The vibration of an elastic wing with an attached cavity in periodically perturbed flows is analyzed. Because the cavity thickness and length L also are perturbed, an excitation with a fixed frequency omega leads to a parametric vibration of the wing, and the amplitudes and spectra of its vibration have nonlinear dependencies on the amplitude of the perturbation. Numerical analysis was carried out for a two-dimensional how of ideal fluid. Wing vibration was described by means of the beam equation. As a result, two frequency bands of a significant vibration increase were found. A high-frequency band is associated mainly with an elastic resonance of the wing, and a cavity can add a certain damping. A low-frequency band is associated with cavity-volume oscillations. The governing parameter fbr the low-frequency vibration is the cavity length-based Strouhal number St(c) = omega L/U, where U is the free-stream speed. The most significant vibration in the low-frequency band corresponds to approximately constant values of Sh(c) and has the most extensive subharmonics. (C) 2000 Academic Press.
