Shark Gill-Inspired Spanwise Blowing: Multi-Nozzle Aerodynamic Flow Experimentation on a Delta Wing

Abstract

A shark gill-inspired spanwise blowing system is experimentally investigated as a novel approach to modify airflow over a low-sweep delta wing. The fuselage design, informed by a blue shark's geometry, defines the size and longitudinal placement of gill slits independently actuated with nozzles to eject airflow. The three gills are located upstream, at, and aft of the leading edge, each ejecting 9.26 psi of air downstream at 22.6 and 45 degrees outboard relative to the fuselage. Wind tunnel testing with a freestream velocity of 20 m/s was conducted for all possible configurations of the gills open individually or simultaneously and the resulting aerodynamic force and moment data was collected. The baseline low sweep delta wing exhibits a transition in dominant lifting mechanisms from attached flow to leading edge vortex induced lift at higher angles of attack as is typical for a delta wing. Results indicate the first and third nozzles produce the most significant changes in aerodynamic behavior including lift, drag, and pitching moment. When the gills airflow is directed more outboard the effect is more pronounced suggesting a greater spanwise airflow interaction. The first gill alone at 45 degrees produced the most dramatic increase in lift and pitch. The first and third gill together reduced drag at both 22.6 and 45 degrees. The first nozzle was found to strengthen attached airflow and leading edge vortices, increasing the pitching-up moment. while the third gill delays vortex breakdown, reducing drag. These findings present motivation for future studies of multi-nozzle spanwise blowing as a flow control technique and demonstrate a new bio-inspired basis for aerodynamic design.