WAVE INTERACTIONS WITH TRIPLE SUBMERGED JARLAN-TYPE PERFORATED BREAKWATERS

Abstract

This study examines wave interactions with triple submerged Jarlan-type perforated breakwaters consisting of two perforated front walls and a solid rear wall. A mathematical model based on an eigenfunction expansion method and a least-squares technique for Stokes second-order waves has been developed. The numerical results obtained for limiting cases for the single solid and single perforated breakwater, double submerged solid vertical plates, single solid and double perforated breakwater, and double Jarlan-type perforated breakwater are in agree reasonably well with previous studies and experimental results. The wave transmission C_T; reflection C_R, and energy-loss C_L coefficients, and the horizontal wave force exerted on the front C_Ff and rear C_Fr walls are examined. The results indicate that the location of the middle wall between the front and rear walls has little effect on C_R, C_T, and C_L. With the increasing value of porous effect parameter G, the values of C_R, C_T, and C_Fr first decreased, attained their minimum values, and then increased. However, the C_Ff decreased monotonously with the increasing G. The C_R is maximum when B/L = 0.48n+0.07 while it is minimum when relative chamber width, B/L = 0.46n+0.26 where n equals to (0, 1, 2,...). It also shows that the triple sub-merged Jarlan-type perforated breakwater significantly reduced C_R values and enhanced the structure’s wave-absorbing ability compared with the double one. The optimum parameters recommended for engineering design were G = 0.1–0.2, relative sub-merged depth d/h = 0.1–0.2, and B/L = 0.3–0.4. For practical engineering, the proposed model can be used to predict the structure's response during the preliminary design stage.