Dear all,
The following image is from “The Unsteady Aerodynamics Module for FAST 8”, page 18.
Does anyone konw where the term in red circle arises from?
Leishman said it is the final value given by the steady linearized subsonic theory. But linearized subsonic just add a compressible correction to a impressible flow, which claim that pitching moment about 1/4 chord is zero due to pitch rate (Unsteady Aerodynamics. Potential and Vortex Methods-Grigorios Dimitriadis, 131).
Best regards,
The term comes from an extension of the circulatory contribution to the quarter-chord pitching moment, which following authors such as [Bisplinghoff, R. L., Ashley, H., and Halfman, R. L. Aeroelasticity.Dover Publications, Inc., 1955] and Johansen [Risø–R–1116(EN)] can be written as \pi / (8 * \beta) = 2 \pi / (16 * \beta) where \beta is the Prandlt-Glauert compressibility factor, and 2*\pi is an approximation for the C_{n_\alpha}. The same approximation is used for the C{N_\alpha} term by other authors.
Thanks,
The following image is a screenshot of report by Johansen [Risø–R–1116(EN)]. As in most literature, the author only cited a certain result in the document without providing a detailed explanation. I’ll dive into Chapter 5 of Aeroelasticity by Bisplinghoff to see if I can find any clues.
