An experimental investigation of reduction effect of damping devices in the rectangular moonpool

With the increase of the equipment size and the operating environment requirement, more and more rectangular moonpools with large aspect ratios are used to instead of the circular or square moonpools with small aspect ratios. However, the research on the rectangular moonpool with a large aspect ratio is few. Firstly, the fluid motion characteristic in the rectangular moonpool with a large aspect ratio is investigated experimentally in this paper. By tracking and quantizing the free surface motion, the moonpool has obvious shielding effects. Then the natural frequency of the piston motion in the moonpool is derived by theoretical methods, which agrees well with the experimental results. When the incident wave's period approximates the moonpool's natural oscillation period, the resonant motion occurs with some adverse effects. Finally, the reduction effects of four damping devices, the positive grid of flaps, negative grid of flaps, grid of baffles and vertical bulkhead, are investigated to reduce the adverse effects. The damping devices have good reduction effects coupling with some incentive effects. The grid of flaps effectively destroy the shear layer self-sustaining oscillations and generate vortices. The grid of baffles increases the fluid motion damping and forms the waterfall. The vertical bulkhead causes interlaced motion.