Surface modifications for drag reduction in flow around circular cylinders: a critical review

Flow past circular cylinders is a classical fluid dynamics problem with wide-ranging engineering applications. This review critically examines passive surface modification techniques aimed at reducing drag and mitigating vortex-induced vibrations (VIV). Following the PRISMA 2020 methodology, 29 peer-reviewed studies published between 2005 and 2025 were analyzed, focusing on surface geometries such as grooves, dimples, riblets, and hybrid textures. These modifications alter boundary-layer development, delay separation, and modify vortex shedding, achieving drag reductions of 10–40% depending on geometry and Reynolds number. Grooves, particularly helical and longitudinal types, were the most frequently studied and demonstrated consistent suppression of wake instabilities, while dimples showed favorable results through boundary-layer reattachment and pressure redistribution. Despite progress, research remains dominated by computational fluid dynamics (CFD), with limited experimental validation and few investigations at high Reynolds numbers. Additional challenges include scalability, durability, and performance consistency under real-world conditions. Future research should prioritize experimental validation, high-Re studies, and optimization of hybrid or adaptive surfaces to enhance robustness and applicability. Overall, passive surface modifications present an energy-efficient strategy for aerodynamic drag reduction in bluff body flows. From an engineering perspective, even modest drag reductions can yield substantial energy savings, improve structural durability, and enhance operational efficiency.