Effect of Three-Dimensional Geometry on Harmonic Gust–Airfoil Interaction

Amanda S. M. Smyth, Anna M. Young, Luca Di Mare

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Two-dimensional (2-D) strip-theory modeling of unsteady gust–airfoil interaction is standard practice in many industrial applications, but the limits of applicability of 2-D unsteady flow modeling on three-dimensional (3-D) wing and rotor geometries are not well understood. This paper investigates the effects of 3-D geometry features (such as finite span, taper, sweep, and rotation) on the unsteady lift response to gusts and the flow-physical differences between 2-D and 3-D geometries in unsteady flow. A frequency-domain inviscid vortex lattice model is validated and used for the 3-D analysis. The results are compared to unsteady transfer functions from 2-D linear analytic theory (for example, Theodorsen and Sears functions). The study agrees with previous research findings that 3-D effects are most significant at low reduced frequencies and low aspect ratios, as well as near the wing tips. The driving cause of 3-D response is shown to be the wake vorticity: both streamwise and spanwise components of unsteady wake vorticity must be modeled. The study concludes by investigating whether unsteady response of more complex 3-D wing and rotor geometries can be represented by the response of a rectangular wing. The results indicate that this is possible for tapered wings and rotating blades, but not for swept wings.

Original languageEnglish
Number of pages14
JournalAIAA Journal
Early online date11 Nov 2020
Publication statusE-pub ahead of print - 11 Nov 2020

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