Frédéric Risso
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View article: Sedimentation of short-lived fluid-solid suspensions
Sedimentation of short-lived fluid-solid suspensions Open
In this study, we propose a particle sedimentation/aggradation law for homogeneous concentrated suspensions. This law, valid in the Stokes flow regime, can be used to describe the sedimentation process observed in short-lived rapid flows, …
View article: Spectral analysis of dispersed multiphase flows in the presence of fluid interfaces
Spectral analysis of dispersed multiphase flows in the presence of fluid interfaces Open
Spectral analysis of dispersed two-phase flows is highly desirable to reveal the interplay of the various flow scales, much larger or much smaller than the size of the dispersed bodies. This is a challenging task as the matching conditions…
View article: Turbulence induced by a swarm of rising bubbles from coarse-grained simulations
Turbulence induced by a swarm of rising bubbles from coarse-grained simulations Open
We performed numerical simulations of a homogeneous swarm of bubbles rising at large Reynolds number, $Re=760$ , with volume fractions ranging from 1 % to 10 %. We consider a simplified model in which the interfaces are not resolved, but w…
View article: Turbulence induced by a swarm of rising bubbles from coarse-grained simulations
Turbulence induced by a swarm of rising bubbles from coarse-grained simulations Open
We performed numerical simulations of a homogeneous swarm of bubbles rising at large Reynolds number, Re = 760 with volume fractions ranging from 1% to 10%. We consider a simplified model in which the interfaces are not resolved, but which…
View article: On the fluctuations generated by a dispersed phase: Slides of the plenary lecture given by Frédéric Risso
On the fluctuations generated by a dispersed phase: Slides of the plenary lecture given by Frédéric Risso Open
International audience
View article: Physical mechanisms for droplet size and effective viscosity asymmetries in turbulent emulsions
Physical mechanisms for droplet size and effective viscosity asymmetries in turbulent emulsions Open
By varying the oil volume fraction, the microscopic droplet size and the macroscopic rheology of emulsions are investigated in a Taylor–Couette turbulent shear flow. Although here oil and water in the emulsions have almost the same physica…
View article: Fall of a large sphere in a suspension of small fluidized particles
Fall of a large sphere in a suspension of small fluidized particles Open
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View article: A few upstream bifurcations drive the spatial distribution of red blood cells in model microfluidic networks
A few upstream bifurcations drive the spatial distribution of red blood cells in model microfluidic networks Open
We show how Red Blood Cell (RBC) transverse migration downstream the first bifurcation of the network has an outsized impact on the RBC distribution at large scale, depending on the network architecture, as illustrated here for a square ne…
View article: Numerical simulations of the agitation generated by coarse-grained bubbles moving at large Reynolds number
Numerical simulations of the agitation generated by coarse-grained bubbles moving at large Reynolds number Open
We present a numerical method for simulating the flow induced by bubbles rising at large Reynolds number. This method is useful to simulate configurations of large dimensions involving a great number of bubbles. The action that each bubble…
View article: Bridge expansion after coalescence of two droplets in air: Inertial regime
Bridge expansion after coalescence of two droplets in air: Inertial regime Open
When two liquid droplets approach at negligible velocity in air, their coalescence spontaneously occurs by jump-to-contact instability and a connecting bridge joining the two facing interfaces at the nanoscale is created. We report experim…
View article: Statistics of velocity fluctuations in a homogeneous liquid fluidized bed
Statistics of velocity fluctuations in a homogeneous liquid fluidized bed Open
International audience
View article: Physical modeling of the dam-break flow of sedimenting suspensions
Physical modeling of the dam-break flow of sedimenting suspensions Open
We develop a physical model of the dam-break flow of fine non-cohesive particles initially fluidized by a gas. By revisiting previous experiments, we show that the dynamics of such flows involves two uncoupled phenomena. On the one hand, the s…
View article: Long-range hydrodynamic forces in liquid FM-AFM
Long-range hydrodynamic forces in liquid FM-AFM Open
We study the effects of hydrodynamic forces in frequency-modulation AFM experiments (FM-AFM) in liquid. We first establish the theoretical equations needed to derive the interaction stiffness k int and the damping β int due to the hydrodyn…
View article: Determination of Interfacial Concentration of a Contaminated Droplet from Shape Oscillation Damping
Determination of Interfacial Concentration of a Contaminated Droplet from Shape Oscillation Damping Open
We present a method to measure the very small interfacial concentration of a contaminant that is irreversibly adsorbed on the interface of a bubble or droplet. It is an application of the linear theory of shape oscillation which relates th…
View article: Fluctuations in inertial dense homogeneous suspensions
Fluctuations in inertial dense homogeneous suspensions Open
International audience
View article: Coalescence of Water Drops at an Oil–Water Interface Loaded with Microparticles and Surfactants
Coalescence of Water Drops at an Oil–Water Interface Loaded with Microparticles and Surfactants Open
This work investigates the coalescence of water droplets settled on a water–oil interface in the presence of microparticles and surfactant. The successive stages of the coalescence process, including interstitial film formation, drainage, …
View article: Sedimentation of gas-fluidized particles with random shape and size
Sedimentation of gas-fluidized particles with random shape and size Open
Observations of the settling velocity of suspensions of irregular particles are found to depend on (i) the difference of density between the particles and the suspension and (ii) a viscosity which depends on the ratio of the concentration …
View article: Interfacial Dynamics and Rheology of a Crude-Oil Droplet Oscillating in Water at a High Frequency
Interfacial Dynamics and Rheology of a Crude-Oil Droplet Oscillating in Water at a High Frequency Open
We report investigations of a pendant diluted crude-oil droplet in water that is forced to oscillate at a frequency ω. The droplet interface contains a significant amount of surface-active agents and displays a marked viscoelastic rheology…
View article: Numerical simulations of a rising drop with shape oscillations in the presence of surfactants
Numerical simulations of a rising drop with shape oscillations in the presence of surfactants Open
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View article: Jump-to-contact instability: The nanoscale mechanism of droplet coalescence in air
Jump-to-contact instability: The nanoscale mechanism of droplet coalescence in air Open
We study experimentally by means of atomic force microscopy (AFM) the jump-to-contact instability between two droplets in air, with radii ranging between 0.7 and 74 μm. This instability which occurs at the nanoscale is responsible for drop…
View article: A model for drop and bubble breakup frequency based on turbulence spectra
A model for drop and bubble breakup frequency based on turbulence spectra Open
In this article, a new Eulerian model for breakup frequency of drops induced by inertial stress in homogeneous isotropic turbulence is developed for moderately viscous fluids, accounting for the finite response time of drops to deform. The…
View article: Mixing mechanism in a two-dimensional bubble column
Mixing mechanism in a two-dimensional bubble column Open
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View article: Rheological behaviour and runout of short-lived, fast-moving flows of hot dense suspensions
Rheological behaviour and runout of short-lived, fast-moving flows of hot dense suspensions Open
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View article: Agitation, Mixing, and Transfers Induced by Bubbles
Agitation, Mixing, and Transfers Induced by Bubbles Open
Bubbly flows involve bubbles randomly distributed within a liquid. At large Reynolds number, they experience an agitation that can combine shear-induced turbulence (SIT), large-scale buoyancy-driven flows, and bubble-induced agitation (BIA…