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

海运每年排放约9.4亿吨二氧化碳。船舶经常受到海洋生物膜的污染，导致摩擦阻力和燃料惩罚增加，从轻微到非常昂贵(约18%的动力惩罚)，这对全球温室气体排放有很大贡献。污垢生物膜在微生物组成、结构和覆盖率方面各不相同。通过涂料开发和船体维护进行有效的污垢管理是全球船体涂料行业的基本目标，并将为海洋脱碳做出重大贡献。虽然生物膜明显增加了船体表面的粗糙度，但它们的阻力影响不能仅用粗糙度来解释。相反，生物膜的机械特性、物理特性、表面积覆盖率及其相互作用被认为是污垢摩擦阻力的重要影响因素。生物膜是一种粘弹性材料，当受到物理压力时，它们会发生一定程度的变形，消耗的能量可能会破坏聚合物基质，导致剥离。然而，超过正常条件的流体动应力会导致生物膜的侵蚀和脱落，改变被污染的表面及其所产生的阻力特性。生物膜基质的机械性能与流动条件有关。纵观全球船队中存在的各种船舶活动情况，污垢生物膜的机械性能可能有很大不同，它们在船舶在水中移动时通过剪切进行流体动力清除的敏感性可能也会有类似的变化。生物膜机械和物理指标可以预测生物膜在不同的水动力条件下的阻力。然而，关键的挑战是目前还没有一种稳健的预测生物膜机械性能的建模和测试技术。在这个项目中，我们的目标是开发以生物力学和流体动力学阻力为核心的预测性生物膜测试和建模技术。这可能会对船体摩擦阻力和全球海洋温室气体排放做出重大贡献。

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.