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A current focus in the quest for improvement in fuel efficiency in aircraft design is the simplification of complex high lift systems. A simpler high lift system in combination with flow separation control is potentially able to meet the current high lift performance requirements, while still reducing overall complexity. Passive flow separation control is promising for its inherent simplicity. This is in line with the main goal of simplification of the high lift system. This thesis covers an exploratory and experimental investigation of a novel type of passive vortex generator: the internal vortex generator. Its distinctive feature, an internal structure for the generation of vortices below the surface, is hypothesized to create strong vortices low inside the boundary layer. Due to this increase in effectiveness the internal vortex generator can potentially outperform external vortex generators. As no literature is currently available on this novel concept, different designs are evaluated using numerical analysis. The wedge type internal vortex generator, similar to a backward wedge external vortex generator, is found to produce the most stable and strong vortices, which are inherently close to the surface. Its close resemblance to the well-documented backward wedge external vortex generator allows for a detailed design that is based on a literature study. Moreover, it allows for an interesting reference case to be present during the experiment test. The internal vortex generator is experimentally tested against its geometrically equivalent external vortex generator. Both vortex generator types are equipped on the same single element high lift model and tested in the Low Speed Low Turbulence Wind Tunnel at the Delft University of Technology. Force measurements indicate a more than 3% increase in maximum lift compared to baseline, while the geometrically equivalent external vortex increases the maximum lift with less than 1%. When the boundary layer is artificially t, Flight Performance and Propulsion, Aerospace Engineering

Relatively high wing loading leads to increase in fuel efficiency in commercial as well as in small general aviation aircraft, but requires sophisticated high lift devices to keep the take-off and landing distances within acceptable limits. High lift devices can in turn have a detrimental effect on cruise performance, and thus fuel efficiency, in the form of additional parasitic drag of the high lift system mechanism fairings under the wing. In addition, the weight and complexity of the high lift system increases with its performance. The purpose of this research is to increase the payload of a highly efficient propeller driven 4-seater general aviation aircraft by improving its plain flap high lift system while the range stays the same. Therefore a detailed design of the high lift system is required, as well as the evaluation of the overall aircraft performance. A study of existing high lift systems in general aviation aircraft is conducted, based on which a preliminary design decision to implement a single-slotted flap with a dropped hinge mechanism is made. An optimization loop is developed within which the flap geometry is generated based on nine design variables (including the position of the hinge point and the flap deflection angle) and the clean configuration airfoil shape. Two-dimensional aerodynamic analysis of the two-element airfoil section is performed by the MSES code at three different angles of attack. A method of reading the maximum value of displacement thickness on the flap upper surface is implemented to algorithmically detect separated flow and discard the flap designs that suffer from separation at low angles of attack in order to avoid jumps in the lift curve. Three-dimensional aerodynamic characteristics of the aircraft with deployed flaps are estimated using semi-empirical methods. The drag of the mechanism fairings is also estimated by a semi-empirical method. A simple performance model is used to predict the payload, which represents the o, Flight Performance and Propulsion, Aerospace Engineering

A current focus in the quest for improvement in fuel efficiency in aircraft design is the simplification of complex high lift systems. A simpler high lift system in combination with flow separation control is potentially able to meet the current high lift performance requirements, while still reducing overall complexity. Passive flow separation control is promising for its inherent simplicity. This is in line with the main goal of simplification of the high lift system. This thesis covers an exploratory and experimental investigation of a novel type of passive vortex generator: the internal vortex generator. Its distinctive feature, an internal structure for the generation of vortices below the surface, is hypothesized to create strong vortices low inside the boundary layer. Due to this increase in effectiveness the internal vortex generator can potentially outperform external vortex generators. As no literature is currently available on this novel concept, different designs are evaluated using numerical analysis. The wedge type internal vortex generator, similar to a backward wedge external vortex generator, is found to produce the most stable and strong vortices, which are inherently close to the surface. Its close resemblance to the well-documented backward wedge external vortex generator allows for a detailed design that is based on a literature study. Moreover, it allows for an interesting reference case to be present during the experiment test. The internal vortex generator is experimentally tested against its geometrically equivalent external vortex generator. Both vortex generator types are equipped on the same single element high lift model and tested in the Low Speed Low Turbulence Wind Tunnel at the Delft University of Technology. Force measurements indicate a more than 3% increase in maximum lift compared to baseline, while the geometrically equivalent external vortex increases the maximum lift with less than 1%. When the boundary layer is artificially t, Flight Performance and Propulsion, Aerospace Engineering

Relatively high wing loading leads to increase in fuel efficiency in commercial as well as in small general aviation aircraft, but requires sophisticated high lift devices to keep the take-off and landing distances within acceptable limits. High lift devices can in turn have a detrimental effect on cruise performance, and thus fuel efficiency, in the form of additional parasitic drag of the high lift system mechanism fairings under the wing. In addition, the weight and complexity of the high lift system increases with its performance. The purpose of this research is to increase the payload of a highly efficient propeller driven 4-seater general aviation aircraft by improving its plain flap high lift system while the range stays the same. Therefore a detailed design of the high lift system is required, as well as the evaluation of the overall aircraft performance. A study of existing high lift systems in general aviation aircraft is conducted, based on which a preliminary design decision to implement a single-slotted flap with a dropped hinge mechanism is made. An optimization loop is developed within which the flap geometry is generated based on nine design variables (including the position of the hinge point and the flap deflection angle) and the clean configuration airfoil shape. Two-dimensional aerodynamic analysis of the two-element airfoil section is performed by the MSES code at three different angles of attack. A method of reading the maximum value of displacement thickness on the flap upper surface is implemented to algorithmically detect separated flow and discard the flap designs that suffer from separation at low angles of attack in order to avoid jumps in the lift curve. Three-dimensional aerodynamic characteristics of the aircraft with deployed flaps are estimated using semi-empirical methods. The drag of the mechanism fairings is also estimated by a semi-empirical method. A simple performance model is used to predict the payload, which represents the o, Flight Performance and Propulsion, Aerospace Engineering