Experimental investigation of regular wave propagation over an idealized reef model
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Available online at https://link.springer.com/journal/42241 http://www.jhydrodynamics.com Journal of Hydrodynamics, 2020, 32(4): 717-726 https://doi.org/10.1007/s42241-020-0046-9
Experimental investigation of regular wave propagation over an idealized reef model * Gan-cheng Zhu, Bing Ren, Hong-jie Wen, Guo-yu Wang, Yong-xue Wang State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China (Received November 25, 2018, Revised March 14, 2019, Accepted April 11, 2019, Published online August 14, 2020) ©China Ship Scientific Research Center 2020 Abstract: The wave transformation over the deep-sea coral reefs is an essential issue in the analysis of the reef ecosystem and the design of large reef-top structures. Extensive wave flume experiments are conducted to investigate the wave transformation processes over an idealized reef model. Detailed measurements of the wave height, the wave set-up and the wave-generated flow on the reef-top are made with and without the reef-top structure at various submerged depths and under different wave conditions. It is found that the reef-top structure has a significant influence on the wave breaking, the wave set-up and the wave-generated flow. The wave set-up increases with the increasing wave height and the decreasing submergence depth. However, the relationship between the wave set-up and the wave period is complex, influenced by the reef-top structure. Key words: Coral reef, wave set-up, reef-top structure, wave breaking, wave-generated flow
Introduction The topography of the coral reefs in many tropical regions is much different from the traditional mild slope of the coastal zone. The reef-face is usually very steep with a very deep water in front of the reef. The water depth changes rapidly from the deep water in front of the reef to the shallow water on the reef-top. The wave breaking at the shallow water zone dissipates most portion of the incident wave energy and results in a much smaller wave height than that in the deeper water part of the reef. A favourable condition is found for the construction of marine structures and facilities on the reef top flats including the ports, the weather stations, the navigation-aids and the artificial islands[1]. However, some extensive damage was occasionally reported in the low-lying coastal areas fronted by coral reefs during storms. Some field observations show that the wave breaking on the fore reefs can raise the water level on the reef flat. The rise of the water level, known as the wave set-up, is a common phenomenon when a wave * Project supported by the National Natural Science Foundation of China (Grant No. 51679032). Biography: Gan-cheng Zhu (1992-), Male, Ph. D. Candidate, E-mail: [email protected] Corresponding author: Bing Ren, E-mail: [email protected]
propagates over a sloping beach[2-4] or a submerged breakwater[5-6], in which cases, it may be significant determining the water levels on the coral reefs particularly in micro tidal environments. A strong current generated b
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