Influence of hard marine fouling on energy harvesting from Vortex-Induced Vibrations of a single-cylinder

Abstract

Marine fouling changes the flow regime around sub-sea structures, such as Vortex-Induced Vibration Aquatic Clean Energy (VIVACE) converters. The present experimental study investigates the effects of marine fouling on mechanical power harvesting performance from the Vortex-Induced Vibration (VIV) of single circular cylinders. The towing tank VIV tests are conducted on elastically mounted rigid cylinders. Hard artificial marine fouling with aggregated spatial distribution is considered. Effects of coverage ratio and spatial distributions are investigated.The test results show that, on the whole, marine fouling suppresses the VIV oscillations. Over the upper branch, lower branch and the de-synchronization zone of the VIV response, energy transfer ratio (η) with the biofouled cylinders stay around 15–36% below that from the corresponding clean cylinder. It is also found that the coverage percentage of the fouling and the fouling irregularity negatively affect the VIV hydro energy transfer ratio. The fouling irregularity effects, however, are less significant than those from the coverage percentage. The results of the study suggest that biofouling growth may considerably degrade the long-term energy extraction performance of a VIVACE device.