Enhancement in Hydrodynamic Performance of a Quarter-Circular Breakwater Using a Porous Shield

Abstract

The study evaluates the hydrodynamic performance of quarter-circular breakwater (QCB) with various types of porous shields (say retrofits) under incident waves. The QCB with (i) vertical shield, (ii) seaside quarter-circular retrofit (QCR), (iii) shoreside QCR, and (iv) partial rectangular retrofit (PRR) are proposed to enhance the performance of QCB. The effect of porous shields is analyzed using the quadratic pressure drop condition and dual boundary element method (DBEM) under the framework of linearized potential flow theory. Study results are validated with the available results reported by the authors after some numerical modifications. The effect of shield porosity, and wave height on the reflection, transmission, energy loss, and vertical and horizontal forces on QCB and shield are reported as a function of relative water depth. A comparative study is performed among all the proposed breakwaters to identify an effective configuration against the incident waves. Around 39%, 30%, 31%, and 56% reduction of wave transmission is obtained for QCB with vertical shield, seaside, shoreside QCR, and PRR, respectively, when compared with QCB alone for kh=1. The wave transmission KT=0.16 and energy loss KL=0.95 are obtained when kh=2 with the addition of the PRR for a QCB, which is observed as an effective porous shield against the incident waves when compared with the other types of shields. The 10–20% retrofit porosity is recommended with clear spacing b/h=0.9 and the QCB radius of R2/h=0.7 for the effective distribution of the scattering coefficients against the incident waves.