Dissipative potential flow models and energy evolution characteristics for curtain-wall caisson breakwaters under wave action

Abstract

Curtain-wall caisson breakwaters are a kind of coastal protection structure, which is composed of semi-submersible vertical thin curtain walls, a rear vertical caisson, and wave chambers formed by the curtain walls and rear caisson. When water waves interact with the curtain-wall caisson breakwater, the wave energy may be partially dissipated owing to the flow separation and vortex formation near the edges of curtain walls. The conventional potential flow solution without considering wave energy dissipation gives unreasonable results of full wave reflection by the curtain-wall caisson breakwater. To address this issue, this study develops a dissipative potential flow model for predicting the hydrodynamic performance of the curtain-wall caisson breakwaters. The wave energy dissipation near the breakwater is considered by introducing a quadratic pressure loss condition at the entrances of wave chambers. By adopting appropriate dimensionless dissipation coefficients, the analytical predictions of the reflection coefficient and the wave amplitude inside chambers are in good agreement with published experimental results. The differences in the hydrodynamic quantities predicted by the dissipative and conventional potential flow solutions are examined, and further discussion based on the dissipative analytical solution is performed. Moreover, viscous numerical simulations based on a meshless particle method are carried out to clarify the characteristics of wave energy evolution, wave energy dissipation, and local fluid motion near the curtain-wall caisson breakwaters. The results show that the front curtain wall plays the leading role in the wave energy dissipation process of the whole double-chamber curtain-wall breakwater.