Aim: The optimisation of a new Platform Supply Vessel hull for a Dutch shipping company on the 10 knots speed range in light and heavy displacement condition.
This optimisation was carried out in 2013 for the Dutch shipping company Vroon under the banner “ShipOpt”, a successful joint venture between Rodrigo Azcueta of Cape Horn Engineering and Jason Ker of Ker Yacht Design, merging the outstanding CFD capabilities and expertise of Cape Horn Engineering with the innovative optimisation techniques developed by Jason for the design of his successful sailing yachts. For more details on ShipOpt read at the end of this case study.
In particular for this vessel, some preliminary investigation on the baseline hull showed that the bow thrusters were very significant flow features. For that reason the computations included thrusters and its fairings and it was clear from the results that the optimisation of these fairings was as important as the optimisation of the hull shape.
A 19% weighted drag reduction was obtained from optimising the bow thruster fairing shape and position, while another 5% of a total of 24% drag reduction came from the new hull shape.
Background on ShipOpt Technology
Our optimisation system was developed for extracting tiny performance improvements from America’s Cup yachts, the Formula One of the Seas, in order to obtain a performance advantage in an environment where every second counts. This technology was perfectly transferable to ship hull optimisation.
We used proprietary optimisation tools and methods based on highly accurate RANS CFD simulations combined with surrogate model optimisation techniques. Hundreds of shapes were created using a parametric CAD model and the drag of those shapes was computed with CFD. We then trained multivariate response surfaces to recognize the correlation between the parametric shape combinations and drag in the considered conditions. Once the response surfaces are trained they are used to compute the drag of over a million virtual shapes, from which a short-list of candidates is decided upon and tested again with CFD, which are then compared against the baseline hull supplied by the client. We regularly use two of the best RANS CFD codes available on the market, and in that way are able to cross-check that the computations are well set up before starting the optimisation process, and then also cross-check its results.