Study on the impact of asymmetric design on the hydrodynamic characterization of the disk-shaped autonomous underwater helicopter surging near the seabed.

This article focuses on improving the hydrodynamic performance of a disk-shaped autonomous underwater vehicle called the autonomous underwater helicopter (AUH) when operating near the seabed boundary. Three modified hull geometries—AUH-R1, AUH-R2, and AUH-R3—were proposed by adjusting the lower hull profile to reduce drag and enhance stability. Using numerical simulations based on Reynolds-averaged Navier–Stokes equations and water-channel experiments, the study found that AUH-R3, with a streamlined semi-elliptical lower hull, exhibited the lowest drag and most stable pressure distribution near the seabed. Two mechanisms were identified to explain hydrodynamic changes near the seabed: a blocking effect that increases drag and lift by obstructing flow beneath the hull, and an acceleration effect that reduces drag and lift by speeding up flow near the hull. The findings suggest that reducing bulges and increasing flat regions on the AUH’s lower hull can optimize its near-bottom hydrodynamic performance.