Measurement and Study of 1-D and 2-D Dispersion Coefficient in the Tidal Reach of Wu-Shi River

• Main Authors: Kung-Chung Jeng, 鄭坤忠
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/qyr9ms

碩士 === 逢甲大學 === 土木及水利工程所 === 90 === In Taiwan most of the researches of tidal reach focused on Danshuei river system, at northern Taiwan especially for Keelung river. The experimental data (current velocity, discharge, water lever and salinity) influenced by tide are deficient for the other part of Taiwan. Wu-shi basin is important due to it''s geography, rich water resources, economy, population and wetland ecosystem. This thesis used salt transport analysis and longitudinal salt gradient collected by measuring cross-section, water lever, current velocity and salinity of Shi-Bin bridge to calculate instant 1-D dispersion coefficient K and tidal average 1-D dispersion coefficient <K>. 2-D transverse dispersion coefficient Ey is obtained by way of instantaneous tracer release. The field transverse concentration distribution is compared with that from diffusion equation of difference Ey to find an appropriate 2-D transverse dispersion coefficient. 2-D longitudinal dispersion coefficient Ex is calculated by theoretical formulate of Elder[22]. The result of this thesis, K is 2~-95 , <K> is —229 , dimensionless diffusion coefficient < > is 8262, and these values are much influenced by tidal intensity. From the salt transport analysis, the effects of tidal pumping, vertical shear dispersion and transverse shear dispersion are the major causes for the dispersion at the Shi-Bin bridge, while the effects of wind、topography and coriolis force are insignificant. Ex , Ey are 1.35 and 0.095 , dimensionless longitudinal and transverse diffusion , are 3 and 1.23 respectively. This thesis establishs 1-D and 2-D experimental procedures of tidal reach of Wu-Shi, analyzes transport mechanism and dispersion coefficient of 1-D and 2-D, and provides references for environmental developmental administration and for water quality model parameters.