Hydraulics of shallow rain-impacted flow near channel boundary

• Main Authors: Hong, gen-haw, 洪健豪
• Other Authors: Fang fuh-min
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/18085732720933852679

碩士 === 國立中興大學 === 土木工程學系 === 85 === ABSRACT The Fiber-optic Laser Doppler Velocimetry （FLDV）technique was used to measure the flow characteristics of the rain-impacted open channel flow over a smooth bed in this reaserch. There are two conditions in this reaserch, i. e. conditions with and without rainfall. In addition to the discuss the physical phenomenon of the near-wall flow,semi-empirical equations were derived for the practical purposes. The main objective of this study was to analyze the mean velocity profiles, and the distributions of the two- dimensional turbulence intensities and the shear stress. Ingeneral, the results of Yoon*s model were consistent with the measured mean velocity profiles. The value of the momentum correction factor was found to increase with an increase of the Reynolds number, the rainfall intensity or the raindrop size, and to gradually approach a value of one. As regard the penetration of flow by raindrop, the results indicated that the critical penetration depth was a function of slope, raindrop diameter, rainfall intensity and the thickness of viscous sublayer rather than a constant value. Several dimensionless semi-empirical formulas were derived to predict the vertical distribution of the two-dimensional turbulence intensity for the case with and without raindrop impact. The results were reasonably consistent with the experimental data. The effect of rainfall on the flow near the channel boundary for the lower Reynolds number was stronger thanthat for the higher one. The ratios of the order of magnitude of the viscous shear stress, mean Reynolds stress and the standard deviation of the Reynolds stress were about 2:1:3. In other words, the mean Reynolds stress is standard deviation of the Reynolds stress is the dominant one. This is especially true for the conditions with low eynolds number.