Article
Mechanics
Vanessa R. Kern, Joshua B. Bostwick, Paul H. Steen
Summary: The study investigates the energetics of drop deposition in different wetting and contact angle conditions. The impacting event is decomposed into three different stages, with observation of contact line dissipation and successful resolution of the slip dynamics of the contact line through high-speed imaging.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Saksham Sharma, D. Ian Wilson
Summary: An analytical solution for the oscillation of an inviscid sessile drop on a flat horizontal plate is presented, yielding resonant frequencies for different vibration modes. The results show excellent agreement with experimental data, particularly for flatter drops and higher vibration modes.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
D. Zrnic, G. Brenn
Summary: This study investigates the nonlinear axisymmetric shape oscillations of an inviscid liquid drop in a vacuum, and its relevance for transport processes across the drop surface. The weakly nonlinear approach is used for theoretical analysis, revealing nonlinear effects for the m = 2 mode of deformation and showing that frequency decrease is a higher order effect with increasing surface deformation. The analysis extends to higher deformation modes, with nonlinearity attributed to coupling of different modes of deformation and capillary pressure forces on different drop cross-sectional areas.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Luke F. L. Alventosa, Radu Cimpeanu, Daniel M. Harris
Summary: This study investigates the rebound behavior of droplets impacting a deep fluid bath through experimental and theoretical research. The experiment generates millimetric drops using a piezoelectric droplet-on-demand generator and observes their impact on a bath of the same fluid. The trajectory and rebound metrics of the droplets are compared with predictions from a linear quasipotential model and direct numerical simulations of the Navier-Stokes equations. The models consider the time-dependent shapes of the bath and droplet, and the quasipotential model effectively explains historical experimental measurements of the coefficient of restitution.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Rahil N. Valani, Jack Dring, Tapio P. Simula, Anja C. Slim
Summary: The emergence of superwalking droplets is achieved by vibrating a bath of silicone oil simultaneously at a given frequency and its subharmonic tone with a relative phase difference between them. By driving the bath at two frequencies with an appropriate phase difference, it allows large droplets to leap over intermediate peaks and exhibit dynamics similar to normal walkers. The relative height difference between successive peaks of the bath motion, controlled by the phase difference, strongly influences the vertical and horizontal dynamics of the droplets.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
D. V. Lyubimov, T. P. Lyubimova, A. A. Cherepanov
Summary: The paper discusses the resonance oscillations of a drop surrounded by a fluid of different density in zero gravity conditions under small amplitude vibrations. When viscosity is small, the resonance oscillations of the drop can be calculated using linear approximation, but finite viscosity has a destabilizing effect on resonance.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Fei Zhang, Xinping Zhou, Hang Ding
Summary: This study investigates the natural oscillations of sessile drops with a free or pinned contact line under different gravity environments. A linear inviscid irrotational theory is employed to analyze the drops' behavior, and a boundary element method model is developed to predict the natural frequencies. The study reveals the frequency shifts due to gravity for various contact angles and Bond numbers, and identifies three types of diagrams reflecting the gravity-induced frequency changes. Additionally, the study shows that gravity can transform the lowest mode and breaks the spectral degeneracy of hemispherical drops, but has no effect on the mode associated with the horizontal motion of the center of mass.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jae Hong Lee, Seungho Kim, Joonoh Kim, Hyoungsoo Kim, Ho-Young Kim
Summary: The study theoretically models the impact of a drop train on a liquid pool, including cavity formation and funnel shape, which align well with experimental results. When liquid inertia dominates, the cavity assumes a parabolic profile. Capillary forces and drop impact force determine the shape of the funnel after the elongated cavity collapses.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Chun-Yu Zhang, Peng Gao, Er-Qiang Li, Hang Ding
Summary: The study investigates the configuration boundaries of compound sessile drops on a flat substrate and focuses on transitions among axisymmetric configurations like encapsulation, lens, and collars. These transitions are influenced by changes in substrate wettability and the volume ratio of different droplet components. The research identifies criteria for configuration transition onset, distinguishes between irreversible and reversible transitions, uncovers dynamic behaviors of transitions not accessible to theoretical analysis, and advances towards controllable reconfiguration of compound sessile drops.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Arnaud Antkowiak
Summary: This study investigates the interaction between a droplet and a liquid bath, identifying two distinct stages with simple and effective models to explain them. The research provides a comprehensive and straightforward understanding of the physics behind creating holes in liquids.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
C. W. Extrand
Summary: This theoretical work estimates the volume and energies associated with the formation of a liquid meniscus along a vertical flat wall using existing equations. A proposed mechanism and energy balance is presented, along with derived equations for wetting work, surface energy, gravitational energy, and dissipation. The analysis indicates that the energy released during wetting is stored in various forms depending on variables such as surface tension, density, and wall wettability.
