Flows involving solid particulates have been widely studied in recent years, but their dynamics are still a complex issue to model because they strongly depend on the interaction with the boundary conditions. We report on laboratory investigations regarding homogeneous and steady flows of identical particles over a loose bed in a rectangular channel. Accurate measurements were carried out through imaging techniques to estimate profiles of the mean velocity, solid concentration, and granular temperature for a large set of flow rates and widths. Vertical and transversal structures observed in the flow change as interparticle interactions become more collisional, and they depend on the bottom over which the flow develops. The lateral confinement has a remarkable effect on the flow, especially for narrow channels compared with the grain size, and a hydraulic analogy is able to show how the walls influence the mechanisms of friction and energy dissipation.
Wood transport during flood events can increase inundation risk and should be included in numerical models to estimate the associated residual risk. This paper presents the application of a fully Eulerian model that considers floating wood as a passive superficial pollutant through the adaptation of the advection–diffusion equation. A set of experiments is performed in a sinusoidal flume with a contraction to model semi-congested wood transport. The variation of the log release position replicates the possible variability of large wood entrainment during real events. The experiments are used to validate the numerical model, providing a comparison of the wood mass transport. Different release modes are also tested. The model predicts the position of the released logs and the overall transported mass, independently of the release position and modes, with an accuracy that varies along the flume length and across the flume axis. The analysis of the experimental and numerical transport velocity shows that modulation of the transport velocity is needed to ensure adequate model performances for semi-congested conditions.
Wood in river plays a significant role in river geomorphology and ecology, by interacting with erosion and sedimentation processes, influencing the nutrients budget and providing physical habitats for a variety of species. However, Large Wood elements (LW, with a trunk diameter > 0.1 cm and a length > 1 m, as defined by Wohl et al. [38] transported during floods can aggravate the expected drawbacks and augment the overall risk at which the urban areas are exposed [7,8,28].LW may cause obstructions along the channel network, mostly in correspondence of bridges or weirs, where it accumulates, clogging the openings and causing a backwater rise upstream. Hydraulic structures can collapse as a result of the increased loads, and unexpected overflowing can occur at the jammed river cross-sections.The formation of LW accumulation is thus a key issue in the hydraulic risk assessment and its mechanism, as well its subsequent modelling, is still object of study [1,10,13,15,32,34]. It is highly affected by the interactions between water, sediments and structures, and it is also influenced by the physical features of LW element and river morphology [30].Due to the potential implications of LW during floods, different types of practical measures have been developed and employed [2, 5] to retain LW upstream of the critical sections (e.g. fins and racks, [26,33] or to reduce its presence in the river. These measures remain highly linked to the expertise of single practitioners, although recent works have proposed physically based designs of safety structures [25] both in mountain streams and low-land rivers.The need of giving a quantitative prediction of wood transport during floods throughout the river network has led researchers to investigate water-wood interactions both at a laboratory scale [3,4,6,9] and through numerical models [19,29]. The motion of floating wood on the water surface has been modelled with different strategies [22,28,35], mostly based on Eulerian-Lagrangian approaches able to trace wood motion and rotation.As an input, the aforementioned models require the volume and distribution of the wood that can be transported by the flood, and these data are affected by high uncertainty and derived through wood budget at basin scale [16,37]. In fact, wood entrained in a river can
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.