Article
Mechanics
P. Garcia-Geijo, E. S. Quintero, G. Riboux, J. M. Gordillo
Summary: Experimental results of water and ethanol drops impacting on different types of sandpapers with embedded particles show that the transition from spreading to splashing can be classified based on the Weber number and the liquid wetting behavior. The critical Weber number for splashing can be predicted using specific parameters, and the splash velocity can be determined for both wetting and non-wetting cases.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Polymer Science
Yuejie Jin, Dingrong Liu, Jinhua Hu
Summary: The study investigated the influence of the hydrophobic chain structures of surfactants on the interfacial film properties and emulsion stability using PGPR and polyglycerol-2 dioleate as model surfactants in constructing water-in-oil emulsions. The results showed that PGPR with a branched chain structure formed interfacial film with higher viscoelastic modulus, leading to good emulsion stability, while polyglycerol-2 dioleate with a straight chain structure had lower viscoelastic modulus and resulted in unstable emulsions.
Article
Mechanics
Yufei Ma, Haibo Huang
Summary: We numerically study the impact of a droplet on superhydrophobic flexible plates and find that the flexible substrate affects the maximum spreading of the droplet. The vertical movement and the change in average acceleration of the flexible substrate due to droplet impact lead to a reduction in the maximum spreading. Through theoretical analysis, we propose a scaling for the droplet's maximum spreading diameter ratio based on an effective Weber number that accounts for the substrate properties.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Mahdi Nasiri, Ghobad Amini, Christian Moreau, Ali Dolatabadi
Summary: In this study, the spreading process of a hollow droplet impacting a rigid surface is investigated through experimental, numerical, and theoretical methods. Numerical simulations successfully predict the shape evolution of the hollow droplet, which is validated by experimental photographs. The results demonstrate that the spreading diameter and height of the hollow droplet increase with impact velocity. Additionally, an optimal bubble size is identified to facilitate the flattening process, and it is found that the ripples on the splats produced by larger bubbles are higher. A theoretical model is developed, which accurately predicts the maximum spreading diameter and agrees well with experimental and numerical results.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Chemistry, Physical
Santhosh Kumar Pandian, Matheu Broom, Miguel Balzan, Geoff R. Willmott
Summary: This study investigates the effects of rheology and surface microstructure on drop impact processes. Experiments were conducted using water, glycerol, and shear-thinning carbopol solutions on microstructured surfaces. The findings show that the presence of micropillars reduces the extent of spreading, and the retraction rate decreases with effective viscosity. The onset of asymmetric spreading is weakly dependent on viscosity, and the number of fingers protruding from the spreading rim is influenced by several factors including the Weber number, effective viscosity, pillar height, and cross-section shape.
Article
Chemistry, Physical
Yuxuan Du, Ji Liu, Yanzhi Li, Jiayu Du, Xinxin Wu, Qi Min
Summary: This study investigates the dynamics of droplet impact on spherical surfaces at various Reynolds and Weber numbers using the phase-field method. It explores the temporal evolution of spreading factor and dimensionless center thickness, and concludes that different forces dominate in different regimes. The study also proposes prediction models for the exponents a, b, and c, which are strongly related to the diameter ratio of spheres and droplets.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2021)
Article
Mechanics
Tongwei Zhang, Jie Wu, Xingjian Lin
Summary: This study investigates the dynamic mechanisms and factors influencing the lateral motion of a solid when impacted by a water droplet on a movable hydrophobic substrate. The experimental results reveal the rules governing the solid's motion and demonstrate the possibility of achieving periodic reciprocating motion under suitable conditions.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Chemistry, Multidisciplinary
Fan Xiao, Kai Li, Wei Wang, Yuntong Ge, Zhipeng Yu, Zeheng Peng, Yingming Liu, Jing Gong
Summary: The stabilization mechanism of water-in-oil emulsions was studied using atomic force microscopy to measure the interactions between water droplets in n-tetradecane. The addition of oil-soluble surfactants (Span 20) was found to prevent water droplet coalescence by adsorbing onto the interface and forming a tight layer. The presence of water-soluble surfactants (SDS/CTAB/Tween 80) had varying effects on droplet stability, with Tween 80 destabilizing the droplets due to competitive adsorption with Span 20.
