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Item Assessment of the Influence of Tip Speed Ratio, Solidity and Reynolds Number on the Aerodynamic Performance of Selected Locally Fabricated Wind Turbines in Tanzania(The University Of Dar Es Salaam, 2019) Kachira, John PeterThe sites with good wind energy conditions in Tanzania have motivated some local craftsmen to manufacture wind turbines using local and imported materials. However, some studies have shown that these turbines have low performance. In this study, theoretical approach has been carried out to assess the influence of TSR, solidity and Re on the aerodynamic performance of nine selected locally fabricated wind turbines in Tanzania. Three manufacturing centers namely, Dar es Salaam, Singida and Makambako were selected and three different HAWT rotor blades from each center were put under testing. Their respective rotor radii and chord widths were measured and used to determine their TSR, solidity and Re. The measured TSRs were 0.63, 0.70, 0.79, 0.90, 1.57, 2.09, 2.51, 3.14, and 4.19. Unlike 4.19, the rest values were below the recommended range between 4 and 10 for which WECS are recommended to generate large scale electricity. The respective measured solidities were, 0.90, 0.10, 0.13, 0.17, 0.18, 0.28, 0.88, 1.07 and 1.22. These solidities were found to be above the proposed range between 0.01 and 0.05 for which WECS are designed to generate large scale electricity. These high solidities lead into high torques reducing rotational speed of the WECS. The measured Res were 86,030, 99,265, 100,589, 102,574, 125,736, 138,972, 145,589, 145,589 and 152,207. These Re values are below the standard Re which is at least 6 110 implying that they exhibit turbulent flow with high level of drag coefficient that influences low performance of the WECS. The 3 - bladed wind turbine from Matiya in Singida was found to have good TSR of 4.19 though its solidity was found to be above the recommended standard values range. It needs an optimization of its chord and radius to improve its efficiency. Therefore, these wind turbines can only generate small scale electricity due to their poor aerodynamic performancesItem Optimization of Incineration Process(Nelson Mandela African Institution of Science and Technology, 2019) Omari, Arthur MngomaMunicipal solid waste management has become a challenge in many cities in the developing countries due to the poor methods of waste disposal, which increase the risk of the spread of diseases, leach and increase the demand of land for waste disposal. Characterization study of waste samples from Arusha shows that the combustible fraction is about 87% and biodegradable is 80%. The Thermal gravimetric analyser and Bomb calorimeter show the energy value of about 12.5 MJ/kg and the degradation of about 85%. The study shows that the municipal solid waste disposal method can be thermal, biological or physical. However, thermal method by incineration process is the most preferred and convenient because it destroys pathogens and reduces waste volume in the fastest way. The waste flow analysis of Arusha city shows that the waste has the annual recoverable potential of 128GWh. The case study used an existing incinerator as showed the variation of effluents with operating conditions. The design optimization using computational fluid dynamic techniques to predict the performance of incinerator showed the deviation of input air by 14%, the mass flow rate by 26.5%, the mass fraction of carbon dioxide by 10.4% and slight deviation of nitrogen dioxide and carbon monoxide. The research suggested removing the ash during the incineration process by using a moving grate mechanism to minimize the possibility of formation of NOX. To feed the incinerator by using mechanical means without direct opening the door, it suggested to incorporating moving grate mechanism. The operating conditions of the incinerator designed should have the optimum values for input air one A1-1 as 0.036 39 kg/s, the input air two A2-1 as 0.030 46 kg/s, the input air three A3-1 as 0.034 09 kg/s, the input fuel value as 19.6 kg/h and the maximum capacity of incinerator as 68 kg/hItem Optimizing the Conjunctive Use of Surface Water and Groundwater in Water Stressed River Basins: Case of Olifants River Basin, South Africa(Tshwane University Of Technology, 2017) Kifanyi, Gislar EdgarOne of the new techniques currently used to address water shortage problems in the developed countries is the optimum conjunctive water use. Optimum conjunctive water use demands that the surface and subsurface reservoirs are fully characterized if deterministic methods are to give reliable results. However, in real world phenomena, full characterization of surface – groundwater reservoirs is neither practically nor economically feasible. This research, therefore, aimed at developing a combined simulation-optimization quantitative conjunctive water use management model which can sustainably manage water resources taking into account input parameter uncertainty. Response matrix technique was used to combine simulation model with optimization model (procedure). The novelty of this research work is that determination of optimum conjunctive water use was determined under scanty data and uncertain condition. Surface water and groundwater conceptual models were developed, and integrated to form a conjunctive water use conceptual model which was converted into numerical simulation model for both deterministic and stochastic simulations. MODFLOW 2000 and RIVER Package (RIV) (together referred to as conjunctive water use simulation model) supported in Visual MODFLOW 2014.2 Classical Interface was used to determine aquifer system responses (drawdowns). These drawdowns were assembled as response matrices and then incorporated into an optimization management model as drawdowns constraints coefficients. The simulation optimization problems were solved and analysed through “Active-Set” (Sequential Quadratic Programming (SQP) optimizer (algorithm)) implemented under the MATLAB 2014a environment. The Retrospective Optimization Approximation (ROA) method was used for solving