sh.sePublikationer
Ändra sökning
Länk till posten
Permanent länk

Direktlänk
Publikationer (10 of 114) Visa alla publikationer
Yada, S., Bazesefidpar, K., Tammisola, O., Amberg, G. & Bagheri, S. (2023). Rapid wetting of shear-thinning fluids. Physical Review Fluids, 8(4), Article ID 043302.
Öppna denna publikation i ny flik eller fönster >>Rapid wetting of shear-thinning fluids
Visa övriga...
2023 (Engelska)Ingår i: Physical Review Fluids, E-ISSN 2469-990X, Vol. 8, nr 4, artikel-id 043302Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Using experiments and numerical simulations, we investigate the spontaneous spreading of droplets of aqueous glycerol (Newtonian) and aqueous polymer (shear-thinning) solutions on smooth surfaces. We find that in the first millisecond the spreading of the shear-thinning solutions is identical to the spreading of water, regardless of the polymer concentration. In contrast, aqueous glycerol solutions show a different behavior, namely, a significantly slower spreading rate than water. In the initial rapid spreading phase, the dominating forces that can resist the wetting are inertial forces and contact-line friction. For the glycerol solutions, an increase in glycerol concentration effectively increases the contact-line friction, resulting in increased resistance to wetting. For the polymeric solutions, however, an increase in polymer concentration does not modify contact-line friction. As a consequence, the energy dissipation at the contact line cannot be controlled by varying the amount of additives for shear-thinning fluids. The reduction of the spreading rate of shear-thinning fluids on smooth surfaces in the rapid-wetting regime can only be achieved by increasing solvent viscosity. Our results have implications for phase-change applications where the control of the rapid spreading rate is central, such as anti-icing and soldering. 

Ort, förlag, år, upplaga, sidor
American Physical Society, 2023
Nyckelord
Additives, Energy dissipation, Friction, Glycerol, Non Newtonian flow, Shear flow, Wetting, Aqueous glycerols, Contact-line frictions, Inertial forces, Newtonians, Polymer concentrations, Rapid wetting, Shear thinning fluids, Shear-thinning, Smooth surface, Spreading rate, Shear thinning
Nationell ämneskategori
Annan materialteknik
Identifikatorer
urn:nbn:se:sh:diva-51424 (URN)10.1103/PhysRevFluids.8.043302 (DOI)000976356900001 ()2-s2.0-85153845237 (Scopus ID)
Tillgänglig från: 2023-05-08 Skapad: 2023-05-08 Senast uppdaterad: 2023-05-22Bibliografiskt granskad
Amberg, G. (2022). Detailed modelling of contact line motion in oscillatory wetting. NPJ Microgravity, 8(1), Article ID 1.
Öppna denna publikation i ny flik eller fönster >>Detailed modelling of contact line motion in oscillatory wetting
2022 (Engelska)Ingår i: NPJ Microgravity, E-ISSN 2373-8065, Vol. 8, nr 1, artikel-id 1Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The experimental results of Xia and Steen for the contact line dynamics of a drop placed on a vertically oscillating surface are analyzed by numerical phase field simulations. The concept of contact line mobility or friction is discussed, and an angle-dependent model is formulated. The results of numerical simulations based on this model are compared to the detailed experimental results of Xia and Steen with good general agreement. The total energy input in terms of work done by the oscillating support, and the dissipation at the contact line, are calculated from the simulated results. It is found that the contact line dissipation is almost entirely responsible for the dissipation that sets the amplitude of the response. It is argued that angle-dependent line friction may be a fruitful interpretation of the relations between contact line speed and dynamic contact angle that are often used in practical computational fluid dynamics.

Ort, förlag, år, upplaga, sidor
Springer Nature, 2022
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:sh:diva-48224 (URN)10.1038/s41526-021-00186-0 (DOI)000744503300001 ()35046394 (PubMedID)2-s2.0-85123105044 (Scopus ID)
Tillgänglig från: 2022-01-24 Skapad: 2022-01-24 Senast uppdaterad: 2022-02-03Bibliografiskt granskad
Yada, S., Lacis, U., van der Wijngaart, W., Lundell, F., Amberg, G. & Bagheri, S. (2022). Droplet Impact on Asymmetric Hydrophobic Microstructures. Langmuir, 38(26), 7956-7964
Öppna denna publikation i ny flik eller fönster >>Droplet Impact on Asymmetric Hydrophobic Microstructures
Visa övriga...
2022 (Engelska)Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 38, nr 26, s. 7956-7964Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Textured hydrophobic surfaces that repel liquid droplets unidirectionally are found in nature such as butterfly wings and ryegrass leaves and are also essential in technological processes such as self-cleaning and antiicing. In many occasions, surface textures are oriented to direct rebounding droplets. Surface macrostructures (>100 mu m) have often been explored to induce directional rebound. However, the influence of impact speed and detailed surface geometry on rebound is vaguely understood, particularly for small microstructures. Here, we study, using a high-speed camera, droplet impact on surfaces with inclined micropillars. We observed directional rebound at high impact speeds on surfaces with dense arrays of pillars. We attribute this asymmetry to the difference in wetting behavior of the structure sidewalls, causing slower retraction of the contact line in the direction against the inclination compared to with the inclination. The experimental observations are complemented with numerical simulations to elucidate the detailed movement of the drops over the pillars. These insights improve our understanding of droplet impact on hydrophobic microstructures and may be useful for designing structured surfaces for controlling droplet mobility.

Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2022
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Identifikatorer
urn:nbn:se:sh:diva-49527 (URN)10.1021/acs.langmuir.2c00561 (DOI)000818745800001 ()35737474 (PubMedID)2-s2.0-85134083336 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet, VR 2015-04019Stiftelsen för strategisk forskning (SSF), SSF-FFL6
Tillgänglig från: 2022-07-07 Skapad: 2022-07-07 Senast uppdaterad: 2022-08-01Bibliografiskt granskad
Lācis, U., Pellegrino, M., Sundin, J., Amberg, G., Zaleski, S., Hess, B. & Bagheri, S. (2022). Nanoscale sheared droplet: volume-of-fluid, phase-field and no-slip molecular dynamics. Journal of Fluid Mechanics, 940, Article ID A10.
Öppna denna publikation i ny flik eller fönster >>Nanoscale sheared droplet: volume-of-fluid, phase-field and no-slip molecular dynamics
Visa övriga...
2022 (Engelska)Ingår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 940, artikel-id A10Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The motion of the three-phase contact line between two immiscible fluids and a solid surface arises in a variety of wetting phenomena and technological applications. One challenge in continuum theory is the effective representation of molecular motion close to the contact line. Here, we characterize the molecular processes of the moving contact line to assess the accuracy of two different continuum two-phase models. Specifically, molecular dynamics simulations of a two-dimensional droplet between two moving plates are used to create reference data for different capillary numbers and contact angles. We use a simple-point-charge/extended water model. This model provides a very small slip and a more realistic representation of the molecular physics than Lennard-Jones models. The Cahn-Hilliard phase-field model and the volume-of-fluid model are calibrated against the drop displacement from molecular dynamics reference data. It is shown that the calibrated continuum models can accurately capture droplet displacement and droplet break-up for different capillary numbers and contact angles. However, we also observe differences between continuum and atomistic simulations in describing the transient and unsteady droplet behaviour, in particular, close to dynamical wetting transitions. The molecular dynamics of the sheared droplet provide insight into the line friction experienced by the advancing and receding contact lines. The presented results will serve as a stepping stone towards developing accurate continuum models for nanoscale hydrodynamics.

Ort, förlag, år, upplaga, sidor
Cambridge University Press, 2022
Nyckelord
breakup/coalescence, contact lines, microscale transport
Nationell ämneskategori
Fysikalisk kemi Nanoteknik Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:sh:diva-48791 (URN)10.1017/jfm.2022.219 (DOI)000778572600001 ()2-s2.0-85129201165 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetEU, Europeiska forskningsrådet, 1.1.1.1/20/A/070Vetenskapsrådet, VR-2014-5680
Tillgänglig från: 2022-04-21 Skapad: 2022-04-21 Senast uppdaterad: 2022-05-19Bibliografiskt granskad
Lee, Y., Amberg, G. & Shiomi, J. (2022). Vibration sorting of small droplets on hydrophilic surface by asymmetric contact-line friction. PNAS nexus, 1(2), Article ID pgac027.
Öppna denna publikation i ny flik eller fönster >>Vibration sorting of small droplets on hydrophilic surface by asymmetric contact-line friction
2022 (Engelska)Ingår i: PNAS nexus, ISSN 2752-6542, Vol. 1, nr 2, artikel-id pgac027Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Droplet spreading and transport phenomenon is ubiquitous and has been studied by engineered surfaces with a variety of topographic features. To obtain a directional bias in dynamic wetting, hydrophobic surfaces with a geometrical asymmetry are generally used, attributing the directionality to one-sided pinning. Although the pinning may be useful for directional wetting, it usually limits the droplet mobility, especially for small volumes and over wettable surfaces. Here, we demonstrate a pinning-less approach to rapidly transport millimeter sized droplets on a partially wetting surface. Placing droplets on an asymmetrically structured surfaces with micron-scale roughness and applying symmetric horizontal vibration, they travel rapidly in one direction without pinning. The key, here, is to generate capillary-driven rapid contact-line motion within the time-scale of period of vibration. At the right regime where a friction factor local at the contact line dominates the rapid capillary motion, the asymmetric surface geometry can induce smooth and continuous contact-line movement back and forth at different speed, realizing directional motion of droplets even with small volumes over the wettable surface. We found that the translational speed is selective and strongly dependent on the droplet volume, oscillation frequency, and surface pattern properties, and thus droplets with a specific volume can be efficiently sorted out.

