Rapid characterisation and modelling of marine biofilm deformation for estimating biofouling frictional drag

Maritime transport emits around 940 million tonnes of CO2 annually. Ships are often fouled by marine biofilms, resulting in increased frictional drag and fuel penalties that can range from minor to very costly (~18% powering penalty), and which contribute significantly to global greenhouse gas emissions. Fouling biofilms are diverse in microbial composition, structure, and coverage. Effective fouling management through coating development and hull maintenance are essential targets for the global ship hull coatings industry and will make significant contributions to marine decarbonisation.

While biofilms demonstrably increase hull surface roughness, their drag impact cannot be explained by roughness alone. Rather, biofilm mechanical properties, physical properties, surface area coverage and their interplay are hypothesised to be important shapers of fouling frictional drag. Biofilms are viscoelastic materials which deform to some degree when physically stressed, dissipating energy that might otherwise rupture the polymer matrix resulting in detachment. Hydrodynamic stress beyond normal conditions, however, can result in biofilm erosion and detachment, altering a fouled surface and its resulting drag properties. The mechanical properties of a biofilm matrix are responsive to flow conditions. Across the range of vessel activity profiles present in the global shipping fleet, fouling biofilms can have significantly different mechanical properties, and their susceptibility to hydrodynamic clearance through shearing as the vessel moves through the water arguably would similarly vary.

Biofilm mechanical and physical metrics that are predictive of biofilm drag across different hydrodynamic conditions. However, the key challenge is that a robust predictive modelling and testing techniques for biofilm mechanical properties are currently not available.

In this project, we aim to develop predictive biofilm testing and modelling techniques centred on biomechanics and hydrodynamic drag. This can potentially make a significant contribution to hull frictional drag and global maritime greenhouse gas emissions.