Propeller-based propulsion technology is experiencing renewed interest owing to its superior propulsive efficiency in comparison to conventional jet engines. This phenomenon is attributed to the capacity to generate thrust by accelerating a significant volume of air through a small velocity differential. Additionally, owing to its compatibility with electrical power systems, propeller-based propulsion offers an opportunity to utilize more environmentally friendly energy sources and configurations like the distributed propulsion systems. To optimize the integration between the propeller-based propulsion system and the airframe, it is imperative to thoroughly understand the interactive aerodynamics of the propeller-wing system.

This thesis presents a comprehensive study on the aerodynamics of propeller-wing interactions, with a specific focus on leading-edge distributed propeller configurations.
The research was conducted through a comparative analysis, employing a single propeller-wing system, modeled based on the ATR 42/300 as the baseline. This involved comparing a conventional single tractor propeller configuration with a three-propeller leading edge distributed configuration. The methodology used is an unsteady panel method
solver, FlightStream, which is a commercially available software, allowing for an in-depth
examination of the two-way interactions between the propeller and wing (Full interaction mode), and allowing for a force-free wake.

The findings of the study highlighted significant aerodynamic benefits of the leading-edge distributed propeller configuration over the traditional single propeller setup. Notably, there was a 2.5% increase in wing efficiency and a 6.1% reduction in induced drag. Additionally, the propeller efficiency in the distributed system saw a 3% increase compared to the single propeller system. However, it’s crucial to note that these propellers operated at different, non-optimal points, which influences their comparative performance. A key result was the reduced power consumption of the three-propeller system, which required 8.1% less power to maintain steady level-flight conditions than the baseline single-propeller model. This finding suggests potential for increased efficiency in aircraft designs incorporating such configurations.

From the desire to reduce the impact of traveling on the environment and the increase in fuel prices over the past years, the propeller has regained interest as a propulsion mechanism in the aviation industry. Two main reasons can be found in their high propulsive efficiency and ability to combine with electric motors. The scaling of the motors is rather insensitive to the efficiency, allowing the propeller to be placed around the aircraft, resulting in new design freedoms.

The influence of the propeller slipstream can increase the aerodynamic performance of a propeller-wing system. Propellers with inboard-up rotational configuration are found to reduce the induced drag of the wing in propeller-wing systems compared to isolated wings. To increase the aerodynamic performance of propeller-wing systems and certify design choices, a detailed understanding of the relative contribution of the lift-induced drag and swirl recovery to the induced drag of propeller-wing systems is desired. A low-order numerical model has been used for a parametric study on propeller-wing systems. From the results follow that the gradient of the spanwise wing lift distribution is of influence on the amount of net swirl recovery that the wing can obtain. It is shown that when a propeller is placed in front of a wing section where the gradient of the isolated spanwise wing lift distribution is positive from root to tip, more swirl recovery can be obtained by the inboard-down rotating configuration. In this case, the difference in lift between the wing sections behind the two propeller sides is increased. The increase of the difference in the lift also increases the lift-induced drag of the wing. With low disk loadings, the contribution of the swirl recovery is found to be higher than the increase in lift-induced drag. Increasing the disk loading results in more significant differences in lift between the wing sections behind the propeller sides, such that the gradient of the spanwise wing lift distribution increases. From this increase, the contribution of the lift-induced drag can become more significant than the contribution of the swirl recovery of the wing, increasing the induced drag of the system.