Computational fluid dynamics study of the motion stability of an autonomous underwater helicopter

In this study, the motion stability of a new type of autonomous underwater vehicle (AUV) named an “autonomous underwater helicopter (AUH)” with a disk-shaped hull was analyzed to better accomplish the complex tasks under the sea, namely, pipeline maintenance, mobile observation network, resources exploration, and isodepth navigation. A Reynolds Averaged Navier-Stokes (RANS) grid for the AUH was created with an ICEM mesh generation tool. The RANS-based computational fluid dynamics (CFD) technique, ANSYS-CFX, was adopted to analyze the AUH's behavior, including its motion stability and maneuverability in the horizontal and vertical planes. Pivotal hydrodynamic technical issues including configurations selection and a trade-off study of the AUH were analyzed with the RANS solver, including computed pressure distribution and comparison of different lengths of aquatic transducers mounted on the AUH for enhanced hydrodynamic performance. The Routh motion stability criterion based on the 6-DOF equations of motion consisting of linear hydrodynamic derivatives was implemented by the RANS solver for the optimized AUH with a service speed in the range of 1-3 knots. The simulation results and experimental tests show that the AUH has ample motion stability for enhanced maneuverability in translational and rotatory motion during under-sea navigation. The results suggest that design configurations of the appended hull can be used on AUVs.