Numerical study on the blockage effect of a towing tank considering ship motion

When performing experiments in a towing tank, if the tank is small relative to the ship's model, the blockage effect cannot be neglected and must be corrected. Using a KCS ship as the object, taking a finite degree of freedom into account, and using the ship's resistance with 1.5%, 1.8%, 2.2%, and 3.0% blocking ratios, the heave and pitch of the ship were calculated. In addition, the resistance of the ship, with ship breadth to tank breadth ratios of 016, 0.18, and 0.21, was calculated, and the influence of ship breadth to tank breadth ratio on the blockage effect was analyzed. Along with an increase in the blockage ratio, the total change in resistance was obvious. According to the results of this correction, the blockage ratio should be less than 1.5%. When the blockage ratio is less than 1.8%, the Scott formula and average flow formula based on the average transverse section are suggested as the major means of correction. The ratio of ship breadth to tank breadth cannot be ignored in the correction of the blockage effect.