Article
Mechanics
C. R. Constante-Amores, J. Chergui, S. Shin, D. Juric, J. R. Castrejon-Pita, A. A. Castrejon-Pita
Summary: In this study, the effect of insoluble surfactants on the retracting dynamics of thin water sheets is investigated using an interface-tracking/level-set method. It is found that the surfactant concentration can delay or prevent the breakup of the sheet edge, revealing the significant role of Marangoni stresses in the retracting dynamics.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Huadan Xu, Xinjin Ge, Tianyou Wang, Zhizhao Che
Summary: In this study, the coalescence of two immiscible droplets on a partial wetting surface is explored experimentally and theoretically. The coalescence process is divided into three stages and the impact of immiscible interface on the process is investigated. The study provides insights into the time scales and force interactions involved in the coalescence of immiscible droplets.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Kuan-Ling Huang, Kuo-Long Pan
Summary: The transition between coalescence and bouncing in droplet impacts is influenced by complex interactions of multiple mechanisms, with controlling parameters such as droplet diameter, fluid viscosities, and surface tension. Observations in experiments show different behaviors of various fluids under atmospheric conditions, highlighting the impact of droplet diameter on the occurrence of coalescence and bouncing.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Edward Beaty, John R. Lister
Summary: When two small fluid drops are close enough, the van der Waals force overcomes surface tension and initiates coalescence. The dynamics can be divided into two regimes: Stokes and inertial-viscous, characterized by the forces that balance the van der Waals attraction. The subsequent dynamics in the inertial-viscous regime is self-similar as contact is approached, with the gap width and deformed region decreasing with time.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Lukas Weimar, Luyang Hu, Tobias Baier, Steffen Hardt
Summary: This study investigates the impact of drops on a porous surface with high contact-angle hysteresis and gas discharge. Four different impact modes of the drops on the surface, ranging from complete repulsion to fast immobilization, are identified and mapped based on the pressure difference of the gas and the impact Weber number. The most notable aspect of the dynamics is the transformation of a drop into a bubble, which occurs when the drop overcomes the repulsion by the gas flow and wets the surface. The transition to the regime where a drop is transformed into a bubble is well described by a simple scaling relationship based on the balance between inertia and the repulsive force due to the gas flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Ryan McGuan, R. Candler, H. P. Kavehpour
Summary: This paper investigates the phenomenon of partial coalescence in a viscous quiescent medium using a liquid metal alloy. The study observes the bouncing of coalescing droplets on the interface and develops models to predict droplet velocity, position, and maximum bounce height.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Someshwar Sanjay Ade, Pavan Kumar Kirar, Lakshmana Dora Chandrala, Kirti Chandra Sahu
Summary: We investigated the morphology and size distribution of satellite droplets resulting from the interaction of a water droplet with a swirling airstream. We found that the droplet exhibited different phenomena depending on the strength of the swirl. In the high-swirl scenario, disintegrations of the nodes, rim, and bag-film contributed to smaller satellite droplets, while in the low-swirl case, the breakup of the rim and nodes resulted in larger droplets. Our results also showed that the volume-weighted droplet size distribution had two peaks for low swirl strength and three peaks for high swirl strength.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
C. R. Constante-Amores, A. Batchvarov, L. Kahouadji, S. Shin, J. Chergui, D. Juric, O. K. Matar
Summary: This study investigates the impact of surfactants on drop-interface coalescence dynamics through full three-dimensional direct numerical simulations, highlighting the crucial role of Marangoni stresses in the flow physics of coalescence. Surfactant-laden cases were found to stiffen the interface compared to surfactant-free cases, providing insight into the observed surfactant-induced phenomena.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Dege Li, Haoren Li, Guodong Yang, Yi Cao, Bingfang Huang, Xinlei Wu, Qiang Sun, Chi Ma, Yu Zhou, Yonghong Liu, Yanzhen Zhang
Summary: This study proposes a confined interface vibration inkjet printing technique that allows for printing patterns in a liquid environment with smaller droplet sizes. By adjusting the intensity of the pulse stimulation, the size and quantity of the dispensed droplets can be controlled, enriching the fundamental theory of inkjet printing in liquid phase.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Zhikun Xu, Tianyou Wang, Zhizhao Che
