Article
Mechanics
Yingxian Estella Yu, Mirco Magnini, Lailai Zhu, Suin Shim, Howard A. Stone
Summary: The research systematically studies the motion of bubbles in a vertical capillary tube under external flows, revealing diverse dynamic phenomena when an external downward flow is applied to the bubble. The study discovers the existence of two distinct solution branches for the film thickness separating the bubble surface and the tube inner wall, as well as non-unique, history-dependent solutions for the steady-state film thickness under the same external flow conditions. Furthermore, inertialess symmetry-breaking shape profiles at steady state are found as the bubble transits near the tipping points of the solution branches, which are verified in experiments and numerical simulations.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Zih-Yin Chen, Alireza Hooshanginejad, Satish Kumar, Sungyon Lee
Summary: This paper investigates the behavior of partially wetting droplets under airflow and demonstrates through experiments that the droplets can oscillate, split, or depin under an impinging jet. The authors develop a lubrication model that incorporates external pressure, capillary pressure, and hydrostatic pressure to simulate the motion of the contact line. The simulations capture a wider range of droplet behaviors and are consistent with experimental observations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
M. Rubio-Rubio, R. Bolanos-Jimenez, C. Martinez-Bazan, J. C. Munoz-Hervas, A. Sevilla
Summary: The experiments demonstrate that bubbles growing and detaching from a superhydrophobic substrate go through a sequence of quasi-equilibrium states, reaching a maximum volume and critical base radius. This ultimate size limit is also observed when bubbles grow on an unbounded, ideally non-wetting surface.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Xiaolong Zhang, Vadim S. Nikolayev
Summary: This theoretical work investigates the dewetting phenomenon in the presence of liquid evaporation. By considering various nanoscale effects, the study provides insights into the acceleration of dewetting due to evaporation.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
He Ming, Jian Qin, Peng Gao
Summary: We numerically investigate the dynamics of a bubble spreading on a partially wettable smooth solid substrate in a viscous liquid. By adopting the Navier-slip model, we relieve the singularity of the moving contact line. The simulation results show that the early-stage spreading of the bubble is characterized by the growth and propulsion of a dewetting liquid rim close to the contact line.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Yanju Wei, Zhiqiang Mu, Yajie Zhang, Yajing Yang, Shenghua Liu, Chung K. Law, Abhishek Saha
Summary: This study reports the dynamics and morphology of a droplet passing through a soap film, providing experimental observation and theoretical explanation. The study identifies four sequential responses of the film during the process, and develops physical models and analytical expressions to reveal the underlying physics.
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
Mechanics
Mainendra Kumar Dewangan, Uddipta Ghosh, Tanguy Le Borgne, Yves Meheust
Summary: This study reveals the importance of fractures in subsurface processes and solving electrohydrodynamic problems will help understand the electro-osmotic effects in fractures. The new theoretical framework allows systematic investigation of various parameters' impact on coupled transport in rough fractures by analyzing a large number of fracture geometries.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
G. Gravina, S. Schwarzacher, O. Soucek, K. Tuma
Summary: In this paper, the phenomenon of particle rebound in a viscous incompressible fluid environment is investigated. The focus is on the important case of no-slip boundary conditions, and conditions are provided to prove that rebound is possible even without topological contact. Numerical simulations are compared with solutions obtained from established partial differential equations to support the conjecture that a qualitative change in the shape of the solid is necessary for a physically meaningful rebound in fluids.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
A. J. Hutchinson, R. J. Gusinow, M. Grae Worster
Summary: We study a viscous gravity current confined to the space between two parallel plates. The flow is divided into an inner region in contact with both plates and an outer annular region along the lower plate. A theoretical model based on a dimensionless parameter is proposed to describe the flow dynamics. Experimental results match the major aspects of the model, but other physics are clearly involved, indicating that a single non-dimensional parameter is not sufficient to fully capture the flow behavior.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Xingyi Shi, Gerald G. Fuller, Eric S. G. Shaqfeh
