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Publications (10 of 12) Show all publications
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 ()2-s2.0-85020027987 (Scopus ID)
Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2020-03-09Bibliographically approved
Wang, Y. (2016). Capillarity and wetting of non-Newtonian droplets. (Doctoral dissertation). KTH Royal Institute of Technology
Open this publication in new window or tab >>Capillarity and wetting of non-Newtonian droplets
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Capillarity and dynamic wetting of non-Newtonian fluids are important in many natural and industrial processes, examples cover from a daily phenomenon as splashing of a cup of yogurt to advanced technologies such as additive manufacturing. The applicable non-Newtonian fluids are usually viscoelastic compounds of polymers and solvents. Previous experiments observed diverse interesting behaviors of a polymeric droplet on a wetted substrate or in a microfluidic device. However, our understanding of how viscoelasticity affects droplet dynamics remains very limited. This work intends to shed light on viscoelastic effect on two small scale processes, i.e., the motion of a wetting contact line and droplet splitting at a bifurcation tip.

 

Numerical simulation is employed to reveal detailed information such as elastic stresses and interfacial flow field. A numerical model is built, combining the phase field method, computational rheology techniques and computational fluid dynamics. The system is capable for calculation of realistic circumstances such as a droplet made of aqueous solution of polymers with moderate relaxation time, impacting a partially wetting surface in ambient air.

 

The work is divided into three flow cases. For the flow case of bifurcation tube, the evolution of the interface and droplet dynamics are compared between viscoelastic fluids and Newtonian fluids. The splitting or non-splitting behavior influenced by elastic stresses is analyzed. For the flow case of dynamic wetting, the flow field and rheological details such as effective viscosity and normal stress difference near a moving contact line are presented. The effects of shear-thinning and elasticity on droplet spreading and receding are analyzed, under inertial and inertialess circumstances. In the last part, droplet impact of both Newtonian and viscoelastic fluids are demonstrated. For Newtonian droplets, a phase diagram is drawn to visualize different impact regions for spreading, splashing and gas entrapment. For viscoelastic droplets, the viscoelastic effects on droplet deformation, spreading radius and contact line motion are revealed and discussed.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. p. 50
Keywords
Dynamic wetting, contact line, diffusive interface, viscoelasticity, non-Newtonian, microfluidics, droplet impact, droplet spreading
National Category
Physical Sciences
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-184146 (URN)978-91-7595-921-4 (ISBN)
Public defence
2016-04-22, Kollegiesalen, Brinellvägen 8, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20160329

Available from: 2016-03-29 Created: 2016-03-28 Last updated: 2016-04-02Bibliographically approved
Wang, Y., Gratadeix, A., Do-Quang, M. & Amberg, G. (2016). Events and conditions in droplet impact: a phase field prediction. International Journal of Multiphase Flow, 87, 54-65
Open this publication in new window or tab >>Events and conditions in droplet impact: a phase field prediction
2016 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 87, p. 54-65Article in journal (Refereed) Published
Abstract [en]

The phenomenon of droplet impact on a smooth, flat, partially wetted surface is studied by phase field simulation. A map of the different impact regimes is constructed for Reynolds numbers ranging from Re = 9 to Re = 9 x 10(4), and Ohnesorge numbers ranging from Oh = 3.3 x 10(-4) to Oh = 1.05. The results are compared with previous experiments from several aspects such as gas bubble entrapment, spreading radius and liquid sheet splashing, etc. The simulation proposes event predictions that are consistent with previous experiments. Our results and discussions give an overview of important characteristics during droplet impact, and provide insights on the droplet spreading after impact.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Physical Sciences
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-184142 (URN)10.1016/j.ijmultiphaseflow.2016.08.009 (DOI)000386645300006 ()2-s2.0-84987942203 (Scopus ID)
Note

QC 20191014

Available from: 2016-03-28 Created: 2016-03-28 Last updated: 2019-10-14Bibliographically approved
Wang, Y., Do-Quang, M. & Amberg, G. (2016). Viscoelastic droplet dynamics in a y-shaped capillary channel. Physics of fluids, 28(3), 033103
Open this publication in new window or tab >>Viscoelastic droplet dynamics in a y-shaped capillary channel
2016 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 28, no 3, p. 033103-Article in journal (Refereed) Published
Abstract [en]

Non-Newtonian droplet dynamics commonly exist in microfluidic systems. We report simulations of viscoelastic (VE) droplets traveling in a two dimensional capillary bifurcation channel. A numerical system combining phase field method, VE rheology, and Stokes flow equations is built. As a generic microfluidic two-phase problem, we study how a non-Newtonian droplet that approaches a channel bifurcation will behave. We identify conditions for when a droplet will either split into two or be directed into one of the branches. In particular, we study the importance of the non-Newtonian properties. Our results reveal two different non-Newtonian mechanisms that can enhance splitting and non-splitting of droplets with respect to Newtonian droplets, depending on the size of droplet and capillary number.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Natural Sciences
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-184141 (URN)10.1063/1.4943110 (DOI)000373600600020 ()2-s2.0-84960904107 (Scopus ID)
Note