the stochastic optimization problem and to v investigate the impact of uncertainty on optimal management strategies. ROA procedure solves and evaluates a sequence of optimization sub-problems in an increasing number of realizations. Results indicated that the study area aquifer has potential groundwater resource which is undeveloped. Deterministic approach underestimates the water withdrawal rates. The optimal withdrawal rates designed based on ROA approach were relatively higher than those designed based on deterministic approach. Moreover, the overall percentages of contribution of surface water and groundwater sources to the total water demand obtained through ROA approach was about 58% and 42%, respectively while the overall percentages contribution obtained through deterministic approach was about 85% and 15%, respectively. This is about ±27 % variation (i.e., Differences between the approaches realized) of percentages of contribution of the two water sources to the total water demand. Furthermore, findings indicated that ROA conjunctive water use management technique has potential to ensure sustainability of limited water resources of river basins. Through ROA approach the expected total optimal objective function value converged to its maximum value within a relatively few iterations (6 to 8 iterations) in about 2.30 Hrs computational time. In conclusion, results demonstrated that the ROA approach is a promising technique for use in managing conjunctive water use under uncertainty conditions. It is recommended that guidelines for determination of the sequence of sample sizes for use in ROA method framework should be established. The use of parallel computer processors to enhance computational time efficiency for large optimization problems should be explored. Quantitative methods for determination of weights for estimating values of objective functions should be investigated. The application of the ROA approach to multi-objectives optimization problems should be explored.Item Uncertainty Reduction in Climate and Hydrological Models Predictions at Catchment Scale In the Upper Great Ruaha River Sub-Basin, Tanzania(Sokoine University of Agriculture, 2019) Mutayoba, Edmund IshengomaWater resources have become scarce in most tropical areas of Tanzania due to climate change. Any changes to the hydrological cycle may have significant effects on the water resources in the river basins of Tanzania. The impact of climate change on water resources in Tanzania have been studied using General Circulation Models (GCM) which run at low spatial resolutions of 100-300 km. The resolution is too coarse to provide useful information about climate change impact in small catchments as many physical processes which control local climate e.g.; vegetation, hydrology, topography is not fully parameterized and hence results on uncertainty in model prediction. The main aim of this research was to quantify the uncertainty in model predictions for the Mbarali River Sub-catchment of the Upper Great Ruaha River Sub-basin in the Rufiji River Basin, Tanzania. Three research objectives were analyzed; the first objective was to evaluate the performance of the Coordinated Regional Downscaling Experiment Regional Climate Model (CORDEX, Regional Climate Models) in simulating rainfall characteristics of the Mbarali River Sub catchment. The area weighted average method was used to calculate the average rainfall from the CORDEX RCMs and from ERA-Interim reanalysis over the entire Mbarali River sub-catchment. Comparison between rainfall data from CORDEX RCMs and ERA-Interim reanalysis was done to test the ability of the CORDEX RCMs to reproduce the annual cycles, interannual variability, annual total and trends of rainfall as presented by the ERA-Interim reanalysis. The second objective assessed the impact of climate change on hydrological characteristics using the Soil and Water Assessment Tool (SWAT) model. The ability of the SWAT model to simulate catchment processes was assessed through a calibration and iii validation process, which was a key factor in reducing uncertainty and increasing user confidence in its predictive abilities. The SWAT model was driven by high resolution climate simulations for historical climate condition (1971-2000) as well as future climate projections (2011-2040, 2041-2070 and 2071-2100) for two Representative concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Furthermore, Ensemble of RCMs was applied into SWAT to simulate water resources availability and the results were compared with individual models (HIRHAM5, CCLM4, RACMO22T, RCA4). The Rainfall and Temperature data were obtained from the selected four CORDEX RCMs driven by three different General Circulation Models (GCMs). Inverse Distance Weight Average (IDWA) was used to interpolate model gridded climate simulation to the location of weather station. The third objective assessed the impacts of land use and land cover change on the hydrology using integration of remote sensing data, QGIS and SWAT model. The land use and land cover (LULC) maps for three window period snapshots, 1990, 2006 and 2017 were created from Landsat TM and OLI_TIRS. Supervised classification was used to generate LULC maps using the Maximum Likelihood Algorithm and Kappa statistics for assessment of accuracy. The findings of the first objective are that CORDEX RCMs were able to capture well the seasonal and annual cycles of rainfall. However, they underestimated the amount of rainfall in March, April and May (MAM) and overestimated in October, November and December (OND) respectively. CORDEX RCMs reproduce interannual variation of rainfall. The source of uncertainties was revealed when the same RCMs driven by different GCMs and when different RCMs driven by the same GCM in simulating rainfall. It was found that the error and biases from RCMs and driving GCMs contribute roughly equally. Overall, the evaluation found reasonable (although variable) model capability in representing the mean climate, interannual variability and rainfall trends. iv The results suggest that CORDEX RCM is suitable in simulating rainfall, maximum temperature and