Mean Velocity and Entropy in Wide Channel Flows

For decades many authors have used entropy-based models to predict velocity distribution in open channel flows. Such models use maximum and mean velocity in an assigned domain to obtain velocity distribution. However, while the signification of maximum velocity is clear, the use of mean velocity is sometimes misleading. This paper thus clarifies, for the case of wide channel flows, both, the signification and role of mean velocity within certain existing entropy-based models. It also demonstrates, for some widely cited approaches, the need to pay attention to the difference between the expected value of velocity and the average cross-sectional velocity.