Browsing by Author "Geldenhuys, Heinrich Jacques"

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    Aerodynamic development of a contra-rotating shrouded rotor system for a UAV
    (Stellenbosch : Stellenbosch University, 2015-03) Geldenhuys, Heinrich Jacques; Van der Spuy, S. J.; Von Backstrom, T. W.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Unmanned aerial vehicles with vertical take-off and landing capabilities have received extensive attention worldwide in the last decade. Their low detectability, high manoeuvrability in confined spaces, and their capability for out-of-sight operations make them practical solutions for an array of military and civilian missions. The main advantage of shrouded rotors in hover and low speed conditions is the decreased blade tip induced drag when the tip gap is small enough. A well-designed shroud augments the rotor thrust in hover and low axial flight conditions. It also provides noise reduction and safety. A contra-rotating rotor system eliminates the need for separate anti-torque devices, thus producing a smaller footprint and a more compact vehicle. In this study a more efficient coaxial rotor for the ducted coaxial rotor system as published by (Lee 2010) was developed. The first phase of the design process consisted of the selection and numerical analysis of the best suited parent airfoils for the rotors by using XFOIL and XFLR 5. The second phase dealt with the design of a counter-rotating rotor system for the existing cambered shroud as published by (Lee, 2010), using the DFDC-070ES2a two dimensional code, specifically written for ducted rotor optimization. The final phase of the study dealt with the Computational Fluid Dynamic (CFD) verification of the design in ANSYS-CFX 15.07. A comparison between the CFX predictions of the newly designed rotor system and the reference design indicates a 33% improvement in hover thrust at the design power input.
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    The development of an implementation framework for green retrofitting of existing buildings in South Africa
    (Stellenbosch : Stellenbosch University, 2017-03) Geldenhuys, Heinrich Jacques; Brent, Alan C.; De Kock, Imke; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: In this study frameworks related to retrofitting were investigated in order to develop a holistic framework for the green retrofitting of existing buildings in South Africa. The developed framework consists of five phases: retrofit feasibility, pre-project planning, construction, post-retrofit activities, and finally operation and maintenance. The framework was validated by means of a case study. The time required by the organisation involved to obtain the necessary funds for constructing the retrofit far exceeds the available time of this study. Therefore only the first two phases of the developed frameworks, retrofit feasibility and pre-project planning, were validated. The framework was developed to be a generic representation for South African retrofit projects, and as with the maintenance phase, many aspects were selected and adapted for the South African context. One of the main barriers for green buildings in South Africa, identified from literature, is the high cost perception South Africans have regarding green buildings. In the case study it was demonstrated how internal resources and expertise of the organisation can be used to reduce the total retrofit cost. Combining a retrofit with maintenance actions can further reduce the additional amount needed to invest in a green retrofit. Fourteen retrofit features are suggested and grouped into seven smaller independent projects according to the types of skills that are required for each installation. This minimises the time, external expertise and resources needed for specific jobs. These sub-projects are generally not fixed to a pre-defined schedule and can be attempted at stages the organisation finds suitable.
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    Transitioning existing cities’ urban infrastructure towards smart sustainable cities.
    (Stellenbosch : Stellenbosch University, 2023-03-01) Geldenhuys, Heinrich Jacques; Brent, Alan Colin; De Kock, Imke H.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Traditionally, the development and management of urban subsystems was seen as a basic engineering and administrative task. The infrastructural system approaches developed throughout the 20th century within the Western context are not adequate to address the current and future challenges that face cities. Smart cities and sustainable cities are urban concepts in their own right, both aimed to address these challenges. Individually both present advantages, shortcomings and discrepancies towards the other. Sustainable cities tend to focus on the resource management of a city, and the sustainability impacts within the city boundaries. Smart cities have the ability to address complex urban challenges, especially related to city infrastructure and its operation and functionality. Recent research has motivated a focus towards amalgamating sustainability and smart city design, giving rise to the smart sustainable city concept. Cities are complex adaptive and dynamic systems-of-systems with embedded social and technical interdependences, which evolved and developed over many years. It is therefore important to address urban transformation in terms of scale, and linkages across levels, systems and regions. Transformation towards smart sustainable cities requires transitioning and the modernisation of urban infrastructure systems. There is currently an absence in literature of a holistic management framework for smart sustainable city transitions. An extensive literature review is presented investigating important themes, such as the origins, characteristics, benefits, challenges, perspectives, and evaluation of smart sustainable cities. Complex systems theory is explored, whereby a complex adaptive systems perspective is identified as a meaningful way to conceptualise and understand smart sustainable cities and the associated dynamics. Existing approaches and methods regarding city and infrastructure transitioning were also reviewed to draw understanding, requirements and guidelines useful to the design of the framework. The conceptual framework is established through synthesis of knowledge and insight gathered from literature to form a unique solution for the planning, development and management of smart sustainable infrastructure transitions. A collective case study analysis is used to validate the theoretical framework, testing twenty foundational aspects of city transitions. Minor adaptations, based on the reflections made regarding the aspects, were made to successfully address any shortcomings. The framework was then also subjected to a validation process testing the appropriateness of the framework’s design using a Delphi technique and industry experts. After adapting the framework according to the feedback from experts, all of them were certain the framework would hold up in practice. The framework is intended as a generic guideline useful to municipal managers, city-planners, and project portfolio managers appointed to plan, direct and manage the transition of an existing city towards a smart sustainable city. The framework provides explicit guidelines needed to guide and manage the city transitioning process in practice, and can be adapted to align with the unique context and needs of the specific city it is applied to. The research contributes to knowledge creation at the intersection of three knowledge domains, namely: smart sustainable cities, urban infrastructure transitioning, and complex adaptive systems.