Techniques for Reducing Frictional Resistance to Enhance Hydrodynamic Performance and Fuel Efficiency

The rising fuel cost and stricter emission regulations have intensified the need for innovative drag-reduction methods in marine vessels to improve fuel efficiency and reduce environmental impact. A reduction in frictional resistance, a significant contributor to overall drag, is the key to these requests. This review paper explores two innovative strategies for reducing frictional drag: Air Lubrication System (ALS) and Surface Treatment methods, with a focus on Micro-Bubble Drag Reduction (MBDR), Air Cavity System (ACS), and Biomimetic Shark Skin Treatment. ALS involves the injection of air or air bubbles around the hull surface to create a barrier between the hull and water. Through methods like Micro-Bubble Drag Reduction (MBDR) and Air Cavity Systems (ACS), the significant potential was demonstrated, with MBDR and ACS achieving up to an 80% and 35% reduction in drag under ideal conditions respectively. With promising real-world applications like the Mitsubishi Air Lubrication System (MALS) and the Damen Air Cavity System (DACS) reaching fuel consumption improvements of 5% and 7% - 12% namely, the potential of ALS was clearly shown. Meanwhile, Biomimetic surface treatment, a method involving applying shark skin-inspired riblet structures to the hull surface, reducing frictional resistance by minimizing shear stress, achieved a modest reduction of 3.89% to 5.2%. While each method offers substantial benefits, limitations in scalability and applicability across various vessel types remain challenges. Future research is crucial to optimize these technologies for better compatibility and drag reduction efficiency, paving the way for more sustainable and cost-effective marine transportation.