Determination of shear velocity in a mild-sloping open channel flow
2018
Mendoza-González,Ángel | Aguilar-Chávez,Ariosto
Abstract Objective: To present a methodology that allows experimentally determining shear velocity, considering the log-law as a model of velocity distribution in the outer region of turbulent flow. Mathodology: The experimental study was carried out in a rectangular-shaped, variably-sloped channel with a 0.245-m-wide base and 5 m long. Flow velocity was measured with an Acoustic Doppler Velocimeter (ADV), and the measurement area was 12 mm. Shear velocity was determined by the instantaneous velocity equation ( u i , j). Results: The log-law model had a good statistical fit with the shear velocity estimated from the experimental data. Study limitations: The experimental tests were conducted only in subcritical regime with low aspect ratios. In addition, in all tests, the measurement of instantaneous velocities was carried out only in a 12-mm profile, as close as possible to the wall. Originality: The model to calculate the shear velocity is presented explicitly, and the statistical approach employed supports the use of the median as an estimator of the shear velocity. Conclusions: The presented methodology shows low uncertainty in the estimation of shear velocity. The Anderson-Darling test showed that the results do not follow a normal distribution, so the median is the statistical parameter to define the shear velocity value.
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