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

Small amplitude vortex-induced vibrations of flexible cylinders are co ntrolled using a robust adaptive Least Mean Square (LMS) algorithm. Th e algorithm, with its adaptive control capabilities, provides an excel lent means of rejecting the effect of the periodic vortex-induced exci tations which act persistently on the flexible cylinders. It is also c apable of accommodating a considerable amount of uncertainty of the st ructural parameters of the vibrating cylinders. The LMS control action is developed using a hot-wire anemometer placed in the wake of the cy linder to generate a reference signal which is indicative of the vorte x-shedding excitation. The resulting signal is manipulated and fed for ward to minimize the structural vibration at critical locations. In th is manner, the LMS method presents a simple yet powerful alternative t o classical control methods or disturbance-counteracting laws. The eff ectiveness of the LMS controller in suppressing small amplitude vortex -induced vibrations of flexible cylinders is demonstrated experimental ly at various flow conditions. The effect of the design parameters of the LMS controller on its performance is also investigated. The result s obtained emphasize the potential of the LMS method as an effective a nd robust means for attenuating undesirable vortex-induced vibrations. (C) 1996 Academic Press Limited