Power extraction using flow-induced vibration of a circular cylinder placed near another fixed cylinder

• A tandem arrangement of two cylinders was experimentally examined in a towing tank.
• One cylinder was movable and another one was fixed.
• Vortex- and wake-induced vibrations were observed depending on towing directions.
• The wake-induced vibration has a larger amplitude than the vortex-induced vibration.
• The wake-induced vibration was found to be useful for extracting flow energy.

We conducted an experiment in a towing tank to investigate the performance of an energy extraction system using the flow-induced vibration of a circular cylinder. This experiment tested three different cases involving the following arrangements of cylinder(s) of identical diameter: the upstream fixed–downstream movable arrangement (case F); the upstream movable–downstream fixed arrangement (case R); and a movable isolated cylinder (case I). In cases F and R, the separation distance (ratio of the distance between the centers of the two cylinders to their diameters) is fixed at 1.30. Measurement results show that while cases F and I generate vortex-induced vibration (VIV) resonance responses, case R yields wake-induced vibration (WIV) at reduced velocity over 9.0, which is significantly larger than that of the VIV response, leading to the induction of higher electronic power in a generator. Accordingly, primary energy conversion efficiency is higher in the case involving WIV.