Summary: This study examines the asymmetric flows of aqueous surfactant films over an air bubble. The distribution of surfactants and surface tension gradients generated by the squeezing motion result in axisymmetric Marangoni flow. The external force of raising the bubble creates an axisymmetric dimpled film. When the bubble stops rising, the flow demonstrates symmetry breaking. Linear stability analysis reveals the mechanism behind the disturbance growth.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Ehud Yariv
Summary: This study investigates the slipperiness of compound surfaces composed of solid patches and free surfaces. The slip length is quantified and found to diverge in the limit of small solid fractions.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Edward M. Hinton, Duncan R. Hewitt, Andrew J. Hogg
Summary: This study theoretically investigates the interaction between steady free-surface flows of viscoplastic material and a surface-piercing obstruction of square cross-section on an inclined plane. The flow thickness increases upstream of the obstruction and decreases in its lee. The flow behavior depends on two dimensionless parameters: an aspect ratio and a Bingham number, which quantify the flow thickness, obstruction width, plane inclination, and the yield stress. The results show that the flow forms static 'dead' zones near the upstream and downstream stagnation points, and the properties of the flow are influenced by the width and shape of the obstruction as well as the magnitude of the yield stress.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Peter F. Pelz, Tobias Corneli, Seyedmajid Mehrnia, Maximilian M. G. Kuhr
Summary: This paper discusses the measurement, interpretation, and technical impact of temperature-dependent wall slip and its activation energy for polar and non-polar hydrocarbon Newtonian fluids moving relative to machined metal surfaces. A newly developed apparatus called the slip length tribometer (SLT) is used to measure the slip length at different temperatures over a sufficiently large wetted area, providing experimental data that shows the independence of bulk viscosity and slip length to shear rate. The paper also explores the differences in activation energies for wall slip and bulk shear, as well as the impact of wall slip on Sommerfeld's similarity theory and the resulting Stribeck curve, using a generalized Eyring model and solving Reynolds' equation generalized for wall slip.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Martin H. Essink, Anupam Pandey, Stefan Karpitschka, Cornelis H. Venner, Jacco H. Snoeijer
Summary: Elastohydrodynamic lubrication, also known as soft lubrication, is a key physical mechanism to minimize friction and wear, where the thickness of the lubricant layer is related to parameters like entrainment velocity and mechanical loading. This work provides an overview of soft lubrication mechanisms for two-dimensional cylinders in contact with compliant walls, focusing on thin elastic coatings and establishing missing scaling laws through analysis of elastohydrodynamic boundary layers.
JOURNAL OF FLUID MECHANICS
(2021)
Review
Chemistry, Physical
Ivan U. Vakarelski, Fan Yang, Sigurdur T. Thoroddsen
Summary: The outcome of bubble collision is determined by hydrodynamic interaction forces, influenced by the tangential mobility of gas-liquid interfaces. Bubbles with mobile surfaces coalesce easier due to lower hydrodynamic resistance, resulting in stronger rebound from a mobile liquid interface with lower viscous dissipation.
CURRENT OPINION IN COLLOID & INTERFACE SCIENCE
(2022)
Article
Energy & Fuels
Yuan Si Tian, Zi Qiang Yang, Sigurbur T. Thoroddsen, Ehab Elsaadawy
Summary: The separation of water droplets from water-in-crude-oil emulsions is crucial in the petroleum industry. A new experimental method involving optical-access flow, Near-Infrared laser illumination, and high-speed video imaging can help select the optimal demulsifier concentration by quantifying coalescence probability.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Ivan U. Vakarelski, Kenneth R. Langley, Fan Yang, Sigurdur T. Thoroddsen
Summary: This study examines the accuracy of numerical simulations in predicting the dynamics of thin liquid film drainage during the collision of bubbles or droplets. Experimental investigations of millimetric bubbles colliding with a flat glass interface in pure water were compared with numerical simulations using the open source Gerris flow solver. The simulation results showed excellent agreement with experimental observations in terms of the bounce trajectory and thin liquid film profile. The study highlights the potential of numerical simulations in resolving the complex processes of high velocity bubble and droplet collisions.
Article
Chemistry, Multidisciplinary
Adair Gallo, Nayara H. Musskopf, Xinlei Liu, Ziqiang Yang, Jeferson Petry, Peng Zhang, Sigurdur Thoroddsen, Hong Im, Himanshu Mishra
Summary: Recent research on the formation of hydrogen peroxide (H2O2) in water microdroplets has attracted significant attention. The presence of ozone (O-3) in the air has been found to have the most significant impact on H2O2 formation in these water microdroplets. Increased gas-liquid surface area facilitates the conversion of O-3 into H2O2.
