Article
Mechanics
Manas Ranjan Behera, Anirvan Dasgupta, Sudipto Chakraborty
Summary: The evolution of a vortex ring generated by drop impinging on a liquid pool was studied experimentally, numerically, and analytically. A novel analytical model for a finite vortex core was developed and validated with experimental results. The controlling parameters governing the viscous diffusion-driven evolution of the vortex ring were uncovered. The study provided valuable insights into the formation and viscous diffusion process of the vortex ring through a combination of experimental, numerical, and analytical approaches.
Article
Mechanics
Ming Long, Jalil Hasanyan, Sunghwan Jung
Summary: This study examines the spreading dynamics of raindrops on curved surfaces, finding that drops on curved surfaces spread farther than on flat surfaces. A new analytical model is developed based on volume conservation and temporal energy balance, showing good agreement with experimental results.
Article
Thermodynamics
Changjian Wang, Xu Zhang, Yubiao Huang, Jia Xie, Mingjun Xu, Jiaqing Zhang
Summary: The impact of a water droplet on stratified oil-water and the subsequent flame expansion was observed using a high-speed digital camera. The flame expansion scales were calculated and analyzed under various conditions, considering the water droplet diameter and impact height. The findings indicate that the flame expansion in burning oil pools is primarily due to steam explosion, while impact on stratified oil-water leads to the expansion of flame through the increased contact area between fuel and air. The duration, height, and volume of flame expansion increase with water droplet diameter and impact height, while the frequency of flame pulsation decreases with increased impact height. The flame volume expansion is significantly different between burning diesel oil pools and burning diesel layers on water surface.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Chemistry, Physical
Yi-Bo Wang, Yi-Feng Wang, Yan-Ru Yang, Xiao-Dong Wang, Min Chen
Summary: The study investigates the kinematic time and maximum spreading time for the impact of nanodroplets of different types of fluids on solid surfaces with different wettability. It demonstrates that the capillary regime persists for nanodroplet impact, even at the nanoscale, and proposes a universal scaling law that agrees well with molecular dynamics simulations for various liquids and surface wettability.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Engineering, Mechanical
Qiang Wei, Zifeng Li
Summary: This study investigates the dynamic bifurcation of a column when it impacts a rigid plane vertically, which is different from the classical Eulerian static buckling. The findings show that either the dimensionless critical buckling time or the dimensionless critical buckling velocity can be used to determine whether buckling has occurred. Different dimensionless initial defects in the column result in different dimensionless displacement responses, and the nonlinear effect influences the analysis results.
INTERNATIONAL JOURNAL OF IMPACT ENGINEERING
(2024)
Article
Mechanics
Jie Yao, Weiyu Shen, Yue Yang, Fazle Hussain
Summary: The dynamics of two slender Hopf-linked vortex rings were studied at different vortex Reynolds numbers, revealing that at high Re, the vortex rings reconnected to form smaller rings that then broke up into turbulent clouds. The global helicity H was not conserved at very high Re, with twist playing a significant role in helicity dynamics at high Re.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Materials Science, Multidisciplinary
Meng Yan, Tao Li, Peiru Zheng, Fan Chen, Yanyan Jiang, Hui Li
Summary: The impact behavior of a droplet falling into its bulk liquid surface is determined by the impact velocity, leading to various coalescence behaviors such as rebound, calm coalescence, deformation, and coating. Molecular dynamics simulations have shown that a cavity can form in the liquid bulk at high impact velocities due to momentum transfer. As the Weber number increases, the degree of mixing also increases, with a critical Weber number separating rebound and coalescence behaviors. The study provides insights into how temperature and impact velocity influence droplet coalescence behavior.
RESULTS IN PHYSICS
(2021)
Article
Mechanics
Changhun Park, Jeong-Hyun Kim
Summary: This study investigates the bouncing dynamics of glycerol/water droplets impacting a grooved hydrophobic surface by changing the viscosity and impact speed of the droplets. It found that as the viscosity of the droplets increased, the Weber number range in which petal bouncing occurred decreased.
Article
Mechanics
Zhiheng Fan, Daoyin Liu, Suyang Pan, Jiliang Ma, Xiaoping Chen
Summary: In this study, collision experimentation was used to investigate the spatial and temporal variation of droplets on a target particle surface. Image processing was employed to capture the microscopic and evolutionary features of droplets. Theoretical analysis revealed the relationship between the dimensionless liquid film thickness and spreading area, and the influence of Weber and Reynolds numbers on the dynamic contact angle was also examined.
