Cape Horn Engineering has been the exclusive provider of CFD and performance analysis for the winning VOR70 class boats of 3 consecutive Volvo Ocean Race editions. In partnership with renown Argentinian Juan Kouyoumdjian as lead designer we have dominated ocean racing for almost a decade.
First success came with Team ABN Amro in the 2005/6 race. The team participated with two boats; so called ABN Amro One won overall race victory, while ABN Amro Two broke the 24 hours distance world record. In the following edition 2008/9 success came with the Ericsson Racing Team 2 boats campaign. In that occasion, Ericsson 4 also broke the 24 hours distance world record. And finally for the 2011/12 edition we were appointed to design the boats of 3 teams, Groupama, Telefonica and Puma. Groupama secured the overall victory in that edition.
2011/12 Volvo Ocean Race, Teams Telefónica, PUMA and Groupama
2008/09 Volvo Ocean Race, Ericsson Racing Team
2005/06 Volvo Ocean Race, Team ABN AMRO
The Technology Behind the Success:
The VOR70 Class boats present a new, very complex, design problem. Compared to America’s Cup Yachts there are many more design variables; the Volvo 70’s are designed to a box rule and experience sailing conditions from all over the world. Boat speed ranges from 6 knots as a displacement hull to 30 knots planing and surfing down waves. The boats also have canting keels and water ballast which drastically changes the displacement and center of gravity. All of these variables lead to very large testing matrices. Here CFD becomes very attractive; each variable usually can be changed simply by changing a number and running the simulation again.
Thus, at Cape Horn Engineering we have forgone traditional towing tank and wind tunnel tests in favor of an exclusively CFD based design philosophy. Our simulations are cheaper, faster and more reliable than traditional tests. We run all simulations at full scale which eliminates the inherent error in scaled test results. Enhanced flow visualization and force decomposition give designers much greater understanding of flow phenomena. Usually we run all hydrodynamic and aerodynamic simulations separately. Hydrodynamic simulations are used to research hull form, yacht behavior in waves, and appendage shape and position. Early in the design process, aerodynamic simulations are used to determine the sail forces which are in turn used as input in hydrodynamic simulations. Later we return to aerodynamic simulations in order to optimize sail shapes and investigate new sail concepts. Our hydrodynamic cases are run at full scale with rudders, keels and foils. The free surface is modeled using a volume fraction (VoF) method, and simulations allow at least for dynamic trim and sinkage.
We usually run hundreds of sailing points for each design candidate, and as many candidates as the campaign time allows. The best design is found by comparing all candidates. Each candidate is also compared against a reference design to understand the effects of specific design features.
We use advanced visualization techniques to understand performance differences between design features. We either analyze the flow ourselves, or provide the visualization files to our clients. We use the Ensight post processing suite, one of the best in the market, to generate 3D visualization files called ‘scenarios’. These files can be viewed using free viewing software which allows users to rotate, zoom, pan, and switch on and off the different parts of the body or flow features, such as free surface, pressure, friction coefficient, stream lines, turbulence, separation, vorticity and so on.
VOR60 Behaviour in Waves
This movie shows the simulation capabilities available to Cape Horn Engineering at the time of the design of the winning Volvo Ocean Race VOR60 yachts that dominated the ocean race for almost a decade. This series of movies shows the complex behaviour of sailing yachts in waves with all the 6 DoF let free during unsteady RANS simulation. The fist one compares two different VOR60 hulls reaching in following waves, the second one shows the yacht beating in moderate waves, the third one compares the motions in waves for 2 different water ballast configurations and the last one compares the effect of the bow shape on drag beating in a chop wave.