An Unmanned Aerial Vehicle (UAV) whose wing consist of a combination of two different airfoils presents opportunity for improve aerodynamic performance; and research in this area has potential for significant innovation. This study employed a Computational Fluid Dynamic (CFD) technique to predict drag and lift coefficients and aerodynamic efficiency of the wing of Ichoku-18 (IU-18) UAV. The wing of the IU-18 UAV consists of two different aerofoil sections, NACA2415 at the root and SD7032 at the tip. The study investigates the aerodynamic characteristics of the wing at different Angle of Attack (AoA), AoA = 0°,4°, 8°, 12°, 16°, 20° and 24°. Using a standard and realizable k-ε turbulence models, the minimum and maximum drag coefficients and aerodynamic efficiencies were obtained at AoA = 0° and AoA = 24°. Both turbulence models predicted the critical angle of attack occurs at AoA = 16°. The results obtained were in agreement with analytical design data of the UAV and findings from the literature. While the standard k-ε turbulence model overpredicted the drag coefficients of the wing of IU-18 UAV, the values predicted by the realizable k-ε turbulence model were in closer agreement with the experimental data. Also, the lift coefficients predicted by the realizable k-ε turbulence model were more realistic and in closer agreement with that obtained analytically. Similarly, while the realizable k-ε turbulence models prediction of the CLmax is in closer agreement with the analytical data, the standard k-ε model underpredicted the variation of aerodynamic efficiency with AoA.

Sewage sludge to energy conversion is a sustainable waste management technique and a means of militating against the environmental concerns associated with its disposal. Amongst the various conversion technologies, anaerobic digestion and gasification have been identified as the two most promising. Therefore, this study is focused on a detailed evaluation of the anaerobic digestion and gasification of sewage sludge for energy production. Moreover, the key challenges hindering both technologies are discussed, as well as the practical measures for addressing them. The applicable pretreatment measures for efficient transformation into valuable energy vectors were further evaluated. Specifically, the study evaluated various properties of sewage sludge in relation to gasification and anaerobic digestion. The findings showed that a high ash content in sewage sludge results in sintering and agglomeration, while a high moisture content promotes tar formation, which has been identified as one of the key limitations of sewage sludge gasification. More importantly, the application of pretreatment has been shown to have some beneficial features in promoting organic matter decomposition/degradation, thereby enhancing biogas as well as syngas production. However, this has additional energy requirements and operational costs, particularly for thermal and mechanical methods.