1 research outputs found
Schlieren Studies of Compressibility Effects on Dynamic Stall of Airfoils in Transient Pitching Motion
Compressibility effects on the flowfield of an airfoil
executing rapid transient pitching motion from 0 - 60 degrees
over a wide range of Mach numbers and pitching
rates were studied using a stroboscopic schlieren flow visualization
technique. The studies have led to the first direct
experiments] documentation of multiple shocks on the
airfoil upper surface flow for certain conditions. Also, at
low Mach numbers, additional coherent vortical structures
were found to be present along with the dynamic stall vortex,
whereas at higher Mach numbers, the flow was dominated
by a single vortex. The delineating Mach number
for significant compressibility effects was 0.3 and the dynamic
stall process was accelerated by increasing the Mach
number above that value. Increasing the pitch rate monotonically
delayed stall to angles of attack as large as 27
degrees.AFOSR-MIPR-87-0029 and 88-0010NAVAIRAR