QC 20160329

Available from: 2016-03-28 Created: 2016-03-28 Last updated: 2020-02-19Bibliographically approved
Wang, Y., Minh, D.-Q. & Amberg, G. (2015). Dynamic wetting of viscoelastic droplets. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 92(4), Article ID 043002.
Open this publication in new window or tab >>Dynamic wetting of viscoelastic droplets
2015 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 92, no 4, article id 043002Article in journal (Refereed) Published
Abstract [en]

We conduct numerical experiments on spreading of viscoelastic droplets on a flat surface. Our work considers a Giesekus fluid characterized by a shear-thinning viscosity and an Oldroyd-B fluid, which is close to a Boger fluid with constant viscosity. Our results qualitatively agree with experimental observations in that both shear thinning and elasticity enhances contact line motion, and that the contact line motion of the Boger fluid obeys the Tanner-Voinov-Hoffman relation. Excluding inertia, the spreading speed shows strong dependence on rheological properties, such as the viscosity ratio between the solvent and the polymer suspension, and the polymeric relaxation time. We also discuss how elasticity can affect contact line motion. The molecular migration theory proposed in the literature is not able to explain the agreement between our simulations and experimental results.

Place, publisher, year, edition, pages
[Wang, Yuli; Minh, Do-Quang; Amberg, Gustav] Royal Inst Technol, Dept Mech, Linne FLOW Ctr, S-10044 Stockholm, Sweden. [Wang, Yuli] Jiangsu Univ, Sch Energy & Power Engn, Zhenjiang 212013, Peoples R China.: , 2015
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-176343 (URN)10.1103/PhysRevE.92.043002 (DOI)000362445200021 ()2-s2.0-84945179169 (Scopus ID)
Note

QC 20151109

Available from: 2015-11-09 Created: 2015-11-03 Last updated: 2017-12-01Bibliographically approved
Gong, C., Yang, M., Kang, C. & Wang, Y. (2015). The acquisition and measurement of surface waves of high-speed liquid jets. Journal of Visualization
Open this publication in new window or tab >>The acquisition and measurement of surface waves of high-speed liquid jets
2015 (English)In: Journal of Visualization, ISSN 1343-8875, E-ISSN 1875-8975Article in journal (Refereed) Published
Abstract [en]

Abstract: The instability analysis of the liquid jet issuing into ambient air was conducted with an emphasis placed upon the evolution of surface waves of the jet. An experiment was designed to visualize the microscopic morphology on the surface of a liquid jet. A spectral method was proposed to measure wavelength from the obtained jet images. We also discuss key setup parameters that significantly affect the resolution of desired jet features and the accuracy of the spectral measurement. The results show that the liquid jet near the nozzle exit can be divided into a laminar section, a transition section, an instability section, and a turbulence section. Surface wave scales range from 0.06 to 0.11 times of the nozzle diameter with the atomization breakup regime. For the atomization breakup regime, the growth ratio of the surface waves of the instability section is 0.06 which is 1.5 times the value of the second wind-introduced breakup regime and 3 times the value of the first wind-introduced breakup regime. Graphical abstract: [Figure not available: see fulltext.]

Keywords
Breakup regime, High-speed microscopic photography, Image processing, Surface wave, Wavelength measurement
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-175621 (URN)10.1007/s12650-015-0307-9 (DOI)000379431500007 ()2-s2.0-84939240648 (Scopus ID)
Note

QC 20151027

Available from: 2015-10-27 Created: 2015-10-19 Last updated: 2017-12-01Bibliographically approved
Gong, C., Yang, M., Wang, Y., Yan, L. & Gao, B. (2015). Turbulence structure on the surface of high speed liquid jet. In: ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015: . Paper presented at ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015, 26 July 2015 through 31 July 2015. American Society of Mechanical Engineers
Open this publication in new window or tab >>Turbulence structure on the surface of high speed liquid jet
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2015 (English)In: ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015, American Society of Mechanical Engineers , 2015Conference paper, Published paper (Refereed)
Abstract [en]

The structures on the surface of high-speed capillary liquid jet were captured with the help of high-speed camera and microscope. Apower spectral density method is used to deal with the jet images. Based on captured jet image, the variation of surface structures near the exit of the nozzle is divided into three sections: laminar section, instability section and turbulence section. There is no clearly surface structures in the laminar section. The wave-like structures come out in the instability section with a sudden and are regularly increase with a small slope along the streamwise. The degree of order is rather weak in the turbulence section. The increase of the Reynolds numbers which based on the momentum thickness at the exit of the nozzle will accelerates the jet surface transition from the laminar section to turbulence section.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers, 2015
Keywords
High-speed camera, Liquid jet, Power spectral density method, Surface wave, Cameras, High speed cameras, Jets, Liquids, Nozzles, Reynolds number, Spectral density, Surface structure, Surface waves, Turbulence, Degree of order, High Speed, Jet surfaces, Liquid jets, Momentum thickness, Turbulence structures, Fighter aircraft
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-227908 (URN)10.1115/AJKFluids2015-09512 (DOI)2-s2.0-85044252518 (Scopus ID)978-0-7918-5722-9 (ISBN)
Conference
ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015, 26 July 2015 through 31 July 2015
Note

