Analytical and Experimental Investigation of Waves Propagating through Thin, Porous Walls for Coastal Protection Applications

Abstract

Chen, Y.-H.; Chu, T., and Wang, K.-H., 2019. Analytical and experimental investigation of waves propagating through thin, porous walls for coastal protection applications. Journal of Coastal Research, 35(6), 1294–1306. Coconut Creek (Florida), ISSN 0749-0208.This paper presents a combined analytical and experimental investigation of the interaction between either a linear monochromatic or a nonlinear solitary wave and a thin, porous wall as a breakwater for coastal protection. This study will determine with validation a unique porous-wall property defined as a material constant in Darcy's law based on theoretical formulation of the porous flow condition using the laboratory data and will evaluate the effectiveness of the porous walls on the transmitted waves through the analytical solutions derived for both the monochromatic and solitary wave conditions. A series of wave tank experiments were performed to record wave elevations in front of and behind the porous walls. Monochromatic waves with various incident wave conditions were first generated to test eight thin, porous walls with varying pore sizes and porosities. The porous-wall properties determined and validated with monochromatic wave data are found to be dependent on the porosity and pore size. The transmitted wave height is reduced as the porosities of the walls decrease. When comparing two porous walls with the same porosity, less incident wave energy gets transmitted through the wall with a smaller pore diameter. Additionally, those porous walls were applied in laboratory tests with inputs of incident solitary waves of varying wave heights. The derived analytical solutions with the determined porous-wall material constants for the cases of solitary waves are verified with the results, similar to the monochromatic wave cases, showing good matches between the predicted and measured wave profiles. Overall, this study provides an important analytical approach with confirmed experimental verifications to be used for coastal engineering application analyzing waves interacting with a thin, porous wall.