Experimental investigation on effect of sloshing on ship added resistance in head waves

Engineering practice presents some impact of sloshing and ship motion interaction on added resistance in waves, and this paper is an attempt to figure out the effect of such impact through experiment while theoretical investigation is troubling scholars due to the complexity of this problem. A Liquefied Natural Gas (LNG) carrier scaled to 1/27.384, with one prismatic tank, is modeled for free running tests in regular head waves of 6 different wavelengths in the deepwater towing tank of China Scientific Research Center (CSSRC). For each wave case, the revolution rate of propeller, the ship speed, and corresponding torque and thrust are measured, and the added resistance is thereafter obtained by subtracting the still water resistance from the mean total resistance on assumption of a constant thrust deduction. The experimental results are comparatively discussed in conditions of sloshing and ballast weight. It is found that under current test conditions, internal sloshing affects ship motion by reducing its value, and the added resistance in waves decreases accordingly while the energy consumption decreases. The experimental results that liquid sloshing has an evident influence on the added resistance shall be a very important consideration for the development of green LNG cargos.