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Flow-induced vibrations of a pitching and plunging airfoil
Published online by Cambridge University Press: 06 January 2020
Abstract
The flow-induced vibration (FIV) of an airfoil freely undergoing two-degrees-of-freedom (2-DOF) motions of plunging and pitching is numerically investigated as a function of the reduced velocity and pivot location in a two-dimensional free-stream flow. This investigation covers a wide parameter space spanning the flow reduced velocity range of $0<U^{\ast }=U/(\,f_{n}c)\leqslant 10$ and the pivot location range of $0\leqslant x\leqslant 1$, where $U$ is the free-stream velocity, $f_{n}$ is the natural frequency of the system set equal in the plunge and pitch directions, $c$ is the chord length of the foil and $x$ is the normalised distance of the pivot point from the leading edge. The numerical simulations were performed by employing an immersed boundary method at a low Reynolds number ($Re=Uc/\unicode[STIX]{x1D708}=400$, with $\unicode[STIX]{x1D708}$ the kinematic viscosity of the fluid). Through detailed analyses of the dynamics of the 2-DOF vibrations and wake states, a variety of FIV response regimes are identified, including four regions showing synchronisation or near-synchronisation responses (labelled as S‐I, S‐II, S‐III and S‐IV) and four transition regimes (labelled as T‐I, T‐II, T‐III and T‐IV) that show intermittent, switching or chaotic responses, in the $x{-}U^{\ast }$ space.
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- © 2020 Cambridge University Press
References
Wang et al. supplementary movie 1
A 2T wake mode observed at $(x, U^*) = (0.50, 1.32)$ in regime S-I.
Wang et al. supplementary movie 2
A 2P wake mode observed at $(x, U^*) = (0.50, 1.63)$ in regime S-I.
Wang et al. supplementary movie 3
A 2T wake mode observed at $(x, U^*) = (0.50, 2.87)$ in regime S-I.
Wang et al. supplementary movie 4
A multiple P (mP) wake mode observed at $(x, U^*) = (0.50, 3.49)$ in regime S-I.
Wang et al. supplementary movie 5
A P+S wake mode observed at $(x, U^*) = (0.50, 9.07)$ in regime S-III.
Wang et al. supplementary movie 6
A P+C wake mode observed at $(x, U^*) = (0.35, 9.07)$ in regime S-II.
Wang et al. supplementary movie 7
A mP+C wake mode observed at $(x, U^*) = (0.85, 9.07)$ in regime S-IV.
Wang et al. supplementary movie 8
A stable 2(P+2S) mode observed at $(x, U^*) = (0.65, 1.01)$ in regime S-I.
Wang et al. supplementary movie 9
An unstable 2(P+2S) mode observed at $(x, U^*) = (0.85, 1.32)$ in regime S-I.
Wang et al. supplementary movie 10
A stable 2S mode observed at $(x, U^*) = (0.4, 1.32)$ in regime S-I.
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