Characterization of Variable Hydrodynamic Coefficients and Maximum Responses in Two Dimensional Vortex Induced Vibrations With Dual Resonances

Abstract

A phenomenological model and analytical–numerical approach to systematically characterize variable hydrodynamic coefficients and maximum achievable responses in twodimensional vortexinduced vibrations with dual twotoone resonances are presented. The model is based on double Duffing and van der Pol oscillators which simulate a flexibly mounted circular cylinder subjected to uniform flow and oscillating in simultaneous crossflow/inline directions. Depending on system quadratic and cubic nonlinearities, amplitudes, oscillation frequencies and phase relationships, analytical closedform expressions are derived to parametrically evaluate key hydrodynamic coefficients governing the fluid excitation, inertia and added mass force components, as well as maximum dualresonant responses. The amplification of the mean drag is ascertained. Qualitative validations of numerical predictions with experimental comparisons are discussed. Parametric investigations are performed to highlight the important effects of system nonlinearities, mass, damping, and natural frequency ratios.