The interference between the demi-hulls of a catamaran depend on their distance, and has a large impact on the total resistance. We conducted a benchmarking exercise where we conducted a CFD study of resistance for various demi-hull separation distances. The catamaran is a publicly available design known as the Delft catamaran, used by Broglia et al. in their paper "Experimental investigation of interference effects for high-speed catamarans", where they published experimental results which we used as a reference.

We have conducted benchmarking studies for catamarans before, e.g. https://cloudtowingtank.com/benchmark-calm-water-resistance-of-a-catamaran/, however in the present case the Froude numbers range from 0.3 to 0.75, going well inside the semi-displacement sailing regime. In the previous study, the Froude numbers were lower, effectively in the displacement range.

Simulations were carried out for five Froude numbers and three different demi-hull distances. A forth configuration was also conducted, for a single demi-hull, giving the reference resistance of a single hull. The resistance and dynamic trim trends are well predicted, with differences typically around 5 % for resistance. In some cases resistance showed larger differences, especially in the low speed range, where the measured forces are fairly small, around 15-30 N. Graphs below show the comparison for resistance and sinkage for demi hull separation of 0.5 meters in model scale. For complete results and more details, please download the white paper by following the link below.