Article
Materials Science, Characterization & Testing
Younes El Omari, Mohamed Yousfi, Jannick Duchet-Rumeau, Abderrahim Maazouz
Summary: The development of a new high temperature resistant interfacial rheology setup has enabled direct measurement of polymer-polymer interface at temperatures up to 200 degrees C. This allows for exploration of surface/interfacial properties of model fluids with different structures and viscoelastic characteristics, as well as the testing of molten semicrystalline polymer systems for the first time. Additionally, a new lightweight titanium based biconical geometry was designed to enable more sensitive measurement of interfacial rheological properties.
Article
Forestry
Liang Wen, Xuan Wang, Qin Xu, Jiewei Tong, Wanwan Zhao, Yaoli Zhang, Jianxiong Lv, Liping Cai, Changlei Xia
Summary: The monthly variation of dynamic viscosity and interfacial tension of xylem sap in different tree species and their influencing factors were analyzed. The dynamic viscosity and interfacial tension of poplar and metasequoia samples changed in a similar manner each month, but the metasequoia samples had higher values than the poplar samples. The differences in organic components and inorganic cations concentration in their xylem sap due to disparate xylem structures resulted in the variation in dynamic viscosity and interfacial tension between poplar and metasequoia samples.
Article
Chemistry, Physical
Ahmed M. Othman, Andreas S. Poulos, Ophelie Torres, Alexander F. Routh
Summary: Droplets containing polyvinylpyrrolidone (PVP) dissolved in ethanol exhibit a distinctive scalloped pattern on high-energy surfaces, with surface tension gradient and substrate surface energy being the dominant factors influencing the instability. The scalloped instability can be suppressed by eliminating water and the Marangoni forces.
Article
Mechanics
Yi-Feng Wang, Yi-Bo Wang, Xin He, Ben-Xi Zhang, Yan-Ru Yang, Xiao-Dong Wang, Duu-Jong Lee
Summary: This study investigates the dynamics of low-viscosity nanodroplets impacting surfaces with static contact angles, and obtains the morphologies and dominant forces at different spreading states. Scaling laws of spreading time and contact time are proposed, and an impact number is introduced to determine the importance of viscous force.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Biophysics
Hashem Ahmadi Tighchi, Mohammad Hasan Kayhani, Ali Faezian, Samira Yeganehzad, Reinhard Miller
Summary: Licorice (Glycyrrhiza glabra) is a useful plant in the Fabaceae family with sweet-tasting roots. The root extract of licorice contains natural surfactants and shows promising potential in reducing surface tension and improving foam properties. This study investigates the surface tension, rheology, foamability, and foam stability of licorice root extract (LRE) and aims to contribute to the development of commercial applications involving foams.
COLLOIDS AND SURFACES B-BIOINTERFACES
(2023)
Article
Physics, Multidisciplinary
Jingcheng Ma, Ishrat Zarin, Nenad Miljkovic
Summary: Solid-liquid interfacial free energy (gamma SL) is difficult to measure, but this study presents a direct experimental measurement method for different solid materials. The results show that water-metal adhesion is 80% stronger than the cohesion energy of bulk water, which is consistent with previous quantum chemical calculations.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Lei Xing, Shuai Guan, Minghu Jiang, Longlong Shi
Summary: In this study, the directional transportation of droplets on a surface with controllable wettability was investigated numerically. The mechanisms of directional migration and morphological evolution of droplets impacting on the superhydrophobic-hydrophobic interface were revealed, and the effects of the impacting position on the migration velocity, rebound height, and transport distance of droplets were analyzed. Theoretical models were derived for predicting the transport distance and rebound height of droplets. The simulation results showed different stages in the process of droplet impacting on the superhydrophobic-hydrophobic interface compared to a normal surface. The study also found the existence of an optimal adhesion length for maximizing the transport distance of the droplet. The results contribute to the fundamental theory of droplet directional migration and have practical applications.
Article
Chemistry, Physical
Alexander Ashikhmin, Mikhail Andropov, Maxim Piskunov, Pavel Strizhak, Vyacheslav Yanovsky
Summary: This study investigated the thermal stability of fuel microemulsions based on diesel fuel and vegetable additive stabilized by surfactants. The introduction of the bioadditive was found to narrow the range of existence of the microemulsion. The temperature effect on the dynamic viscosity of the microemulsion systems was also analyzed.
JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Alexandra Semyonova, Nikita Khomutov, Sergey Misyura, Maxim Piskunov
Summary: This paper presents experimental results on the spreading, fingering, and corona-like splashing of water-in-oil emulsion droplets in collision with a solid surface. The effects of Weber numbers, wall temperatures, and the assumptions explaining the behavior of the maximum spreading diameter of emulsion droplets are examined. The results provide insights into predicting the behavior of the corona based on the relationship between the viscous dissipation of the spreading liquid and the energy transferred to the liquid from the wall.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Maxim Piskunov, Nikita Khomutov, Alexandra Semyonova, Alexander Ashikhmin, Sergey Misyura
Summary: This work proposes a mechanism that considers the vortex motion of a liquid inside an emulsion droplet during its collision with a wall. The motion of the liquid leads to increased dissipative energy losses, which affect spreading, corona splashing, and droplet relaxation. The study also found that the equilibrium shape of the droplet during liquid relaxation is influenced by the temperatures of the liquid and wall.
Article
Engineering, Aerospace
D. O. Glushkov, K. K. Paushkina, A. O. Pleshko, V. A. Yanovsky
Summary: A study was conducted on oil-filled cryogels with fine particles (Al, Cu, Fe, carbonaceous, inert) and without them to prepare elastically deformable gel fuel compositions. When exposed to radiant heating at an oxidizer temperature of 600-1000 degrees C, the fuel particles consistently ignited with dispersion that had a positive effect on the intensity of the fuel component burnout. Different fuel compositions exhibited varying ignition delay times, velocities, and average diameters of the burnout area. The gel fuel composition with fine carbonaceous particles ignited most rapidly, while the composition with Al particles had the highest ignition delay times and lowest velocities of fine fragments.
Article
Energy & Fuels
Elena Khan, Kadir Ozaltin, Damiano Spagnuolo, Andres Bernal-Ballen, Maxim V. Piskunov, Antonio Di Martino
Summary: In this study, biodiesel fuel was produced from rapeseed oil and sunflower oil using transesterification reaction. The impact of alcohol type, concentration, and reaction time on the yield and quality of biodiesel was evaluated. Results showed that the optimal conditions for rapeseed oil were a 15:1 molar ratio of alcohol to oil, a 60-minute reaction time, and a temperature of 50 degrees C. For sunflower oil, the best conditions were an 18:1 molar ratio, a 40-minute reaction time, and a temperature of 50 degrees C. Methanol provided the highest yields of biodiesel in both cases, and the obtained products met the required standards and showed similarity to mineral diesel.
Article
Thermodynamics
Alexander Ashikhmin, Alexandra Semyonova, Vladislav Fedorov, Sergey Misyura, Maxim Piskunov
Summary: The collision of fuel droplets with the walls of the combustion chamber plays a significant role in the formation of the air-fuel mixture. This study focuses on the hydrodynamic parameters of the drop-wall interaction in the nucleate boiling process of an n-decane-based water-in-oil emulsion, and their influence on heat transfer. Experimental measurements are used to derive empirical models for the contact time of droplets and the heat flux density at the solid-liquid interface during nucleate boiling. These models provide insights into the heat transfer characteristics during the formation of an air-fuel mixture in the combustion chamber of an engine.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Thermodynamics
Maxim Piskunov, Alexandra Semyonova, Alexander Ashikhmin, Vladislav Fedorov, Nikita Khomutov, Sergey Misyura
Summary: The experimental study investigates the unstable equilibrium of an emulsion drop's lamella and rim after colliding with a solid surface at high temperatures, taking into account the emulsion concentration and the presence of a stable boundary vapor layer. It reveals the relationship between the delay time of lamella destabilization and the characteristics of diffusive and convective heat transfer. The study also demonstrates the combined effect of Weber number and emulsion concentration on the critical Rayleigh and Marangoni numbers.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Energy & Fuels
Alexander Ashikhmin, Nikita Khomutov, Roman Volkov, Maxim Piskunov, Pavel Strizhak
Summary: The effect of coal hydrophilic particles in water-glycerol drops on the maximum spreading diameter along a hydrophobic solid surface was experimentally studied. The analysis of internal flow velocity by Particle Image Velocimetry (PIV) revealed the interrelated influence of Weber numbers and the concentration of coal particles on the maximum absolute velocity of internal flows. At We = 120, the spreading of particle-laden drops was mainly determined by the dynamics of the deformable Taylor rim. An increase in Weber numbers resulted in more noticeable differences in convection velocities in spreading drops. The presence of coal particles caused a general tendency to reduce drop spreading.