Article
Mechanics
M. A. Herrada, A. Ponce-Torres, M. Rubio, J. Eggers, J. M. Montanero
Summary: In this study, we numerically investigate the nonlinear stationary states of a droplet covered with an insoluble surfactant in a uniaxial extensional flow. We find that the presence of surfactant significantly reduces the stability interval of capillary numbers and has little effect on the droplet deformation and stability in relation to droplet viscosity. Tip streaming only occurs in the presence of surfactants, and the critical eigenmode for tip streaming is similar to the central pinching mode for a clean interface. Viscous surface stress decreases the damping rate of the dominant mode, and shear viscous surface stress alters the nature of tip streaming in the supercritical regime.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Chunheng Zhao, Vanessa R. Kern, Andreas Carlson, Taehun Lee
Summary: When a water droplet contacts an immiscible oil film, complex interfacial dynamics are observed. The oil spreads onto the droplet's liquid-air interface, forming a liquid bridge that drives the droplet spreading motion and later engulfs the droplet. This process is studied using simulations and experiments, revealing the effects of inertial and viscous limitations. The growth of the liquid bridge is insensitive to the film height, but the engulfment dynamics and interface profiles are significantly affected by the ratio of film height to droplet radius.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
B. Gorin, D. Bonn, H. Kellay
Summary: This study investigates the impact of cooled liquid droplets on surfaces. The freezing process affects the spreading dynamics and surface coverage of the droplets. Experimental observations and a freezing model reveal that droplet arrest occurs when a solid layer of the liquid forms on the substrate, and a simple model can efficiently predict the maximum spreading diameter of droplets at different impact velocities and surface temperatures below the freezing point.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
J. Sakakeeny, C. Deshpande, S. Deb, J. L. Alvarado, Y. Ling
Summary: This study reveals the relationship between the natural frequency of lateral oscillation of a liquid drop pinned on a vertical surface, equilibrium contact angle, and Bond number. As the Bond number increases, the lateral oscillation frequency decreases, suggesting that resonance frequencies are amplified in reduced gravity environments.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Mechanical
X. Shao, C. T. Gabbard, J. B. Bostwick, J. R. Saylor
Summary: The experimental results demonstrate that the presence of a meniscus is necessary for the formation of capillary waves, while the lack of a meniscus prevents the formation of these waves. A meniscus of either positive or negative curvature serves equally well in enabling capillary wave formation.
EXPERIMENTS IN FLUIDS
(2021)
Article
Mechanics
X. Shao, P. Wilson, J. R. Saylor, J. B. Bostwick
Summary: This study analyzed the dynamics of surface waves excited by mechanical vibration in a cylindrical container, finding that control of the meniscus geometry had a significant effect on the generation and mixing of edge waves and Faraday waves. Theoretical predictions using the Rayleigh-Ritz procedure were in excellent agreement with experimental results.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
X. Shao, P. Wilson, J. B. Bostwick, J. R. Saylor
Summary: The study investigates edge waves excited at the boundary of a mechanically vibrated cylindrical container, using two materials with tunable properties to analyze the effects of viscoelasticity on wave behavior. Frequency sweeps and long-exposure white-light imaging were utilized to quantify wave slope, revealing resonance peaks and bandwidths that vary with viscosity and elasticity. Experimentally observed results align well with theoretical models, highlighting the role of viscosity, elasticity, and surface tension in governing the behavior of viscoelastic fluids in cylindrical containers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Analytical
Mahmud Kamal Raihan, Purva P. Jagdale, Sen Wu, Xingchen Shao, Joshua B. Bostwick, Xinxiang Pan, Xiangchun Xuan
Summary: Investigating the flow of five types of non-Newtonian fluids through a microchannel, it was found that fluid inertia plays a key role in developing vortices in the expansion flow, while shear thinning and elasticity have different effects on the flow properties. In a contraction-expansion microchannel, the flow characteristics are significantly influenced by the confinement.
