Force-Feedback Control in VIV Experiments

A force-feedback control system for VIV experiments is designed and evaluated for the purpose of achieving high accuracy free vibration tests. Through an organized approach, this work details specific methods for minimizing the combined effect of mass and damping using control system fundamentals. The dynamics of the closed-loop system are analyzed, a numerical model constructed and a control scheme is chosen and implemented in real-time. The control system performance is evaluated by performing frequency response tests in air. Free vibrations of a smooth aluminum cylinder are performed at Reynolds number 19000. Test series with damping ratios of one, two and five percent are performed, all with nondimensional mass four. A peak amplitude ratio of 1.15 is observed for the case of lowest damping. Forced vibration tests with the same setup are performed and compared to the free vibration results, giving consistent results.