QC 20180516

Conference code: 117507; Export Date: 14 May 2018; Conference Paper

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-06-07Bibliographically approved
Gong, C., Yang, M., Wang, Y. & Kang, C. (2015). Wavelength measurement of a liquid jet based on spectral analysis of image intensity. Advances in Mechanical Engineering, 7(8), Article ID 1687814015595165.
Open this publication in new window or tab >>Wavelength measurement of a liquid jet based on spectral analysis of image intensity
2015 (English)In: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 7, no 8, article id 1687814015595165Article in journal (Refereed) Published
Abstract [en]

The instability analysis of the liquid jet issuing into ambient gas was conducted with the emphasis placed upon the evolution of surface wave on the jet surface. First, an experimental method was developed to visualize the microscopic surface wave on the liquid jet. Camera setting parameters significantly affecting the detection of desired jet features were discussed. Second, a spectral method was applied to process the obtained jet images. The accuracy of this method was validated in several ways. The results show that wavelengths increase monotonically along the streamwise direction and decrease with the increase in Reynolds number which corresponds to the boundary layer momentum thickness at nozzle exit. Various patterns of wave structures on jet surface are revealed. In this article, the pattern transforms from three-dimensional to two-dimensional at Reynolds number of 134.53.

Keywords
Liquid jet, surface wave, high-speed microscopic photography, spectral analysis
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-173776 (URN)10.1177/1687814015595165 (DOI)000360429700003 ()2-s2.0-84940923956 (Scopus ID)
Note

QC 20150921

Available from: 2015-09-21 Created: 2015-09-18 Last updated: 2017-12-04Bibliographically approved
Yang, M., Lu, J., Wang, Y., Gong, C. & Yan, L. (2014). Analysis of eddy viscosity models in predicting flow field of high-speed water jet. Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery, 45(7), 306-312
Open this publication in new window or tab >>Analysis of eddy viscosity models in predicting flow field of high-speed water jet
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2014 (English)In: Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery, ISSN 1000-1298, Vol. 45, no 7, p. 306-312Article in journal (Refereed) Published
Abstract [en]

Three commonly used two-equation turbulence models were adopted. The computed velocity field was compared with the data from corresponding laser Doppler anemometer measurement to analyze the accuracy of these models. By adjusting the model parameters, the simulation data can fit into the experimental result. The optimal viscosity coefficients Cμ in these used eddy viscosity models were presented. It is shown that the RNG k-ε model is more sensitive to Cμ, while the results from Standard k-ε model vary almost linearly with the change of the Cμ value. Study on the simulated flow field gives that if the peak of turbulence kinetic energy appears within the radial span, it will affect the velocity distribution along the jet axis; otherwise, it will modify the velocity magnitude. The proposed numerical scheme reduces the physical complexities involved in ultra-high pressure injection process so that it can be applied to archive fast production from relevant CAE workflow.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-161048 (URN)10.6041/j.issn.1000-1298.2014.07.047 (DOI)2-s2.0-84904397708 (Scopus ID)
Note

QC 20150309

Available from: 2015-03-09 Created: 2015-03-06 Last updated: 2016-12-05Bibliographically approved
Wang, Y., Yang, M.-G. -. & Gao, B. (2013). Dynamics of ultra-high speed liquid jets in still gas. Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, 34(9), 1654-1658
Open this publication in new window or tab >>Dynamics of ultra-high speed liquid jets in still gas
2013 (English)In: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, ISSN 0253-231X, Vol. 34, no 9, p. 1654-1658Article in journal (Refereed) Published
Abstract [en]

Instability of free liquid jets is an important fundamental problem rising from multiple engineering fields such as material processing, energy production, etc. Ultra-high speed condition brings new difficulties to stability research. This work demonstrates flow patterns of ultra-high speed liquid jet (UHSLJ) and points out the potential challenges in relevant investigation, from a turbulence point of view. A PDA measurement of flow velocity and droplet size on a cross-section of UHSLJ is present. Flow physics involved in the jet is discussed together with the limitation of this measurement. It is found that the velocity profile on the measured section obeys 1/7 power law. Concentration of droplets has an inverse gradient (from outer region of a jet pointing to the inner region) in the breakup section. Flow properties hold an axisymmetric distribution in the atomization section while this section itself has an evident two-layer (core-outer) structure. The length scales (size of drop) that be resolved by the present experiment is estimated to be only 0.1% of the entire scales.

Keywords
PDA, Stability, Turbulence, Ultra-high pressure liquid jet, Energy productions, Engineering fields, Flow properties, Liquid jets, Material processing, Ultra high speed, Velocity profiles, Convergence of numerical methods, Drop breakup, Liquids, Jets
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-140012 (URN)2-s2.0-84886308768 (Scopus ID)
Note

QC 20140122

Available from: 2014-01-22 Created: 2014-01-16 Last updated: 2014-01-22Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5915-0789

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