Dominique Legendre

Dominique Legendre
Institute of Fluid Mechanics of Toulouse, French National Centre for Scientific Research | IMFT · INTERFACE

Professor

About

201
Publications
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5,319
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Publications

Publications (201)
Preprint
Full-text available
The study of gas bubble dynamics in liquids is justified by the numerous applications and natural phenomena where this two-phase flow is encountered. Gas bubbles move as forces are applied to them; their dynamics are full of nuances that need to be addressed carefully. Since the mass of gas bubbles is practically negligible, in comparison to that o...
Article
Full-text available
We study numerically the flow around a spherical droplet set fixed in a linear shear flow with moderate shear rates ( $Sr\leq 0.5$ , $Sr$ being the ratio between the velocity difference across the drop and the relative velocity) over a wide range of external Reynolds numbers ( $0.1<{{Re}}\leq 250$ , ${{Re}}$ based on the slip velocity and the visco...
Article
Chemical reactions can have a significant impact on the overall rate of mass transfer in fluid-fluid applications (such as gas absorption in a liquid or liquid-liquid extraction). However, as for non reacting systems, the rate at which a solute is exchanged between the two fluids is difficult to predict accurately. Yet from a theoretical point of v...
Article
Rotating drums play important roles in numerous industrial applications, such as mineral processing. This work is focused on the numerical study of the interface evolution in liquid-liquid and liquid-gas phases rotating drum. A new coupling strategy between Volume of Fluid (VoF) and Immersed Boundary Method (IBM) approaches is developed. Relevant d...
Article
Airtanker firefighting is the most spectacular tool used to fight wildland fires. However, it employs a rudimentary large-scale spraying technology operating at a high speed and a long distance from the target. This review gives an overview of the fluid dynamics processes that govern this practice, which are characterized by rich and varied physica...
Article
Full-text available
Background Airtankers are able to drop volumes of liquid (suppressant or fire retardant) varying from less than 1 m³ to several tens of cubic metres directly on a fire or with the objective to form barriers of retardant to stop or reduce fire propagation. Aims The objective of this work is to demonstrate that Computational Fluid Dynamics can be us...
Article
This paper is devoted to a specific motion observed for glycerin droplets sliding on a horizontal hydrophobic substrate under the influence of a shear flow. In this regime, the droplet elongates in the flow direction, adopting a rivulet shape. Waves develop on the droplet sheared surface, resulting in a wavy contracting and stretching motion mechan...
Article
Full-text available
During the solidification of a sessile drop, the effect of heat exchange from the gaseous environmental medium is generally ignored. However, by combining experimental observations, direct numerical simulations, and a theoretical model, we have demonstrated that the environmental medium, particularly one with high thermal conductivity such as a liq...
Article
The total force experienced by a droplet embedded in a uniform oscillating flow can be divided into four contributions: steady drag force, inertial or pressure gradient force, added-mass force, and Basset-Boussinesq history force. The effect of the history force is often neglected, due to numerical difficulties for its time integration, but also be...
Article
Bubbles appear when a carbonated drink is poured in a glass. Very stable bubble chains are clearly observed in champagne, showing an almost straight line from microscopic nucleation sites from which they are continuously formed. In some other drinks such as soda, such chains are not straight (not stable). Considering pair interactions for spherical...
Article
Effects of surfactants on lift coefficients, C<sub>L</sub> , of single ellipsoidal bubbles rising through linear shear flows were investigated. Two types of surface-active agents, Triton X-100 and 1-octanol, were used. The liquid properties except for the surface tension were identical to those in a clean system of logM = -5.5, where M is the Morto...
Article
In this study we report an experimental investigation of droplet sliding under the influence of a laminar or turbulent airflow for water and glycerin droplets. The onset of sliding is described thanks to a critical Weber number, based on the mean airflow velocity impacting the droplet, depending upon the contact angle hysteresis and a drag coeffici...
Preprint
Full-text available
Bubbles appear when a carbonated drink is poured in a glass. Very stable bubble chains are clearly observed in champagne, showing an almost straight line from microscopic nucleation sites from which they are continuously formed. In some other drinks such as soda, such chains are not straight (not stable). Considering pair interactions for spherical...
