Accession Number:

AD0670957

Title:

TWO-DIMENSIONAL TESTS OF AIRFOILS OSCILLATING NEAR STALL. VOLUME 1. SUMMARY AND EVALUATION OF RESULTS

Descriptive Note:

Final technical rept.

Corporate Author:

BOEING VERTOL CO PHILADELPHIA PA

Personal Author(s):

• Liiva, Jaan
• Davenport, Franklyn J.
• Gray, Lewis
• Walton, Ivor C.

Report Date:

1968-04-01

Pagination or Media Count:

146.0

Abstract:

An experimental investigation into rotor blade dynamic stall was conducted. Two typical airfoils, the NACA 0012 modified and the Vertol 23010- 1.58, were tested by measuring the differential pressures acting during pitching and translatory oscillations over a range of angles of attack covering the stall regime. There were two main objectives. The first was to determine the influence of stall on the aerodynamic pitching moment of an airfoil executing pitching motions corresponding to the elastic torsional oscillations of a rotor blade. The second was to determine the extent to which time-varying angle of attack could affect the maximum aerodynamic lift that a rotor blade can develop. The cambered profile remained free of negative damping for 3 to 6 degrees beyond the point where the symmetrical section encountered negative damping in the Mach 0.2 to 0.4 range. The cambered section exhibited higher attainable C sub Ns than the symmetrical section under all conditions of motion, except for the highest frequency tested at Mach 0.6.

Descriptors:

• *HELICOPTERS
• *ROTOR BLADES(ROTARY WINGS)
• *STALLING
• AERODYNAMIC LOADING
• AIRFOILS
• ANGLE OF ATTACK
• CAMBER
• DAMPING
• HELICOPTER ROTORS
• LIFT
• MODEL TESTS
• OSCILLATION
• PITCH(MOTION)
• PREDICTIONS
• TWO DIMENSIONAL FLOW
• WIND TUNNEL MODELS

Subject Categories:

• Aerodynamics
• Helicopters

Distribution Statement:

APPROVED FOR PUBLIC RELEASE