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Ingeniería agrícola y biosistemas

On-line version ISSN 2007-4026Print version ISSN 2007-3925


MENDOZA-GONZALEZ, Ángel  and  AGUILAR-CHAVEZ, Ariosto. Determination of shear velocity in a mild-sloping open channel flow. Ing. agric. biosist. [online]. 2018, vol.10, n.1, pp.3-12.  Epub Aug 24, 2020. ISSN 2007-4026.


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.


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).


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.


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.


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.

Keywords : shear stress; acoustic Doppler velocimetry; log-law.

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