Article
Water droplet freezing is a common phenomenon in our daily life. In both natural scenarios and industrial production, different surface inclinations bring distinctive deformation and freezing dynamics to frozen droplets. We explore the freezing of pendent and sessile droplets at different Bond number regimes. The effect of gravity on the droplet fr...
Article
We report an experimental investigation of the structure of the wake and oscillation dynamics of gas-liquid compound drops rising at high Reynolds numbers. Particle image velocimetry (PIV) and high-speed shadowgraph techniques were used to determine the conditions required for the motion to become unstable and to gain insight into the origin of the...
Article
The motion of a free rising skirt bubble is studied using direct numerical simulation covering the range of Eötvös (Bond) and Morton numbers where they can be observed. We investigate the skirt bubble motion (terminal velocity and drag), the flow field structure (inside the skirt film, around the bubble, and inside the gas film that forms the skirt...
Preprint
Full-text available
Water droplet freezing is a common phenomenon in our daily life. In both natural scenarios and industrial production, different surface inclinations bring distinctive deformation and freezing dynamics to frozen droplets. We explore the freezing of pendent and sessile droplets at different Bond number regimes. The effect of gravity on the droplet fr...
Article
Interfacial tension gradients drive flow along fluid-fluid interfaces in a process known as the Marangoni effect. Such gradients can be caused by surfactants, as extensively studied in the literature. Less is known of its nanoscale behavior, where molecular interfaces exhibit specific properties such as interfacial viscosity. In this work we study...
Article
Full-text available
The performance of multiphase flow processes is often determined by the distribution of phases inside the equipment. However, controllers in the field are typically implemented based on flow variables, which are simpler to measure, but indirectly connected to performance (e.g., pressure). Tomography has been used in the study of the distribution of...
Article
A hybrid IBM-LES method is presented with the objective to simulate high-Reynolds number pipe flows on coarse Cartesian meshes. The IBM method is first used to simulate a laminar pipe flow and results have shown to converge with second order accuracy to the exact solution. A new forcing scheme inside the IBM wall thickness improves significantly nu...
Chapter
O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...
Article
The canonical problem of the icing of a water drop lying on a cold substrate is revisited to take into account the effects of atmospheric conditions on the icing front kinetics and on the tip formation. Here, we demonstrate both experimentally and theoretically that the air humidity induces liquid-vapor phase change at the icing droplet interface a...
Article
Gas-liquid mass transfer from spherical bubbles is studied by DNS for various Reynolds numbers (1⩽Re⩽300), Schmidt numbers (1⩽Sc⩽500) and bubble surface contamination degrees (0°⩽θcap⩽180°). Computed separation angles, drag coefficients and average Sherwood numbers for both clean and fully contaminated bubbles are favorably compared to literature....
Preprint
Full-text available
Interfacial tension gradients drive flow along liquid-liquid interfaces in a process known as the Marangoni effect. Such gradients can be caused by surfactants, which has been extensively studied in the literature. Less is known of its nanoscale properties, where molecular interfaces display properties separate from bulk liquid matter such as inter...
Article
Full-text available
Multiphase flows management is a major challenge in many space applications given the different gravity levels involved. While many of the numerical investigations of liquid-gas phenomena deal with the radial bubble behavior and thus the heat exchange, only a few studies have been conducted on the translational motion of bubbles. We present a numer...
Article
Full-text available
Faraday instability is a classic problem that occurs due to the relative displacement of the interface that separates two immiscible fluids placed in a closed container under oscillating acceleration parallel to gravity. The interface deformation and the induced flow patterns of this two-phase flow are very complex and numerical simulations could a...
Article
The behaviour of compound drops rising at high Reynolds numbers, roughly 60 to 700, was studied experimentally for a wide range of diameter ratios and three different combinations of the internal and external fluids. Two rising regimes were identified, namely a rectilinear and an oscillatory trajectory. The governing effects in each motion regime w...
