Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/43299
Title: Experimental study on velocity profiles with different roughness elements in a flume
Authors: Wang, XK
Ye, C
Wang, BJ
Yan, XF
Issue Date: 2015
Source: Acta geophysica, 2015, v. 63, no. 6, p. 1685-1705
Abstract: The classical log law for velocity profile is applied to engineering practice. Field observations indicate that the composition of the bed materials obviously influences the shape of vertical velocity distribution. To clearly understand the roughness effect, six types of materials were laid separately at various depths for the investigation of the effects of roughness elements on the vertical velocity distribution. A down-looking 3D acoustic Doppler velocimeter was used to measure the velocity profiles. The experimental results showed that the curve characteristics of velocity profiles are strongly dependent on the roughness scale and related flow parameters. If d/R, Fr, and Re are larger than 0.15, 0.47, and 60 000, respectively, the velocity distribution may resemble an S-shape profile. The inflexion position Z∗/H for a given S-shape profile was empirically deduced as Z∗/H = -0.4481d/R + 0.3225. Otherwise, the velocity profile agrees well with the logarithmic law. The findings of this study are useful in engineering practice (i.e., depth-averaged velocity and flow rate estimate).
Keywords: Acoustic doppler velocimeter
Logarithmic law
Roughness elements
S-shape curve
Velocity profiles
Publisher: De Gruyter
Journal: Acta geophysica 
ISSN: 1895-6572
DOI: 10.1515/acgeo-2015-0063
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