Numerical investigation on concomitant VIV and parametric excitation in a rigid cylinder mounted on an elastic support

This work focuses on a numerical investigation on the response of a rigid cylinder mounted on an elastic support subjected to simultaneous vortex-induced vibration (VIV) and parametric excitation. The rigid cylinder has diameter D, mass ratio m * = 2.6 and is immersed in a uniform flow characterized by its free-stream velocity U ∞ . The parametric excitation is emulated by means of a time-dependent stiffness with the form k y ( t ) = k y ¯ + Δ k y cos ( Ω y t ) . The fluid loads are modeled by means of a wake-oscillator model and only oscillations in the cross-wise direction are allowed. The main objective is to assess the influence of the parametric excitation on the VIV phenomenon, discussing the obtained results under the light of experimental and numerical data from flexible cylinders. It is shown that, contrary to observed for flexible cylinders, the parametric excitation amplifies the VIV response only in a narrow range of reduced velocities close to the peak of cylinder response. This increase in the cylinder response amplitudes follows the increase in the force coefficients. Other numerically obtained results include amplitude-modulated time histories and the enrichment of the spectral content. This latter results are confirmed by an analytical study developed using the method of multiple scales.