Effects of leading edge tubercles on drone propeller performance

Bio-inspired designs are widely adopted in aerodynamics to enhance performance. One such design, derived from the tubercles found on the pectoral fins of humpback whales, has shown potential as a passive flow control device by manipulating flow patterns. Tubercles generate localized vortices at their leading edge, promoting an earlier transition of the laminar boundary layer to turbulent. Depending on the Reynolds number, this can delay stall and improve the overall aerodynamic performance of control surfaces. This is why humpback whales can perform fast, tight-turning manoeuvres despite their large mass and dimensions. This thesis focuses on the application of tubercles, modelled in a sinusoidal shape, to the leading edge of a 30-centimeter diameter propeller, intended for use in drone and UAV propulsion systems. At this scale, propellers work within a Reynolds number range where laminar separation bubbles can form, causing performance losses due to flow separation and negatively impacting aeroacoustic behaviour. The goal of this thesis is to investigate the effects of tubercles on the overall performance of this propeller, analysing their impact on the laminar separation bubble, which has been previously studied by other researchers. The analysis is conducted using the commercial CFD code Ansys Fluent, investigating the suitability of the Multiple Reference Frame approach, commonly used in turbomachinery and propeller simulations, to achieve this goal. The thesis is structured into six chapters. The first chapter reviews the current literature on bio-inspired tubercles applications and their effects. The next two chapters provide an overview of propeller design and characteristics, followed by a description of the turbulence and transition models used to solve the fluid dynamics equations. In Chapter 4, the CFD simulation setup of the baseline propeller is presented to verify and validate the accuracy of the numerical model. In the following chapter, the modified propeller design, incorporating tubercles along the leading edge, is developed and simulated. Finally, conclusions and potential future work are discussed.