Author(s): Christophe Reymond; David Huther; Giovanni De Cesare

Linked Author(s):

Keywords: Sediment transport; Energetic flow regimes; ACVP; Two-phase flows

Abstract: Benthic sediment transport in river and coastal waters plays a major role in shaping aquatic habitats, regulating nutrients, pollutant fluxes, and maintaining the long-term ecohydraulic stability of fluvial, estuarine and deltaic systems. Accurate prediction of benthic sediment transport rate involving both bedload and suspended load is of particular importance for reliable predictions of benthic habitat vulnerability and resilience to climatic energetic flood events. New high-resolution experimental datasets are urgently needed for the development, calibration, and validation of recent numerical sediment transport models for high Shields number (energetic) flows. However, the majority of existing experimental sediment transport datasets have not been obtained under controlled energetic flow and sediment transport regimes, furthermore, they principally rely on (single- phase) flow mixture modeling approaches and measurements, assuming that sediments follow fluid parcels without any inertial lag (except for the gravitational settling velocity). Mixture theory based approaches (Guo & Julien, 2001; McTigue, 1981) and (sediment-fluid) mixture flow measurements (Guta et al., 2022, 2024; Revil-Baudard et al., 2015, 2016) limit strongly our understanding of the key benthic sediment transport processes when compared to recent two-phase fluid-particle modelling applied to sediment transport predictions (Cheng et al., 2018; Mathieu et al., 2022; Salimi et al., 2021). Indeed, these modelling approaches have offered new perspectives in improved numerical predictions of sediment transport rate under climatic energetic flow events, however, the lack of existing two-phase measurement systems and corresponding experimental datasets, represents currently, the major scientific bottleneck. As discussed by Finn and Li (2016), these geophysical sediment-laden flows are subject to dominant turbulent two-phase fluid-particle interaction processes for which two-way (in dilute mixtures) and four-way (for dense mixtures) couplings occur between the carrying water flow phase and the dispersed sediment phase. To fill this gap in process-oriented experimental datasets, this study, divided into 2 separate parts presents a new set of sediment transport experiments carried out in steady, uniform, hydraulically rough, open-channel flows over a wide range of transport conditions. Part I of this study presents the development and validation of a new multi-frequency Acoustic Concentration and Velocity Profiler (ACVP), designed to simultaneously measure co-located velocity and concentration profiles at high spatio-temporal resolution. The present part II describes a new experimental facility design and corresponding experimental protocol, using the n ovel multi-frequency ACVP for studying transport processes of heavy sand-laden open-channel flows. This new experimental setup will be the basis for a new open -source dataset covering a wide range of hydraulic conditions and sediment dynamical behavior.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.297

Year: 2026