Wind Tunnel Investigation of Airfoils Oscillating in Reverse Flow. Volume 1. Summary and Evaluation of Results
BOEING VERTOL CO PHILADELPHIA PA
Pagination or Media Count:
The report presents the results of an experimental investigation of the dynamic airloads on an airfoil Vertol 23010-1.58 immersed in reverse flow such as occurs on the retreating side of a helicopter rotor disc in forward flight. Forces and moments in two-dimensional flow were determined from airfoil differential pressures measured during pitching oscillation. Mach number, Reynolds number, and mean angle-of-attack ranges corresponded to those typically encountered under full-scale flight conditions. Frequencies of oscillation were varied between values corresponding to the 1rev and typical first elastic torsional frequency of rotor blades. Pitching oscillation was shown to postpone normal force and pitching moment stall to angles of attack well beyond static values. Large increases in dynamic CN and CM maxima due to reduced frequency and pitch rate effects were observed, while variations due to Mach number were found to be relatively small.
- Fluid Mechanics