying theory of it are discussed in this thesis. Different test scenarios including steady and fully hydrodynamic states simulation for two and three-dimensional geometries were considered in this simulation to achieve the most accurate results. In order to determine the required mesh size, the mesh sensitivity tests were conducted on the 2 dimensional and 3 dimensional models. Finally, the pressure readings and water levels produced by numerical models are discussed through a validation process by comparing the CFD model results with the results obtained from physical models. The outcome proved that CFD models are able to map the behaviour of both flow phases since they exhibited a close correlation to those achieved in the physical models. Even though some slight differences in values were revealed, the graphical trend remains reasonably similar for all test results. / AFRIKAANSE OPSOMMING: Moderne gerekenariseerde vloeidinamika numeriese modelle (CFD) word deesdae dikwels deur ingenieurs gebruik. Projekontwerpe sluit tans die gebruik van CFD tegnieke asook fisiese skaalmodellering in om komplekse, vinnig-veranderede en turbulente vloei te ontleed. Hierdie tipe vloeie is moeilik om met fisiese modellering te ontleed. Die gebruik van CFD numeriese modelle in hidrouliese ingenieurswese is besig om toe te neem, Die bevindinge van CFD modelering word tans vergelyk met die bevindinge van ander ontwerptegnieke, maar in die toekoms mag dit moontlik gebruik word as die enigste modelleringstegniek in hidrouliese struktuurontwerp. Die doel met hierdie navorsing is om CFD modelering te gebruik om die vloei oor twee ogee-vormige afvoergeute wat in die hidrouliese labrotorium van die Universiteit van Stellenbosch ge-installeer is, te ondersoek. Ten einde hierdie vloei, wat die interaksie tussen water en lug insluit, te simuleer, is die vloeigedrag deur ”volume van vloeistof” (VOF) en die "𝑘−𝜀" turbulensie numeriese modules, gemodeleer. Die VOF en "𝑘−𝜀" numeriese modules simuleer onderskeidelik die vry oppervlakte vloei van die twee-fase vloei en turbulente vloei. Die ontwerp van ’n tipiese ”ogee”-tipe dam oorloop word bespreek, gevolg deur die beskrywing van die geometrie van die fisiese modelle, die toetsprosedure en die eksperimentele toetsresultate. Vir die CFD modellering is die CFD pakket, Ansys-Fluent, gebruik. Vir die simulering van die fisiese model is die Reynolds-gemiddeld Navier-Stokes vergelykings tesame met die k-ε eddy-viskositeit geslote module gebruik. Die proses van CFD ontwikkeling en die onderliggende teorie daarvan word bespreek. Verskillende toets-scenario’s wat 2D en 3D simulasies insluit, uitgevoer. Ten einde die toepaslike berekeningsrooster grootte vir die numeriese model te verkry, is sensitiewiteitstoetse uitgevoer op die twee- en drie-dimensionele numeriese modelle. Laastens is die CFD numeries gesimuleerde drukke en die watervlakke met die van die fisiese modelle vergelyk om die akkuraatheid van die CFD resultate te verkry. Die uitkomstes het getoon dat CFD modelle gebruik kan word om die gedrag van albei vloei fases te simuleer aangesien dit goed vergelyk het met die uitkomstes van die fisiese modellering. Daar was wel klein verskille in die druk waardes, maar die tendense in drukverspreiding was ooreenstemmend.

Meshless Local Petrov-Galerkin method based on Rankine source solution (MLPG_R) has been developed by Dr. Qingwei Ma (Ma, 2005b) and has been used to simulate the nonlinear water wave problems in 2D cases without the occurrence of the breaking waves. In this thesis, MLPG_R method has been further developed to numerically simulate breaking waves and the interactions between breaking waves and structures in 2D and 3D cases. The main difference between this meshless method and conventional mesh-based methods is that the governing equations are solved in terms of particle interaction models, without the need of computational meshes. Therefore, this method avoids the time-consuming mesh generating and updating procedures which may be necessary and may need to be frequently performed in the mesh-based methods. Furthermore, in order to simulate the breaking waves well, several novel numerical techniques are developed and adopted. The numerical technique for implementing the solid boundary condition for meshless methods is proposed, which is more robust than others in terms of accuracy and efficiency. A technique for meshless interpolation (SFDI scheme) is adopted, which is as accurate as the more costly moving least square (MLS) method generally but requires much less computational time than the latter. A newly developed technique for identifying the free surface particles is presented, which is much more robust than those existing in literature. A semi-analytical method for numerical evaluation of integrals in a local domain and on its surface is presented to form the matrix for the algebraic equations, which makes it possible to modelling the 3D problems on personal computers. The newly extended MLPG_R method is applied to simulate the waves generated by a wave maker and their propagations, overturning and breaking over flat and sloped seabed. And it is also applied to 2D and 3D dam breaking cases and violent sloshing cases. The convergence properties of this method in different cases are investigated. Some of the results have been validated by experimental data and numerical results obtained by other methods. Satisfactory agreements are achieved. Based on these numerical investigations, a number of conclusions have been made, including that the breaking waves can cause large pressure with several peaks when they impact on structures; the behaviour of pressure strongly depends on the relative locations of structures to the breaking point of breaking waves. Breaking waves in a sloshing container can also cause more than one peaks, which is correlated with the direction change of water motion within the container. These investigations can give us better understanding of the impact pressure, breaking wave and interactions between breaking wave and structures.