minimum temperature. The findings of the second objective showed that SWAT model simulated stream flow and water balance components differently when two different RCMs were forced by the same GCMs as well as when the same RCMs were forced by different GCMs. The differences are related to the formulation of the RCMs themselves. For example, RACMO22T and HIRHAM5 driven with the same GCM (ICHEC-EARTH) simulate different amount of stream flows, surface runoff, water yield and groundwater yield in historical (1971–2000) as well as in present century (2011-2040), mid-century (2041- 2070) and end century (2071-2100). Ensemble RCMs projected decrease in stream flows by 13.67% under RCP 8.5. However annual rainfall was shown to increase in averages by 1.62% under RCP 4.5 and by 1.96% for RCP 8.5 relative to the 1177.1mm of the baseline period (1971-2000). The results also showed that, temperature will slightly increase relative to the baseline during present century (2011-2040) for RCP 4.5 and RCP 8.5. The ensemble average project that the minimum temperature will increase by 14% (1.90C) under RCP 8.5 and maximum temperature by 7.68% (1.8oC) under RCP 4.5 The findings of the third objective showed that there were significant changes in land use and cover for the three-time periods (1990, 2006 and 2017). The cultivated land and built up area increased from 25.69% in 1990 to 31.53% in 2006 and 43.57% in 2017 compared to other land classes. Increase of cultivated land and built up area led to decrease in forest cover. Forests occupied 7.54% in 1990, but decreased to 5.51% in 2006 and 5.23% in 2017. This decrease in forest cover has resulted in increased surface runoff for the same v periods (2006-2017). The increase in surface runoff in the study area could be attributed to deforestation and poor land husbandry, where during land preparation much of the vegetation is cleared, hence decreasing canopy interception and allowing water to drain off. Also, poor farming practices including cultivation on hillslopes without soil conservation, reducing soil compaction, hence allowing more water to drain as surface runoff. The calibrated SWAT model using the three different land use and land cover change of 1990, 2006 and 2017 indicate that during the wet season, the mean monthly flow increased by 1.48% relative to the 28.09 m3 /s of the baseline 1990 while during the dry season, the mean monthly flow decreased by 16.7% relative to the 0.20 m3 /s baseline flow. Assessment of the impacts of land use and land cover changes on catchment water balance component revealed that surface runoff increased by 3.9% in 2006 and 9.01% in 2017 while groundwater contribution to stream flow decreased by 6.3% and 12.86% in 2006 and 2017, respectively. The decrease in stream flow could also be attributed to abstraction of water for irrigation activities upstream of the Igawa gauge station. The findings of the study may help basin water officers, planners in water sector and agriculture sector in addressing uncertainty in policy and decision-making specifically when preparing strategies and adaptations plans for river catchment. The science used in this study can be applicable to another river basin in Tanzanian in a climate change impact study.Item Characterisation of Titanium Alloy Processed By Constrained Bending and Straightening Severe Plastic Deformation(The University Of Johannesburg, 2020) Mwita, Wambura MwiryenyiMost Severe Plastic Deformation (SPD) processes lack both the capability for continuous process and the homogeneity of tailored material properties in processed samples. These challenges have limited the adaptation of SPD technology to process titanium alloys for biomedical and structural applications. This thesis presents microstructural and mechanical characterization of Ti6Al4V titanium alloy processed by a Constrained Bending and Straightening (CBS) SPD technique. The proposed CBS method was intended for a continuous process of titanium sheets with improved magnitude and homogeneity of the entailed strain, hardness and tensile properties. The CBS process tool was designed and fabricated in the University of Johannesburg workshop. The tool was used to process Titanium Alloy Grade 5 (Ti6Al4V) sheets at a combination of (2, 4, 6) passes (N) and (6 mm, 12 mm) feeds (F) designated as N2F6, N4F6, N6F6, N2F12, N4F12 and N6F12. Sub-samples were cut from the processed sheets. The samples were prepared, and their respective microstructural analysis, hardness and tensile tests were performed. A numerical model for the CBS process was built and simulated with ABAQUS Standard Finite Element Analysis (FEA) method. The model was used to predict the magnitude and the homogenity of the Effective Plastic (EP) strain, the tensile yield strength and the hardness of the material. The simulation results were validated with the experimental data. The experimental results showed that vi comparing with the As Received (AR) samples, the processed samples showed a decrease in the average grain size from 10µm to 3µm, together with the formation of new finer subgrains. The tensile strength, the yield strength and the hardness of the material increased by 29.3%, 33.5% and 24.4%, respectively. The values of these material properties at the F6 feed were higher than those at the F12 feed. The simulated results showed that the maximum mean EP strain of 2.87 induced in the material correlated with the highest strain homogeneity that corresponded to the lowest Coefficient of strain Variation (CV) of 18.9%. A comparison of the results from both methods on the yield strength and the hardness showed a direct correlation at the N2 and the N4 passes. A relative inverse correlation was observed at the N6 pass due to the saturation of the material hardening and the onset of yielding. Results from this study have quantitatively shown that the CBS method performed well the intended work. However, this method needs desirable improvement at a commercial level before it is viable as an alternative method for the continuous production of the titanium alloy sheets enhanced with the homogeneous microstructural and mechanical properties