Experimental study on wave-in-deck loading under focused wave conditions

Abstract

This paper presents experimental results related to the wave-in-deck phenomena caused by focused waves. A series of experiments were conducted in a two-dimensional wave flume using varying deck clearances and focused waves with varying wave crest heights to measure the water velocity profiles, vertical forces, and pressure distributions under the deck. The velocity fields of the water under the deck were obtained using the particle image velocimetry (PIV) system, which was synchronized with the force and pressure measurement systems. The linear momentum and kinetic energy with and without the deck were calculated from the PIV velocity maps. The velocity profiles, linear momentum, and kinetic energy of the water under the deck were compared with those of the incident focused waves to investigate the effect of the deck on the water kinematics in relation to the force and pressure measurements recorded during the loading process. Meanwhile, the forces and pressure caused by the focused waves were compared with those caused by regular waves, and the results indicated that the upward vertical force and pressure caused by the focused waves were larger than those caused by the regular waves but that the downward force exhibited an opposite behavior. Based on the force measurements, the peak and impulse of the vertical force indicated negative linear relationships with the deck clearance, whereas the wave crest height was found to have a less significant effect on the vertical force than the deck clearance. The distribution of the peak pressure along the deck was analyzed in terms of the corresponding impulsiveness and pressure impulse to evaluate the severity of the local wave loads, and the results indicated that the region near the leading edge would likely experience a greater structural damage due to the wave-in-deck load compared with the region near the trailing edge.