Summary: This study experimentally investigated the breakup process of particle-laden droplets in airflow. The results showed that particles have a heterogeneous effect on the breakup process, accelerating the fragmentation of the liquid film and promoting localized rapid piercing. A correlation length was proposed to characterize the concentration fluctuation scale during the breakup process, and the scaling results agreed well with experimental data.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
K. Ashoke Raman, Juan Manuel Rossello, Hendrik Reese, Claus-Dieter Ohl
Summary: This study investigates the interaction between a laser-induced cavitation bubble and a submillimetre-sized water droplet submerged in silicone oil. It is found that the droplet elongates towards the collapsing bubble during the bubble collapse, and the viscosity of the silicone oil affects the way the droplet interacts with the bubble. This research is important for understanding the interaction process between bubbles and droplets.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Subhankar Roy, Vikky Anand, Rochish M. Thaokar
Summary: An intriguing observation of a very low critical electric field in electrocoalescence of water-in-oil emulsions challenges the existing experimental and theoretical predictions. A numerical, analytical and experimental study on the interaction between multiple unequal-sized droplets in an electric field reveals that the critical capillary number is reduced as the radius ratio of the smaller droplet to the bigger droplet decreases. The nonlinearity in the system and the electrostatic interaction between the droplets play important roles in determining the onset of non-coalescence.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Ye Tian, Hong Wang, Xin Zhou, Zhenting Xie, Xun Zhu, Rong Chen, Yudong Ding, Qiang Liao
Summary: The impinging dynamic of a droplet on a superhydrophobic substrate in an electric field is investigated through visualization experiments and numerical simulations. Four ejection modes and three rebound modes are experimentally observed, and the filamentous ejecting phenomenon is discovered for the first time. The numerical simulation reveals the strong coupling between the distribution of electric charge and the evolution of droplet profile, and proposes a charge scaling law for ejection droplets. The results provide important characteristics for droplet manipulation and electrostatic spraying, and have implications for the design and operation of droplet equipment.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Cosan Daskiran, Fangda Cui, Michel C. Boufadel, Ruixue Liu, Lin Zhao, Tamay Ozgokmen, Scott Socolofsky, Kenneth Lee
Summary: Understanding the size of oil droplets released from a jet in crossflow is crucial for estimating the trajectory of hydrocarbons and the rates of oil biodegradation/dissolution in the water column. Experimental results and simulations show that the size of oil droplets increases with elevation across the plume, likely due to the individual rise velocity of droplets. The simulation effectively captures the top and bottom boundaries of the plume, with smaller droplets observed at the center axis compared to the side boundaries due to the formation of counter-rotating vortex pair.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Alberto Vela-Martin, Marc Avila
Summary: The research shows that drop deformation in fluid flows is controlled by the exchange between kinetic energy and surface energy, with stretching or compression of the drop surface being the key factor. A new decomposition method isolates the local effects of drop-induced surface energy exchange from non-local turbulent fluctuations. It is found that a significant contribution to surface energy increments in drop breakup arises from non-local stretching of the fluid-fluid interface by eddies far from the drop surface.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
Molly S. C. Gravett, Ryan C. Cocking, Alistair P. Curd, Oliver Harlen, Joanna Leng, Stephen P. Muench, Michelle Peckham, Daniel J. Read, Jarvellis F. Rogers, Robert C. Welch, Sarah A. Harris
Summary: Rapid advances in experimental biophysical techniques are generating a wealth of information about cellular cytoskeleton and its motors, but the need for new computational tools to integrate these data is essential. This article discusses the experimental advances and computational tools, proposing how to successfully combine emerging experimental data on cytoskeletal motors.
WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE
(2022)
Article
Chemistry, Applied
Daniel Francis, A. John Blacker, Nikil Kapur, Stephen P. Marsden
Summary: The new modular photochemical continuous stirred-tank reactor (CSTR) design utilizes light-source units developed for the fReactor CSTR platform, making it suitable for both homogeneous and multiphasic reactions. By using slurries as input feeds, the system intensifies photochemical brominations, and its modular nature facilitates the integration of downstream reaction steps.
