Journal of the Japan Society of Erosion Control Engineering, Vol.58,No.1,2005
The application of bed load measurements to hydraulic model experiments
using the hydrophones
Akira ODA Yuji HASEGAWA Takahisa MIZUYAMA
Kuniaki MIYAMOTO Michinobu NONAKA
Abstract
The estimation of grain size distribution has arisen as the subject of bed load
measurements using hydrophones. Although field bed load measurements using hydrophones
in some rivers have already begun, its application to hydraulic model experiments
is still in its infancy. In this study, we investigated the estimation of the
grain size distribution of mixed sand through a systematic experiment executed
in a linear rectangular channel. We further show an exemplary hydraulic model
experiment using a hydraulic model equipped with a hydrophone at both the cross]section
of the downstream end of the model and the cross]section of the planned slit sabo
dam installed in the middle of the model segment. The relationship between the
non]dimensional grain size distribution and the sensitivity of the channel in
this hydraulic measurement system for recording pulse numbers indicated good agreement,
provided that the sensitivity of the channel for recording the number of pulses
is ideal for the objective mixed sand. The applicable range of the channel sensitivity
is, however, narrow, thereby lacking in general application. Therefore, in order
to estimate the grain size distribution of mixed sand, it is necessary to adjust
the channel sensitivity. From the hydraulic model experiment using hydrophones
for measuring bed load, the reason that the peak of bed load sediment occurs at
the downstream end of the hydraulic model could be explained by the changes of
the number of pulses at the slit sabo dam. The result of our hydraulic model experiment
suggests that a rational explanation of the phenomena of bed material transport
is made possible by applying hydrophones to the hydraulic model experiments.
Key words:hydrophone, bed load, measurement, hydraulic model experiment, grain
size distribution
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