Ort, förlag, år, upplaga, sidor
Oxford University Press, 2022
Nyckelord
asymmetric contact-line friction, droplet, hydrophilic surface, wetting
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:sh:diva-51086 (URN)10.1093/pnasnexus/pgac027 (DOI)001063384200002 ()36713314 (PubMedID)
Tillgänglig från: 2023-02-24 Skapad: 2023-02-24 Senast uppdaterad: 2024-01-08Bibliografiskt granskad
Yada, S., Allais, B., van der Wijngaart, W., Lundell, F., Amberg, G. & Bagheri, S. (2021). Droplet Impact on Surfaces with Asymmetric Microscopic Features. Langmuir, 37(36), 10849-10858
Öppna denna publikation i ny flik eller fönster >>Droplet Impact on Surfaces with Asymmetric Microscopic Features
Visa övriga...
2021 (Engelska)Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, nr 36, s. 10849-10858Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The impact of liquid drops on a rigid surface is central in cleaning, cooling, and coating processes in both nature and industrial applications. However, it is not clear how details of pores, roughness, and texture on the solid surface influence the initial stages of the impact dynamics. Here, we experimentally study drops impacting at low velocities onto surfaces textured with asymmetric (tilted) ridges. We found that the difference between impact velocity and the capillary speed on a solid surface is a key factor of spreading asymmetry, where the capillary speed is determined by the friction at a moving three-phase contact line. The line-friction capillary number Caf = μfV0/σ (where μf,V0, and σ are the line friction, impact velocity, and surface tension, respectively) is defined as a measure of the importance of the topology of surface textures for the dynamics of droplet impact. We show that when Caf ≪ 1, the droplet impact is asymmetric; the contact line speed in the direction against the inclination of the ridges is set by line friction, whereas in the direction with inclination, the contact line is pinned at acute corners of the ridges. When Caf ≫ 1, the geometric details of nonsmooth surfaces play little role.

Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2021
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:sh:diva-46339 (URN)10.1021/acs.langmuir.1c01813 (DOI)000697110000021 ()34469168 (PubMedID)2-s2.0-85115030147 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet, 2015-04019Stiftelsen för strategisk forskning (SSF), SSF-FFL6
Tillgänglig från: 2021-09-07 Skapad: 2021-09-07 Senast uppdaterad: 2021-10-08Bibliografiskt granskad
Shen, B., Liu, J., Amberg, G., Do-Quang, M., Shiomi, J., Takahashi, K. & Takata, Y. (2020). Contact-line behavior in boiling on a heterogeneous surface: Physical insights from diffuse-interface modeling. Physical Review Fluids, 5(3), Article ID 033603.
Öppna denna publikation i ny flik eller fönster >>Contact-line behavior in boiling on a heterogeneous surface: Physical insights from diffuse-interface modeling
Visa övriga...
2020 (Engelska)Ingår i: Physical Review Fluids, E-ISSN 2469-990X, Vol. 5, nr 3, artikel-id 033603Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Enhancement of boiling heat transfer on biphilic (mixed-wettability) surfaces faces a sudden reversal at low pressures, which is brought about by excessive contact-line spreading across the wetting heterogeneities. We employ the diffuse-interface approach to numerically study bubble expansion on a heating surface that consists of opposing wettabilities. The results show a dramatic shift in the dynamics of a traversing contact line across the wettability divide under different gravities, which correspond to variable bubble growth rates. Specifically, it is found that the contact-line propagation tends to follow closely the rapidly expanding bubble at low gravity, with only a brief interruption at the border between the hydrophobic and hydrophilic sections of the surface. Only when the bubble growth becomes sufficiently weakened at high gravity does the contact line get slowed down drastically to the point of being nearly immobilized at the edge of the hydrophilic surface. The following bubble expansion, which faces strong limitations in the direction parallel to the surface, features a consistent apparent contact angle at around 66.4 degrees, regardless of the wettability combination. A simple theoretical model based on the force-balance analysis is proposed to describe the physical mechanism behind such a dramatic transition in the contact-line behavior.

