| Summary: | 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.
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