Twin-skegs are becoming increasingly popular in the Norwegian fishing fleet due to the excellent compromise they offer between manoeuvrability and efficiency. However, the twin-skeg concept development is decades behind the likes of conventional single screw hull. Automatic parametric optimization process is then an excellent tool to catch up the development timeline and design vessels that have a minimum environmental footprint. When automatic optimization of ship hulls is selected as design approach, it is generally aiming at minimizing the hull resistance.
However, resistance does not always correlate with propulsive efficiency. The focus in EFFTROP was therefore to begin developing an optimization framework for twin-skeg hulls with as objective to maximize propulsive efficiency of the vessel. EFFTROP created a foundation for the optimization process and performing efficient CFD self-propulsion simulations for calculating propulsive efficiency. The validity of the method was demonstrated by optimizing the skeg shapes with a simplified ducted propeller model. This resulted in a variation of 12 % in propulsive efficiency between the different skeg variations, all of whom were considered as reasonable designs. As EFFTROP was a pre-project, we aim at fully developing our method in the project EFFTRÅL (application currently under review) to make SINTEF Ocean and SINTEF Ålesund leading providers of unconventional ship hull optimization.
