An analytical model for oblique wave interaction with a partially reflective harbor structure

Abstract

An analytical model of the interaction of oblique incident regular waves with a maritime structure is developed and extended to irregular waves. The structure is composed of a semi-submergible vertical impermeable plate enclosing a chamber. Linear wave theory is considered, taking into account the head loss due to the constriction of the flow. The results are compared to those obtained with computational fluid dynamics models, revealing that the proposed model is capable to efficiently describe the performance of these systems for weakly non-linear incident waves. The influence of fundamental design parameters, such as geometric and wave characteristics, on the hydrodynamic behavior and the loadings on the plate is analyzed. When dealing with irregular waves, the spectra at the seaward region and inside the chamber show a nodal and antinodal structure that varies with the distance to the reflector. This structure, as well as the phase lag between the free surface elevations at both sides of the plate, affect the total loads over the plate. The statistical analysis of the free surface elevation, wave heights, and crests and throughs of the forces is also presented to evaluate the effect of the geometry in both regions and over the plate. The results show that the model allows to efficiently test different configurations to control wave reflection at the structure and the oscillation in the chamber. It can therefore be applied e.g. for the optimization of the design towards (i) harbor tranquility in the seaward region, (ii) energy extraction inside the chamber and (iii) loads on the structure. As an application, a failure mode defined as the excess of a critical predefined load over the plate, is analyzed by means of Monte Carlo simulations using known theoretical distributions fitted to the random variables. The results show the importance of the analysis of the performance of the system regarding not only the effect inside the chamber but also on the structure.