Thesis (MSc)--Stellenbosch University, 2015. / 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. / AFRIKAANSE OPSOMMING: Onbemande lugvaartuie met vertikale opstyg en landings vermoëns het uitgebreide aandag wêreldwyd in die laaste dekade geniet. Hul lae waarneembaarheid, hoë beweegbaarheid in beperkte ruimtes, en hul vermoë om buite-sig operasies uit te voer maak dat hulle praktiese oplossings vir 'n verskeidenheid van militêre en burgerlike missies is. Die grootste voordeel van gehulde rotors in hangvlug en lae spoed omstandighede is die afname in die lem punt sleepkrag wanneer die lem punt gaping klein genoeg is. 'n Goed ontwerpde omhulsel dra by tot die rotor stukrag in hangvlug en lae aksiale vlug omstandighede. Dit bied ook geraasreduksie en veiligheid. 'n Kontra-roterende rotorstelsel skakel die vereiste van afsonderlike anti-wringkrag toestelle uit, wat lei tot 'n kleiner voetspoor en 'n meer kompakte voertuig. In hierdie studie is 'n meer doeltreffende koaksiale rotor vir die gehulde koaksiale rotor stelsel soos gepubliseer deur (Lee 2010) ontwikkel. Die eerste fase van die ontwerp-proses het bestaan uit die seleksie en numeriese analise van die mees geskikte lemprofiele vir die rotors deur die gebruik van XFOIL en XFLR 5. Fase twee het die ontwerp van 'n teen-roterende rotor stelsel vir die bestaande omhulsel soos gebruik in (Lee, 2010) se publikasie behels. Die ontwerp is met behulp van DFDC-070ES2a, ‘n twee dimensionele kode wat spesifiek vir gehul-rotor optimering geskryf is, gedoen. Die verifikasie van die nuwe ontwerp is in die finale fase met behulp van die berekeings vloeidinamika sagteware, ANSYS-CFX 15.07 gedoen. ‘n Vergelyking tussen die CFX prestasie voorspelling vir die nuwe rotorstelsel en die gepubliseerde data van (Lee, 2010) toon ‘n 33% toename in hangvlug stukrag by die ontwerpsdrywing.

Formula Student is Europe’s most established engineering competition, with teamsall over the world. Practical problem solving in combination with applyingacademic knowledge, give students the opportunity to explore their field of study inan exciting and meaningful way. Aerodynamic development of race cars have seen significant results in competitionsince its introduction in the 1960s. Initial designs were adaptations of aerospaceconcepts for ground vehicles. Development relied solely on track- and wind tunneltesting but despite their rudimentary designs, significant performance increaseswere made. The purpose of aerodynamic development of race cars is to balance thecar, getting it to behave as desired. As a consequence of the forces generated, thevehicle corners faster at the cost of acceleration and top speed. With more powerfulcomputers, earlier unsolvable equations started to get numerically solved andcomputational fluid dynamics was born. CFD introduced the possibility for rapiditeration and exploration of more intricate designs. This report will solely utilizeCFD as a simulation tool, recognising its limitations in accuracy and real worldcorrelation. The aim of this study is to increase downforce on the front wing, whilst beingcautious of downstream impact. The goal set by the team is an adjustable frontwing that generates as much downforce as possible, whilst allowing for adjustmentsto shift the center of pressure by promoting more air to the side-structure. Toachieve this, an iterative design process based on literature is the chosen method.Continuous cross evaluations with other parts of the design team is of the highestimportance to avoid poor interaction between aerodynamic devices. The (negative) lift coefficient was increased from 4.7 to 5.7 for the entire vehicle, byonly improving the front wing. This was very satisfactory as increases upstreamoften lead do degraded performance downstream. An increased lift coefficient ofover 20%, with improvements to front wheel drag and similar side-structureperformance, demonstrate the quality and effectiveness of the design.