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  1. Article: An edge-based interface-tracking method for multiphase flows.

    Chirco, Leonardo / Zaleski, Stéphane

    International journal for numerical methods in fluids

    2022  Volume 95, Issue 3, Page(s) 491–497

    Abstract: We propose a novel class of edge-based interface-tracking (EBIT) methods in the field of multiphase flows for advecting the interface. The position of the interface is tracked by marker points located on the edges of the underlying grid, making the ... ...

    Abstract We propose a novel class of edge-based interface-tracking (EBIT) methods in the field of multiphase flows for advecting the interface. The position of the interface is tracked by marker points located on the edges of the underlying grid, making the method flexible with respect to the choice of spatial discretization and suitable for parallel computation. In this article we present a simple EBIT method based on two-dimensional Cartesian grids and on a linear interface representation.
    Language English
    Publishing date 2022-10-19
    Publishing country England
    Document type Journal Article
    ZDB-ID 1491176-0
    ISSN 1097-0363 ; 0271-2091
    ISSN (online) 1097-0363
    ISSN 0271-2091
    DOI 10.1002/fld.5144
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: General wetting energy boundary condition in a fully explicit nonideal fluids solver.

    Zhao, Chunheng / Limare, Alexandre / Zaleski, Stephane

    Physical review. E

    2023  Volume 108, Issue 5-2, Page(s) 55307

    Abstract: We present an explicit finite-difference method to simulate the nonideal multiphase fluid flow. The local density and momentum transport are modeled by the Navier-Stokes equations and the pressure is computed by the van der Waals equation of the state. ... ...

    Abstract We present an explicit finite-difference method to simulate the nonideal multiphase fluid flow. The local density and momentum transport are modeled by the Navier-Stokes equations and the pressure is computed by the van der Waals equation of the state. The static droplet and the dynamics of liquid-vapor separation simulations are performed as validations of this numerical scheme. In particular, to maintain the thermodynamic consistency, we propose a general wetting energy boundary condition at the contact line between fluids and the solid boundary. We conduct a series of comparisons between the current boundary condition and the constant contact angle boundary condition as well as the stress-balanced boundary condition. This boundary condition alleviates the instability induced by the constant contact angle boundary condition at θ≈0 and θ≈π. Using this boundary condition, the equilibrium contact angle is correctly recovered and the contact line dynamics are consistent with the simulation by applying a stress-balanced boundary condition. Nevertheless, unlike the stress-balanced boundary condition for which we need to further introduce the interface thickness parameter, the current boundary condition implicitly incorporates the interface thickness information into the wetting energy.
    Language English
    Publishing date 2023-12-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2844562-4
    ISSN 2470-0053 ; 2470-0045
    ISSN (online) 2470-0053
    ISSN 2470-0045
    DOI 10.1103/PhysRevE.108.055307
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Book ; Online: Statistics of drops generated from ensembles of randomly corrugated ligaments

    Pal, Sagar / Crialesi-Esposito, Marco / Fuster, Daniel / Zaleski, Stéphane

    2021  

    Abstract: The size of drops generated by the capillary-driven disintegration of liquid ligaments plays a fundamental role in several important natural phenomena, ranging from heat and mass transfer at the ocean-atmosphere interface to pathogen transmission. The ... ...

    Abstract The size of drops generated by the capillary-driven disintegration of liquid ligaments plays a fundamental role in several important natural phenomena, ranging from heat and mass transfer at the ocean-atmosphere interface to pathogen transmission. The inherent non-linearity of the equations governing the ligament destabilization lead to significant differences in the resulting drop sizes, owing to small fluctuations in the myriad initial conditions. Previous experiments and simulations reveal a variety of drop size distributions, corresponding to competing underlying physical interpretations. Here, we perform numerical simulations of individual ligaments, the deterministic breakup of which is triggered by random initial surface corrugations. Stochasticity is incorporated by simulating a large ensemble of such ligaments, each realization corresponding to a random but unique initial configuration. The resulting probability distributions reveal three stable drop sizes, generated via a sequence of two distinct stages of breakup. The probability of the large sizes is described by volume-weighted Poisson and Log-Normal distributions for the first and second breakup stages, respectively. The study demonstrates a precisely controllable and reproducible framework, which can be employed to investigate the mechanisms responsible for the polydispersity in drop sizes found in complex fluid fragmentation scenarios.
    Keywords Physics - Fluid Dynamics ; Physics - Computational Physics ; Physics - Data Analysis ; Statistics and Probability
    Subject code 612
    Publishing date 2021-06-30
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Book ; Online: Bags mediated film atomization in a cough machine

    Kant, Pallav / Pairetti, César / Saade, Youssef / Popinet, Stéphane / Zaleski, Stéphane / Lohse, Detlef

    2022  

    Abstract: We combine experiments and numerical computations to examine underlying fluid mechanical processes associated with bioaerosol generation during violent respiratory manoeuvres, such as coughing or sneezing. Analogous experiments performed in a cough ... ...

