Comparative numerical analysis of grooved, microbubble, and coupled surfaces for underwater vehicle drag reduction

Surface drag reduction technology has the potential to significantly decrease the frictional resistance in underwater vehicles, thereby improving their speed, propulsive efficiency, and operational flexibility under diverse conditions. In this paper, numerical simulations are utilized to explore the drag-reducing effects of grooved surfaces, microbubble-covered surfaces, and groove–microbubble coupled surfaces, with particular focus on the influence of microbubble diameter, flow rate, and the positioning of drag-reducing surfaces on underwater vehicles. The results reveal that the microbubble-covered surface offers the highest drag reduction, achieving up to 97.16 % reduction on the lower surface of the vehicle at a flow velocity of 1 m/s. When combined, the grooved and microbubble-covered surfaces interact in a way that limits the movement of microbubbles, reducing their coverage on the drag-reducing surface and resulting in a lower overall drag reduction compared to the microbubble-covered surface alone. Despite this, the groove structure enhances microbubble retention, particularly in areas where buoyancy effects lead to rapid gas depletion, thus reducing drag in adjacent surface. This comprehensive analysis highlights the potential of groove-microbubble coupled surfaces for optimizing drag reduction on underwater vehicles under various flow conditions.