Diffuse sources of sediment may have important implications for flood risk management (FRM), especially as catchment sediment yields are predicted to increase in future. UK legislation requires FRM to work with natural processes wherever possible, including accounting for sediments. However, the importance of wash-material load to FRM has been under researched and both a robust evidence-base and practical sediment models are needed to identify, prioritise and justify sediment-related catchment management. Research addressing these issues was centred on the River Tone, a sub-catchment of the Parrett, in which features excessive inputs of sediment in its upper catchment combined with high potential for deposition in its lower reaches. Links between sediment sources, water and sediment runoff, and downstream sediment sinks were established and the research examined the role played by sediment, especially wash-material load, within the fluvial system. The greatest sediment-related threats to the functioning of this lowland river stem from either: a protracted, major reduction in wash-material load; or a significant increase in bed-material load. Imbalance in the Tone fluvial-sediment system may not significantly affect flood risk directly, but has implications for FRM operations, maintenance and monitoring. Impacts on land quality result from soil loss. For example, ~2.5 million tonnes of soil has been eroded from the Parrett catchment since WWII. Water quality issues include delivery of phosphate and other pollutants into the river, and potentially more frequent dredging that remobilises contaminants. The thesis defines the key sediment-related components of sustainable, integrated catchment management and provides an improved evidence-base upon which to engage stakeholders. It tests and benchmarks sediment assessment tools including the Sediment Impact Assessment Model (SIAM). An approach to catchment-scale sediment assessment for lowland rivers is recommended, which involves a nested-approach using routinely collected and project-specific field data, stream power screening and SIAM.

A novel configuration of vertical downflow constructed wetland was used to treat up to 75 m3 per day of sugar beet processing wastewaters. The 403 m2, two-stage pilot system included planted and unplanted cells of a variety of sand depths (0.15 - 0.4 m) and sand particle size distributions (d10 = 0.07 - 1.2 mm). The hydraulic regime of each bed was also manipulated. Typical beet processing wastewaters contained 235 mg BOD l-1, 45 mg NH4-N l-1, 0.03 mg PO4-P l-1, 16 mg TSS l-1, at pH 8.2 and 29 °C. Overall performance of the pilot system, with respect to BOD, NH4-N, and TSS removal, was similar to, or better than, comparable two-stage vertical flow wetland systems. In vertical flow systems, influent BOD concentrations >600 mg l-1 were coincident with reduced rates of nitrification. Mean BOD removal rate in the pilot system was 38.8 g BOD m-2 d-1, with a mean loading rate of 40.4 g BOD m-2 d-1. The first-order reaction rate for BOD removal was calculated to be 0.369 m d-1 over the whole system. High rates of oxygen transfer and efficient removal of organic solids were seen as the most important factors enhancing BOD removal. Mean NH4-N removal rate in the pilot system was 5.6 g NH4-N m-2 d-1, with a mean loading rate of 7.3 g NH4-N m-2 d-1. The temperature corrected first-order reaction rate for NH4-N removal was calculated to be 0.23 m d-1 over the whole system. Nitrification accounted for between 85% and 99% of TKN removal. Evidence is presented which supports the hypothesis that cycles of assimilation/adsorption and release of NH4-N may play an important role in nitrification mechanisms in vertical flow constructed wetlands. In bed 1, removal of BOD and NH4-N were at their most efficient in the vegetated cell with the deepest (0.21 m), coarsest (d10 = 1.2 mm) sand layer. TSS removal was highest in an unvegetated cell with shallower (0.15 m), finer (d10 = 0.56 mm) sand. In bed 2, removal of BOD, NH4-N, and TSS were all at there most efficient in the vegetated cell with the deepest (0.4 m), coarsest (d10 = 0.1 mm) sand layer. Low influent phosphate concentrations may have limited nitrification rates in the pilot system. The surface area available for biofilm attachment, and media depth, both provided good models of NH4-N removal, whilst cell surface area was more important in solids removal. Media hydraulic conductivity at the beginning of the dosing cycle was five times higher in vegetated cells than in unvegetated cells. After 12 hours of dosing, media particle size distribution became the dominant factor determining media hydraulic conductivity. High influent BOD concentration was more closely associated with cell logging than hydraulic loading, TSS concentration, or BOD or TSS loading. Growth of one provenance of Phragmites australis was limited by phosphate availability. However, populations of nitrifying bacteria were highest in samples of media and roots taken from plots containing this provenance. No correlation was demonstrated between nitrifying bacteria population and root biomass. Water stress caused by high media hydraulic conductivity and inadequate influent distribution resulted in sub-optimal conditions for reed growth in bed 1. The study concludes with details of the proposed design of a full scale system designed to treat up to 1000 m3 d-1 of beet processing effluents.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2017 / The development of methods which are better able to predict the effect of large scale emergent roughness elements on the flow characteristics requires a better understanding of the drag coefficient under conditions likely to occur in the field. A laboratory investigation was carried out with newly developed equipment to quantify the drag force on various shaped cylinders, as well as the drag on an individual cylinder surrounded by an array of cylinders. The relationship between the drag coefficient and cylinder Reynolds number for a single circular cylinder was found to be of similar form but larger in magnitude than the established relationship for an infinitely long cylinder; the relationship departs from the infinite cylinder relationship for low cylinder Reynolds numbers. Contrary to previous research, the results for the multiple cylinder investigation did not reveal a clear relationship between the cylinder density and drag coefficient. Equations were developed and verified with existing laboratory data. These should be improved and extended by further research for field use. / MT2017

