Dynamics of high-speed micro-drop impact: numerical simulations and experiments at frame-to-frame times below 100 ns

C.W. Visser, P.E. Frommhold, S. Wildeman, R. Mettin, Detlef Lohse, Chao Sun

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Abstract

Technologies including (3D-) (bio-)printing, diesel engines, laser-induced forward transfer, and spray cleaning require optimization and therefore understanding of micrometer-sized droplets impacting at velocities beyond 10 m s−1. However, as yet, this regime has hardly been addressed. Here we present the first time-resolved experimental investigation of microdroplet impact at velocities up to V0 = 50 m s−1, on hydrophilic and -phobic surfaces at frame rates exceeding 107 frames per second. A novel method to determine the 3D-droplet profile at sub-micron resolution at the same frame rates is presented, using the fringe pattern observed from a bottom view. A numerical model, which is validated by the side- and bottom-view measurements, is employed to study the viscous boundary layer inside the droplet and the development of the rim. The spreading dynamics, the maximal spreading diameter, the boundary layer thickness, the rim formation, and the air bubble entrainment are compared to theory and previous experiments. In general, the impact dynamics are equal to millimeter-sized droplet impact for equal Reynolds-, Weber- and Stokes numbers (Re, We, and St, respectively). Using our numerical model, effective scaling laws for the progression of the boundary layer thickness and the rim diameter are provided. The dimensionless boundary layer thickness develops in time (t) according to Image ID:c4sm02474e-t1.gif, and the diameter of the rim develops as Image ID:c4sm02474e-t2.gif, with drop diameter D0 and inertial time scale τ = D0/V0. These scalings differ from previously assumed, but never validated, values. Finally, no splash is observed, at variance with many predictions but in agreement with models including the influence of the surrounding gas. This confirms that the ambient gas properties are key ingredients for splash threshold predictions
Original languageEnglish
Pages (from-to)1708-1722
Number of pages15
JournalSoft matter
Volume11
Issue number9
DOIs
Publication statusPublished - 2015

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rims
boundary layer thickness
high speed
Boundary layers
Computer simulation
simulation
Experiments
Numerical models
Gases
diesel engines
entrainment
predictions
Air entrainment
gases
ingredients
progressions
printing
scaling laws
cleaning
Scaling laws

Keywords

  • METIS-311030
  • IR-96675

Cite this

@article{bf1b0ba3044d45c7a82777431b7c4dad,
title = "Dynamics of high-speed micro-drop impact: numerical simulations and experiments at frame-to-frame times below 100 ns",
abstract = "Technologies including (3D-) (bio-)printing, diesel engines, laser-induced forward transfer, and spray cleaning require optimization and therefore understanding of micrometer-sized droplets impacting at velocities beyond 10 m s−1. However, as yet, this regime has hardly been addressed. Here we present the first time-resolved experimental investigation of microdroplet impact at velocities up to V0 = 50 m s−1, on hydrophilic and -phobic surfaces at frame rates exceeding 107 frames per second. A novel method to determine the 3D-droplet profile at sub-micron resolution at the same frame rates is presented, using the fringe pattern observed from a bottom view. A numerical model, which is validated by the side- and bottom-view measurements, is employed to study the viscous boundary layer inside the droplet and the development of the rim. The spreading dynamics, the maximal spreading diameter, the boundary layer thickness, the rim formation, and the air bubble entrainment are compared to theory and previous experiments. In general, the impact dynamics are equal to millimeter-sized droplet impact for equal Reynolds-, Weber- and Stokes numbers (Re, We, and St, respectively). Using our numerical model, effective scaling laws for the progression of the boundary layer thickness and the rim diameter are provided. The dimensionless boundary layer thickness develops in time (t) according to Image ID:c4sm02474e-t1.gif, and the diameter of the rim develops as Image ID:c4sm02474e-t2.gif, with drop diameter D0 and inertial time scale τ = D0/V0. These scalings differ from previously assumed, but never validated, values. Finally, no splash is observed, at variance with many predictions but in agreement with models including the influence of the surrounding gas. This confirms that the ambient gas properties are key ingredients for splash threshold predictions",
keywords = "METIS-311030, IR-96675",
author = "C.W. Visser and P.E. Frommhold and S. Wildeman and R. Mettin and Detlef Lohse and Chao Sun",
note = "Open access. Supplementary info, see: http://dx.doi.org/10.1039/C4SM02474E",
year = "2015",
doi = "10.1039/C4SM02474E",
language = "English",
volume = "11",
pages = "1708--1722",
journal = "Soft matter",
issn = "1744-683X",
publisher = "Royal Society of Chemistry",
number = "9",

}

Dynamics of high-speed micro-drop impact: numerical simulations and experiments at frame-to-frame times below 100 ns. / Visser, C.W.; Frommhold, P.E.; Wildeman, S.; Mettin, R.; Lohse, Detlef; Sun, Chao.

