Delta type VLFS for open sea

Roy Gafter, Faculty of Mechanical Engineering (Technion Israel Institute of Technology)
Nitai Drimer, Faculty of Mechanical Engineering (Technion Israel Institute of Technology)

Incorporating an integrated sheltered basin, the Delta type, a new concept of VLFS, provides broad operational space while maintaining good stability and accessibility under severe weather conditions. Its utilization may extend over a wide range of applications and provides sustainable solution for the development of coastal zones. Our research focuses on the hydrodynamic attributes and preliminary structural design of the vessel, aiming to present feasible and practical concept.

For the hydrodynamic study we setup a parametric Boundary Elements Model (BEM) of wave-structure interaction. The effects of geometrical variation of the unique hull shape are studied in terms of their motion response, comfort and operability at regular and real sea representations. The optimal configuration is further studied applying a time domain simulation, analyzing the motion of the moored structure under extreme weather conditions at the East Mediterranean Sea.
The results of the hydrodynamic study indicate that the structure maintains comfort motion under severe seas as well as proper shelter in the basin. The study shows favorable results to the narrow configurations heading the incoming waves. Moored by a Single Point Mooring (SPM) system, the structure keeps optimal position as well as acceptable load effects in the components of the mooring system.

Following promising results of hydrodynamic aspects, we study the structural design aspects. As a first design iteration, we analyzed the global primary loads by means of a box-girder representation, verifying the cross-section strength to withstand the splitting loads. This preliminary analysis has led to improve the geometrical design to reduce the primary global loads.
The hydrodynamic attributes of the new design are improved as well. Currently we develop a parametric 3D structural model, which applies the hydrodynamic loads from the BEM results to a structural FEM and analyzes the load effects.

Keywords – VLFS, Hydrodynamics, Structural Design, Wave-Structure Interaction


Roy Gafter is a PhD student in Mechanical Engineering at the faculty of Mechanical Engineering in Technion, Israel Institute of Technology, Haifa. His current and Msc. research fields are Marine Engineering, Hydrodynamics and Structural Design. His research interests include Marine Structural Design, and the application of computerized simulations in Hydrodynamic Analysis.

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