Article
Scaling of the lift reversal for a deformed bubble in the surface tension-inertial force dominant regime was discussed. Lift data of bubbles in water recently reported in literature were used. The negative lift component was well correlated in terms of the drag coefficient, which, in turn, implies that the vorticity produced at the bubble surface p...
Article
The spreading of a n-decane liquid film induced by the impingement of a spray generated by a high-pressure injector is studied experimentally. The experimental setup uses the Refractive Index Matching (RIM) method to observe the development and propagation of the wall film. The influence of injection time, injection pressure, temperature, and injec...
Article
This work is devoted to the development of a new hybrid VoF-IBM method for the simulation of freezing liquid films and freezing drops. The VoF and IBM methods are coupled with the temperature equation to be able to solve the icing front, the dilatation induced by the density difference between the liquid and the ice as well as the drop deformation...
Article
We investigate the dynamics of films of partially wetting liquids falling down a vertical plane in the presence of air. We focus on the little-studied case where the film is not in contact with lateral walls and thus has two side contact lines. By way of 3D direct numerical simulations, we study the fingering instability and the distribution of riv...
Article
Hydrodynamics and conjugate mass transfer from a spherical droplet at low to moderate Reynolds number have been investigated by direct numerical simulation. The study particularly focuses on the coupling between the internal and external flows, and their respective effects on the resulting mass transfer of a solute under 2D axi-symmetric configurat...
Article
The interaction between an AFM probe and a thin film of water deposited over a flat substrate is studied using Molecular Dynamics (MD). The effects of the film thickness and of the probe radius on both the deformation height of the liquid interface, and the distance of the jump to contact at which the liquid comes in direct contact with the probe,...
Article
Full-text available
Mezcal is a traditional Mexican spirit, obtained from the distillation of fermented agave juices. Its preparation has been conducted for centuries in an artisanal manner. The method used to determine the correct alcohol content is of particular interest: a stream of the liquor is poured into a small vessel to induce surface bubbles. These bubbles,...
Article
Full-text available
This text structures the application of Wire-Mesh sensors and Electrical Resistance Tomography in the control of an Inline Swirl Separator. It introduces a mechanistic model of the two-phase flow inside the device, which is linearized around an ideal perfect operation, and implemented in a Model Predictive Controller. The whole text is structured a...
Article
Despite the prevalence of surface bubbles in many natural phenomena and engineering applications, the effect of surfactants on their surface residence time is not clear. Numerous experimental studies and theoretical models exist but a clear understanding of the film drainage phenomena is still lacking. In particular, theoretical works predicting th...
Article
Full-text available
Inline fluid separation is a concept, which is used in the oil and gas industry. Inline fluid separators typically have a static design and hence changing inlet conditions lead to less efficient phase separation. For introducing flow control into such a device, additional information is needed about the relationship of upstream and downstream condi...
Data
Three dimensonal Direct Numerical Simulation of a bubble rising in a stagnant liquid. The colors represent the concentration of surfactant on the bubble surface. The level set method is used to transport the interface.
Article
The lift force acting on an ellipsoidal bubble is known to change its sign, depending on the bubble aspect ratio. The lift reversal has often been modeled in terms of the Eötvös number defined by using the bubble major axis to account for the deformation effect on the negative lift component. This paper presents a physically reliable scaling accoun...
Article
Full-text available
Today's mechanical fluid separators in industry are mostly operated without any control to maintain efficient separation for varying inlet conditions. Controlling inline fluid separators, on the other hand, is challenging since the process is very fast and measurements in the multiphase stream are difficult as conventional sensors typically fail he...
Article
We propose a model for the acceleration of micro-bubbles (smaller than the dissipative scale of the flow) subjected to the drag and fluid inertia forces in a homogeneous and isotropic turbulent flow. This model, that depends on the Stokes number, Reynolds number and the density ratio, reproduces the evolution of the acceleration variance as well as...
Article
We consider the Basset-Boussinesq (history) force experienced by a spherical drop. We seek to determine the kernel of the Basset-Boussinesq force when internal circulation of the fluid occurs. We first characterize the slip at a fluid-sphere interface. Under both steady and unsteady conditions, the corresponding slip length is remarkably uniform al...
