Executive Summary : | The size and capacity of the ships have increased tremendously in the last decade. A ship with larger capacity results in larger revenue for the ship operator. Today, the largest has a length of approx. 400 m and a carrying capacity of more than 21000 TEU (Twenty feet Equivalent Unit) containers and has a deadweight of approx. 2Lakh tonne. Even though they are economical in operation, their huge size brings about lots of technical challenges. For e.g., the recent accident happened with the containership EverGiven which blocked the Suez Canal and resulted in a traffic block for weeks. Even though the ship had trouble manoeuvring against a strong gust, large containership design poses challenges in many other aspects too. Structural design is one of those challenges which need very special attention. Unlike other ships, the containerships have a very large opening in order to facilitate the loading and unloading of containers. This results in poor torsional rigidity. Because of their open cross-section, they are susceptible to both torsion and warping. Since the shear center of the cross-section lies below the keel of the ship, there is a strong coupling between horizontal and torsional bending. In addition, since these ships are long and slender (length to Breadth ratio is approx. 8), their hull is highly flexible. Therefore, hydroelasticity plays an important role in the structural responses. Hydroelasticity results in a two-way coupling between the fluid and structural domain. Here, the fluid forces are affected by the structural deformation and vice versa. In the past, a few research (including the previous works of PI) has been published on the hydroelastic responses of large containerships. However, those studies were limited to symmetric responses, i.e. hull bending in the longitudinal plane which is also called a vertical bending moment (VBM). It is necessary that a detailed investigation needs to be conducted on the anti-symmetric responses of the large containerships which include the coupled effects of horizontal, torsional, and warping responses. This is essential to ensure the safety and structural integrity of the ships, particularly big containerships with large openings. Therefore, in this project, we envisage developing a numerical tool that will help to assess the global loads acting on ships. The proposed numerical tool should be fast and accurate enough for practical ship design problems. Computation Fluid Dynamics (CFD) based methods require huge computational resources and time. Therefore, a potential flow-based method will be developed and coupled with a Navier-Stokes-based solver whenever necessary (e.g. estimation of impact or slamming loads during extreme sea conditions). Further, the hydrodynamics tool will be coupled with a structural solver. The accurate prediction of loads will ensure the safety of the crew, passengers, and cargo and helps to maintain the structural integrity of the hull. |