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##### Publications (10 of 114) Show all publications
Shen, B., Liu, J., Shiomi, J., Amberg, G., Do-Quang, M., Kohno, M., . . . Takata, Y. (2018). Effect of dissolved gas on bubble growth on a biphilic surface: A diffuse-interface simulation approach. International Journal of Heat and Mass Transfer, 126, 816-829
Open this publication in new window or tab >>Effect of dissolved gas on bubble growth on a biphilic surface: A diffuse-interface simulation approach
2018 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 126, p. 816-829Article in journal (Refereed) Published
##### Abstract [en]

In this paper, we numerically study pool boiling of a binary (water and nitrogen) mixture on a surface endowed with a combination of hydrophobicity and hydrophilicity (i.e., the so called biphilic surface). Here we adopt a numerical approach based on the phase field theory, where the vapor-liquid interface is assumed to be of a finite thickness (hence diffusive in nature) and requires no explicit tracking schemes. The theoretical modeling of two-phase heat and mass transfer in water diluted with nitrogen demonstrates the signiant impact of impurities on bubble dynamics. The simulations show that locally high concentrations of nitrogen gas within the vapor bubble is essential to weakening the condensation effect, which results in sustained bubble growth and ultimately (partial) departure from the surface under the artificially enlarged gravity. Simply increasing the solubility of nitrogen in water, however, turns out to be counterproductive because possible re-dissolution of the aggregated nitrogen by the bulk water could deprive the bubble of vital gas contents, leading instead to continuous bubble shrinkage and collapse. Additionally, it is found that with the significant accumulation of nitrogen, the bubble interface is increasingly dominated by a strong interfacial thermocapillary flow due to the Marangoni effect.

##### Place, publisher, year, edition, pages
Pergamon Press, 2018
##### Keywords
Boiling, Bubble pinch-off, Binary mixture, Surface wettability, Diffuse-interface method
##### National Category
Water Engineering
##### Identifiers
urn:nbn:se:kth:diva-234556 (URN)10.1016/j.ijheatmasstransfer.2018.06.043 (DOI)000442972700069 ()2-s2.0-85048525356 (Scopus ID)
##### Note

QC 20180919

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-09-19Bibliographically approved
Nita, S., Do-Quang, M., Wang, J., Chen, Y.-C., Suzuki, Y., Amberg, G. & Shiomi, J. (2017). Electrostatic cloaking of surface structure for dynamic wetting. SCIENCE ADVANCES, 3(2), Article ID e1602202.
Open this publication in new window or tab >>Electrostatic cloaking of surface structure for dynamic wetting
2017 (English)In: SCIENCE ADVANCES, ISSN 2375-2548, Vol. 3, no 2, article id e1602202Article in journal (Refereed) Published
##### Abstract [en]

Dynamic wetting problems are fundamental to understanding the interaction between liquids and solids. Even in a superficially simple experimental situation, such as a droplet spreading over a dry surface, the result may depend not only on the liquid properties but also strongly on the substrate-surface properties; even for macroscopically smooth surfaces, the microscopic geometrical roughness can be important. In addition, because surfaces may often be naturally charged or electric fields are used to manipulate fluids, electric effects are crucial components that influence wetting phenomena. We investigate the interplay between electric forces and surface structures in dynamic wetting. Although surfacemicrostructures can significantly hinder spreading, we find that electrostatics can " cloak" themicrostructures, that is, deactivate the hindering. We identify the physics in terms of reduction in contact-line friction, which makes the dynamic wetting inertial force dominant and insensitive to the substrate properties.

