Publications by Christophe Ancey

Automated grain sizing from uncrewed aerial vehicles imagery of a gravel-bed river: Benchmarking of three object-based methods

Christophe Ancey, Ivan Pascal, Raphaël Miazza

Measuring grain sizes in gravel-bed rivers is crucial when studying river dynamics and sediment transport. Automated methodologies have been developed in recent years for detecting individual grains and measuring their size on digital imagery. These object ...

2024

Refractive Index Matched (RIM) PIV in Free Surface Flows of Particle-Laden Yield Stress Fluids

Christophe Ancey, Yanan Chen

Flow of lava, avalanches, mudslides, and many geophysical and planetary flow systems are examples of free-surface flows of Yield Stress Fluids (YSFs). This category of fluids is known for its dual behavior below- and above a yielding threshold for the appl ...

2024

Probabilistic Modeling of Sediment Dynamics in Braided River Systems

Christophe Ancey

Understanding the relationship between bedload transport and morphological changes is crucial in braided river systems, particularly those on steep slopes. Despite significant research efforts in recent decades, unraveling this interplay remains a complex ...

2024

Segregation of sediments in meandering river channels

Christophe Ancey, Yanan Chen

Particle segregation is widespread in river channels and significantly influences bed grain size distribution. To date, most studies have investigated particle size segregation in straight river channels. Less studied is the case where particles segregate ...

2024

Particle segregation in an annular shear cell

Christophe Ancey, Yanan Chen

Particle segregation is a widespread process that affects particle composition in granular materials. Particles tend to segregate into distinct regions according to their size, density, and shape. To date, most studies investigate particles segregating in ...

2024

Vegetation Submergence Effects on Bedload Transport Rate

Christophe Ancey

We conducted a series of laboratory experiments to investigate the impact of vegetation on bedload transport rates depending on submergence. In the experiments, we used aluminum rods to simulate rigid vegetation, with vegetation submergence ratios (i.e., t ...

2024

Instability of Antidune Incipience under Low Submergence Conditions

Christophe Ancey, Ivan Pascal

Investigating the stability of river bedforms is essential for understanding their occurrence and evolution over time. Whereas the formation of ripples and dunes has been extensively studied [1, 2], little is known about antidune stability in the early sta ...

2024

Bed Topography Inference from Velocity Field Using Deep Learning

Christophe Ancey, Mehrdad Kiani Oshtorjani

Measuring bathymetry has always been a major scientific and technological challenge. In this work, we used a deep learning technique for inferring bathymetry from the depth-averaged velocity field. The training of the neural network is based on 5742 labora ...

2023

Temporal Prediction of Landslide-Generated Waves Using a Theoretical-Statistical Combined Method

Christophe Ancey, Zhenzhu Meng, Yating Hu

For the prediction of landslide-generated waves, previous studies have developed numerous empirical equations to express the maximums of wave characteristics as functions of slide parameters upon impact. In this study, we built the temporal relationship be ...

MDPI2023

Scaling behavior of bedload transport: what if Bagnold was right?

Christophe Ancey

There is a paradox in the relationship between bedload transport rates and flow variables: laboratory and field studies have reported on how bedload transport rates depend on flow variables through a power law, but none of the empirical laws fitted to the ...

2023

The concept of the mobilized domain: how it can explain and predict the forces exerted by a cohesive granular avalanche on an obstacle

Christophe Ancey, Betty Sovilla, Johan Alexandre Philippe Gaume, Michael Lukas Kyburz

The calculation of the impact pressure on obstacles in granular flows is a fundamental issue of practical relevance, e.g. for snow avalanches impacting obstacles. Previous research shows that the load on the obstacle builds up, due to the formation of forc ...

2022

An experimental investigation of turbulent free-surface flows over a steep permeable bed

Christophe Ancey

Steep streams involve shallow, supercritical turbulent flows over a permeable bed made up of coarse particles. They usually exhibit higher flow resistance and stronger mass and momentum exchanges between the stream and subsurface flow than low-gradient str ...

Cambridge University Press2022

Do Antidune Trains Undergo Morphological Changes When These Bedforms Migrate Upstream?

Christophe Ancey, Ivan Pascal

Upstream migrating antidunes develop in streams under supercritical flow conditions. These bedforms are often organised in trains (i.e. sequences of well-developed antidunes). In shallow flows over coarse sediments, the dynamics of a single antidune can be ...

Madrid2022

An experimental scaling law for particle-size segregation in dense granular flows

Christophe Ancey

Particles of differing sizes are notoriously prone to segregation in shear driven flows under the action of gravity. This has important implications in many industrial processes, where particle-size segregation can lead to flow problems and reduced product ...

Cambridge University Press2021

A conveyor belt experimental setup to study the internal dynamics of granular avalanches

Christophe Ancey, Tomás Alfredo Trewhela Palacios

This paper shows how a conveyor belt setup can be used to study the dynamics of stationary granular flows. To visualise the flow within the granular bulk and, in particular, determine its composition and the velocity field, we used the refractive index mat ...

SPRINGER2021

Large particle segregation in two-dimensional sheared granular flows

Christophe Ancey, Tomás Alfredo Trewhela Palacios

We studied the segregation of single large intruder particles in monodisperse granular materials. Experiments were carried out in a two-dimensional shear cell using different intruder and media diameters, whose quotient defined a size ratio R that ranged f ...

2021

The variability of antidune morphodynamics on steep slopes

Christophe Ancey, Ivan Pascal

Steep streams on rough beds are generally characterised by supercritical flow conditions under which antidunes can develop and migrate over time. In this paper, we present flume experiments that we conducted to investigate the variability of antidune geome ...

2021

Bedload transport: a walk between randomness and determinism. Part 1. The state of the art

Christophe Ancey

This paper outlines the various approaches used to calculate bedload transport. As bedload transport exhibits considerable spatial and temporalvariations, computing the bedload transport rates and morphological changes experienced by streambeds is difficul ...

Taylor & Francis Ltd2020

Bedload transport: a walk between randomness and determinism. Part 2. Challenges and prospects

Christophe Ancey

By the late nineteenth century, the scientific study of bedload transport had emerged as an offshoot of hydraulics and geomorphology. Since then, computing bedload transport rates has attracted considerable attention, but whereas other environmental scienc ...

Taylor & Francis Ltd2020

Scanning PIV of turbulent flows over and through rough porous beds using refractive index matching

Christophe Ancey, Gauthier Paul Daniel Marie Rousseau

This paper presents image velocimetry measurements on turbulent flows adjacent to a permeable bed made of randomly packed glass particles. For measuring flow velocities inside the bed, the refractive index of the glass particles was matched with that of th ...

SPRINGER2020