Hydraulic performance and wave loadings of perforated/slotted coastal structures: A review

The interaction of oblique monochromatic incident waves with horizontal/inclined/dual porous plates is investigated in the context of two-dimensional linear potential theory and Darcy's law (the normal velocity of fluid passing through a thin porous plate is linearly proportional to the pressure difference across it). The developed theory is verified by both small-scale and full-scale experiments. First, matched eigenfunction expansion (MEE) solutions for a horizontal porous plate are obtained. The relationship between the plate porosity and the porous parameter is obtained from systematic model tests by using six porous plates with different sizes and spacing of circular holes. Secondly, a multi-domain boundary-element method (BEM) using simple-sources (second-kind modified Bessel function) is developed to confirm the MEE solutions and to apply to more general cases including inclined or multiple porous plates. The BEM-based inner solutions are matched to the eigenfunction-based outer solutions to satisfy the outgoing radiation condition in the far field. Both analytical and BEM solutions with the developed empirical porous parameter agree with each other and correlate well with both small-scale data from a two-dimensional wave-tank test and full-scale measurement in a large wave basin. Using the developed predictive tools, wave-absorption efficiency is assessed for various combinations of porosity, water depth, submergence depth, wave heading, and plate/wave characteristics. In particular, it is found that the performance can be improved by imposing the proper inclination angle near the free surface. The optimal porosity is near porosity P=0.1 and the optimal inclination angle is around 10° as long as the plate length is greater than 20% of the wavelength. Based on the selected optimal parameters (porosity=0.1 and inclination angle=11.3°), the effective wave-absorption system for MOERI's square basin is designed.

Wave absorbing system using inclined perforated plates

The present paper aims at getting the porous effect parameter G of a thin permeable wall. The reflection and transmission coefficients of a thin vertical porous wall with different porous shapes an...

Porous effect parameter of thin permeable plates

Wave interactions with double slotted barriers

1. Introduction 2. Review of hydromechanics 3. Linear surface waves 4. Nonlinear surface waves 5. Random seas 6. Wave modification and transformation 7. Waves in the coastal zone 8. Coastal engineering considerations 9. Wave-induced forces and moments on fixed bodies 10. Introduction to wave-structure interaction 11. Floating bodies 12. Wave-induced motions of compliant structures.

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Ocean Engineering Mechanics: With Applications

On a highly effective wave absorber

A study on the improvement for the problem of wave transmission in deeply submerged break- water is carried out in this paper. In the theoretical analysis the complex eigenfunction approach is employed. In this study the submerged breakwater is assumed to be a rectangular form and vertically stratified with multislice porous material. Theoretical computations are performed for both single-slice (nonstratified) and mul- tislice submerged breakwaters. Half of the water depth is selected as the submergence of the breakwater. The computational results show that, for a single-slice breakwater, the transmission coefficient could be effectively reduced, while the porosity of structure material is as high as 0.8 and the thickness-depth ratio b/h =2 0 (b is the structure thickness, and h is the water depth). A large transmission coefficient can be predicted for a deeply submerged breakwater without sufficient thickness-depth ratio. However, this problem could be improved by adopting a multislice structure concept in which the breakwater structures with more slices are more effective in reducing the transmission coefficient.

Sheng-Wen Twu

Papers

On a highly effective wave absorber

Wave damping characteristics of deeply submerged breakwaters

A highly wave dissipation offshore breakwater

Wave damping characteristics of vertically stratified porous structures under oblique wave action

Interaction of non-breaking regular waves with a periodic array of artificial porous bars