Article
We consider the implementation of a friction contact angle model in a Navier-Stokes VoF-CSF solver for the simulation of moving contact lines at the nano-scale. A liquid-liquid interface confined in a Couette flow generated by two solid walls moving at the same velocity in opposite directions is considered to discuss the relevance of the friction m...
Article
The motion of a bubble sliding over an inclined wall from moderate to high bubble Reynolds number is studied experimentally for a wide range of liquid properties and bubbles sizes, considering wall inclination angles from nearly horizontal to nearly vertical. All experiments are restricted to sliding behavior, below the transition to steady bouncin...
Article
Full-text available
In the in-line bright-field image of a pancake-like bubble, a ring-shaped zone of maximum intensity is visible, called the glare ring. It is due to multiple interactions of light with the bubble interface. In this study, we develop a method to measure the thickness of the lubrication film around a pancake-like bubble translating inside a microchann...
Preprint
Full-text available
Mezcal is a traditional alcoholic Mexican spirit distilled from fermented agave juices that has been produced for centuries. Its preparation and testing involves an artisanal method to determine the alcohol content based on pouring a stream of the liquid into a small vessel: if the alcohol content is correct, stable bubbles, known as pearls, form a...
Article
We consider single bubble mass transfer of an non-condensible gas into a volatile liquid phase in industrial conditions, as observed for example in hydrocarbons liquid phase oxidation processes. Instantaneous bubble size, shape and velocity are measured using image processing with a particle tracking method. The mass transfer rate nitrogen into hot...
Article
Full-text available
In this work an image processing technique is proposed to improve the measurement of ellipsoidal objects, such as bubbles in dispersed flows. This novel algorithm devoted to the measurement of bubble size, shape and trajectory is applied to binarised images from a gray-level gradient filter. To improve data statistics, an ellipse fitting method is...
Article
In this study, we investigate, using direct numerical simulation, the motion of a small bubble in a horizontal microchannel filled with a liquid containing surfactants. In particular, we study the combined effect of surfactants and bubble deformability on the bubble shape, the bubble-liquid relative velocity, the velocity field in the liquid, the l...
Article
This work is devoted to the development of a penalization method for the simulation of bubbly flows. Spherical bubbles are considered as moving penalized obstacles interacting with the fluid and a numerical method for ensuring the shear free condition at the liquid–bubble interface is proposed. Three test-cases (curved channel, inclined channel and...
Article
The 2D front tracking method is enhanced to control the development of spurious velocities for non-uniform distributions of markers. The hybrid formulation of Shin et al. (2005) [7] is considered. A new tangent calculation is proposed for the calculation of the tension force at markers. A new reconstruction method is also proposed to manage non-uni...
Article
Full-text available
According to Kirkinis and Davis [J. Fluid Mech. 746, R3 (2014)], the motion of a contact line can produce a sequence of moving eddies, commonly known as Moffatt vortices. In this work, we extend the formulation given in Kirkinis and Davis for the moving contact line between two viscous fluids and a nonzero static contact angle, and we consider the...
Conference Paper
Full-text available
The evaluation of the lifetime of bubbles at the surface of a liquid has been used as an empirical technique in the traditional production of Mezcal (an artisanal distilled agave spirit from Mexico) to determine the desired concentration of alcohol. We investigated this problem in light of computational fluid dynamics (CFD) using a level-set method...
Conference Paper
Full-text available
This paper presents a new model developed to predict the area of wall films that may develop in gasoline direct injection engines (GDI). In a always more restrictive legislation on gas emissions the injection process in internal combustion (IC) engines has been highlighted as a domain of great concern in order to satisfy these requirements. Many sp...
Article
We experiment the interaction between a liquid puddle and a spherical probe by Atomic Force Microscopy (AFM) for a probe radius R ranging from 10 nm to 30 μm. We have developed a new experimental setup by coupling an AFM with a high-speed camera and an inverted optical microscope. Interaction force-distance curves (in contact mode) and frequency sh...
