A Study of the Characteristic of Bragg Reflection of Waves Propagating over a Series of Submerged Breakwaters and the Diffusion Experiments

• Main Authors: Lin, Po-Ting, 林柏廷
• Other Authors: Wen, Chih-Chung
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/44306194387959859967

碩士 === 弘光科技大學 === 環境工程研究所 === 95 === This study is adopting the mild-slope-equation numeral model (EEMSE) (Hsu, 2003), the numeral hydraulic experiments is conducted to study the distribution result of water waves over a series of submerged breakwaters. Based on the results of different water waves over different layout of submerged breakwaters, the distribution of reflection rate and the relationship between Bragg reflection representative parameters (R, 2S/L) and wave conditions parameters (N, S/B, D/h) is studied and analyzed. The discovery from the above mentioned result, there is only slight variation occurred on the reflection peak (2S/L)max under the condition of same S/B relative spacing of submerged breakwaters and number of submerged breakwaters greater than four. The maximum peak value of Bragg reflection peak value Rmax , occurred under the condition of spacing of submerged breakwaters S/B greater than 3 and less than 4. As a result, the hydraulic experiments to study Bragg refection for waves over a serious of submerged breakwaters is conducted under setting up fixed number of submerged breakwaters (N=4) , relative spacing of submerged breakwaters (S/B=3.0) and relative height of submerged breakwater (D/h=0.5) as variables. Three different reflection values are derived. Individually, they are R=0.69 (T=1.86sec and 2S/L=0.93), R=0.30 (T=1.70sec and 2S/L=1.00 ) and R=0.10 (T=1.58sec and 2S/L=1.10). The diffusion test of injected salt under water waves over a series of submerged breakwaters are perforated based on above mentioned conditions. Three different concentration NaCl are applied C0= 1M , 0.5M and 0.25M. Such as after constantly spraying NaCl for 400 seconds, the observation is conducted during t=101~150sec (the beginning of spreading) and t=301~350sec (spreading stabilizing).Salt concentration at different horizontal and vertical locations are investigated. Based on the observation, while the reflection rate is stronger followed by the spreading range in the water of the test is wider. Due to the water particle vibration will be getting active when the salt reflection rage is getting stronger. Therefore, the spreading range will be wider in both horizontal and vertical directions.