Numerical and Experimental Studies on the Resistance of a Fast Catamaran in Accelerated Forward Speed Motion

This paper provides comprehensive numerical and experimental studies on the unsteady resistance of the world’s first battery-driven, zero-emissions high-speed catamaran, the MS Medstraum, in accelerated forward speed motion. These studies suggest that for a certain speed range of around Froude 0.50 (the so-called last hump of wave resistance), the corresponding unsteady resistance is significantly less than the originally anticipated value, namely, up to 40% less when adding to the steady resistance, the conventional added mass term. This surprising result could be explained by both experimental resistance tests and CFD calculations, as well as by inspection of the numerically generated wave patterns. Thus, care must be taken when applying the traditional approach to the unsteady resistance of a ship in accelerated or decelerated forward speed motion. As such, this positively affects the estimation of the required power capacity to accelerate the ship to full operational speed. This leads to reduced (fitted) battery weight and positively affects the ship’s displacement, allowing the vessel to achieve higher speeds. The present research finally yielded notable results of interest for seakeeping and ship maneuvering simulation studies; namely, comprehensive CFD simulations for the studied slender catamaran have shown that calculated added mass values for surge motion in real-flow conditions are up to six times higher than those initially estimated by ideal flow potential theory methods.