##### National Category
Mechanical Engineering
##### Identifiers
urn:nbn:se:kth:diva-205150 (URN)10.1126/sciadv.1602202 (DOI)000397039500032 ()2-s2.0-85041698410 (Scopus ID)
##### Note

QC 20170412

Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2017-06-29Bibliographically approved
Weihong, Y., Do-Quang, M. & Amberg, G. (2017). Impact of viscoelastic droplets. Journal of Non-Newtonian Fluid Mechanics, 243, 38-46
Open this publication in new window or tab >>Impact of viscoelastic droplets
2017 (English)In: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 243, p. 38-46Article in journal (Refereed) Published
##### Abstract [en]

We conduct numerical experiments on viscoelastic droplets hitting a flat solid surface. The results present time-resolved non-Newtonian stresses acting in the droplet. Comparing with the simulation of the impact of a Newtonian droplet, the effects of viscoelasticity on droplet behaviors such as splashing, the maximum spreading diameter and deformation are analyzed. With detailed information on the contact line region, we demonstrate how the contact line behaves according to the transition of the fluid property from elasticity dominated to shear-thinning dominated when a droplet expands and contracts on the substrate. The propose of this work is to discuss whether and how the elasticity in an impinging droplet takes effect.

Elsevier, 2017
##### Keywords
Contact line, Diffuse interface, Droplet impact, Dynamic wetting, Viscoelasticity, Drops, Elasticity, Non Newtonian flow, Shear thinning, Contact line regions, Contact lines, Droplet behaviors, Numerical experiments, Spreading diameters, Drop breakup
##### National Category
Applied Mechanics
##### Identifiers
urn:nbn:se:kth:diva-207327 (URN)10.1016/j.jnnfm.2017.03.003 (DOI)000401379500004 ()2-s2.0-85016417160 (Scopus ID)
##### Note

QC 20170608

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2017-11-10Bibliographically approved
Moradi Nour, Z., Amberg, G. & Do-Quang, M. (2017). Kinematics and dynamics of suspended gasifying particle. Acta Mechanica, 228(3), 1135-1151
Open this publication in new window or tab >>Kinematics and dynamics of suspended gasifying particle
2017 (English)In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 228, no 3, p. 1135-1151Article in journal (Refereed) Published
##### Abstract [en]

The effect of gasification on the dynamics and kinematics of immersed spherical and non-spherical solid particles have been investigated using the three-dimensional lattice Boltzmann method. The gasification was performed by applying mass injection on particle surface for three cases: flow passing by a fixed sphere, rotating ellipsoid in simple shear flow, and a settling single sphere in a rectangular domain. In addition, we have compared the accuracy of employing two different fluid-solid interaction methods for the particle boundary. The validity of the gasification model was studied by comparing computed the mass flux from the simulation and the calculated value on the surface of the particle. The result was used to select a suitable boundary method in the simulations combined with gasification. Moreover, the reduction effect of the ejected mass flux on the drag coefficient of the fixed sphere have been validated against previous studies. In the case of rotating ellipsoid in simple shear flow with mass injection, a decrease on the rate of rotation was observed. The terminal (maximum) velocity of the settling sphere was increased by increasing the ratio of radial flux from the particle boundary.

##### Place, publisher, year, edition, pages
SPRINGER WIEN, 2017
##### National Category
Fluid Mechanics and Acoustics
##### Identifiers
urn:nbn:se:kth:diva-205480 (URN)10.1007/s00707-016-1748-5 (DOI)000395107300021 ()2-s2.0-84995783715 (Scopus ID)
##### Note

QC 20170523

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2018-02-12Bibliographically approved
Wang, Y., Amberg, G. & Carlson, A. (2017). Local dissipation limits the dynamics of impacting droplets on smooth and rough substrates. PHYSICAL REVIEW FLUIDS, 2(3), Article ID 033602.
Open this publication in new window or tab >>Local dissipation limits the dynamics of impacting droplets on smooth and rough substrates
2017 (English)In: PHYSICAL REVIEW FLUIDS, ISSN 2469-990X, Vol. 2, no 3, article id 033602Article in journal (Refereed) Published
##### Abstract [en]

A droplet that impacts onto a solid substrate deforms in a complex dynamics. To extract the principal mechanisms that dominate this dynamics, we deploy numerical simulations based on the phase field method. Direct comparison with experiments suggests that a dissipation local to the contact line limits the droplet spreading dynamics and its scaled maximum spreading radius beta(max). By assuming linear response through a drag force at the contact line, our simulations rationalize experimental observations for droplet impact on both smooth and rough substrates, measured through a single contact line friction parameter mu(f). Moreover, our analysis shows that dissipation at the contact line can limit the dynamics and we describe beta(max) by the scaling law beta(max) similar to (Re mu(l)/mu(f))(1/2) that is a function of the droplet viscosity (mu(l)) and its Reynolds number (Re).

##### Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:kth:diva-206290 (URN)10.1103/PhysRevFluids.2.033602 (DOI)000399155400001 ()
##### Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2017-05-09Bibliographically approved
Kékesi, T., Amberg, G. & Prahl Wittberg, L. (2016). Corrigendum to: "Drop deformation and breakup". Int. J. Multiphase Flow, 66, (2014) 1-10. International Journal of Multiphase Flow
Open this publication in new window or tab >>Corrigendum to: "Drop deformation and breakup". Int. J. Multiphase Flow, 66, (2014) 1-10
2016 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533Article in journal (Refereed) Published
Elsevier, 2016
##### National Category
Mechanical Engineering
##### Identifiers
urn:nbn:se:kth:diva-194588 (URN)10.1016/j.ijmultiphaseflow.2016.02.002 (DOI)2-s2.0-84964816414 (Scopus ID)
##### Note

Correspondence Address: Kékesi, T.email: timea@mech.kth.se. QC 20161102

Available from: 2016-11-02 Created: 2016-10-31 Last updated: 2019-01-28Bibliographically approved
Liu, J., Amberg, G. & Do-Quang, M. (2016). Diffuse interface method for a compressible binary fluid. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 93(1), Article ID 013121.
Open this publication in new window or tab >>Diffuse interface method for a compressible binary fluid
2016 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 93, no 1, article id 013121Article in journal (Refereed) Published
##### Abstract [en]

Multicomponent, multiphase, compressible flows are very important in real life, as well as in scientific research, while their modeling is in an early stage. In this paper, we propose a diffuse interface model for compressible binary mixtures, based on the balance of mass, momentum, energy, and the second law of thermodynamics. We show both analytically and numerically that this model is able to describe the phase equilibrium for a real binary mixture (CO2 + ethanol is considered in this paper) very well by adjusting the parameter which measures the attraction force between molecules of the two components in the model. We also show that the calculated surface tension of the CO2 + ethanol mixture at different concentrations match measurements in the literature when the mixing capillary coefficient is taken to be the geometric mean of the capillary coefficient of each component. Three different cases of two droplets in a shear flow, with the same or different concentration, are simulated, showing that the higher concentration of CO2 the smaller the surface tension and the easier the drop deforms.

##### Place, publisher, year, edition, pages
American Physical Society, 2016
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:kth:diva-182155 (URN)10.1103/PhysRevE.93.013121 (DOI)000368517500016 ()2-s2.0-84955590690 (Scopus ID)
##### Note

QC 20160218

Available from: 2016-02-18 Created: 2016-02-16 Last updated: 2017-11-30Bibliographically approved
Kekesi, T., Amberg, G. & Prahl Wittberg, L. (2016). Drop deformation and breakup in flows with shear. Chemical Engineering Science, 140, 319-329
Open this publication in new window or tab >>Drop deformation and breakup in flows with shear
2016 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 140, p. 319-329Article in journal (Refereed) Published
##### Abstract [en]

A Volume of Fluid (VOF) method is applied to study the deformation and breakup of a single liquid drop in shear flows superimposed on uniform flow. The effect of shearing on the breakup mechanism is investigated as a function of the shear rate. Sequential images are compared for the parameter range studied; density ratios of liquid to gas of 20, 40, and 80, viscosity ratios in the range 0.5-50, Reynolds numbers between 20, a constant Weber number of 20, and the non-dimensional shear rate of the flow G = 0-2.1875. It is found that while shear breakup remains similar for all values of shear rate considered, other breakup modes observed for uniform flows are remarkably modified with increasing shear rate. The time required for breakup is significantly decreased in strong shear flows. A simple model predicting the breakup time as a function of the shear rate and the breakup time observed in uniform flows is suggested.