Article
Engineering, Industrial
Jennifer Shaffer Brown, Caleb Wilson, Charles Bohlen, Hongseok Choi, Lonny Thompson, Joshua B. Bostwick
Summary: An automated UAS system was used to study the effects of processing parameters on solder joint quality, revealing novel failure surface types with distinct behavior. The growth of a surface oxide layer was observed to impact joint quality, suggesting further research is necessary to refine the UAS process.
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY
(2022)
Article
Physics, Fluids & Plasmas
P. Wilson, X. Shao, J. R. Saylor, J. B. Bostwick
Summary: This study investigates Faraday waves generated by mechanically vibrating a cylindrical container. Frequency scans are used to measure the acceleration threshold for the appearance of surface waves, and the spatial structure of the waves is determined using imaging techniques. Theoretical models are developed to calculate the natural oscillations of different materials in the cylindrical container under varying boundary conditions, with good agreement between theoretical predictions and experimental observations.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Multidisciplinary Sciences
Jonathan M. Ludwicki, Vanessa R. Kern, Joshua McCraney, Joshua B. Bostwick, Susan Daniel, Paul H. Steen
Summary: This article investigates the joint experimental and numerical study of water droplets on surfaces with different wetting properties. By comparing the data from experiments and numerical simulations, it is found that the Davis-Hocking model with the measured mobility parameter performs better in describing wetting phenomena.
Article
Multidisciplinary Sciences
Saiful I. Tamim, Joshua B. Bostwick
Summary: The dynamics of a soft viscoelastic drop are governed by the balance between surface tension, viscosity, and elasticity, with rheology often being frequency dependent. The study focuses on the free and forced oscillations of a soft material with arbitrary rheology, particularly analyzing the cases of a Kelvin-Voigt and Maxwell model relevant to soft gels and polymer fluids. The complex frequencies, characterized by oscillation frequency and decay rate, depend on dimensionless elastocapillary and Deborah numbers, and map the boundary between regions of underdamped and overdamped motions.
Article
Mechanics
Michael Dacus, Mahmud Kamal Raihan, Micah Baghdady, Chase Gabbard, Sen Wu, Joshua B. Bostwick, Yongxin Song, Xiangchun Xuan
Summary: The addition of the neutral surfactant Tween 20 has a weak influence on the flow behavior of water and homogeneous polymer solutions. It does not significantly affect the shear viscosity and extensional flow of Newtonian fluids, but reduces the shear viscosity and shear-thinning behavior of xanthan gum and polyacrylamide solutions with strong shear-thinning effects. The addition of Tween 20 also stabilizes the flow and delays flow instability.
Article
Mechanics
D. Ding, J. B. Bostwick
Summary: This study investigates the frequency spectrum of pressure disturbances in drop-on-demand printing applications, which is influenced by the static contact angle and an empirical constant relating the reservoir pressure to volume exchanged. Instabilities in axisymmetric and non-axisymmetric modes are found to be related to center-of-mass motions, and the model parameters affect the spectral degeneracy of the Rayleigh drop modes.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
D. Ding, J. B. Bostwick
Summary: We study the linear stability of a compressible sessile bubble on a partially wetting planar solid support, and report two instability modes related to volume change and the horizontal center-of-mass motion of the bubble. The respective instability mechanisms are revealed through an energy analysis. We also show a complex dependence between classical volume and shape change modes for wetting conditions that differ from neutral wetting.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
J. McCraney, V Kern, J. B. Bostwick, S. Daniel, P. H. Steen
Summary: In this study, shape oscillations of sessile water drops with fully mobile contact lines aboard the International Space Station were analyzed. Experimental observations, which agree with spectral predictions, helped elucidate the phenomenon of terrestrial droplet inertial spreading.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
J. McCraney, J. Ludwicki, J. Bostwick, S. Daniel, P. Steen
Summary: In this experiment conducted aboard the International Space Station, centimeter-sized sessile drop coalescence was observed. The results showed that the Davis-Hocking model is an appropriate contact line model for inertial-capillary spreading.
Article
Mechanics
Saiful Tamim, Joshua B. Bostwick
Summary: In this study, lubrication theory was applied to investigate the spreading dynamics of liquid droplets on soft viscoelastic substrates, revealing the mechanisms through which substrate properties affect the spreading rate.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Chemistry, Physical
S. Tamim, J. B. Bostwick
Summary: This study examines the instability of soft cylindrical interfaces and cylindrical cavities due to the competition between elasticity and capillarity. Elasticity stabilizes the instability while compressibility destabilizes it. The critical wavenumber shows a more complex dependence upon compressibility for the cylinder but exhibits a predictable trend for the cylindrical cavity.