Article
Engineering, Chemical
Yuan Si Tian, Er Qiang Li, Ehab Elsaadawy, Jia Ming Zhang, Ivan U. Vakarelski, Sigurdur T. Thoroddsen
Summary: In this study, microfluidic techniques were used to investigate the coalescence dynamics of water-in-oil emulsions in a simple shear flow. Experimental results showed a strong correlation between the coalescence time and the droplet approach velocity, effective diameter, offset, and continuous-phase viscosity. A scaling law for the dimensionless time needed for coalescence was also revealed.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Nanoscience & Nanotechnology
Yi Lu, Shibin Krishna, Che-Hao Liao, Ziqiang Yang, Mritunjay Kumar, Zhiyuan Liu, Xiao Tang, Na Xiao, Mohamed Ben Hassine, Sigurdur T. Thoroddsen, Xiaohang Li
Summary: This article introduces a method for transferring Ga2O3 thin film to arbitrary flexible and adhesive tape, enabling vertical and flexible configurations of electronic devices. Vertical photodetectors fabricated using this method demonstrate good optoelectronic performance.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Ivan U. Vakarelski, Farrukh Kamoliddinov, Sigurdur T. Thoroddsen
Summary: This study investigates the interaction between millimeter-sized bubbles and the seawater-air interface in seawater samples collected from the Red Sea coastal area. It demonstrates that high concentrations of electrolytes and organics in seawater do not affect the mobility of the bubble interfaces during free-rise and bouncing.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2022)
Article
Materials Science, Multidisciplinary
M. Jimenez-Valdez, E. Tomay, J. O. Marston, F. Pacheco-Vazquez
Summary: This study investigated the formation of doublet craters, which are created by binary projectiles impacting simultaneously at low speed on a sand bed. The morphology of the craters varied depending on the initial separation between the projectiles, including two well-defined craters, overlapping craters, or a single larger circular crater when the separation was negligible. The delay between impacts caused asymmetry in the ridge and ejecta curtains, with the delayed projectile penetrating deeper due to bed fluidization and material displacement from the first impact.
Article
Mechanics
Yuan Si Tian, Zi Qiang Yang, Sigurdur T. Thoroddsen
Summary: Fast microjets can be produced when drop-impact craters rebound or when a bubble bursts, and they play a crucial role in climate and olfactory senses as a source of aerosols. The most unique and fastest jets are generated when a small dimple forms at the crater bottom and rebounds without pinching off a small bubble. High-resolution numerical simulations reveal a new focusing mechanism that explains the extreme sensitivity to initial conditions observed in experiments of this phenomenon.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Materials Science, Multidisciplinary
Esraa Fakeih, Andres A. Aguirre-Pablo, Sigurdur T. Thoroddsen, Khaled N. Salama
Summary: This study investigates the design and fabrication of porous microneedles (MNs) and finds that injection through porous MNs results in a broader diffusion spread compared to hollow MNs. Three different designs of porous MNs with a constant pore size and controlled pore locations are fabricated using two-photon polymerization (2PP), and factors such as diffusion spread, mixing capabilities, and mechanical resilience are examined. The results show that porous MNs can cover 16 times the injection area of hollow MNs and demonstrate good mixing capabilities and mechanical strength.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Mechanics
Farrukh Kamoliddinov, Ivan U. Vakarelski, Sigurdur T. Thoroddsen, Tadd T. Truscott
Summary: In this experimental study, we investigated the hydrodynamics of a buoyant sphere accelerated along an air-water interface. The sphere displayed different behaviors depending on its speed, from floating on the surface to oscillating underwater and generating air cavities. These underwater air cavities were attached to the sphere surface near the laminar flow separation point. By changing the pulling angle and counterweight-induced velocity, we explored the effects on the hydrodynamics. Additionally, we analyzed the complex fluid-solid interactions and the influence of the air cavity on drag and lift coefficients and overall sphere hydrodynamics, particularly above the critical Froude number of 1.2.
Article
Physics, Fluids & Plasmas
Ahmed Al Brahim, Sigurdur T. Thoroddsen
Summary: This study focuses on the dynamical rearrangement of a multilayer fluid in a Hele-Shaw cell, and observes various dynamics of stirring and breakthrough. The study reveals that air can break through a high viscosity layer and erupt as a hemisphere into a lower-viscosity layer, accompanied by high-speed airflow. Using high-speed video, the details of the eruptions and the key roles of wetting, contact lines, and three-dimensionality are characterized. Additionally, the study finds counterflows in the center-of-mass trajectories and the interchangeability of top and bottom layers through intermediate layers.