Biofouling-induced blockage effects on the hydrodynamic and structural responses of netting panels

Marine interception systems are critical for protecting coastal infrastructure and ecosystems, such as nuclear power plants, by preventing debris accumulation and biological invasions. During long-term service in marine environments, biofouling progressively accumulates on netting surfaces, increasing the effective twine diameter and blockage ratio, thereby altering the hydrodynamic loading and structural response of the nets. However, the quantitative characterization of biofouled netting panel loads under different blockage conditions remains insufficiently understood. To address this gap, this study proposes an equivalent blockage-ratio wall-load mapping method for evaluating the hydrodynamic and structural responses of netting panels with different levels of biofouling accumulation. In this method, varied blockage ratios are represented by modifying the effective strand diameter in the fluid domain, while a radial coordinate interpolation technique is introduced to project the resulting wall-pressure distributions onto a consistent structural geometry. This treatment enables quantitative comparison of the mechanical responses of netting panels under different biofouling-induced blockage conditions. Based on this method, a series of one-way fluid–structure interaction simulations was conducted to systematically investigate the effects of blockage ratio, flow velocity, mesh geometry, and material properties on netting performance. The results show that, with increasing blockage ratio, the drag coefficient initially increases and then slightly decreases after reaching a peak, while the maximum deformation and von Mises stress increase monotonically. The largest deformation occurs in the central region of the netting panel, whereas stress concentrations mainly appear at the strand-frame junctions. Compared with square meshes, diamond meshes induce greater drag and deformation but promote more uniform stress distributions. In addition, increasing the flow velocity amplifies deformation and stress levels while generally reducing the drag coefficient.