Marine hydrokinetic energy harvesting performance of diamond and square oscillators in tandem arrangements

The global demand for renewable energy sources has arisen significant research interests in marine hydrokinetic energy harvesting from flow induced vibrations. The current study deals with the hydrokinetic energy harvesting potentials of diamond and square oscillators at various inline configurations. Both the sharp edge sections and the wake induced vibrations in tandem arrangement can lead to galloping type of instability with high energy efficiency ratios. The present in-water towing tank experiments comprise 1DoF vibrating systems at Re ranging from 2 × 103 to 4.8 × 104. The results show that the upstream wake generally enhances the system efficiency and the mechanical work done by the oscillating square cylinder. With tandem diamond cylinders, the upstream vortices enrich both the overall oscillations and the harvested mechanical power by the downstream cylinder. The energy efficiency in the tandem configuration is 3–5 times higher than a single diamond cylinder. The TOPSIS algorithm is applied to sort the energy performance of different configurations. The study proves the extreme advantages of tandem diamond oscillators over square configuration in the extraction of the hydroelastic energy. High-amplitude, high-frequency vibrations of tandem diamond cylinders make them even surpass the typical circular cross-sections in generating the mechanical power. •Square wake reduces response amplitude but enhances energy harvesting performance.•Diamond wake enriches both the oscillations and the harvested mechanical power.•Tandem square and diamond configurations both show resonance type of responses.•Tandem diamond is superior over circular and square shapes in energy harvesting.