Effect of Leading-Edge Tubercles on Post-Stall Flow over a Paraglider Canopy

Abstract

This study investigates the effects of leading-edge tubercles on the aerodynamic performance of a paraglider canopy in the post-stall regime. The canopy equipped with tubercles exhibited, on average, a 15% increase in lift-to-drag ratio compared to the baseline configuration. Flow characteristics were examined using particle image velocimetry (PIV). Due to its multi-cell structure, a typical paraglider canopy possesses surface grooves that generate spanwise flow and influence the direction of surface airflow. The introduction of tubercles altered the interaction between the incoming flow and these surface grooves. Spanwise flow induced by the grooves varied with the angle of attack, and its interaction with the tubercles modified the overall flow behavior. While the base model displayed fully separated flow in the post-stall region, the tubercled model demonstrated a bistable flow pattern characterized by alternating attached and separated flow over time. This bistability was particularly evident in the trough regions of the tubercles. The underlying mechanisms driving this behavior will be discussed in the presentation.