碩士 / 國立成功大學 / 水利及海洋工程學系 / 89 / ABSTRACT
In this thesis, the 2-D movable bed model experiment skill has been applied to investigate the influence of pit on water wave propagation and beach profile change due to regular wave.
For the laboratory experiment setup, sand with median grain diameter of 0.19mm is placed in a wave tank to form an initial plane beach with slope of 1/20 and 1/30 on where a trapezoid pit that concaves 15cm deep and 150 cm width. The pit is dug at 20, 30 and 40 cm under water surface, respectively. The height and period of the incident waves were 7.5 cm, 1.5 seconds and 16.9 cm, 1.7 seconds. The whole section water surface elevation and bottom topography measuring process are executed at the 0th, 4th, 8th, 12th, 16th, and 20th hour of wave making duration.
The result showed that as the wave propagated through the pits, partial energy was reflected. The reflection coefficient, Kr, was 0.01 ~ 0.13, which increase 22% ~ 87% compared with that through sloping beach without pits. In addition, 5.8% ~ 16.5% of the wave energy was transferred from first harmonic into high frequency component. Therefore, the maximum wave height at which the waves attain breaking limits decreased relatively 0.429% ~ 7.465% in comparison with that in the sloping beach without pits. According to the semi-empirical criterion on whether a beach will erode or accrete which proposed by Sunamura and Horikawa (1974), the decrease of the wave height caused by the pit does not have significant effect on the transformation of the classification of beach profile type, but the distance between pit and breaking point does.
This article is proposed that the effect on beach profile change caused by pits can be divided into four types corresponding to the value of , and the accretion of the shoreline and beach-face is the most significant when the value of is between 0 and 1.
| Identifer | oai:union.ndltd.org:TW/089NCKU0083059 |
| Date | January 2001 |
| Creators | Lai Jian-Wu, 賴堅戊 |
| Contributors | Ching-Ton Kuo, 郭金棟 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 66 |
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