Nyckelord
Fluid Flow and Transfer Processes, Modelling and Simulation, Computational Mechanics
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:sh:diva-47796 (URN)10.1103/physrevfluids.5.033603 (DOI)000518538200001 ()
Tillgänglig från: 2021-12-13 Skapad: 2021-12-13 Senast uppdaterad: 2021-12-13Bibliografiskt granskad
Lācis, U., Johansson, P., Fullana, T., Hess, B., Amberg, G., Bagheri, S. & Zaleski, S. (2020). Steady moving contact line of water over a no-slip substrate: Challenges in benchmarking phase-field and volume-of-fluid methods against molecular dynamics simulations. The European Physical Journal Special Topics, 229(10), 1897-1921
Öppna denna publikation i ny flik eller fönster >>Steady moving contact line of water over a no-slip substrate: Challenges in benchmarking phase-field and volume-of-fluid methods against molecular dynamics simulations
Visa övriga...
2020 (Engelska)Ingår i: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 229, nr 10, s. 1897-1921Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

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 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.

Ort, förlag, år, upplaga, sidor
Springer, 2020
Nationell ämneskategori
Teknisk mekanik
Identifikatorer
urn:nbn:se:sh:diva-41996 (URN)10.1140/epjst/e2020-900280-9 (DOI)000569876100011 ()2-s2.0-85091011554 (Scopus ID)
Tillgänglig från: 2020-10-01 Skapad: 2020-10-01 Senast uppdaterad: 2020-12-04Bibliografiskt granskad
Yada, S., Bagheri, S., Hansson, J., Do-Quang, M., Lundell, F., Van Der Wijngaart, W. & Amberg, G. (2019). Droplet leaping governs microstructured surface wetting. Soft Matter, 15(46), 9528-9536
Öppna denna publikation i ny flik eller fönster >>Droplet leaping governs microstructured surface wetting
Visa övriga...
2019 (Engelska)Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, nr 46, s. 9528-9536Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Microstructured surfaces that control the direction of liquid transport are not only ubiquitous in nature, but they are also central to technological processes such as fog/water harvesting, oil-water separation, and surface lubrication. However, a fundamental understanding of the initial wetting dynamics of liquids spreading on such surfaces is lacking. Here, we show that three regimes govern microstructured surface wetting on short time scales: spread, stick, and contact line leaping. The latter involves establishing a new contact line downstream of the wetting front as the liquid leaps over specific sections of the solid surface. Experimental and numerical investigations reveal how different regimes emerge in different flow directions during wetting of periodic asymmetrically microstructured surfaces. These insights improve our understanding of rapid wetting in droplet impact, splashing, and wetting of vibrating surfaces and may contribute to advances in designing structured surfaces for the mentioned applications.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry, 2019
Nyckelord
Drops, Liquids, Microstructure, Petroleum transportation, Micro-structured surfaces, Numerical investigations, Oil water separation, Short time scale, Structured surfaces, Technological process, Vibrating surface, Wetting dynamics, Wetting
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:sh:diva-39596 (URN)10.1039/c9sm01854a (DOI)000502539900011 ()2-s2.0-85075748095 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet, 2015-04019
Tillgänglig från: 2019-12-13 Skapad: 2019-12-13 Senast uppdaterad: 2020-01-03Bibliografiskt granskad
Kékesi, T., Altimira, M., Amberg, G. & Prahl Wittberg, L. (2019). Interaction between two deforming liquid drops in tandem and various off-axis arrangements subject to uniform flow. International Journal of Multiphase Flow, 112, 193-218
Öppna denna publikation i ny flik eller fönster >>Interaction between two deforming liquid drops in tandem and various off-axis arrangements subject to uniform flow
2019 (Engelska)Ingår i: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 112, s. 193-218Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A Volume of Fluid (VOF) method is applied to study the interaction between two liquid drops with the same initial diameter in uniform flow. Various arrangements of the drops are studied, based on two parameters, namely the initial separation distance and the angle between the line connecting the centres of the drops and the free-stream direction. Initial separation distances of 1.5–5 drop diameters, and angles between β=0∘ and 90° are considered. Simulations for a Weber number of We=20, two Reynolds numbers Re=20 and 50, and density and viscosity ratios in the range ρ*=20–80 and μ*=0.5–50 are performed. The movement of the secondary drop with respect to the primary drop, and estimates on the time required for the breakup of the secondary drop as compared to those observed for single drops are evaluated. It is found that the drops collide only in cases corresponding to the shortest initial displacements, while in others they deform and break up independently, similarly or identically to single drops. The same behaviour is reflected in the time required for breakup. Cases where the drops behave independently show breakup times close to those observed for single drops.

Nyckelord
Fluid Flow and Transfer Processes, General Physics and Astronomy, Mechanical Engineering
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:sh:diva-47798 (URN)10.1016/j.ijmultiphaseflow.2018.11.009 (DOI)
Forskningsfinansiär
Vetenskapsrådet
Tillgänglig från: 2021-12-13 Skapad: 2021-12-13 Senast uppdaterad: 2021-12-13Bibliografiskt granskad
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-3336-1462

Sök vidare i DiVA

Visa alla publikationer