Energy extraction from galloping of a prism restricted to oscillate at a fixed magnitude

We discuss a method to extract energy from galloping of a bluff body by restricting the amplitude of oscillations of a prism to a prescribed fixed value in the flow velocity range where galloping is expected. In this study, we conducted a series of experiments in a recirculating water tunnel over a wide range of reduced velocities and for different values of prescribed amplitudes of oscillations, and we used an electromagnetic generator to extract the energy of the oscillating prism. We show that both the oscillation frequency and the extracted power increase with increasing reduced velocity and the relation between the extracted power and the oscillation frequency is independent from the prescribed amplitude of oscillations. We also show that efficiencies are highest at the lowest reduced velocity where galloping is expected to occur, and while the efficiency decreases with increasing reduced velocity, it never reaches zero, as galloping can be observed up to the maximum reduced velocity for which the system is operational.