In: Soft matter, Vol. 11, No. 9, 2015, p. 1708-1722.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Dynamics of high-speed micro-drop impact: numerical simulations and experiments at frame-to-frame times below 100 ns

AU - Visser, C.W.

AU - Frommhold, P.E.

AU - Wildeman, S.

AU - Mettin, R.

AU - Lohse, Detlef

AU - Sun, Chao

N1 - Open access. Supplementary info, see: http://dx.doi.org/10.1039/C4SM02474E

PY - 2015

Y1 - 2015

N2 - Technologies including (3D-) (bio-)printing, diesel engines, laser-induced forward transfer, and spray cleaning require optimization and therefore understanding of micrometer-sized droplets impacting at velocities beyond 10 m s−1. However, as yet, this regime has hardly been addressed. Here we present the first time-resolved experimental investigation of microdroplet impact at velocities up to V0 = 50 m s−1, on hydrophilic and -phobic surfaces at frame rates exceeding 107 frames per second. A novel method to determine the 3D-droplet profile at sub-micron resolution at the same frame rates is presented, using the fringe pattern observed from a bottom view. A numerical model, which is validated by the side- and bottom-view measurements, is employed to study the viscous boundary layer inside the droplet and the development of the rim. The spreading dynamics, the maximal spreading diameter, the boundary layer thickness, the rim formation, and the air bubble entrainment are compared to theory and previous experiments. In general, the impact dynamics are equal to millimeter-sized droplet impact for equal Reynolds-, Weber- and Stokes numbers (Re, We, and St, respectively). Using our numerical model, effective scaling laws for the progression of the boundary layer thickness and the rim diameter are provided. The dimensionless boundary layer thickness develops in time (t) according to Image ID:c4sm02474e-t1.gif, and the diameter of the rim develops as Image ID:c4sm02474e-t2.gif, with drop diameter D0 and inertial time scale τ = D0/V0. These scalings differ from previously assumed, but never validated, values. Finally, no splash is observed, at variance with many predictions but in agreement with models including the influence of the surrounding gas. This confirms that the ambient gas properties are key ingredients for splash threshold predictions

AB - Technologies including (3D-) (bio-)printing, diesel engines, laser-induced forward transfer, and spray cleaning require optimization and therefore understanding of micrometer-sized droplets impacting at velocities beyond 10 m s−1. However, as yet, this regime has hardly been addressed. Here we present the first time-resolved experimental investigation of microdroplet impact at velocities up to V0 = 50 m s−1, on hydrophilic and -phobic surfaces at frame rates exceeding 107 frames per second. A novel method to determine the 3D-droplet profile at sub-micron resolution at the same frame rates is presented, using the fringe pattern observed from a bottom view. A numerical model, which is validated by the side- and bottom-view measurements, is employed to study the viscous boundary layer inside the droplet and the development of the rim. The spreading dynamics, the maximal spreading diameter, the boundary layer thickness, the rim formation, and the air bubble entrainment are compared to theory and previous experiments. In general, the impact dynamics are equal to millimeter-sized droplet impact for equal Reynolds-, Weber- and Stokes numbers (Re, We, and St, respectively). Using our numerical model, effective scaling laws for the progression of the boundary layer thickness and the rim diameter are provided. The dimensionless boundary layer thickness develops in time (t) according to Image ID:c4sm02474e-t1.gif, and the diameter of the rim develops as Image ID:c4sm02474e-t2.gif, with drop diameter D0 and inertial time scale τ = D0/V0. These scalings differ from previously assumed, but never validated, values. Finally, no splash is observed, at variance with many predictions but in agreement with models including the influence of the surrounding gas. This confirms that the ambient gas properties are key ingredients for splash threshold predictions

KW - METIS-311030

KW - IR-96675

U2 - 10.1039/C4SM02474E

DO - 10.1039/C4SM02474E

M3 - Article

VL - 11

SP - 1708

EP - 1722

JO - Soft matter

JF - Soft matter

SN - 1744-683X

IS - 9

ER -