A pilot scale study of the dynamics of the break-up of curved liquid jets is presented. This work is motivated by an industrial process called prilling which is used in the manufacture of pellets. In this process a sieve-like cylindrical can spins rapidly on its central vertical axis. Molten liquid is pumped into the top of the can and flows from the holes in the form of curved liquid jets. Experiments are described which were carried out on a pilot scale rig. Some differences between the break-up modes observed in this study and previous work using a small laboratory scale rig are discussed. Previous theories describing break-up mechanisms of curved liquid jets were extended to include viscosity and gravity. Break-up lengths and drop sizes were obtained theoretically and compared with experimental results. Experiments were carried out using insonification, a process where sound waves are fired at the jet to control satellite drop formation. Three different frequencies of wave were used, 10, 100 and 200 Hz at four different rotation rates. It was observed that insonification was successful at eliminating satellite drops at low rotation rates and when frequencies of 100 or 200 Hz were used. Insonification was included in the theory. The theory predicted that insonification eliminated satellite drops for a large range of frequencies in the experimental regimes for sufficiently large acoustic volume. The theory also predicted that satellite drops were eliminated in parameter regimes outside the experimental regimes. The trajectory of the jet was allowed to become unsteady, in a rotating frame of reference. Simulations were carried out in inviscid and viscous regimes.

Phosphorus is one of the most important nutrients, which significantly influences the extraordinary growth of algae. Consequently, this leads to eutrophication of aquatic life. Eutrophication of water bodies due to phosphorus coming from wastewater is a serious problem. Therefore, additional work on many wastewater treatment plants is required in order to meet the required standards, particularly in relation to nutrient removal. Recently, continuous upflow filters CoUFs have been found to be a suitable technology for upgrading or expanding the wastewater treatment plants. On the other hand, investigation of different sorts of low-cost materials has been shown to be an attractive solution as phosphate sorbent materials PSMs, which represents a sustainable solution based on economical and environmental factors. This PhD study seeks to determine materials that are capable of removing phosphate from wastewater at tertiary treatment within a short time when they are packed in CoUFs. In order to select the suitable PSMs a comprehensive study has been conducted to describe their physical and chemical characteristics, affinity to retain orthophosphate (phosphate) and bonding time. This work was carried out through subjecting these materials to examinations such as scanning electron microscopy SEM and X-ray fluorescence analysis XRF to identify their characteristics, and conducting a batch test and constructing a lab-scale upflow filter to investigate the filter materials’ affinity to phosphate. Based on the phosphate removal efficiency and characteristics of selected materials an innovative and sustainable coating technology has been proposed to introduce a new type of filter material capable of removing phosphate effectively. Filtration materials coated with metallic oxides are presented as a good method for phosphate sorption. However, most of the researchers utilize chemicals as a source of metallic oxides and heating process to set the chemicals over the filtration materials. In this study, the method of creating new filter media involves coating a solid material via waste materials containing metallic oxides; the ordinary Portland cement (OPC) was utilized as a binder for the mixture materials. Water is the factor which is responsible for activating the OPC. All factors have been subjected to an optimization process. The results revealed that the limestone particles coated by furnace bottom ash (FBA) indicated a high capacity for phosphate sorption and possibility of regenerating their efficiency. In conclusion, this study introduces a new approach regarding creating and developing the characteristics of the filter media which fit the sustainability requirements.

