Wave Scattering by Two Unequal Surface-Piercing Vertical Plates With Stepped-Bottom
- Zhengzhi Deng (Zhejiang University) | Lixian Wang (Wuhan University of Technology)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- two unequal thin plates, wave force, reflection and transmission coefficients, Stepped bottom topography
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In this study, scattering of normally incident water waves by two unequal surface-piercing thin vertical rigid plates with stepped bottom topography is investigated based on linear water-wave theory. By using the matching eigenfunction expansion method and a least square approach, analytical solutions are sought for the established boundary value problem. The reflection and transmission coefficients as well as the horizontal wave forces acting on the plates are obtained for various parameters, including the location and the vertical elevation of the step, and the width between the two plates.
the rise of world population in recent years, there is a rapid increase of developmental activities along the coast regions around the world. To ensure the safe coastal engineering practices such as bays, ports and harbors, protection of these coastal infrastructures from rough wave conditions has been paid much attention. Breakwaters, as of one the most important coastal structures, are often constructed near the coastline to protect coastal infrastructures. After interacting with waves incoming from the open sea, suitable breakwaters can effectively reduce the wave energy transmitted through them. Traditional breakwaters such as rubble mound breakwaters and concrete caissons are widely used for the construction of harbours and for shore protection works. The cost of these types of breakwaters is generally high if they are employed in deep water regions.
Since the wave energy is concentrated near the water free surface, breakwaters such as partially immersed twin vertical barriers were proposed (Isaacson et al., 1999), which are believed to be able to reflect the wave energy effectively. To understand physics of these breakwater concepts, many researchers have investigated the wave scattering by two vertical thin rigid plates on the free surface, such as Evans and Morris (1972), Newman (1974), McIver (1985), Porter and Evans (1995), Das et al. (1997), Neelamani and Vedagiri (2002), De et al. (2010), and Roy et al. (2016). In most of these studies, the two plates are identical except those by McIver (1985), Neelamani and Vedagiri (2002), and Roy et al. (2016). Using the eigenfunction expansion method, McIver (1985) investigated the scattering of a normally incident wave by two unequal partially submerged plates below the free surface in water of finite uniform depth. It was found that total reflection or total transmission was possible for two identical plates while total transmission no longer exists for two unequal plates. Similar observations were also found by Roy et al. (2016), who investigated this problem by considering an obliquely incident plane wave in infinitely deep water. A one-term Gerlerkin approximation method was employed to obtain the reflection and transmission coefficients. Neelamani and Vedagiri (2002) experimentally studied the performance of barriers configured by two unequal surface-piercing plates and found that the transmission coefficient reduced significantly with the increased relative water depth. In addition, the unequal immersion configuration was found superior to the equal immersion configuration near the deep water condition.
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