In November, 2015, the Sailing Yacht Research Foundation (SYRF) published the tank test data from their "Wide Light Yacht Project" for the hydrodynamics of a modern, high performance, semi-planing yacht. This comprehensive data set, comprising canoe body with and without appendages in upright, heeled and yawed conditions, provides an important validation base for CFD codes; previously, such data were not readily accessible mainly due to proprietary issues. The SYRF report includes a number of comparative results from commercial CFD codes, the RANS program Star-CCM+ results in general showing the best correlations with the measured data, albeit with some significant departures.
In this paper, we present results computed using an advanced Boundary Element Code, FloSim, these calculations being compared against the test matrix of "Wide Light" measured data and also Star-CCM+ calculated results. Times for computer model preparation and case execution are discussed together with computer requirements.
An outline of the FloSim method is presented; it is an unsteady code with a coupled integral boundary layer analysis for viscous effects such as skin friction resistance and boundary layer displacement effect. Its time-stepping procedure has free convection and rollup of vortex wake elements providing non-linear lift properties and includes a number of modeling techniques for treating "real world" effects, such as flow separation and wave breaking. The free surface wave development uses a non-linear mixed Eulerian-Lagrangian treatment at each time step. For the higher speed cases in the SYRF data set that have a breaking bow wave crest, FloSim's Wave-Breaker treatment is applied to convert excessive energy in the bow wave to a "dead-weight" pressure applied on the free surface; this effectively attenuates downstream wave amplitudes consistent with the loss of energy at the breaking crest.
FloSim, already used in America's Cup and Volvo racing yacht analyses, was developed specifically to bridge the gap between basic potential flow panel methods and RANS codes, with the objective of providing accurate, practical solutions on a laptop computer within a reasonable turnaround time and cost. In essence, the results presented so far in this paper demonstrate these objectives have been achieved. The comparisons of FloSim's essentially "low-order" results against test data and Star-CCM+ RANS calculations, provide a measure of tradeoff between calculation accuracy versus cost and turnaround time for a case. Throughout the discussions presented below, the reader should keep in mind that this was not a "blind" comparison as it was for the original Wide Light Project participants who published their numerical results.