Elsevier, 2016
##### Keywords
Drop deformation, Drop breakup, Shear flow, Volume of Fluid (VOF)
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:kth:diva-180581 (URN)10.1016/j.ces.2015.10.019 (DOI)000367117300028 ()2-s2.0-84946594865 (Scopus ID)
##### Note

QC 20160121

Available from: 2016-01-21 Created: 2016-01-19 Last updated: 2019-01-28Bibliographically approved
Albernaz, D. L., Do-Quang, M., Hermanson, J. C. & Amberg, G. (2016). Droplet deformation and heat transfer in isotropic turbulence.
Open this publication in new window or tab >>Droplet deformation and heat transfer in isotropic turbulence
##### Abstract [en]

The heat and mass transfer of deformable droplets in turbulent flows is crucial to a wide range of applications, such as cloud dynamics and internal combustion engines. This study investigates a droplet undergoing phase change in isotropic turbulence using numerical simulations with a hybrid lattice Boltzmann scheme. We solve the momentum and energy transport equations, where phase separation is controlled by a non-ideal equation of state and density contrast is taken into consideration. Deformation is caused by pressure and shear stress at the droplet interface. The statistics of thermodynamic variables is quantified and averaged in terms of the liquid and vapor phases. The occurrence of evaporation and condensation is correlated to temperature fluctuations, surface tension variation and turbulence intensity. The temporal spectra of droplet deformations are analyzed and related to the droplet surface area.Different modes of oscillation are clearly identified from the deformation power spectrum for low Taylor Reynolds number $Re_\lambda$, whereas nonlinearities are produced with the increase of $Re_\lambda$, as intermediate frequencies are seen to overlap. As an outcome a continuous spectrum is observed, which shows a decrease that scales as $\sim f^{-3}$.Correlations between the droplet Weber number, deformation parameter, fluctuations of the droplet volume and thermodynamic variables are also examined.

##### National Category
Fluid Mechanics and Acoustics
##### Research subject
Engineering Mechanics
##### Identifiers
urn:nbn:se:kth:diva-183484 (URN)
##### Funder
Swedish Research Council, 2010-3938Swedish Research Council, 2011-5355
##### Note

QS 2016

Available from: 2016-03-14 Created: 2016-03-14 Last updated: 2016-03-14Bibliographically approved
Tahir, A. M., Malik, A. & Amberg, G. (2016). Modeling of the primary rearrangement stage of liquid phase sintering. Modelling and Simulation in Materials Science and Engineering, 24(7), Article ID 075009.
Open this publication in new window or tab >>Modeling of the primary rearrangement stage of liquid phase sintering
2016 (English)In: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 24, no 7, article id 075009Article in journal (Refereed) Published
##### Abstract [en]

The dimensional variations during the rearrangement stage of liquid phase sintering could have a detrimental effect on the dimensional tolerances of the sintered product. A numerical approach to model the liquid phase penetration into interparticle boundaries and the accompanied dimensional variations during the primary rearrangement stage of liquid phase sintering is presented. The coupled system of the Cahn-Hilliard and the Navier-Stokes equations is used to model the penetration of the liquid phase, whereas the rearrangement of the solid particles due to capillary forces is modeled using the equilibrium equation for a linear elastic material. The simulations are performed using realistic physical properties of the phases involved and the effect of green density, wettability and amount of liquid phase is also incorporated in the model. In the first step, the kinetics of the liquid phase penetration and the rearrangement of solid particles connected by a liquid bridge is modeled. The predicted and the calculated (analytical) results are compared in order to validate the numerical model. The numerical model is then extended to simulate the dimensional changes during primary rearrangement stage and a qualitative match with the published experimental data is achieved.

##### Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
##### Keywords
COMSOL multiphysics, dimensional variations, liquid phase penetration, particle motion, primary rearrangement, phase field modeling, sintering
##### National Category
Materials Engineering
##### Identifiers
urn:nbn:se:kth:diva-196414 (URN)10.1088/0965-0393/24/7/075009 (DOI)000385682800004 ()2-s2.0-84991758299 (Scopus ID)
VINNOVA
##### Note

QC 20161128

Available from: 2016-11-28 Created: 2016-11-14 Last updated: 2017-06-28Bibliographically approved
##### Identifiers
ORCID iD: orcid.org/0000-0003-3336-1462

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