An experimental and theoretical analysis of floating wood diffusion coefficients

Meninno, Sabrina; Persi, Elisabetta; Petaccia, Gabriella; Sibilla, Stefano; Armanini, Aronne

doi:10.1007/s10652-019-09693-x

Cited by 7 publications

(22 citation statements)

References 50 publications

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“…The diffusion coefficients of the matrices K R and K L are derived from the results presented in [30], in which streamwise and transversal coefficients (K s , K t ) were provided as a function of the particle Froude number Fr p and of the transversal relative release distance t Rr of the mass concentration (Equation 16). These values are combined according to the local velocity orientation to obtain the elements of the diffusion matrices (Equation 17).…”

Section: Outlines Of the Coupled Systemmentioning

confidence: 99%

“…A different approach is here proposed to overcome these limits, which is particularly suitable for the congested transport condition, i.e., the transport of several LW pieces, strongly interacting and behaving like a carpet [29]. Such an approach, already drafted in [30], considers the ensemble of transported logs like a continuous quantity floating on the water surface. The total mass of the logs is thus treated as a passive and conservative substance, so that an advection-diffusion equation is numerically coupled with the SWE, allowing for the coupled solution of the water flow and the LW transport.…”

Section: Introductionmentioning

confidence: 99%

“…In this contribution (i) the mathematical model outlined in [30] is discussed, and the advection-diffusion equation for wood mass transport is implemented in the twodimensional code ORSA2D [31]; (ii) the main parameters of the advection-diffusion equation, i.e., the transport velocity and the diffusion coefficients, are calibrated to the typical situation of large wood thanks to the analysis of available experimental campaigns [30] and, finally, (iii) the performances of the proposed model are evaluated against flume experiments [30,32], providing a global measurement of how the model can replicate LW transport.…”

Section: Introductionmentioning

confidence: 99%

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A One-Way Coupled Hydrodynamic Advection-Diffusion Model to Simulate Congested Large Wood Transport

et al. 2021

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An advection-diffusion model is proposed to simulate large wood transport during high flows. The mathematical model is derived from the wood mass balance, taking into consideration both the wood mass concentration and the log orientation, which affects log transport and, most importantly, wood accumulation. Focusing on wood mass transport, the advection-diffusion equation is implemented in a hydrodynamic model to provide a one-way coupled solution of the flow and of the floating wood mass. The model is tested on a large series of flume experiments, involving at least 30 logs and different control parameters (flow Froude number, log length, diameter, release point). The validation through the experimental data shows that the proposed model can predict the correct displacement of the most probable position of the logs and to simulate with a sufficient accuracy the planar diffusion of the wooden mass. Transversal wood distribution is more accurate than the streamwise one, indicating that a higher control on the longitudinal diffusion needs to be implemented.

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Section: Outlines Of the Coupled Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A One-Way Coupled Hydrodynamic Advection-Diffusion Model to Simulate Congested Large Wood Transport

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“…The topics dealt with in the papers range from the development and validation of numerical models to describe the interaction between flow and driftwood [11,17,21,23] to the experimental assessment of the Large Wood blocking at inline structures [14,20,27,31], to the evaluation of the stability of riparian vegetation during flood events and its consequent entrainment in the flow [12].…”

mentioning

confidence: 99%

“…Meninno et al [21] propose a completely Eulerian model to represent large wood-transport, where advection-diffusion equations are obtained for the space concentration of floating logs and for the probability density function of the orientation of a log in a specific spatial position. In both equations, dispersion due to surface turbulence is modelled through a diffusive term, which in turn depends from diffusion coefficients.…”

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Recent developments in the analysis of Large Wood dynamics in fluvial systems

Sibilla

Meninno²,

Canelas

2020

Environ Fluid Mech

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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

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Characterization of trajectories and drag coefficients of large wood in sharp river bends from flume experiments

Innocenti

Branß

Zaid

et al. 2022

Earth Surf Processes Landf

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The transport of large wood (LW) has been a focus of research in the last decades because of its importance for river ecosystems, fluvial dynamics and flood protection.Riverine processes connected with the presence of LW have largely been based on laboratory experiments carried out in straight or weakly bended channels. The dynamics of LW in sharp river bends has received less attention, so there exist many open questions regarding how LW is transported through such channel parts. For this reason, this paper presents results of unique laboratory experiments designed to study the trajectories of single wooden dowels in sharp bends. Dowel trajectories were determined for four dowel sizes, two initial dowel orientations with respect to the main channel axis and three inlet positions. Information about the 3D velocity field in the bend were obtained from a previous study that used the same channel with identical hydraulic boundary conditions. Furthermore, a force-balance analysis was developed for interpreting the dowel trajectory and drag coefficient of LW in sharp river bends. The experimental results show that the dowel length is the main parameter controlling dowel trajectory in a sharp bend, and indicate the role of inertial effects that drive the dowel drift along the bend. The obtained drag coefficients ranged between 0.35 and 1, which is in agreement with previous values for submerged, or semi-submerged, fixed pieces of wood in straight river reaches.

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An experimental and theoretical analysis of floating wood diffusion coefficients

Cited by 7 publications

References 50 publications

A One-Way Coupled Hydrodynamic Advection-Diffusion Model to Simulate Congested Large Wood Transport

A One-Way Coupled Hydrodynamic Advection-Diffusion Model to Simulate Congested Large Wood Transport

Recent developments in the analysis of Large Wood dynamics in fluvial systems

Characterization of trajectories and drag coefficients of large wood in sharp river bends from flume experiments

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