Impact of Helix Characteristics on Slipstream Deformation in Propeller–Wing–Flap Interaction

This paper explores the influence of the characteristics of the helical vortex system of a propeller slipstream on the resulting propeller–wing interaction, with a particular focus on how variations in helix angle impact slipstream deformation. Slipstream characteristics are changed by controlling the thrust and torque coefficient of the propeller through adjustments in blade pitch, advance ratio, and blade count. We conducted experimental measurements of a propeller–wing–flap model using seven-hole pressure probes, oil flow visualization, and infrared thermography in both cruise and high-lift configurations (with deployed slotted flap). The results presented in this paper demonstrate the dominance of the torque coefficient, and thereby longitudinal vorticity in the slipstream, on the slipstream deformation. The paper also underscores the role of the nacelle integration in the development of the slipstream, as well as the flow on the wing surface. The insights into the slipstream deformation provided in this work are essential for future closely coupled propeller–wing designs, particularly when it comes to high-lift configurations.