There is a lack of knowledge on the hydrodynamic behaviour of an AdBm Noise Mitigation System (NMS) designed to reduce sound during monopile piling, which is relevant for improving design and safety. The NMS contains panels designed to mitigate underwater noise. Model tests were performed on both an actual AdBm panel and geometry-based perforated panels, and hydrodynamic coefficients in the form of added mass (C_a), drag (C_d), and linear damping (C_b) were determined for the heave and surge directions, improving the understanding of hydrodynamic loads on the NMS.

Experiments were conducted in the Towing Tank No. 2 at TU Delft, where both forced oscillation and wave tests were performed with test conditions based on regular environmental waves. The hydrodynamic coefficients in heave and surge have been determined and show that the nondimensional Keulegan-Carpenter number (KC) is the most dominant parameter, which leads to the coefficients being expressed as functions of KC. Tests were performed with a single panel and three panels in series to study interaction effects. The main findings showed a significant decrease in C_d and C_b up to 70% within the tested KC range using panels in series, resulting in lower hydrodynamic loads compared to using a single panel. Furthermore, the results of the forced oscillation and wave tests were compared. The hydrodynamic coefficients were found to be similar for low KC values, but the forced oscillation results increasingly overestimated the hydrodynamic coefficient values as KC increased. However, the range of comparison was constrained due to limitations in the wave maker capabilities. The findings contribute to a better understanding of the hydrodynamic loads on the perforated models that reduce the knowledge gap of the hydrodynamic behaviour of the NMS, providing a basis for improving the design parameters for the deployment system.