NTRS - NASA Technical Reports Server

Back to Results
Computation of aerodynamic interference effects on oscillating airfoils with controls in ventilated subsonic wind tunnelsLift interference effects are discussed based on Bland's (1968) integral equation. A mathematical existence theory is utilized for which convergence of the numerical method has been proved for general (square-integrable) downwashes. Airloads are computed using orthogonal airfoil polynomial pairs in conjunction with a collocation method which is numerically equivalent to Galerkin's method and complex least squares. Convergence exhibits exponentially decreasing error with the number n of collocation points for smooth downwashes, whereas errors are proportional to 1/n for discontinuous downwashes. The latter can be reduced to 1/n to the m+1 power with mth-order Richardson extrapolation (by using m = 2, hundredfold error reductions were obtained with only a 13% increase of computer time). Numerical results are presented showing acoustic resonance, as well as the effect of Mach number, ventilation, height-to-chord ratio, and mode shape on wind-tunnel interference. Excellent agreement with experiment is obtained in steady flow, and good agreement is obtained for unsteady flow.
Document ID
Document Type
Conference Paper
Fromme, J. A. (Nevada Univ. Las Vegas, NV, United States)
Golberg, M. A. (Nevada, University Las Vegas, Nev., United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1979
Subject Category
Report/Patent Number
AIAA PAPER 79-0346
Meeting Information
American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting(New Orleans, LA)
Funding Number(s)
Distribution Limits