A multi-physics model for modelling noise mitigation using an air-bubble curtain in impact pile driving

Abstract

Underwater noise from offshore pile driving has raised significant concerns over its potentially destructive impact on marine habitat. Assessment and mitigation of the underwater noise is usually required to ensure that sound levels stay within the noise thresholds. The air-bubble curtain system is one of the most widely applied noise mitigation techniques. This paper presents a multi-physics approach for modelling an air-bubble curtain system in application to offshore pile driving. The complete model consists of four modules: (i) a hydraulic model for modelling the transport of compressed air from the offshore vessel to the perforated hose located into the sea bed; (ii) a hydrodynamic model for capturing the characteristics of bubble clouds in varying development phases through depth; (iii) an acoustic model for predicting the sound insertion loss of the air-bubble curtain; and (iv) a vibroacoustic model for the prediction of underwater noise from pile driving which is coupled to the acoustic model in (iii) through a boundary integral formulation. The waterborne and soilborne noise transmission paths are examined separately, allowing us to explore the amount of energy channelled through the seabed and through the bubble curtain in the water column. The model allows for a large number of simulations to examine difference configurations of a single bubble curtain and a double big bubble curtain. Model predictions are validated with measured data.