Traditionally America's Cup Class appendage development has been heavily based on wind tunnel testing. In these wind tunnel tests the appendages are mounted upside down on a flat plate in the wind tunnel.
During the campaign for the 32nd America's Cup we validated our CFD methods using wind tunnel tests of two bulb designs. Our CFD simulations showed the same trends as the wind tunnel tests, giving a clear advantage to the first bulb.
We then used the same bulbs in simulations which included the hull up to the DWL. In these simulations the two bulbs showed much smaller differences in performance. We ran further simulations allowing deformation of the free surface and dynamic sinkage and trim of the hull. In these cases the trends reversed and the second bulb performed better than the first.
This highlights the importance of testing the entire system as a whole, which is not possible in a wind tunnel. Similar results were found during the winglet design process, emphasizing the value of using CFD.
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