A DEMONSTRATION OF ADAPTIVE LEAST-MEAN-SQUARE CONTROL OF SMALL AMPLITUDE VORTEX-INDUCED VIBRATIONS

Abstract

Small amplitude vortex-induced vibrations of flexible cylinders are controlled using a robust adaptive Least Mean Square (LMS) algorithm. The algorithm, with its adaptive control capabilities, provides an excellent means of rejecting the effect of the periodic vortex-induced excitations which act persistently on the flexible cylinders. It is also capable of accommodating a considerable amount of uncertainty of the structural parameters of the vibrating cylinders. The LMS control action is developed using a hot-wire anemometer placed in the wake of the cylinder to generate a reference signal which is indicative of the vortex-shedding excitation. The resulting signal is manipulated and fed forward to minimize the structural vibration at critical locations. In this manner, the LMS method presents a simple yet powerful alternative to classical control methods or disturbance-counteracting laws. The effectiveness of the LMS controller in suppressing small amplitude vortex-induced vibrations of flexible cylinders is demonstrated experimentally at various flow conditions. The effect of the design parameters of the LMS controller on its performance is also investigated. The results obtained emphasize the potential of the LMS method as an effective and robust means for attenuating undesirable vortex-induced vibrations.