ORGANIC PROCESS RESEARCH & DEVELOPMENT
(2022)
Article
Chemistry, Multidisciplinary
Hamish R. Stephen, Sarah Boyall, Christiane Schotten, Richard A. Bourne, Nikil Kapur, Charlotte E. Willans
Summary: Due to the heterogeneous nature of electrochemical reactions, mass transport plays a crucial role in reaction and reactor development. Experimental studies and computational fluid dynamics have been used to investigate the impact of different flow channel geometries on mass transfer in a continuous electrochemical reactor. The results show that the channel shape has a modest effect on the mass transfer coefficient, while the polarity switching of the reaction solution during flow has the greatest impact.
REACTION CHEMISTRY & ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Shuheng Zhang, Ouassef Nahi, Li Chen, Zabeada Aslam, Nikil Kapur, Yi-Yeoun Kim, Fiona C. Meldrum
Summary: Remarkable control can be achieved over the chemical composition and structure of crystalline calcium carbonate by driving a pseudomorphic transformation of amorphous calcium carbonate thin films using heat. This has relevance to both synthetic and biological systems.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Engineering, Biomedical
Foteini Zagklavara, Peter K. Jimack, Nikil Kapur, Osvaldo M. Querin, Harvey M. Thompson
Summary: A surrogate-enabled multi-objective optimization methodology is proposed for continuous flow Polymerase Chain Reaction (CFPCR) systems, allowing the exploration of the effect of PCR protocol and channel width on practical objectives. Accurate surrogate models of DNA amplification efficiency, total residence time, total substrate volume, and pressure drop are created using high fidelity conjugate heat transfer simulations and Machine Learning. Single objective optimizations demonstrate improvements in DNA concentration, pressure drop, residence time, and substrate volume, while multi-objective optimizations provide a Pareto surface that shows how cost reductions and DNA amplification efficiency can be achieved simultaneously.
BIOMEDICAL MICRODEVICES
(2022)
Article
Chemistry, Multidisciplinary
Shuheng Zhang, Ouassef Nahi, Xuefeng He, Li Chen, Zabeada Aslam, Nikil Kapur, Yi-Yeoun Kim, Fiona C. Meldrum
Summary: The use of amorphous calcium carbonate allows organisms to have excellent control over the formation of calcite and aragonite biominerals. Researchers have demonstrated a straightforward method for controlling the crystallization of amorphous calcium carbonate thin films, allowing the generation of sub-millimeter calcite single crystals and the creation of various crystal morphologies by independently controlling nucleation and growth.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Engineering, Chemical
Stefanos Michaelides, Kotaybah W. Hashlamoun, Thibaut Charpentier, Gregory de Boer, Paul Hunt, Helen Sarginson, Claire Ward, Nashaat N. Nassar, Mark C. T. Wilson, David Harbottle
Summary: This study investigated the drag reduction effect of polymers on fluids using a rotational rheometer. The results showed that the polymer charge and concentration have significant impacts on the rheology and drag reduction performance of the fluids. Both polymers induced drag reduction, but SPAM had a better drag reduction effect than PAM. For PAM, the drag reduction effect decreased with time and was sensitive to high flow conditions. In contrast, the drag reduction effect of SPAM was relatively stable and independent of flow conditions and polymer concentration.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Chemistry, Multidisciplinary
Adam D. Clayton, Edward O. Pyzer-Knapp, Mark Purdie, Martin F. Jones, Alexandre Barthelme, John Pavey, Nikil Kapur, Thomas W. Chamberlain, A. John Blacker, Richard A. Bourne
Summary: The optimization of multistep chemical syntheses is crucial for rapid development of new pharmaceuticals. A continuous flow platform was developed to automate the optimization of telescoped reactions. By integrating Bayesian optimization techniques, an 81% overall yield was achieved in just 14 hours, and a favorable competing pathway for the desired product was identified.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Jiatong Jiang, Frankie Jackson, Suparit Tangparitkul, Mark C. T. Wilson, David Harbottle
Summary: The study investigates the irregular and discontinuous dewetting of a substrate caused by localized heterogeneity during the recession of a droplet. The experiments utilize the sessile drop method and Lattice Boltzmann method simulation to examine the effect of surface treatments and boundary conditions on droplet dynamics. The findings demonstrate that surface modifications lead to distorted and non-uniform droplet recession.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Peter M. Pittaway, Ghadir Ghasemi, Stephen T. Knox, Olivier J. Cayre, Nikil Kapur, Nicholas J. Warren
Summary: Miniaturised continuous-flow reactors provide a safe and cost-effective method for the synthesis of high-value chemical products. In this study, a miniature continuous stirred-tank reactor (CSTR) cascade was used for continuous-flow RAFT polymerisation, which showed high performance and close resemblance to the theoretical CSTR cascade. The reactor's performance was evaluated for different polymerisation processes, and it was found that the residence time distribution (RTD) plays a crucial role in determining the properties of the resulting polymers.
