Abstract
The fully autonomous surface ships will be a reality and the ongoing construction of ships like "MV Yara Birkeland" is promising. In this context, the ongoing research project "ROV Revolution" aims to design and develop a small autonomous mother-ship that can handle the ROV operations become significant. This funded project is led by Kongsberg Maritime in collaboration with SINTEF Ocean, NTNU, and other industrial partners. The hydrodynamic interaction and relative motion between such a small autonomous mother-ship and ROV are critical considerations to ensure a safe launch and recovery operations of the ROV.\\
The multi-body model test experiments with monohull and ROV models were conducted at SINTEF Ocean's ocean basin laboratory. The experiment was characterized by a setup in which the forces from the ROV model were measured and used to get relative RAO of motions between the mother-ship and the ROV. Both regular and irregular wave tests were carried out. A significant influence from the stiffness on the results was found in the investigation.\\
Numerical analyses were carried out using the WAMIT program. Single body analysis of the mother-ship and ROV were carried out separately. The results from this were compared with a multi-body analysis carried out on the mother-ship and ROV together. The relative RAOs from both the results were compared to study the hydrodynamic interaction effects.\\
From both numerical analysis and experiments, it was found that there is hydrodynamic interaction between the mother-ship and ROV in heave motions. However, it is difficult to clearly say the magnitude of interactions and the hydrodynamic interactions observed for other DOFs. Further studies are required to quantify hydrodynamic effects accurately and consider other uncertainties.