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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Special sessions : Analysis of scattered acoustic signals to characterise the behaviour of the freesurface of shallow w...
Analysis of scattered acoustic signals to characterise the behaviour of the freesurface of shallow water flows
Author : DOLCETTI G.(1), KRYNKIN A.K.(2) , HOROSHENKOV K.V.(3) & TAIT S.J.(4)
ing free-surface flows in open channels and partially filled pipes are
becoming increasingly popular. This paper reports on instrumentation that was used to investigate the Doppler spectra of
airborne ultrasonic waves that are back-scattered from the rough free-surface of shallow turbulent water flows. An
acoustic measurement technique has been developed and tested in a laboratory flume for a range of flow regimes
(Reynolds number based on the mean depth averaged velocity and mean water depth varying between 5,600 and
48,800). The results show that the patterns of the rough water surface travel at the velocity close to the mean surface flow
velocity. These patterns are believed to originate from the direct interaction between the free-surface and the turbulence
in the flow. Additional surface waves are also observed that propagate at velocities typical to gravity-capillary waves in
shallow water. A numerical model based on the Kirchhoff integral and Monte Carlo method has been developed in order
to provide a better understanding of the acquired data. The comparison between the experimental results and the
predictions from the model suggests that the power spatial spectrum of the free-surface follows a power law function of
the wavenumber with exponent -2, which stands for all measured flow regimes. The results have implications for the
interpretation of Doppler spectra from acoustic and radio wave back scatter instrumentation which is used to measure the
surface flow velocity and hence channel/conduit flow rate.Form Required :Published Date : 123
File Size : 502,800 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Special sessions
Date Published : 20/08/2015
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