Merchant marine officers have multiple specific duties and responsibilities to perform. Moreover, there is a need for a well-trained workforce to operate modern ships. In this era, the development of technological tools to assist in the delivery of the syllabus, and develop the marine cadets’ practical knowledge during training on-board is highly required. This study reviewed literature concerning Maritime Education and Training, in addition to personalised learning and online mobile learning. The research proposes the creation, assessment and validation of generic Interactive Maritime Education and Training (iMET) application, that is utilising Near Field Communication (NFC) technology, as a personalised interactive self-study mobile tool, with respect to cadets’ different learning preferences. The main aim of this research is to test the hypothesis that, the iMET tool has a direct positive impact on the Maritime Education and Training process on-board the training ship, and it is an accepted technology, hence will be actually used by the cadets on-board. In order to evaluate the research hypothesis, the researcher developed a generic prototype of iMET handheld application, as a proof of concept. Moreover, the researcher adapted a Technology Acceptance Model (TAM), from the existing TAM models, that had been used in previous research, in order to asses cadets’ acceptance to the proposed iMET application. Data collection in this research was based on triangulation, in order to measure the perception and expectations of the different maritime stakeholders affiliated with the iMET tool implementation. Accordingly, a questionnaire survey, a semi-structured interview and a quiz for cadets’ assessment was conducted. Data collection and surveys were conducted twice, in the pre iMET intervention development phase and post iMET intervention validation phase, in order to support justifying and validating the proposed technological tool in the current study. This research philosophy is a pragmatic research approach that applied a mixed methodology, to measure the cadets’ technology acceptance of iMET and their behavioural intention towards its actual usage. Finally, the research will discuss in detail the outcomes and finding.

This thesis reports on research work aimed at improving methods for predicting the fluid loading on fixed- and compliant offshore structures in waves. In focusing on slender member fluid-interaction models, the limitations and uncertainties associated with the widely-used Morison equation are examined. An improved empirical model has been developed and tested extensively alongside the Morison equation, using real experimental data. This improved model gives a better representation of the frequency dependency of the fluid-loading coefficients: this is particularly important in compliant motion conditions where the so-called relative velocity concept still needs to be verified under carefully controlled experimental conditions. The model is based entirely on the use of linear wave kinematics, thus simplifying calibration in irregular conditions and avoiding the need for a consistent non-linear wave theory (which is still lacking). By appropriate adaptation the improved model can also be extended to include amplitude dependency in the loading coefficients. The Improved Model has been developed through an analysis of experimental data. For this purpose the experimental work was focused on a horizontal cylinder, at model scale, located in a wave tank at the University of Sussex. The fluid loading experienced by a fixed cylinder, in both regular and irregular waves conditions, was measured and examined in detail. In addition, a comprehensive study of the loading on compliant cylinders, in both regular and irregular waves, was undertaken. Extensive use was made of appropriate parameter estimation techniques with initial attention (using simulated data) given to their accuracy for use with noisy experimental measurements. The effects of subtle (but undesirable) tank characteristics were also carefully taken into account. The study shows that, for fixed horizontal cylinders, benefits can be clearly identified in using the improved model, with frequency dependent coefficients, over the frequency dependent Morison equation. Moreover, the study shows that the relative velocity concept is more appropriate for use with the improved model than with the Morison model.

abstract: One of the two objectives of this dissertation is an investigation into the possible correlation between rainfall events and increased levels of E. coli and Mycobacterium using an existing data set. The literature states that levels of microbial concentrations do increase after rainfall events, but there are no studies to indicate this correlation applies in any Arizona water systems. The data analyzed for the bacterial concentrations project suggested the possibility of a correlation along one river but it is not conclusive to state that any correlation exists between rainfall events and the microbial concentration for many other sites included in the analysis. This is most likely due to the highly engineered water delivery systems that are not directly impacted. The secondary objective was to determine if there are environmental variables collected from an ongoing project which would be a good candidate for making predictions about any of the project data parameters. Of the 79 possible opportunities for the model to accurately predict the dependent variable, it showed strong statistical favorability as well as experimentally favorable results towards Dissolved Organic Carbon as the best dependent variable from the data set, resulting in an accuracy of 41%. This is relevant since Dissolved Organic Carbon is one of the most important water quality parameters of concern for drinking water treatment plants where disinfection by-products are a limiting factor. The need for further analysis and additional data collection is an obvious result from both studies. The use of hydrograph data instead of rainfall would be a logical new direction for the heavily engineered water delivery systems. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018