    Abstract We combine experiments and numerical computations to examine underlying fluid mechanical processes associated with bioaerosol generation during violent respiratory manoeuvres, such as coughing or sneezing. Analogous experiments performed in a cough machine -- consisting of a strong shearing airflow over a thin liquid film, allow us to illustrate the changes in film topology as it disintegrates into small droplets. We identify that aerosol generation during the shearing of the liquid film is mediated by the formation of inflated bag-like structures. The breakup of these bags is triggered by the appearance of retracting holes that puncture the bag surface. Consequently, the cascade from inflated bags to droplets is primarily controlled by the dynamics and stability of liquid rims bounding these retracting holes. We also reveal the stabilizing role of fluid viscosity that eventually leads to the generation of smaller droplets.
    Keywords Physics - Fluid Dynamics
    Subject code 660
    Publishing date 2022-02-28
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Host-to-Host Airborne Transmission As a Multiphase Flow Problem For Science-Based Social Distance Guidelines

    Balachandar, S / Zaleski, Stephane / Soldati, Alfredo / Ahmadi, Goodarz / Bourouiba, Lydia

    medRxiv

    Abstract: COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the ... ...

    Abstract COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the context of human to human transmission. It is also increasingly clear that airborne transmission is an important contributor to rapid spreading of the disease. In this paper, we discuss the processes of droplet generation by exhalation, their potential transformation into airborne particles by evaporation, transport over long distances by the exhaled puff and by ambient air turbulence, and final inhalation by the receiving host as interconnected multiphase flow processes. A simple model for the time evolution of droplet/aerosol concentration is presented based on a theoretical analysis of the relevant physical processes. The modeling framework along with detailed experiments and simulations can be used to study a wide variety of scenarios involving breathing, talking, coughing and sneezing and in a number of environmental conditions, as humid or dry atmosphere, confined or open environment. Although a number of questions remain open on the physics of evaporation and coupling with persistence of the virus, it is clear that with a more reliable understanding of the underlying flow physics of virus transmission one can set the foundation for an improved methodology in designing case-specific social distancing and infection control guidelines.
    Keywords covid19
    Language English
    Publishing date 2020-09-01
    Publisher Cold Spring Harbor Laboratory Press
    Document type Article ; Online
    DOI 10.1101/2020.08.28.20183814
    Database COVID19

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  6. Book ; Online: Steady moving contact line of water over a no-slip substrate

    Lācis, Uǧis / Johansson, Petter / Fullana, Tomas / Hess, Berk / Amberg, Gustav / Bagheri, Shervin / Zaleski, Stephané

    2020  

    Abstract: The movement of the triple contact line plays a crucial role in many applications such as ink-jet printing, liquid coating and drainage (imbibition) in porous media. To design accurate computational tools for these applications, predictive models of the ... ...

    Abstract The movement of the triple contact line plays a crucial role in many applications such as ink-jet printing, liquid coating and drainage (imbibition) in porous media. To design accurate computational tools for these applications, predictive models of the moving contact line are needed. However, the basic mechanisms responsible for movement of the triple contact line are not well understood but still debated. We investigate the movement of the contact line between water, vapour and a silica-like solid surface under steady conditions in low capillary number regime. We use molecular dynamics (MD) with an atomistic water model to simulate a nanoscopic drop between two moving plates. We include hydrogen bonding between the water molecules and the solid substrate, which leads to a sub-molecular slip length. We benchmark two continuum methods, the Cahn-Hilliard phase-field (PF) model and a volume-of-fluid (VOF) model, against MD results. We show that both continuum models can reproduce the statistical measures obtained from MD reasonably well, with a trade-off in accuracy. We demonstrate the importance of the phase field mobility parameter and the local slip length in accurately modelling the moving contact line.

    Comment: 26 pages, 13 figures, 4 tables, post-review version, under consideration for publication in "European Physical Journal Special Topics"
    Keywords Physics - Fluid Dynamics
    Subject code 621
    Publishing date 2020-03-27
    Publishing country us
    Document type Book ; Online
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  7. Article ; Online: Self-similar wave produced by local perturbation of the Kelvin-Helmholtz shear-layer instability.

