Numerical and experimental study on free-surface wave generation by a submerged moving body in a towing tank

초록

Free surface waves were generated by a submerged moving body in a towing tank using a numerical and a physical towing tank. Unlike a circulating water channel, a towing tank allows easy to control of acceleration and deacceleration range of the body motion. Numerical and experimental analysis can make the same moving conditions of the submerged body. Using a Numerical Towing Tank (NTT), free surface elevation was calculated according to body velocities, submerged depths and body volumes. The measured experimental data agreed well with the results of a fully nonlinear simulation and the data was also compared with the Russell comprehensive error method. The nonlinearity of the free surface waves increased as the submerged depth of the body became shallower and the body velocity became faster. The increase in wave height according to the increase of the body velocity or the increase in the wave height according to the decrease in the submerged depth of the body generally showed a proportional relationship. Overall, the nonlinear free surface boundary condition needs to be applied when calculating the free surface wave due to the motion of a submerged body. The ratio of wave height difference according to body displacement was similar to the ratio (percentage) of increase in body displacement to NACA shape displacement as body velocity becomes faster.

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