Investigation of arbitrarily-shaped encapsulated bubbles for attenuation low-frequency underwater sound
Ana Carolina Azevedo Vasconcelos (TU Delft - Mechanical Engineering)
Jovana Jovanova (TU Delft - Mechanical Engineering)
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Abstract
The increasing installation of large offshore monopiles for wind turbine foundations generates harmful underwater noise during pile driving, particularly at low frequencies. Existing noise mitigation systems target noise around 1000 Hz, however, their performance reduces for lower frequency noise expected for the upcoming monopiles. To address this, this paper develops and investigates a new noise mitigation system – a metamaterial-based curtain, or meta-curtain-using metamaterials and smart materials to filter sound waves generated during the pile installation, focusing mainly on the primary noise source – from pile to water. The meta-curtain is developed via a design methodology that covers the understanding of bubble fundaments, the attenuation performance in the pile-water system, and the structural integrity and deployment mechanism of the curtain frame. This paper focuses mainly on the steps related to the acoustic of the new bubble designs and their attenuation performance. Future work explores the structural performance of the meta-curtain. This work opens the door to the investigation of new designs that can potentially reduce the propagation of low-frequency waves from monopile installations.
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