|
The Fiber-optic Laser Doppler Velocimetry (FLDV) was adopted in
this experimental study to investigate the
characteristics of the steep open channel flow over a
smooth boundary. In this study, the aspect ratio varied from
3.79 to 11.36, the Reynolds number varied from 10000 to 80000,
and the channel bed slope of 0.3%, 1% and 2% were selected.
Both two-dimensional and three-dimensional flow were discussed.
The Froude number ranged from 0.96 to 2.72, and most of the
experiments belonged to supercritical flow. The
objectives of this research were to study the mean velocity
profiles, the turbulence intensities, and the Reynolds stress of
the steep open channel flow.The measured velocity profiles
were compared with the law of the wall, the velocity defect
law, the one-seventh power law and Chiu''s velocity
theorem. The velocity profiles for conditions with the maximum
point velocity occurred above and below the water surface were
discussed. The measured distributions of the turbulence
intensities and the Reynolds stress were analyzed and
compared with the results of Nezu and Rodi (1986), and Tominaga
and Nezu (1992).
In addition, a preliminary study for the characteristics of the
deep narrow natural river flow was also performed. It was
found that the amount of depression of the point of
maximum velocity below the water surface increased with an
decrease of the aspect ratio (ratio of width to depth), which
was consistent with the results of the laboratory
experiment.
|