Impact of a Plunging Breaker on a Cube at Various Streamwise Positions

This study investigates the impact of a deep-water plunging breaker on a cube with a dimension of L = 30.5 cm and its bottom edge located 0.44L below the mean water level. A dispersive focusing technique is used to generate a wave packet with a nominal wavelength λ = 118 cm, resulting in a wave crest that reaches a maximum height at X_m = 643.9 cm relative to the wave maker and subsequently becomes a plunging breaker in open water. The front face of the cube is oriented vertically and its streamwise position is varied within a range from X_m-0.076λ to X_m+0.236λ. Synchronized time-resolved measurements of the free surface profiles and pressures on the cube front face are conducted using a laser induced fluorescent technique and piezoelectric sensors, respectively. Three distinct impact classifications—flip-through, low-aeration, and high-aeration—are identified based on the cube location and the unique characteristics of the wave impact. Notably, low-aeration impacts exhibit higher peak pressure values compared to the other classifications. In a flip-through condition, the velocity of the intersection between the free surface and the cube front face is found to follow a power law in time, similar to a finite-time singularity observed in some free-surface focusing phenomena.