Estimation of Unsteady Lift on a Pitching Airfoil From Wake Velocity Surveys

TITLE AND SUBTITLE:
Estimation of Unsteady Lift on a Pitching Airfoil From Wake Velocity Surveys

AUTHOR(S):
K.B.M.Q. Zaman, J. Panda, and C.L. Rumsey

REPORT DATE:
January 1993

FUNDING NUMBERS:
WU-505-52-62

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-7465

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, D.C. 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-105947

SUPPLEMENTARY NOTES:
Prepared for the 31st Aerospace Sciences Meeting and Exhibit sponsored by the American Institute of Aeronautics and Astronautics, Reno, Nevada, January 11-14, 1993.

ABSTRACT:
The results of a joint experimental and computational study on the flowfield over a periodically pitched NACA0012 airfoil, and the resultant lift variation, are reported in this paper. The lift variation over a cycle of oscillation, and hence the lift hysteresis loop, is estimated from the velocity distribution in the wake measured or computed for successive phases of the cycle. Experimentally, the estimated lift hysteresis loops are compared with available data from the literature as well as with limited force balance measurements. Computationally, the estimated lift variations are compared with the corresponding variation obtained from the surface pressure distribution. Four analytical formulations for the lift estimation from wake surveys are considered and relative successes of the four are discussed.

SUBJECT TERMS:
Dynamic stall; Unsteady separation; Lift; Wake; Airfoil

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