Numerical study on hydrodynamic performance of underwater manipulator in the subcritical region

The hydrodynamic performance of an underwater manipulator is critical for establishing a hydrodynamic model for precise positioning or grasping. However, elucidating the variable hydrodynamic performance is difficult owing to the different working attitudes in the usage of underwater manipulators. Therefore, this study aims to investigate the hydrodynamic coefficients and flow field characteristics of the underwater manipulator with different motion attitudes in Cartesian coordinates. The effects of section shape, spacing, and interaction on the hydrodynamic performance are investigated in the subcritical range. Results indicated that the lift and drag coefficient of the elliptical section were 76.15 and 51.30% lower than that of the circular section, respectively. Furthermore, the amplitude of the downstream elliptical section was affected primarily by the spacing. However, when arm 2 was in the upstream, the lift coefficient of arm 1 was 3.4 times greater than that of arm 2. This implied that the underwater manipulator is more stable when arm 2 was in the upstream. This study will provide theoretical guidance to reveal the hydrodynamic performance of the underwater manipulator and other marine equipment, such as risers and submarine cable.