Celerity and Height of Aggradation Fronts in Gravel-Bed Laboratory Channel

Zanchi, Barbara; Radice, Alessio

doi:10.1061/(asce)hy.1943-7900.0001923

Cited by 3 publications

(6 citation statements)

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“…The sediment characteristics were determined by Unigarro Villota (2017) as follows: the particle equivalent diameter d is 3.8 mm with a uniformity coefficient f 1.04, the density ρ s is 1443 kg/m 3 , and the porosity p is 0.45. The Manning roughness coefficient of the sediment particles is n s = 0.015 s/m 1/3 as determined during preliminary tests by Zanchi and Radice (2021).…”

Section: Methodsmentioning

confidence: 99%

“…An aggradation experiment is designed in such a way that the sediment feeding rate exceeds the sediment transport capacity of the channel in the initial state. Furthermore, the propagation of an aggradation front may depend on a load ratio, intended as the ratio of the feeding rate to the initial transport capacity (e.g., Soni 1981;Yen et al 1992;Alves and Cardoso 1999;Zanchi and Radice 2021). Therefore, one needs to estimate the sediment transport capacity Q s0 of the experimental channel in the initial condition where the bed is not affected yet by the aggradation phenomenon.…”

Section: Estimation Of the Initial Sediment Transport Capacity Of The...mentioning

confidence: 99%

“…The "continuity" method is based on the mass conservation law and is an evolution of the method used by Zanchi and Radice (2021). In an aggradation experiment, some sediment material is fed into the channel, some is deposited in the channel and some leaves it through the outlet.…”

Section: Estimation Of the Initial Sediment Transport Capacity Of The...mentioning

confidence: 99%

“…The present manuscript is a follow-up of an earlier experimental campaign carried out at the Politecnico di Milano (Radice and Zanchi 2018;Zanchi et al 2019;Zanchi and Radice 2021) where sediment aggradation was studied in subcritical flow, providing simple predictors for the celerity of propagation and the height of an aggrading front and numerically reproducing some benchmark experimental results. Furthermore, in the prior campaign, ad hoc image-based measurement methods were devised for measuring the relevant parameters.…”

Section: Introductionmentioning

confidence: 95%

“…Experimental studies aim at phenomenological interpretation, at quantitative depiction and at providing enough data for calibration and validation of numerical models that are mostly used in engineering practice to analyze real situations. In this work, we are concerned with channel aggradation induced by sediment overloading, a process that can increase hydraulic risk during flash floods (e.g., Zanchi and Radice 2021).…”

Section: Introductionmentioning

confidence: 99%

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On how defining and measuring a channel bed elevation impacts key quantities in sediment overloading with supercritical flow

et al. 2022

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The manuscript presents the results of an aggradation experiment performed in a laboratory channel with supercritical flow. The channel was fed with a stationary sediment load exceeding the transport capacity of the flow in the initial condition, thus inducing sediment aggradation and an increase of the bed slope. The experiment is part of a laboratory campaign mimicking sediment overloading in mountain rivers, a process that can determine increased hydraulic risk levels at key spots. A crucial issue in measuring sediment aggradation is the definition and determination of the bed elevation, this issue being quite relevant in experiments with a relatively large transport capacity, where a thick bed-load layer exists and hinders the possibility to determine with confidence a reference bed elevation. The determination of the bed elevation, in turn, impacts the quantification of a number of properties, including the initial sediment transport capacity of the flow, temporal scales of the aggradation process, water depth and Froude number. The manuscript presents a sensitivity analysis of the results to two extreme definitions for the bed elevation: the first one locates the bed at the upper edge of the bed-load layer, while the second one at the lower edge of the bed-load layer where the particles do not move. The presentation of the two alternatives is focused on the experimental methods they use, consistently with the intent of the special issue. Furthermore, it is demonstrated that the definition of the bed elevation also has a major impact on numerical models of the process. The experimental results have been reproduced numerically, demonstrating that the calibration parameters returning a best fit are also impacted significantly by how the bed is defined. The preferred definition for analyzing an experimental campaign is locating the bed below the bed-load layer.

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Section: Methodsmentioning

confidence: 99%