Study on the control mechanisms of pulsed co-flow jet based on Lagrangian coherent structures

Pulsed co-flow jet, as an efficient flow control technology, can significantly enhance the aerodynamic performance of airfoils. However, its complex near-wall coupled flow phenomena result in intricate control mechanisms. This study adopts a Lagrangian perspective to investigate the flow phenomena and explore the underlying control mechanisms. First, the control effects of pulsed co-flow jet and steady co-flow jet are compared. Then, Lagrangian coherent structures are introduced into the study of pulsed co-flow jet flow control. Through numerical simulations, the material transport phenomena within the flow field of a pulsed co-flow jet airfoil based on the National Advisory Committee for Aeronautics (NACA) 0012 airfoil are examined in detail. Additionally, by combining fluid dynamics methods with the pressure coefficient distribution, the primary reasons for the lift enhancement of the pulsed co-flow jet airfoil are analyzed. Finally, the impact of material transport on the flow field topology is discussed. The results show that material transport during the flow field evolution occurs in four distinct stages, each characterized by unique flow dynamics. Notably, the jet-induced vortex consists of an internal core and an external coupling region, with the suction slot significantly influencing the flow field, as captured in this study.