Wake Interaction Effects on Performance of Low Reynolds Number Co-Rotating Coaxial Rotors

This study explores the aerodynamic performance and wake interactions of co-rotating coaxial rotors for unmanned aerial system (UAS) applications, focusing on the low Reynolds number regime. The investigation examines how stacking distance and index angle influence rotor performance using computational fluid dynamics (CFD) simulations. Two rotors with a 9-inch diameter and a NACA 23012 airfoil profile were analyzed at stacking distances of 0.15, 0.25, and 0.35, with index angles ranging from 0 degrees to 150 degrees in 30-degree increments. The results show that thrust and torque are highly sensitive to both stacking distance and index angle, with the strongest variations occurring at the smallest stacking distance. These trends are attributed to complex wake dynamics and tip vortex interactions between the rotors. Vorticity contour plots reveal key flow phenomena, such as tip vortex impingement and wake deformation, and demonstrate how the relative positioning of the upstream rotor’s tip vortices with respect to the downstream rotor critically influences performance. These findings advance the understanding of wake interactions in co-rotating coaxial rotor systems, offering valuable insights for optimizing rotor performance in compact UAS designs.