REACTION CHEMISTRY & ENGINEERING
(2023)
Article
Chemistry, Applied
James Daglish, A. John Blacker, Gregory de Boer, Alex Crampton, David R. J. Hose, Anna R. Parsons, Nikil Kapur
Summary: The problems of extracting products efficiently from reaction workups, such as emulsions and rag layer formation, can cause manufacturing inefficiencies. An image processing methodology has been developed to automatically track the interface between liquid-liquid phases and measure the separation rate quantitatively. The algorithm has been successfully applied to 29 cases and demonstrated its robustness in different liquid mixtures.
ORGANIC PROCESS RESEARCH & DEVELOPMENT
(2023)
Article
Chemistry, Multidisciplinary
Katarzyna A. Maltby, Krishna Sharma, Marc A. S. Short, Sannia Farooque, Rosalie Hamill, A. John Blacker, Nikil Kapur, Charlotte E. Willans, Bao N. Nguyen
Summary: A theoretical framework has been established to predict, rationalize, and adapt water-accelerated reactions into sustainable flow processes. The study reveals the complex and varied nature of these reactions and their potential impact on the sustainability of chemical manufacturing processes. By calculating the rate acceleration of known water-accelerated reactions, computational estimations are provided, which correlate with experimental data. Furthermore, through in-depth study and analysis, a multiphase flow process with superior green metrics has been developed.
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
(2023)
Article
Biotechnology & Applied Microbiology
William A. Davis A. Birch, Ines B. Moura, Duncan J. Ewin, Mark H. Wilcox, Anthony M. Buckley, Peter R. Culmer, Nikil Kapur
Summary: This paper presents a scalable Mini Gut (MiGut) platform that closely mimics the physiology of the colon, while maintaining in vivo reflectiveness. MiGut has shown excellent repeatability and consistency in a demanding 9-week study, and it has the capability to run multiple models simultaneously for more detailed exploration of microbiome-xenobiotic interactions.
MICROBIAL BIOTECHNOLOGY
(2023)
Article
Tropical Medicine
Anna Littlejohns, Helen Please, Racheal Musasizi, Stuart Murdoch, Gorret Nampiina, Ian Waters, William Davis Birch, Gregory de Boer, Nikil Kapur, Tumwesigye Ambrozi, Ninsiima Carol, Nakigudde Noel, Jiten Parmar, Peter Culmer, Tom Lawton, Edith Namulema
Summary: This article reviewed the use of the LeVe CPAP system for respiratory support in COVID-19 patients at Mengo Hospital in Uganda. The study found that the LeVe CPAP system was the most commonly used CPAP device at the hospital during the pandemic, providing critical respiratory support to patients when no alternative devices were available.
TROPICAL MEDICINE AND HEALTH
(2023)
Article
Chemistry, Multidisciplinary
Johanna M. Galloway, Zabeada P. Aslam, Stephen R. Yeandel, Alexander Kulak, Martha A. Ilett, Yi-Yeoun Kim, Angela Bejarano-Villafuerte, Boaz Pokroy, Rik M. Drummond-Brydson, Colin L. Freeman, John H. Harding, Nikil Kapur, Fiona C. Meldrum
Summary: The cylindrical pores of track-etched membranes provide a suitable environment for studying confinement-induced effects on crystallization. By varying the pore diameter and utilizing anisotropic morphologies, crystal orientation can be directed. However, the inability to visualize individual crystals within the pores has limited the understanding of underlying mechanisms. In this study, we investigate the crystallization of calcium sulfate within track-etched membranes and discover that different forms of gypsum, bassanite, and anhydrite form in pores of different sizes. We coat the membranes with an amorphous titania layer to create electron transparent nanotubes, allowing visualization of evolutionary pathways of crystals within the pores, revealing multiple nucleation events and early determination of orientation. The transformation of bassanite to gypsum within the pores is also studied using experiments and calculations, providing important insights into confinement effects on crystallization relevant to natural mineral formation.