13 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
An Assessment of the Impact of Compressibility on Dynamic Stall
The effect of compressibility on dynamic stall is assessed, based on a review of past research in this area. A careful discussion of recent research is presented focusing on both model rotor, and 2-D dynamic stall studies where compressibility effects have been quantified. Examples from the various research efforts are discussed, and detailed analysis of the influence of compressibility on the dynamic stall process is presented. Differences between incompressible and compressible dynamic stall physics are identified, and the role of computation in the modeling of the compressible dynamic stall process is discussed.ARO-MIPR-125-93U.S. AFOS