    Hoepffner, Jérôme / Blumenthal, Ralf / Zaleski, Stéphane

    Physical review letters

    2011  Volume 106, Issue 10, Page(s) 104502

    Abstract: We show that the Kelvin-Helmholtz instability excited by a localized perturbation yields a self-similar wave. The instability of the mixing layer was first conceived by Helmholtz as the inevitable growth of any localized irregularity into a spiral, but ... ...

    Abstract We show that the Kelvin-Helmholtz instability excited by a localized perturbation yields a self-similar wave. The instability of the mixing layer was first conceived by Helmholtz as the inevitable growth of any localized irregularity into a spiral, but the search and uncovering of the resulting self-similar evolution was hindered by the technical success of Kelvin's wavelike perturbation theory. The identification of a self-similar solution is useful since its specific structure is witness of a subtle nonlinear equilibrium among the forces involved. By simulating numerically the Navier-Stokes equations, we analyze the properties of the wave: growth rate, propagation speed and the dependency of its shape upon the density ratio of the two phases of the mixing layer.
    Language English
    Publishing date 2011-03-11
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.106.104502
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  8. Book: Direct numerical simulations of gas-liquid multiphase flows

    Tryggvason, Grétar / Scardovelli, Ruben / Zaleski, Stéphane

    2011  

    Title variant DNS
    Author's details Grétar Tryggvason; Ruben Scardovelli; Stéphane Zaleski
    Keywords Gas-liquid interfaces ; Multiphase flow/Mathematical models
    Language English
    Size X, 324 S., Ill., graph. Darst.
    Publisher Cambridge Univ. Press
    Publishing place Cambridge u.a.
    Document type Book
    Note Includes bibliographical references (p. 295 - 321) and index
    ISBN 9780521782401 ; 0521782406
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  9. Book: Direct numerical simulations of gas-liquid multiphase flows

    Tryggvason, Grétar / Scardovelli, Ruben / Zaleski, Stéphane

    2011  

    Title variant DNS
    Author's details Grétar Tryggvason; Ruben Scardovelli; Stéphane Zaleski
    Keywords Gas-liquid interfaces ; Multiphase flow/Mathematical models
    Language English
    Size X, 324 S., Ill., graph. Darst.
    Publisher Cambridge Univ. Press
    Publishing place Cambridge u.a.
    Document type Book
    Note Includes bibliographical references (p. 295 - 321) and index
    ISBN 9780521782401 ; 0521782406
    Database Former special subject collection: coastal and deep sea fishing

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  10. Article ; Online: Histopathologic and Ultrastructural Features of Gold Thread Implanted in the Skin for Facial Rejuvenation.

    Moulonguet, Isabelle / Arnaud, Eric / Plantier, Françoise / da Costa, Patrick / Zaleski, Stéphane

    The American Journal of dermatopathology

    2015  Volume 37, Issue 10, Page(s) 773–777

    Abstract: The authors report the histopathologic and ultrastructural features of gold threads, which were implanted in the cheek subcutis of a 77-year-old woman 10 years ago. These particles did not give rise to any adverse reactions and were fortuitously ... ...

    Abstract The authors report the histopathologic and ultrastructural features of gold threads, which were implanted in the cheek subcutis of a 77-year-old woman 10 years ago. These particles did not give rise to any adverse reactions and were fortuitously discovered by the surgeon during a facelift. Histopathology showed a nonpolarizing exogenous material consisting of black oval structures surrounded by a capsule of fibrosis and by a discrete inflammatory reaction with a few giant cells. In some cases, only a long fibrous tract surrounded by a moderate mononucleate infiltrate was observed. The wires were characterized with scanning electron microscopy, and X-ray microanalysis revealed a specific peak at 2.2 keV representative of gold that was absent in the control skin sample. As this value is specific for gold, it confirms the presence of the metal in the patient's skin. The histopathologic appearance of gold threads is particularly distinctive and easily recognizable by dermatopathologists.
    MeSH term(s) Aged ; Biopsy ; Cosmetic Techniques ; Electron Probe Microanalysis ; Female ; Gold/analysis ; Gold/therapeutic use ; Humans ; Microscopy, Electron, Scanning ; Rejuvenation ; Skin Aging ; Treatment Outcome
    Chemical Substances Gold (7440-57-5)
    Language English
    Publishing date 2015-10
    Publishing country United States
    Document type Case Reports ; Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 448469-1
    ISSN 1533-0311 ; 0193-1091
    ISSN (online) 1533-0311
    ISSN 0193-1091
    DOI 10.1097/DAD.0000000000000220
    Database MEDical Literature Analysis and Retrieval System OnLINE

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