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Fourier functional analysis for unsteady aerodynamic modelingA method based on Fourier analysis is developed to analyze the force and moment data obtained in large amplitude forced oscillation tests at high angles of attack. The aerodynamic models for normal force, lift, drag, and pitching moment coefficients are built up from a set of aerodynamic responses to harmonic motions at different frequencies. Based on the aerodynamic models of harmonic data, the indicial responses are formed. The final expressions for the models involve time integrals of the indicial type advocated by Tobak and Schiff. Results from linear two- and three-dimensional unsteady aerodynamic theories as well as test data for a 70-degree delta wing are used to verify the models. It is shown that the present modeling method is accurate in producing the aerodynamic responses to harmonic motions and the ramp type motions. The model also produces correct trend for a 70-degree delta wing in harmonic motion with different mean angles-of-attack. However, the current model cannot be used to extrapolate data to higher angles-of-attack than that of the harmonic motions which form the aerodynamic model. For linear ramp motions, a special method is used to calculate the corresponding frequency and phase angle at a given time. The calculated results from modeling show a higher lift peak for linear ramp motion than for harmonic ramp motion. The current model also shows reasonably good results for the lift responses at different angles of attack.
Document ID
Document Type
Contractor Report (CR)
Lan, C. Edward (Kansas Univ. Center for Research, Inc. Lawrence, KS, United States)
Chin, Suei (Kansas Univ. Center for Research, Inc. Lawrence, KS, United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1991
Subject Category
Report/Patent Number
NAS 1.26:187964
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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