Thesis (MEng) -- Stellenbosch University, 2000. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: This document contains the work done on the bearingless rotor hub for the 24% scale model of the Rooivalk Attack Helicopter situated at the CSIR in Pretoria. This work forms part of the MSc Ing degree of Johannes Steyn. This work was deemed necessary because of a movement away from the fully articulated rotor to one of hingeless and more recently bearingless rotors. The main emphasis of this thesis is to be a technology demonstrator more than the design of a fully working bearingless rotor hub. With this in mind the final design in this report is not an optimal one, but the procedures and methodology in getting to a design are laid out in this document. To verify the design, tests were identified and created. The procedures for these tests are also included in this document. For the fatigue test a test bench had to be designed and built. This document also includes the design of this test bench / AFRIKAANSE OPSOMMING: Die dokument lewer verslag van die aktiwiteite vir die ontwerp van ‘n laerlose rotor van die 24% skaal model van die Rooivalk Helikopter, gelee by die WNNR in Pretoria. Die werk gedoen vorm deel van die MSc Ing graad van Johannes Steyn. Die werk is nodig geag omdat daar ‘n tendens is om weg te beweeg van die volledig geartikuleerde rotor na die van ‘n skanierlose en meer huidig ‘n laerlose rotor. Die hoof klem van die tesis is om as tegnologie demonstrator op te tree, eerder as die daarstel van ‘n werkende laerlose rotor. Na aanleiding van bogenoemde stelling kan die finale ontwerp nie as optimaal beskou word nie. Die prosedures en metodiek wat gevolg is om die ontwerp te kry word uitgele in die dokument. Om die ontwerp te verifieer is toetse gei'dentifiseer. Die prosedures vir elk van die toetse word ook in die dokument ingesluit. Vir die uitputtingstoetse moes ‘n spesiale toetsbank ontwerp en gebou word. Die ontwerp van hierdie toetsbank is ook in die dokument.

An experimental investigation was undertaken to test the effectiveness of a novel design for controlling the aerodynamics of an airfoil. A synthetic jet actuator (SJA) was placed inside a NACA 0015 airfoil with its jet at 12.5% of the chord length, hereby referred to as the leading edge actuator. Four centrifugal fans across the span were mounted at 70% of the chord and the jet formed by them was located at 99% of the chord, hereby referred to as the trailing edge actuator. The effects of these actuators on the aerodynamic properties were studied, separately and then in conjunction, with varying angles of attack. The leading edge actuator delays the onset of stall up to 24 degrees, the maximum angle of attack that could be attained. The control of the aerodynamics was achieved by controlling the amount of separated region. There was no effect of the actuation at lower angles of attack. The trailing edge actuator provides aerodynamic control at both low and high angles of attack. The study investigated the effect of jet momentum coefficient on the aerodynamic properties for various angles of attack. The data obtained shows that lift control (in both positive and negative direction) was achieved even at low angles. The actuator enhances the aerodynamic properties by changing the pressure distribution as well as by delaying flow separation. Study of the combined actuation shows that the synthetic jet actuator was very effective in delaying stall when the trailing edge jet was ejected from the upper surface. For the case when the jet is ejected from the lower surface, there is less control. This can be accounted for by the difference in aerodynamic loading for both cases.