Article
Thermodynamics
Henrik Sontheimer, Alireza Gholijani, Peter Stephan, Tatiana Gambaryan-Roisman
Summary: This study investigates the hydrodynamics and heat transport during the vertical coalescence of multiple drops impacting successively onto a hot wall using numerical simulations and experiments. The numerical model considers evaporation and uses the volume of fluid method within the OpenFOAM library. Experimental data is compared with numerical results for low impact frequency case, and the appearance of high heat flux rings during the impingement of the second drop is analyzed. The impact of a drop chain consisting of five drops at a high frequency is also studied numerically.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Mechanics
Santosh Kumar Panda, Basanta Kumar Rana
Summary: This article thoroughly elucidates the evolution of an entrained gaseous cusp in a viscous liquid pool caused by a fully immersed horizontal revolving circular drum. The numerical simulations using the finite volume-based open source Gerris provide comprehensive characterization of the cusp's length and width by varying the rotational flux strength and depth of immersion. The locus and travel rate of the cusp tip are also explored as functions of time, rotational flux strength, and depth of immersion. The bubble ejection mechanism from the cusp's advancing end is reported, showing a strong dependency on rotational flux strength and depth of immersion. The effects of gravitational pull and viscous drag on the entrainment patterns are investigated, and correlations are developed to estimate the cusp width and steady length. The proposed analytical model shows satisfactory agreement with the computational results.
Article
Mechanics
Xianheng Guan, Anantha P. Sarma, Eashwaren Kakarla Hamesh, Junyu Yang, Nhung Nguyen, Enrique Cerda, Luka Pocivavsek, Sachin S. Velankar
Summary: In this study, we investigated the buckling behavior of a thin elastic film bonded to a viscous substrate under compression at a fixed rate. Experimental results revealed two distinct buckling modes, sinusoidal wrinkles under high compression rate or large liquid thickness, and localized tall ridges under low compression rate or small liquid thickness. We also summarized the relationships between wrinkle amplitude, interridge distance, compression rate, and liquid thickness. Additionally, we found that wrinkles formed during compression can transform into ridges under quiescent conditions.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2022)
Article
Physics, Fluids & Plasmas
Yi-Bo Wang, Yi-Feng Wang, Xin Wang, Ben-Xi Zhang, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang, Min Chen
Summary: This study uses molecular dynamics simulations to investigate the splash of water nanodroplets on surfaces with different wettability, finding significant influence of surface wettability on the internal breakup of nanodroplets, which differs from the mechanism of macroscopic droplets splash.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Martin Woerner
Summary: This study focuses on the maximum diameter of a drop impacting on a flat solid surface, assuming axisymmetric spreading without splashing. Two novel concepts are introduced to close the energy balance between the initial state of the drop and its maximum spread. An approximate spherical cap model is proposed for the gas-liquid surface area, and viscosity-induced energy loss is related to the total energy dissipation when the drop comes to rest. The fractional dissipation during maximum spread is modeled as a function of an impact parameter (P) that combines the power laws of capillary and viscous regimes.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Engineering, Chemical
Manas Ranjan Behera, Anirvan Dasgupta, Sudipto Chakraborty
Summary: The coalescence dynamics of a liquid drop on a liquid pool, considering air or another liquid as the surrounding fluid, are investigated. The study reveals the existence of partial coalescence and complete coalescence regimes, which can be further divided into different sub-regimes. Quantitative analysis of the coalescence dynamics is conducted, providing insights into various parameters of the process.
CHEMICAL ENGINEERING SCIENCE
(2022)
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
Farrukh Kamoliddinov, Ivan U. Vakarelski, Sigurdur T. Thoroddsen
Summary: Through varying the pulling force, we investigate the hydrodynamic regimes of a floating sphere on a water surface, observing transitions from low to high Froude number regimes as the force increases.
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
Mechanics
Han Li, Han Chen, Er-Qiang Li, Chun-Yu Zhang, Hang Ding
Summary: The impact of a millimetric superhydrophobic sphere on a water pool covered by a thin oil layer is experimentally investigated. The interfacial tension and viscosity of the oil layer are found to significantly affect the fate of the impacting spheres, determining whether they sink or float.
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
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
Chemistry, Physical
Zi Qiang Yang, Peng Zhang, Meng Shi, Ali Al Julaih, Himanshu Mishra, Enzo Di Fabrizio, Sigurdur T. Thoroddsen
Summary: Polymer filaments have important applications in biology, tissue engineering, and molecular machines. Researchers have developed a simple method to deposit stretched polymer fibers between micro-pillars, allowing for characterization of filament-forming configurations and their properties.
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.