2025 , Volume 30, № 2, p.38-53

Purpose. When coastal structures are located in close proximity to each other, abnormally high free surface elevations can occur in the gap between them, which can lead to an extreme increase in the wave forces acting on them. This problem is called the Gap Resonance Problem and almost all previous studies have considered the case of short periodic waves. The purpose of this paper was to consider the case of long incident waves.

Methods. In the present work we employ previously developed numerical algorithm based on a mathematical model of two-dimensional potential flows of an ideal fluid with a free boundary.

Results. We determine the dependencies of the maximum runup and wave force on the amplitude and length of the incoming single wave, length and draught of the semi-immersed body and the distance between the body and the vertical impermeable wall. The parameter values that lead to the extremely large values of runup and wave forces are found.

Conclusions. The gap resonance phenomenon can also occur for long incident waves. The runup on the back edge decreases as the gap between the body and the wall widens, the same as in the case of short periodic waves. The runup on the back edge of a body always exceeds the runup on the front edge, while the opposite is true for a body located far away from the wall. The maximum horizontal force acting on a vertical wall is mostly dependent on the amplitude of the incoming wave and is practically independent of the length of the body and its depth. When the gap width is greater than the resonance width, the maximums of the runup at the rear and front edges of the body, the load on the vertical wall and the vertical component of the wave force monotonically decrease as the distance from the mooring wall increases.