| Abstract |
A Surface Effect Ship (SES) is a vessel that has both an air cushion, like a hovercraft, and twin hulls, like a catamaran. When the air cushion is in use, a small portion of the twin hulls remain in the water. When the air cushion is turned off, the full weight of the vessel is supported by the buoyancy of the twin hulls.
Predicting the overall performance and, in particular, the maneuvering performance of a SES in shallow water region is of paramount importance, as the motion of the ship can be affected by the interaction between the air, the cushion, the ship structure, the seals, the sea waves and the sea bottom in the shallow water region.
Of great concern for the naval community is the safety and operability of the SES in shallow water regions at high speed regimes. There is a need to better understand the interaction of the SES with the sea bottom in shallow waters when the air cushion is in use and the seals are most demanded by the dynamics of the water crest formed in front of them at particular Froude numbers of speed. Several scenarios can occur, including lack of stability of the air cushion when maneuvering the SES in these conditions. It is expected that ONR will provide input with regard to these fenomena. The approach consists on developing a software tool that will be able to compute efficiently the different phenomena at play in order to perform sensitivity analysis taking into account different design parameters of the SES.
In order to develop that software tool, a deep understanding of the behavior of the air cushion and seals in shallow waters and waves is needed. This task will be tackled in Steps 1A and 2A.
The development of the software tool based on a combination of different numerical simulation techniques will be tackled in Steps 1B and 2B.
Project Objectives:
The objectives of the project are twofold. On the one hand, the development, integration and validation of computational methods and software based on innovative finite element methods, particle-type methods and advanced pre-post processing systems to model and study the air cushion and deformable skirt dynamics, and the performance of the seals and transition regions between the skirt and seals near the hulls of a SES T-Craft in the presence of waves. The final aim of the study is to predict skirt and seals performance and air cushion stability. On the other hand, to develop and validate simple, efficient and accurate computational methods and software able to simulate maneuvering operations for SES in shallow waters. |