Article
We study the static and dynamic interaction between a horizontal cylindrical nano-probe and a thin liquid film. The effects of the physical and geometrical parameters, with a special focus on the film thickness, the probe speed, and the distance between the probe and the free surface are analyzed. Deformation profiles have been computed numerically...
Preprint
Full-text available
We study the static and dynamic interaction between a horizontal cylindrical nano-probe and a thin liquid film. The effects of the physical and geometrical parameters, with a special focus on the film thickness, the probe speed, and the distance between the probe and the free surface are analyzed. Deformation profiles have been computed numerically...
Poster
Full-text available
While coalescence behaviour is highly relevant for many industrial processes, understanding and simulation of coalescence mechanisms remains a big challenge, which makes the design and modelling of gravity settlers a difficult task. Coalescence is generally divided into three consecutive steps: drop-drop or drop-free surface approach, film drainage...
Article
Full-text available
In this study we analyze the interaction of a single rising bubble with an inclined wall. We conduct experiments considering different liquids and bubble sizes, to cover a wide range of Reynolds and Weber numbers, with wall angles from nearly horizontal to nearly vertical. For all cases, the bubble initially collides with the wall; after the initia...
Article
The self-propulsion of a spherical squirmer – a model swimming organism that achieves locomotion via steady tangential movement of its surface – is quantified across the transition from viscously to inertially dominated flow. Specifically, the flow around a squirmer is computed for Reynolds numbers ( $Re$ ) between 0.01 and 1000 by numerical solu...
Article
The aim of this study is to discus different numerically models for the simulation of moving contact lines in the context of a Volume of Fluid–Continuum Surface Force (VoF–CSF) method. We focus on the particular situation of spreading drops. We first present the numerical methods used for the simulation of moving contact line i.e. static contact an...
Article
This paper deals with the comparison of Eulerian methods to take into account the capillary contribution in the vicinity of a fluid–fluid interface. Eulerian methods are well-known to produce additional vorticity close to the interface that leads to non-physical spurious currents. Numerical equilibrium between pressure gradient and capillary force...
Article
Experimental measurements of hydrodynamic and interfacial area parameters are carried out over two rectangular pilot scale valve tray columns. The effect of tray path length on extrapolation between the two columns is studied and phenomenological correlations for hydrodynamic and interfacial area are proposed. Correlations are compared both to lite...
Article
Full-text available
Copyright (2015) AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in (Esquivelzeta-Rabell, F. M. et al. Physics of Fluids (1994-present), 27(1), 014108.) and may be found at (http://dx.doi.org/10.1063/1.4906153). Laminar Co...
Article
Full-text available
The dynamic interaction between a local probe and a viscous liquid film, which provokes the deformation of the latter, has been studied. The pressure difference across the air-liquid interface is calculated with a modified Young-Laplace equation, which takes into account the effects of gravity, surface tension, the liquid film-substrate and the pro...
Article
Full-text available
We investigate bubble dispersion in turbulent Taylor-Couette flow. The aim of this study is to describe the main mechanisms yielding preferential bubble accumulation in near-wall structures of the flow. We first proceed to direct numerical simulation of Taylor-Couette flows for three different geometrical configurations (three radius ratios η = R 1...
Article
Full-text available
The present work focuses on the collective effect on both bubble dynamics and mass transfer in a dense homogeneous bubble swarm for gas volume fractions alpha up to 30 %. The experimental investigation is carried out with air bubbles rising in a square column filled with water. Bubble size and shape are determined by means of a high-speed camera eq...
Chapter
Full-text available
The non-linear oscillations of a viscous drop is a fundamental problem in diverse areas of science and technology. In this paper, we analyze the large-amplitude oscillations of an initially elongated liquid drop in two-dimensions by solving the free boundary problem comprised of the Navier-Stokes equations, using two different numerical codes. The...
Chapter
We consider numerical simulations of drops sliding on an inclined solid surface. The simulations are performed using our in house research code JADIM based on the Volume of Fluid formulation of the mass and momentum equations. Special algorithms have been developed for the simulation of the hysteresis of the contact line as well as for the descript...