Analysis and modeling of the aerodynamic ceiling effect on small-scale propellers with tilted angles

Abstract

Micro air vehicles with propellers have been widely used in military and civilian applications due to their high maneuverability and low cost. As the mission scenarios and requirements of rotorcrafts become more complex, proximity effects caused by confined environments, such as the ceiling effect cause significant interference to the performance and stability of rotors. Most researchers have analyzed this phenomenon by considering the ceiling effect in hover conditions. However, few scholars considered the tilt angle between the rotor and the ceiling, which is more likely to occur in real missions, such as the close inspection of bridges or large equipment, flight in narrow indoor environments, and flight near the ceiling for fully actuated multirotors. In this study, a CFD-based study is conducted to evaluate the ceiling effect for small-scale tilted propellers. The aerodynamic analysis was experimentally evaluated through a series of ground tests in a test bench designed for this research. The CFD results were validated by a mesh-independent study and experimental data comparison. The results show that in contrast to the phenomenon of reduced thrust when tilt angles exist between the rotors and ground, the existence of tilt angles between the propeller and the ceiling reduces the thrust-increasing effect of the ceiling when the dimensionless distance is greater than 0.6. When the distance gets smaller, the thrust-increasing effect increases when the tilt angle is greater than 10∘. In particular, when the distance is less than 0.3, the existence of tilt angles will increase the thrust-increasing effect of the ceiling. Additionally, a data-driven model has been proposed to predict the thrust with the distance to the ceiling and the angle inclination between the rotor and the ceiling. This model enables future rotorcrafts that require accurate models to operate in narrow environments.