Reflection and Transmission for a Porous Structure

Kondo, Hideo; Toma, Satoshi

doi:10.1061/9780872620490.107

Cited by 18 publications

(7 citation statements)

References 3 publications

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“…It is also evident from the investigation that up to 12.4% reduction in K t could be achieved by incorporating the perforations on the surface of conical pile head breakwater. The obtained outcome is well matching with the literature 4,25,26,58 where, 10% to 14% lesser K t is reported through perforations.…”

Section: Effect Of Perforationssupporting

confidence: 89%

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Investigation on innovative pile head breakwater for coastal protection

Sathyanarayana

Suvarna

Umesh

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part M:

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Coastal erosion is a global concern that has been augmenting due to the natural evolution of beaches, human activities and sea-level rise. One of the eco-friendly shore protection methods is to dissipate the wave energy by constructing offshore breakwaters. Conical pile head breakwater (CPHB) is one of the eco-friendly innovative offshore structures consisting of closely spaced piles with an enlarged cross-sectional area (conical pile head) in the vicinity of the free surface. In the present study, perforations are incorporated over the conical pile head to achieve higher efficiency by promoting energy dissipation. The influence of the perforations on the performance characteristics, namely wave transmission (Kt), wave reflection (Kr) and energy dissipation (Kd) of the perforated CPHB is comprehensively investigated through physical model studies. The effect of perforations and their distribution around the pile head (Pa), percentage of perforation (P) and size of perforations (S/D) on the wave attenuation characteristics are evaluated to arrive at an optimum configuration. The study is carried out under monochromatic waves of varying wave height (0.06–0.16 m) and wave period (1.4–2 s) at different depths of water (0.35, 0.40 and 0.45 m). A minimum Kt of 0.58 associated with Kr of 0.26 and Kd of 0.78 is obtained with an optimum configuration of Pa = 50%, P = 19.2% and S/D = 0.25. The Kt of the proposed CPHB is about 19 to 35% lesser than that of the perforated hollow pile breakwater under matching test conditions. Overall, providing the perforations is found to be effective in enhancing the wave attenuation capability by up to 12.4%. Further, empirical equations are formulated and validated with the experimental data. The empirical equations estimate the Kt and Kr values accurately with a high coefficient of determination ( R2 ≥ 0.90).

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Section: Effect Of Perforationssupporting

confidence: 89%

“…The analysis of the results is carried out with reference to the trend lines drawn. The scattering of the data points is also witnessed in the literature for the pile breakwater and pile-supported breakwaters by Bilici, 55 Kondo and Toma, 56 Ning et al, 57 Rao et al 27 and Sundar and Subbarao. 11…”

Section: Resultsmentioning

confidence: 53%

Investigation on innovative pile head breakwater for coastal protection

Sathyanarayana

Suvarna

Umesh

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part M:

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“…More recently, Yu and Chwang (1994) applied linear potential theory to analyze the wave motion through two-layer porous structures, and concluded that there is an optimum thickness for a porous structure beyond which any further increase of the thickness may not lead to an appreciable improvement of its functional performance in reducing the transmission of water waves. Studies on wave transmission through porous objects were also carried out by Kondo and Toma (1972), Madsen (1974), and Scarlatos and Singh (1987). These authors, however, emphasized only the long-wave conditions, under which the most progressive wave is important.…”

Section: Introductionmentioning

confidence: 96%

Transmission of Long Waves Induced by Short-Wave Groups Through a Composite Breakwater

Hossain

Kioka

Kitano

2001

Coastal Engineering Journal

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Theoretical findings and laboratory evidences are presented regarding the transmission of long waves induced by short-wave groups through the rubble base of an infinitely long composite breakwater. Multiple-scale perturbation method is applied in describing the long-wave fields in terms of velocity potential, and an analytical solution is derived for transmitted and reflected long waves induced by wave groups. Dependency of the reflection and transmission of free long waves on several parameters is examined through the numerical calculations. It is found that the linear friction factor, the rubble-base height and the modulation of short waves affect the transmission of free long waves significantly. Theoretical results are then compared with the results from laboratory experiments. It is shown that although the conventional rubble-mound breakwaters can reflect short wave energy efficiently, a significant part of the bound long-wave energy associated with shortwave groups is transmitted to the leeward side of the breakwater as free waves.

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“…Modified Jarlan-type breakwaters are proposed, studied by many researchers. These modifications mainly involve breakwaters with two or multiple perforated front walls [7,3,22], partially perforated breakwaters [17,8], and perforated breakwaters with transverse walls [18] or rock fill [4,12]. Morison et al [10] and McCamy and Fuchs [9] estimated an empirical relationship to estimate the drag and inertia forces on members and analytical solutions to estimate the diffraction effects on large cylinders are representative examples of such interest.…”

Section: Introductionmentioning

confidence: 99%

Flow field around outer perforated circular cylinder under regular waves: numerical study

Chandrasekaran

Madhavi

2015

Mar Syst Ocean Technol

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Offshore structures are often subjected to critical environmental loads that cause serious damage; MARS TLP in Gulf of Mexico damaged by hurricane Katrina in 2005 is an example. Existence of external perforated cover reduces hydrodynamic forces on the existing members caused by direct wave impact. The quantification of the force reduction in the offshore structures is reported by many researchers by emphasizing the fact that there is reduction in force on the existing member due to the presence of outer perforated cover. From the existing literature, the annular spacing and the perforation ratio are taken as 0.5 and 11 %. Velocity profile in the cylinder and around the perforation is investigated to give a better understanding of the physics for the considered case. Variation of velocity is also studied along the depth of cylinder and also in the perforation zone to get the clear understanding of the physics using the computational fluid dynamics tool STAR-CCM? for various areas of perforation for different wave steepness (H/L).

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Reflection and Transmission for a Porous Structure

Cited by 18 publications

References 3 publications

Investigation on innovative pile head breakwater for coastal protection

Investigation on innovative pile head breakwater for coastal protection

Transmission of Long Waves Induced by Short-Wave Groups Through a Composite Breakwater

Flow field around outer perforated circular cylinder under regular waves: numerical study

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