Turbulence in Rivers

The study of turbulence has always been a challenge for scientists working on geophysical flows. Turbulent flows are common in nature and have an important role in geophysical disciplines such as river morphology, landscape modeling, atmospheric dynamics and ocean currents. At present, new measurement and observation techniques suitable for fieldwork can be combined with laboratory and theoretical work to advance the understanding of river processes. Nevertheless, despite more than a century of attempts to correctly formalize turbulent flows, much still remains to be done by researchers and engineers working in hydraulics and fluid mechanics. In this contribution we introduce a general framework for the analysis of river turbulence. We revisit some findings and theoretical frameworks and provide a critical analysis of where the study of turbulence is important and how to include detailed information of this in the analysis of fluvial processes. We also provide a perspective of some general aspects that are essential for researchers/ practitioners addressing the subject for the first time. Furthermore, we show some results of interest to scientists and engineers working on river flows

Velocity distribution in non-prismatic compound channels

River-flow modelling relies on accurate prediction of the stage–discharge relationship. Additionally, the lateral distribution of the longitudinal velocity component should be estimated for sediment transport investigations. In compound channels, the shear stress at the interface between the floodplains and the main channel strongly affects both conveyance and velocity distribution. This effect is reinforced when mass transfer occurs between subsections due to channel non-prismaticity. The stage–discharge relationship and the velocity distribution in prismatic compound channels can be computed using the lateral distribution method (LDM). The present paper investigates an extension of the LDM to non-prismatic channels. The physical meaning of the so-called secondary-current term is discussed. Numerical results are compared with previous velocity measurements in a symmetrically narrowing compound channel and to new bed shear-stress measurements in the same geometry. </jats:p