Author(s): Yue Liang; Shuyou Cao; Fengguang Yang
Linked Author(s):
Keywords: Velocity distribution; Inner region; Outer region; Logarithmic law
Abstract: Open-channel flows were divided into two regions: An inner region and an outer region， several formulas have been proposed for computing the velocity distribution separately for viscous sublayer, and outer region but they are not applicable directly to the transitional regimes. However, for practical purposes, a single velocity distribution that applies for all flow regimes is often required. Some researchers succeeded to get an uniform equation which is applied for the conditions from inner region to outer region. But not every formula adapts to the actual situation well. On the other hand, it is crucial which formula is used because accurate velocity distribution is important to project practice. Various generalized velocity equations in smooth wide open channel flows that are subject to some assumptions have been used in previous studies. This study provides a quantitative assessment of the previous developed velocity equations by comparing them to experimental data which were collected under smooth bed conditions. The data used comprise 143 runs by Nezu and Rodi (1986), 77 runs by Cardoso et al. (1989), and 64 runs by Swamee (1993). Four generalized formulae were selected from the literature for comparison. The results show that the all the predicted values using the four tested equations can fit the experimental data quite well. The Cheng (2008) equation provides the best estimates for y+>600. In general, Yang et al. (2011) equation provides the minimum average error, that is to say the formula of Yang et al. (2011) gives the best prediction by comparing the computed result of every formulae with the experimental data and is proposed to calculate the velocity distribution for smooth wide open channel flows in engineering.
Year: 2013