Numerical Investigation into Hydrodynamic Interactions Between an Open-Frame Underwater Cleaning Robot and a Full-Scale Floating Production Storage and Offloading

Most of the published work related to the influence of ship hulls on hydrodynamic characteristics of underwater robots takes ship hulls as nearly infinite planes, paying less attention to the effect of hull shape. Thus using an unsteady Reynolds-averaged Navier-Stokes solver, this work investigates hydrodynamic interactions between an open-frame underwater cleaning robot (OFUCR), which is put into commercial use, and the parallel middle body of a real full-scale floating production storage and offloading (FPSO) with round bilge. Calculated results are validated by some published results. In simulation, the OFUCR moves at a speed of 1 kn, and keeps 0.1 m away from the hull. Drag and lateral forces of OFUCR, and repulsive force due to the interference of FPSO are calculated. Further, dynamic pressure, velocity and vorticity in the gap between OFUCR and FPSO are drawn. The influence of longitudinal and lateral currents is concerned. As a result, drag obviously increases with the presence of FPSO owing to the wall shear stress and drop of dynamic pressure. Lateral force is found to be a repulsion force as OFUCR moves along ship bottom, and an attraction force as OFUCR moves along ship bilge and ship side.