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1
Kan, Zhe, Qinghua Zhu, Haizhou Ren et Mengyan Shen. « Femtosecond Laser-Induced Thermal Transport in Silicon with Liquid Cooling Bath ». Materials 12, no 13 (26 juin 2019) : 2043. http://dx.doi.org/10.3390/ma12132043.
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Nanostructured regular patterns on silicon surface are made by using femtosecond laser irradiations. This is a novel method that can modify the surface morphology of any large material in an easy, fast, and low-cost way. We irradiate a solid surface with a 400-nm double frequency beam from an 800-nm femtosecond laser, while the solid surface is submerged in a liquid or exposed in air. From the study of multiple-pulses and single-pulse irradiations on silicon, we find the morphologies of nanospikes and capillary waves to follow the same distribution and periodicity. Thermal transport near the solid surface plays an important role in the formation of patterns; a simulation was done to fully understand the mechanism of the pattern formation in single pulse irradiation. The theoretical models include a femtosecond laser pulse function, a two-temperature model (2-T model), and an estimation of interface thermal coupling. The evolution of lattice temperature over time will be calculated first without liquid cooling and then with liquid cooling, which has not been well considered in previous theoretical papers. The lifetime of the capillary wave is found to be longer than the solidification time of the molten silicon only when water cooling is introduced. This allows the capillary wave to be frozen and leaves interesting concentric rings on the silicon surface. The regular nanospikes generated on the silicon surface result from the overlapping capillary waves.
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Duan, Li, Qi Kang et Wenrei Hu. « Characters of surface deformation and surface wave in thermal capillary convection ». Science in China Series E : Technological Sciences 49, no 5 (octobre 2006) : 601–10. http://dx.doi.org/10.1007/s11431-006-2013-2.
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Agrawal, Shubham, Prashanta K. Das et Purbarun Dhar. « Thermo-capillarity in microfluidic binary systems via phase modulated sinusoidal thermal stimuli ». Physics of Fluids 34, no 3 (mars 2022) : 032012. http://dx.doi.org/10.1063/5.0084216.
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In this article, we have explored the theoretical aspects of thermo-capillarity driven hydrodynamics at the interface of an immiscible binary-fluid system within a microfluidic domain. The top and bottom walls of the microfluidic confinement are exposed to sinusoidal thermal stimuli with different mean values, wave numbers, and phase differences. We explore the influence of different governing parameters on the thermal and hydrodynamic transport due to interfacial thermo-capillarity and within the constituent fluids. To this end, we deduce the full solutions for the temperature field, hydrodynamics, and the interfacial deformation characteristics in an analytical framework, by appealing to the assumption of the creeping flow (vanishingly small Reynolds, Marangoni, and Capillary number regime) and nearly un-deformed interface. Complicated spatial distribution of the isotherms is generated across the fluids, leading to spatially varying thermal gradients across and along the interface. This leads to periodic circulation of the fluids within the microchannel due to the sinusoidal thermal stimulus. It is observed that the interfacial flow strength depends on the relative film thickness and the thermal conductivities of the two fluids. Vortex enveloping phenomenon is observed for lower values of film thickness ratio when the thermal conductivity of the lower fluid is higher relative to the upper fluid. The findings may hold significance for the design and development of thermal stimulus-controlled spatial mixing and solute transport mechanisms in reactive micro- and nano-fluidic devices.
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Shah, Maulik S., Volkert van Steijn, Chris R. Kleijn et Michiel T. Kreutzer. « Thermal fluctuations in capillary thinning of thin liquid films ». Journal of Fluid Mechanics 876 (14 août 2019) : 1090–107. http://dx.doi.org/10.1017/jfm.2019.595.
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Thermal fluctuations have been shown to influence the thinning dynamics of planar thin liquid films, bringing predicted rupture times closer to experiments. Most liquid films in nature and industry are, however, non-planar. Thinning of such films not just results from the interplay between stabilizing surface tension forces and destabilizing van der Waals forces, but also from drainage due to curvature differences. This work explores the influence of thermal fluctuations on the dynamics of thin non-planar films subjected to drainage, with their dynamics governed by two parameters: the strength of thermal fluctuations, $\unicode[STIX]{x1D703}$, and the strength of drainage, $\unicode[STIX]{x1D705}$. For strong drainage ($\unicode[STIX]{x1D705}\gg \unicode[STIX]{x1D705}_{tr}$), we find that the film ruptures due to the formation of a local depression called a dimple that appears at the connection between the curved and flat parts of the film. For this dimple-dominated regime, the rupture time, $t_{r}$, solely depends on $\unicode[STIX]{x1D705}$, according to the earlier reported scaling, $t_{r}\sim \unicode[STIX]{x1D705}^{-10/7}$. By contrast, for weak drainage ($\unicode[STIX]{x1D705}\ll \unicode[STIX]{x1D705}_{tr}$), the film ruptures at a random location due to the spontaneous growth of fluctuations originating from thermal fluctuations. In this fluctuations-dominated regime, the rupture time solely depends on $\unicode[STIX]{x1D703}$ as $t_{r}\sim -(1/\unicode[STIX]{x1D714}_{max})\ln (\sqrt{2\unicode[STIX]{x1D703}})^{\unicode[STIX]{x1D6FC}}$, with $\unicode[STIX]{x1D6FC}=1.15$. This scaling is rationalized using linear stability theory, which yields $\unicode[STIX]{x1D714}_{max}$ as the growth rate of the fastest-growing wave and $\unicode[STIX]{x1D6FC}=1$. These insights on if, when and how thermal fluctuations play a role are instrumental in predicting the dynamics and rupture time of non-flat draining thin films.
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Aziz, M. S. Abdul, M. Z. Abdullah, C. Y. Khor, Z. M. Fairuz, A. M. Iqbal, M. Mazlan et Mohd Sukhairi Mat Rasat. « Thermal Fluid-Structure Interaction in the Effects of Pin-Through-Hole Diameter during Wave Soldering ». Advances in Mechanical Engineering 6 (1 janvier 2014) : 275735. http://dx.doi.org/10.1155/2014/275735.
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An effective simulation approach is introduced in this paper to study the thermal fluid-structure interaction (thermal FSI) on the effect of pin-through-hole (PTH) diameter on the wave soldering zone. A 3D single PTH connector and a printed circuit board model were constructed to investigate the capillary flow behavior when passing through molten solder (63SnPb37). In the analysis, the fluid solver FLUENT was used to solve and track the molten solder advancement using the volume of fluid technique. The structural solver ABAQUS was used to examine the von Mises stress and displacement of the PTH connector in the wave soldering process. Both solvers were coupled by MpCCI software. The effects of six different diameter ratios (0.1 < d/ D < 0.97) were studied through a simulation modeling. The use of ratio d/ D = 0.2 yielded a balanced filling profile and low thermal stress. Results revealed that filling level, temperature, and displacement exhibited polynomial behavior to d/ D. Stress of pin varied quadratically with the d/ D. The predicted molten solder profile was validated by experimental results. The simulation results are expected to provide better visualization and understanding of the wave soldering process by considering the aspects of thermal FSI.
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Sharizal Abdul Aziz, Mohd, Mohd Zulkifly Abdullah et Chu Yee Khor. « Influence of PTH offset angle in wave soldering with thermal-coupling method ». Soldering & ; Surface Mount Technology 26, no 3 (27 mai 2014) : 97–109. http://dx.doi.org/10.1108/ssmt-08-2013-0021.
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Purpose – The aim of this study is to investigate the effects of offset angle in wave soldering by using thermal fluid structure interaction modeling with experimental validation. Design/methodology/approach – The authors used a thermal coupling approach that adopted mesh-based parallel code coupling interface between finite volume-and finite element-based software (ABAQUS). A 3D single pin-through-hole (PTH) connector with five offset angles (0 to 20°) on a printed circuit board (PCB) was built and meshed by using computational fluid dynamics preprocessing software called GAMBIT. An implicit volume of fluid technique with a second-order upwind scheme was also applied to track the flow front of solder material (Sn63Pb37) when passing through the solder pot during wave soldering. The structural solver and ABAQUS analyzed the temperature distribution, displacement and von Mises stress of the PTH connector. The predicted results were validated by the experimental solder profile. Findings – The simulation revealed that the PTH offset angle had a significant effect on the filling of molten solder through the PCB. The 0° angle yielded the best filling profile, filling time, lowest displacement and thermal stress. The simulation result was similar to the experimental result. Practical implications – This study provides a better understanding of the process control in wave soldering for PCB assembly. Originality/value – This study provides fundamental guidelines and references for the thermal coupling method to address reliability issues during wave soldering. It also enhances understanding of capillary flow and PTH joint issues to achieve high reliability in PCB assembly industries.
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Peirson, William L., James W. Walker et Michael L. Banner. « On the microphysical behaviour of wind-forced water surfaces and consequent re-aeration ». Journal of Fluid Mechanics 743 (5 mars 2014) : 399–447. http://dx.doi.org/10.1017/jfm.2013.681.
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AbstractA detailed laboratory investigation of the mechanical and low-solubility gas coupling between wind and water has been undertaken using a suite of microphysical measurement techniques. Under a variety of wind conditions and in the presence and absence of mechanically generated short waves, approximately fetch-independent surface conditions have been achieved over short laboratory fetches of several metres. The mechanical coupling of the surface is found to be consistent with Banner (J. Fluid Mech. vol. 211, 1990, pp. 463–495) and Banner & Peirson (J. Fluid Mech. vol. 364, 1998, pp. 115–145). Bulk observations of re-aeration are consistent with previous laboratory studies. The surface kinematical behaviour is in accordance with the observations of Peirson & Banner (J. Fluid Mech. vol. 479, 2003, pp. 1–38). Also, their predictions of a strong enhancement of low-solubility gas flux at the onset of microscale breaking is confirmed and direct observations show a concomitant onset of very thin aqueous diffusion sublayers. It is found that the development of strong parasitic capillary waves towards the incipient breaking limit does not noticeably enhance constituent transfer. Across the broad range of conditions investigated during this study, the local instantaneous constituent transfer rate remains approximately log-normally distributed with an approximately constant standard deviation of $0.62\pm 0.15({\mathrm{log}}_e(\mathrm{m}~ {\mathrm{s}}^{-1}))$. Although wind-forced water surfaces are shown to be punctuated by intense tangential stresses and local surface convergence, localized surface convergence does not appear to be the single critical factor determining exchange rate. Larger-scale orbital wave straining is found to be a significant constituent transfer process in contrast to Witting (J. Fluid Mech. vol. 50, 1971, pp. 321–334) findings for heat fluxes, but the measured effects are consistent with his model. By comparing transfer rates in the presence and absence of microscale breaking, low-solubility gas transfer was decomposed into its turbulent/capillary ripple, gravity-wave-related and microscale breaking contributions. It was found that an efficiency factor of approximately $17\, \%$ needs to be applied to Peirson & Banner’s model, which is extended to field conditions. Although bulk thermal effects were observed and thermal diffusion layers are presumed thicker than their mass diffusion counterparts, significant thermal influences were not observed in the results.
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Da Mota, J. C., A. J. De Souza, D. Marchesin et P. W. Teixeira. « A SIMPLIFIED OXIDATION MODEL FOR TWO-PHASE FLOW IN POROUS MEDIA ». Revista de Engenharia Térmica 1, no 2 (31 décembre 2002) : 09. http://dx.doi.org/10.5380/reterm.v1i2.3504.
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This paper describes a simplified mathematical model for thermal recovery by oxidation for flow of oxygen and oil in porous media. Some neglected important physical effects include gravity, compressibility and heat loss to the rock formation, but heat longitudinal conduction and capillary pressure difference between the phases are considered. The mathematical model is obtained from the mass balance equations for air and oil, energy balance and Darcy's law applied to each phase. Based on this model some typical features in low temperature oxidation concerning the wave structure are captured. Numerical simulations showing saturations and temperature profiles are reported.
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Abdul Aziz, M. S., M. Z. Abdullah et C. Y. Khor. « Effects of Solder Temperature on Pin Through-Hole during Wave Soldering : Thermal-Fluid Structure Interaction Analysis ». Scientific World Journal 2014 (2014) : 1–13. http://dx.doi.org/10.1155/2014/482363.
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An efficient simulation technique was proposed to examine the thermal-fluid structure interaction in the effects of solder temperature on pin through-hole during wave soldering. This study investigated the capillary flow behavior as well as the displacement, temperature distribution, and von Mises stress of a pin passed through a solder material. A single pin through-hole connector mounted on a printed circuit board (PCB) was simulated using a 3D model solved by FLUENT. The ABAQUS solver was employed to analyze the pin structure at solder temperatures of 456.15 K (183°C) <T< 643.15 K (370°C). Both solvers were coupled by the real time coupling software and mesh-based parallel code coupling interface during analysis. In addition, an experiment was conducted to measure the temperature difference (ΔT) between the top and the bottom of the pin. Analysis results showed that an increase in temperature increased the structural displacement and the von Mises stress. Filling time exhibited a quadratic relationship to the increment of temperature. The deformation of pin showed a linear correlation to the temperature. TheΔTobtained from the simulation and the experimental method were validated. This study elucidates and clearly illustrates wave soldering for engineers in the PCB assembly industry.
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Genbach, A. A., D. Yu Bondartsev et A. Y. Shelginsky. « Investigation of nanoscale and microscale structured cooling surfaces of thermal power plants ». Safety and Reliability of Power Industry 15, no 1 (6 mai 2022) : 38–44. http://dx.doi.org/10.24223/1999-5555-2022-15-1-38-44.
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Studies were conducted of the heat exchange crisis depending on the coolant excess (which determined the underheating and flow rate), the thermal-physical properties of the heating surface, and the ejection of liquid droplets from the porous structure. A model of dynamics of vapor bubbles born on the solid surface in porous structures and the vapor-generating wall (substrate) has been developed. The model is based on cinematography with an SKS-1M speed camera. The removal of high heat flows (up to 2·106 W/m2) is provided through the joint action of capillary and mass forces with the use of intensifiers. Equations are obtained of critical heat flows through the thermohydraulic characteristics of the boiling process in woven porous structures. The research is of practical importance in the limiting state region of the steam-generating surface protected by cooling from overburning. Three mineral media (tuff, granite, marble) of Zaili and Dzungarian Alatau mountains near the city of Almaty (Kazakhstan) were considered. The method of holographic interferometry was used to study porous thermodynamic screens. The stress and deformed state of the samples was studied. Simulation of the acoustic field of the blast wave with th e thermodynamic field created by three thermal sources has shown its high efficiency. The created powerful thermal screen, due to the generation of strain and thermal stress fields, is an obstacle to the propagation of the reflected blast wave, causing the emergence and development of destructive cracks. Nanoscale and microscale structured surfaces in the form of coatings and mesh structures have been developed, which give an integrated effect of industrial meshes with natural mineral media coatings and have synergistic advantages of combining these two developments in an integrated technology of their production, expansion of critical thermal loads and management of the limiting state of porous coatings.
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Bolognesi, Guido, Yuki Saito, Arwen I. I. Tyler, Andrew D. Ward, Colin D. Bain et Oscar Ces. « Mechanical Characterization of Ultralow Interfacial Tension Oil-in-Water Droplets by Thermal Capillary Wave Analysis in a Microfluidic Device ». Langmuir 32, no 15 (8 avril 2016) : 3580–86. http://dx.doi.org/10.1021/acs.langmuir.5b04702.
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GRIGORIEV, A. I., N. YU KOLBNEVA et S. O. SHIRYAEVA. « SOME FEATURES OF CAPILLARY WAVE ENERGY CONVERSION ON LIQUID SURFACE IN THE PRESENCE OF DYNAMIC SURFACE TENSION ». Коллоидный журнал 85, no 3 (1 mai 2023) : 263–76. http://dx.doi.org/10.31857/s0023291223600128.
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The effect of dynamic surface tension on capillary oscillations of a droplet is studied in the theoretical asymptotic calculations of the first order of smallness with respect to the dimensionless amplitude of oscillations of charged droplets of a polar liquid. The calculations are carried out within the framework of a model of an ideal incompressible electrically conducting liquid. It has been shown that allowance for the effect of dynamic surface tension increases the order of the dispersion equation, which acquires one more damping root relevant to the destruction of the near-surface electrical double layer (disordering of molecules in the near-surface layer). What is interesting about the revealed damping is that it takes place in an ideal liquid, while the characteristic damping time coincides with that measured experimentally. Free energy transformations occur between mechanical, thermal, electromagnetic, and mechanical again forms of energy, with all of the transformations being caused by the effect of the dynamic surface tension. It has been shown that the dynamic surface tension has a weak effect on the low-frequency oscillations of the droplets, while it essentially affects the high-frequency oscillations causing their rapid damping.
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Xia, Zhao, Xiaoming Liu et Jiali Gu. « Laboratory Investigation and Modelling of the Thermal-Mechanical Properties of Soil in Shallow Mineralized Groundwater Area ». Geofluids 2019 (4 novembre 2019) : 1–21. http://dx.doi.org/10.1155/2019/5121740.
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The capillary rise of shallow mineralized groundwater can contribute to the salinization of the soil layers. The excessive salt amounts adversely affect soil physical and mechanical properties, as well as the heat transfer performance, all of which are key factors with regard to the design of geothermal-related earth structures such as geothermal energy piles (GEP), ground source heat pumps (GSHP), and earth-air tunnel heat exchangers (EATHE). Therefore, in this study, the thermal-mechanical properties of saline soils are systematically investigated. A series of thermal and mechanical response tests were carried out under different salinity conditions, and the shear wave velocity-stress behavior of saline soil was measured using a modified oedometric cell coupled with an anchored bender element pair. Experimental results showed that saline soils generally have higher dry density and lower optimum moisture content at higher salt contents. The shear strength of saline soil increased about 5% while the salt concentrations of bulk solution increased from 0 mol/kg to 6 mol/kg, and the shear wave velocity increased by 50% to 83% when the normal load increased from 12.5 kPa to 250 kPa for sodium chloride- (NaCl-) treated soil and 39% to 52% for calcium chloride- (CaCl2-) treated soil. In addition, the thermal conductivity decreased by 0.121 W m-1 K-1 for NaCl-treated soil and 0.129 W m-1 K-1 for CaCl2-treated soil on average when the salt concentration increased from 0 mol/kg to 6 mol/kg. Finally, an elastic shear modulus (G0) model and a thermal conductivity (K) model were formulated for saline soil for the first time, and the effectiveness and feasibility of the proposed models were validated by comparisons of the model predicted values and experimental data.
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Copenhaver, Katie, Marianna Luna et Jason Nadler. « Polymer Patterning via Electrohydrodynamic Instabilities ». MRS Advances 4, no 27 (2019) : 1543–50. http://dx.doi.org/10.1557/adv.2019.63.
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ABSTRACTElectrohydrodynamic (EHD) instabilities can be induced in polymers by placing a polymer film above its Tg in a strong electric field between two capacitor plates or electrodes. The polymer experiences an electrostatic stress at the interface between the polymer and air due to a mismatch in their dielectric constants. This stress, along with thermal fluctuations, induces small magnitude capillary waves in the polymer film, and the minima and maxima of those waves experience slightly different electric field strengths. In a sufficiently strong electric field, the capillary wave maxima, where the distances between the polymer film and the top electrode(s) are the smallest, are eventually drawn up to the top electrode. The wavelength of the instabilities in the film and the ability of the polymer to be drawn upward is a dependent on the competition between surface tension forces and the electrostatic stress imparted on the polymer. While EHD instabilities are typically used to pattern polymer surfaces on a nanometer-scale, instabilities have been induced in polymer films with air gaps up to 500 μm. Upper electrodes with non-planar structures have also been used to induce instabilities in polymer films, resulting in patterned polymer surfaces without contact. Size, shape, arrangement, and placement of the upper electrode relative to the polymer film and lower electrode, as well as the processing conditions such as temperature and applied voltage, can all be modified to produce a desired array of structures with tailored performance characteristics. Patterned polymer surfaces can provide high-index contrast over a periodic matrix with 3-dimensional element shapes. The dielectric contrast and array pitch and height can be tuned to control specular reflection and achieve specific scattering characteristics. Surfaces with tailored scattering characteristics in the aforementioned ranges could be useful in producing frequency-selective windows for glare reduction, anti-reflective solar cells with enhanced efficiency, surface waveguides and whispering gallery-mode resonator arrays for integrated photonics and sensors, and surfaces with controlled emissivity for directed heat dissipation.
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Kobzar, A. N. « Physical and methodological approach to the modern methods of the investigation of dental materials properties ». Journal of Physics : Conference Series 2056, no 1 (1 octobre 2021) : 012061. http://dx.doi.org/10.1088/1742-6596/2056/1/012061.
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Abstract Each medical doctor should be able to complete professional tasks using their knowledge of physics, especially when providing a comprehensive care to a patient. This article reveals how to use knowledge of the course of physics specially developed of a Medical University to help trainee medical doctors to develop skills to complete professional tasks. Content of physics and its tasks for a Medical University must be professionally oriented. This article provides a classification of professionally oriented questions of physics specially made to be taught at a Medical University. It also gives content a sample of a professionally oriented task in physics for a Medical University. All these above mentioned tasks are closely correlating with each other. As an example, the article explains specific of teaching Biophysics at a Medical University. Professionally oriented content of Biomechanics - modern methods of study properties of materials used for dental care. Methods of physics for destructive inspection testing: tensile strength, compressive strength, hardness of materials, Poisson's ratio, fluctuating stress and dynamic testing etc. Methods of physics for non-destructive inspection testing: thermal, acoustic, optical, radio-wave, radiative, capillary, magnetic and electric testing.
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Safiullin, A. R. « Acoustic stability of a superheated liquid with vapor–gas bubbles ». Multiphase Systems 18, no 1 (mai 2023) : 32–36. http://dx.doi.org/10.21662/mfs2023.1.005.
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It is known that the physicochemical properties of liquids in a metastable state are mainly determined by the presence of various inclusions in their composition, for example, gas bubbles or solid particles, and it has been established that, under mechanical and thermal equilibrium, the state of a liquid with gas bubbles distributed over the volume due to the action of capillary forces at the interface, always overheated. In this paper, we consider the propagation of weak perturbations in a superheated water-air bubbly medium, when, in addition to water vapor, the bubbles contain an inert gas (for example, air) that does not participate in phase transitions. To describe the problems under consideration, a system of equations is used, which consists of the laws of conservation of mass, the number of bubbles, momentum equations, the Rayleigh–Lamb equation, the equation of heat conduction and diffusion. The solution is sought in the form of a damped traveling wave. Based on the solution of the dispersion equation, maps of the stability zones of the systems under consideration were constructed depending on the magnitude of the liquid overheating on the plane ”volume content — bubble radius“.
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Martín-Pérez, Ramos, Tamayo et Calleja. « Coherent Optical Transduction of Suspended Microcapillary Resonators for Multi-Parameter Sensing Applications ». Sensors 19, no 23 (20 novembre 2019) : 5069. http://dx.doi.org/10.3390/s19235069.
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Characterization of micro and nanoparticle mass has become increasingly relevant in a wide range of fields, from materials science to drug development. The real-time analysis of complex mixtures in liquids demands very high mass sensitivity and high throughput. One of the most promising approaches for real-time measurements in liquid, with an excellent mass sensitivity, is the use of suspended microchannel resonators, where a carrier liquid containing the analytes flows through a nanomechanical resonator while tracking its resonance frequency shift. To this end, an extremely sensitive mechanical displacement technique is necessary. Here, we have developed an optomechanical transduction technique to enhance the mechanical displacement sensitivity of optically transparent hollow nanomechanical resonators. The capillaries have been fabricated by using a thermal stretching technique, which allows to accurately control the final dimensions of the device. We have experimentally demonstrated the light coupling into the fused silica capillary walls and how the evanescent light coming out from the silica interferes with the surrounding electromagnetic field distribution, a standing wave sustained by the incident laser and the reflected power from the substrate, modulating the reflectivity. The enhancement of the displacement sensitivity due to this interferometric modulation (two orders of magnitude better than compared with previous accomplishments) has been theoretically predicted and experimentally demonstrated.
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Mykhaylenko, O. V., V. D. Mishalov, S. V. Kozlov et Y. A. Varfolomeiev. « Forensic characteristics of injuries from thermo-baric explosive device ». Reports of Morphology 30, no 2 (5 juin 2024) : 24–30. http://dx.doi.org/10.31393/morphology-journal-2024-30(2)-03.
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Since the beginning of the Russian Federation's invasion of Ukraine in 2022, explosive trauma has become an extremely urgent problem, as the main source of bodily injury among both the military in the combat zone and the civilian population in cities has been the impact of explosive devices. The aim of the study is the examination of the forensic characteristics of damage to biological objects that were formed from thermal exposure and shock wave as a result of the explosion of a cumulative munition and in the conditions of an experimental explosion model. The objects of the study were the materials of two examinations on the death of Ukrainian soldiers who died in the war zone (archival "Conclusions of the medical examination" of the Kyiv City Clinical Bureau of Forensic Medical Examination in 2023). Under the conditions of the experiment, studies of pathomorphological changes in the liver and small intestine of 30 white outbred rats from the action of an artificially created air shock wave with an overpressure of 31.62±4.84 kPa were carried out. The injuries were examined macroscopically and using standard laboratory histological techniques. Microscopy of histological sections was performed using an Axio Imager 2 microscope (Zeiss, Germany) at magnifications of ×200 and ×400. Statistical processing of the obtained quantitative results was carried out using the STATISTICA 6.1 software product. Under the condition of the explosion of the ammunition with the cumulative effect of the rocket-propelled infantry flamethrower "Bumblebee" on sectional incisions of the skin and muscles of the thigh in the projection of areas of redness, a picture of a gelatinous consistency of bright red color was macroscopically determined due to abundant blood impregnation of muscles and subcutaneous fat and partial loss of muscle structure with the release of myoglobin. The bright red color of the skin of the thigh and pelvis without burning the hair may indicate the superficial thermal effect of the explosive device and the protection of the skin by clothing. Diffusely located numerous both paired and single abrasions and shallow wounds, small rounded, oblong, circular in shape, which are the result of fragments of a rocket-propelled grenade equipped with a fire mixture, were also determined. The effect of an air shock wave with an overpressure of 31.62±4.84 kPa on the liver parenchyma of rats was determined by focal hemorrhages with rupture of the terminal central vein of the hepatic lobule, edema of the parasinusoidal spaces, and sludges in the sinusoids. In the wall of the small intestine, acute hemodynamic disorders occurred in the form of vasodilation of arterial vessels, venular and capillary stasis. There was layering and swelling of the small intestine wall, rupture of veins, focal hemorrhage. Thus, the revealed characteristic pathomorphological signs of the destructive effect of overpressure as a result of a blast wave (barotrauma) are typical and common both in the areas of the human thigh and pelvis, and in biological objects of experimental animals. The obtained results are consistent with the pathomorphological manifestations of barotrauma in areas of the human body as a result of the action of an explosive device with a cumulative effect.
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Ratanadecho, P., K. Aoki et M. Akahori. « Experimental Validation of a Combined Electromagnetic and Thermal Model for a Microwave Drying of Capillary Porous Materials Inside a Rectangular Wave Guide (Effects of Irradiation Time, Particle Sizes and Initial Moisture Content) ». Journal of Microwave Power and Electromagnetic Energy 37, no 1 (janvier 2002) : 15–40. http://dx.doi.org/10.1080/08327823.2002.11688468.
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Smith, Thomas H. R., Oleg Vasilyev, Anna Maciołek et Matthias Schmidt. « Lateral transport of thermal capillary waves ». EPL (Europhysics Letters) 89, no 1 (1 janvier 2010) : 10006. http://dx.doi.org/10.1209/0295-5075/89/10006.
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Yu, Jia-Jia, Lu Zhang, Ting Shen, Li Zhang et You-Rong Li. « Numerical Simulation of Thermal-Solutal Capillary-Buoyancy Flow of Ge1–xSix Single Crystals Driven by Surface-Tension and Rotation in a Czochralski Configuration ». Crystals 9, no 4 (22 avril 2019) : 217. http://dx.doi.org/10.3390/cryst9040217.
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A series of three-dimensional numerical simulations were performed to understand the thermal-solutal capillary-buoyancy flow of Ge1-xSix melts during Czochralski crystal growth with a rotating crystal or crucible. The crystal and crucible rotation Reynolds numbers in this work are 0∼3.5 × 103 (0∼4.4 rpm) and 0∼−2.4 × 103 (0∼−1.5 rpm), respectively. Simulation results show that if the thermal capillary Reynolds number is relatively low, the flow will be steady and axisymmetric, even though the crystal or crucible rotates at a constant rate. The critical thermal capillary Reynolds number for the initiation of the three-dimensional oscillatory flow is larger than that of pure fluids. As the crystal or crucible rotation rate increases, the critical thermal capillary Reynolds number first increases and then decreases. The dominant flow pattern after the flow destabilization is azimuthal traveling waves. Furthermore, a reversed evolution from the oscillatory spoke pattern to traveling waves appears in the melt. Once the crystal or crucible rotation rate is relatively large, the traveling waves respectively evolve to rotating waves at the crystal rotation and a spindle-like pattern at the crucible rotation. In addition, the maximum amplitude of solute concentration oscillation on the free surface initially decreases, but finally rises with the crystal or crucible rotation rate increasing.
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Aarts, D. G. A. L. « Direct Visual Observation of Thermal Capillary Waves ». Science 304, no 5672 (7 mai 2004) : 847–50. http://dx.doi.org/10.1126/science.1097116.
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Vilk, Alla, Irina Legchenkova, Mark Frenkel et Edward Bormashenko. « Spiral Thermal Waves Generated by Self-Propelled Camphor Boats ». Condensed Matter 5, no 3 (6 août 2020) : 51. http://dx.doi.org/10.3390/condmat5030051.
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Spiral thermal surface waves arising from self-propulsion of the camphor-driven objects are reported. Spiral thermal waves were registered for dissolution and evaporation-guided self-propulsion. Soluto-capillarity is accompanied by thermo-capillarity under self-propulsion of camphor boats. The jump in the surface tension due to the soluto-capillarity is much larger than that due to the thermo-capillarity. The spiral patterns inherent for the surface thermal waves are imposed by the self-rotational motion of camphor grains. The observed thermal effect is related to the adsorption of camphor molecules at the water/vapor interface. The observed spirals are shaped as Archimedean ones.
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Haber, Elad, Mark Douvidzon, Shai Maayani et Tal Carmon. « A Liquid Mirror Resonator ». Micromachines 14, no 3 (8 mars 2023) : 624. http://dx.doi.org/10.3390/mi14030624.
Texte intégralRésumé :
We present the first experimental demonstration of a Fabry‒Perot resonator that utilizes total internal reflection from a liquid–gas interface. Our hybrid resonator hosts both optical and capillary waves that mutually interact. Except for the almost perfect reflection by the oil–air interface at incident angles smaller than the critical angle, reflections from the liquid-phase boundary permit optically examining thermal fluctuations and capillary waves at the oil surface. Characterizing our optocapillary Fabry‒Perot reveals optical modes with transverse cross-sectional areas of various shapes and longitudinal modes that are separated by the free spectral range. The optical finesse of our hybrid optocapillary resonator is Fo = 60, the optical quality factor is Qo = 20 million, and the capillary quality factor is Qc = 6. By adjusting the wavelength of our laser near the optical resonance wavelength, we measure the liquid’s Brownian fluctuations. As expected, the low-viscosity liquid exhibits a distinct frequency of capillary oscillation, indicating operation in the underdamped regime. Conversely, going to the overdamped regime reveals no such distinct capillary frequency. Our optocapillary resonator might impact fundamental studies and applications in surface science by enabling optical interrogation, excitation, and cooling of capillary waves residing in a plane. Moreover, our optocapillary Fabry‒Perot might permit photographing thermal capillary oscillation, which the current state-of-the-art techniques do not support.
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Sobrino, Luis de, et Jože Peternelj. « On capillary waves in the gradient theory of interfaces ». Canadian Journal of Physics 63, no 2 (1 février 1985) : 131–34. http://dx.doi.org/10.1139/p85-020.
Texte intégralRésumé :
We have solved the equations of motion for an inhomogeneous, nondissipative fluid linearized about a two-phase solution in order to determine the dispersion relation for capillary waves of long wavelength. The solution is reasonably rigorous in that no physical assumptions have been introduced. We find that, in accordance with the results of Turski and Langer and contrary to other workers' claims, the dispersion relation agrees with classical capillary theory only if thermal effects are included.
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Willis, A. M., et J. B. Freund. « Thermal capillary waves relaxing on atomically thin liquid films ». Physics of Fluids 22, no 2 (février 2010) : 022002. http://dx.doi.org/10.1063/1.3326077.
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Jamie, E. A. G., G. J. Davies, M. D. Howe, R. P. A. Dullens et D. G. A. L. Aarts. « Thermal capillary waves in colloid–polymer mixtures in water ». Journal of Physics : Condensed Matter 20, no 49 (12 novembre 2008) : 494231. http://dx.doi.org/10.1088/0953-8984/20/49/494231.
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Ocko, B. M., X. Z. Wu, E. B. Sirota, S. K. Sinha et M. Deutsch. « X-ray reflectivity study of thermal capillary waves on liquid surfaces ». Physical Review Letters 72, no 2 (10 janvier 1994) : 242–45. http://dx.doi.org/10.1103/physrevlett.72.242.
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Pershan, P. S. « X-ray scattering from liquid surfaces : Effects of thermal capillary waves ». Synchrotron Radiation News 12, no 2 (mars 1999) : 10–16. http://dx.doi.org/10.1080/08940889908260983.
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Thanh, Mai Duc, et Nguyen Huu Hiep. « On traveling waves in viscous-capillary Euler equations with thermal conductivity ». Applied Mathematics and Computation 234 (mai 2014) : 127–41. http://dx.doi.org/10.1016/j.amc.2014.02.004.
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Wu, Chunmei, Jinhui Chen et Yourong Li. « Mixed Oscillation Flow of Binary Fluid with Minus One Capillary Ratio in the Czochralski Crystal Growth Model ». Crystals 10, no 3 (19 mars 2020) : 213. http://dx.doi.org/10.3390/cryst10030213.
Texte intégralRésumé :
This work presented a series of three-dimensional unsteady numerical simulations on the characteristics of the mixed oscillation flows of binary mixture in a Czochralski crystal growth model. The silicon-germanium melt is investigated and the capillary ratio is minus one. The simulation results showed that, for the special capillary ratio, the thermal and solutocapillary forces are imposed in opposite directions and counteract each other. With the effect of buoyancy, the balance between the capillary forces is disturbed. Mixed with the forced convection driven by rotation, the capillary-buoyancy convection is complex. The basic mixed flow streamlines are presented as various rolling cells. The directions of the rolls are dependent on the combinations of surface and body forces. With the increase of temperature gradient, the basic flow stability is broken, and the oscillations occur. The crucible rotation has an effective influence on the stability enhancement. However, affected by the crystal rotation, the critical condition experiences an increase to a turning point, and then undergoes a sharp reduction to zero. Once the instability is incubated, the surface oscillations are analyzed. For the three-dimensional steady flow, only spatial oscillations are observed circumferentially, and the surface patterns of spokes, rosebud, and pulsating ring are obtained. For the unsteady oscillation flow, the spiral hydrosoultal waves, rotating waves, and superimposition of spirals and spokes are observed, and the oscillation behaviors are also discussed.
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Wu, Chunmei, Bo Yuan et Yourong Li. « Flow Instabilities of Coupled Rotation and Thermal-Solutal Capillary Convection of Binary Mixture in Czochralski Configuration ». Crystals 9, no 2 (30 janvier 2019) : 72. http://dx.doi.org/10.3390/cryst9020072.
Texte intégralRésumé :
In order to understand the flow instabilities of coupled rotation and thermal-solutal capillary convection of binary mixture in a Czochralski configuration subjected to simultaneous radial thermal and solutal gradients, a series of three-dimensional direct numerical simulation have been conducted. The capillary ratio of the silicon-germanium mixture is −0.2. The rotation Reynolds numbers of crystal and crucible, Res and Rec range from 0 to 3506 and 0 to 1403, respectively. Results show that the basic flow is axisymmetric and steady. It has rich flow structures in the meridian plane, depending on the competitions among the driving forces. With the increase of thermocapillary and rotation Reynolds numbers, the basic flow will transit to three dimensional oscillatory flow. For different combination of rotation rate and thermocapillary Reynolds number, the oscillatory flow can be displayed as spoke patterns which is steady in time but oscillate in space, spoke patterns propagate in azimuthal direction, rotational waves or coexistence of spokes and rotational waves. The crucible rotation has an inhibitory effect on the flow instability, inducing the monotonically increase of critical value for flow transitions, however, for crystal rotation, the critical thermocapillary Reynolds number increases at first and then decreases. When the rotation rate is large, two flow transitions are captured.
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Chovnyuk, Yuriy, Petro Cherednichenko, Volodymyr Kravchyuk, Olga Ostapushchenko et Eugenie Ivanov. « MODELING AND ANALYSIS OF THE DEFORMED MEDIA (METAL CONSTRUCTION ELEMENTS) NON STATIONARY THERMAL FIELDS DURING THEIR LASER SHORT WAVES PULSES TREATMENT ». Current problems of architecture and urban planning, no 60 (26 avril 2021) : 277–96. http://dx.doi.org/10.32347/2077-3455.2021.60.277-296.
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Substantiated mathematical model for non-stationary thermoelastic deformed media during their laser processing by short waves pulses fields analysis is proposed . Precise analytical solutions of the thermal conductivity equations which simulate the short laser pulses interaction and allow to further determine their components thermally stress-strain state of the processed materials, in particular, thin porous films, capillary-porous bodies are obtained. Two analysis methods were used: 1) traditional separating variables method (Fourier method), 2) non-Fourier analysis of the non-stationary thermal fields that described by the telegraphic equation known in the literature. The results obtained in this work can be used further to establish the thermo stress-strain state of materials interacting with short waves laser radiation pulses parameters. Such approach is used at the modern building process for the rising of the reliability, durability and strength of the metal construction elements.
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Zhang, Yixin, Duncan A. Lockerby et James E. Sprittles. « Relaxation of Thermal Capillary Waves for Nanoscale Liquid Films on Anisotropic-Slip Substrates ». Langmuir 37, no 29 (12 juillet 2021) : 8667–76. http://dx.doi.org/10.1021/acs.langmuir.1c00352.
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Pittau, F., O. G. Carcassi, M. Servalli, S. Pellegrini et S. Claude. « Hygrothermal characterization of bio-based thermal insulation made of fibres from invasive alien lake plants bounded with mycelium ». IOP Conference Series : Earth and Environmental Science 1078, no 1 (1 septembre 2022) : 012069. http://dx.doi.org/10.1088/1755-1315/1078/1/012069.
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Abstract The European program ‘Renovation Wave’ aims to fasten the energy retrofit of the building stock by increasing by a factor 4 the current renovation rate. Mycelium-based materials gained momentum as insulation solutions in recent years due to their 100% biological composition. However, their durability issues, particularly the risk of fast decay due to high moisture content, need to be investigated to promote a safe use in construction. Two bio-composites were set up at a lab scale, a combination of hemp shives and mycelium and a novel mixture based on the combination of mycelium binder and fibres from a lake plant, Lagarosiphon major, an alien invasive species locally available in many EU internal waters. Samples with different dimensions were used to characterize through experimental tests the thermal conductivity, water absorption (capillarity) and vapor permeability. The results show that these mycelium-based composites present both hydric and thermal properties similar to other bio-based material used in construction. The capillarity tests highlighted that hemp composites absorb more water than lake plant ones. The thermal conductivity is similar for both biocomposites, i.e., around 0.05 W/m.K, while the moisture buffer position both analysed biocomposites in “WS 3” according to the German classification DIN 18947 for water regulators.
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Sinkevich, O. A., V. V. Glazkov, Yu P. Ivochkin et A. N. Kireeva. « Vapor Films under Influence of High Heat Fluxes : Nongravity Surface Waves and Film Explosive Disintegration ». International Journal of Nonlinear Sciences and Numerical Simulation 14, no 1 (21 février 2013) : 1–14. http://dx.doi.org/10.1515/ijnsns-2012-0021.
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Abstract Linear and non-linear stability analysis of the interface between a thin vapor film and a layer of liquid in the presence of a steady heat flux from a metal surface heated to a high temperature, to the vapor film and then from vapor to the subcooled liquid is investigated. The temperature dependence of saturation pressure is taken into account. Boundary conditions on the vapor–liquid interface that generalizes the known correlations on the free surface of liquid in the gravity field are derived. The thermal processes on the phase boundary lead to the generation of weakly decaying periodic surface waves of low amplitude and may cause small length waves (ripple), which are not capillary ones. Thermal processes on the phase interface are capable to provide the stability of a film of lights vapor under a layer of heavy liquid in the gravity field. The explosive instability may arise in the non-linear stage due to a weak variation of the film thickness or superheating of liquids.
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Aurongzeb, Deeder, et Latika Menon. « Magnetic fungal colonies on silicon : a nanoscale diffusion process and evidence of thermal capillary waves ». Nanotechnology 18, no 50 (20 novembre 2007) : 505102. http://dx.doi.org/10.1088/0957-4484/18/50/505102.
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Afanasyev, Anatoly M., et Yulia S. Bakhracheva. « Generalization of the Fourier problem of temperature waves in half-space ». Physics of Wave Processes and Radio Systems 24, no 2 (6 septembre 2021) : 13–21. http://dx.doi.org/10.18469/1810-3189.2021.24.2.13-21.
Texte intégralRésumé :
The problem of asymptotic fluctuations of temperature and moisture content in a half-space whose boundary is blown by an air flow with a temperature varying according to the harmonic law is solved by the method of complex amplitudes. The material filling the half-space consists of a solid base (capillary-porous body) and water. The well-known Fourier solution for temperature fluctuations in half-space in the absence of moisture and under the boundary conditions of heat exchange ofthefirst kind is generalized to the case of a wet material under the boundary conditions of Newton for temperature and Dalton for moisture content. The results of the work can be used in geocryology to model seasonal changes in the thermophysical state offrozen rocks and soils, in the theory of building structures to study the thermal regime of indoor premises with fluctuations in ambient temperature, in the theory of drying by electromagnetic radiation to study the processes of heat and mass transfer inoscillating modes.
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Ma, Xiaolei, et Justin C. Burton. « Self-organized oscillations of Leidenfrost drops ». Journal of Fluid Mechanics 846 (4 mai 2018) : 263–91. http://dx.doi.org/10.1017/jfm.2018.294.
Texte intégralRésumé :
In the Leidenfrost effect, a thin layer of evaporated vapour forms between a liquid and a hot solid. The complex interactions between the solid, liquid and vapour phases can lead to rich dynamics even in a single Leidenfrost drop. Here we investigate the self-organized oscillations of Leidenfrost drops that are excited by a constant flow of evaporated vapour beneath the drop. We show that for small Leidenfrost drops, the frequency of a recently reported ‘breathing mode’ (Caswell, Phys. Rev. E, vol. 90, 2014, 013014) can be explained by a simple balance of gravitational and surface tension forces. For large Leidenfrost drops, azimuthal star-shaped oscillations are observed. Our previous work showed how the coupling between the rapid evaporated vapour flow and the vapour–liquid interface excites the star-shaped oscillations (Ma et al., Phys. Rev. Fluids, vol. 2, 2017, 031602). In our experiments, star-shaped oscillation modes of $n=2{-}13$ are observed in different liquids, and the number of observed modes depends sensitively on the viscosity of the liquid. Here we expand on this work by directly comparing the oscillations with theoretical predictions, as well as show how the oscillations are initiated by a parametric forcing mechanism through pressure oscillations in the vapour layer. The pressure oscillations are driven by the capillary waves of a characteristic wavelength beneath the drop. These capillary waves can be generated by a large shear stress at the liquid–vapour interface due to the rapid flow of evaporated vapour. We also explore potential effects of thermal convection in the liquid. Although the measured Rayleigh number is significantly larger than the critical Rayleigh number, the frequency (wavelength) of the oscillations depends only on the capillary length of the liquid, and is independent of the drop radius and substrate temperature. Thus convection seems to play a minor role in Leidenfrost drop oscillations, which are mostly hydrodynamic in origin.
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Chovniuk, Yurii, Petro Cherednichenko, Anna Moskvitina, Mariia Shyshyna, Nataliia Shudra et Evhen Ivanov. « Hyperbolic models in the analysis of heat and moisture exchange in inhomogeneous porous materials ». