THE POST-HOPF-BIFURCATION RESPONSE OF A LOOSELY SUPPORTED CYLINDER INAN ARRAY SUBJECTED TO CROSS-FLOW .2. THEORETICAL-MODEL AND COMPARISONWITH EXPERIMENTS

A nonlinear quasi-steady model for the analysis of the dynamics of a l oosely supported cylinder, which takes into account position-dependent nonlinear fluid forces as well as nonuniform flow, is formulated. The model includes an approximation for the equivalent viscous damping as sociated with energy dissipation on impact at the support. The nonline ar model shows reasonably good agreement with experiments, in predicti ng the observed bifurcations in the cylinder response. Comparison crit eria include the standard orbital plots, time traces and response spec tra. A borderline chaotic response is found to be predominant over the test velocity range. In this chaotic regime, the theoretical results were verified via attractor fractal-dimension calculations and saddle orbit distributions; theoretical values of these invariant measures co mpare reasonbly well with their experimental counterparts. Two mechani sms leading to chaos have been identified for this system. The first i s a switching mechanism, at the onset of impacting. The second, and mo re prevalent, is the type I intermittency route to chaos.