Author(s): Ilaria Fent
Linked Author(s): Ilaria Fent
Keywords: Dam-break flow, PIV, depth velocity profiles, mobile bed
Abstract: Knowledge of the velocity distribution is a key for understanding and modelling any type of flow. The velocity profile can provide an image of turbulent exchanges inside the flow and constitutes one of the classical ways for evaluating the flow resistance. Moreover, most of depth-averaged 1D and 2D-H numerical models are based on assumptions about the velocity distribution, especially if bed load sediment transport is involved. The velocity distribution is extensively studied in the first half of the 20th century, mainly for steady uniform flows in smooth and rough pipes. Theoretical and experimental approaches apply a logarithmic law in the inner region, in the vicinity of the bed. With the development of non-intrusive measurement techniques, more and more complex situations are investigated: unsteady flows on fixed bed, steady and unsteady flows over mobile bed. Logarithmic velocity distribution is observed in all these cases. In particular, Sumer et al. (1996) experiments on steady flow over mobile bed show that the log-law also prevails in the upper part of the moving sediment layer. This paper presents results in an extreme transient case: a dam-break flow over mobile bed. The velocity distribution in the clear-water layer is observed as quasi uniform, while the sediment layer presents a velocity distribution very similar to the observations made in steady uniform flow cases
Year: 2017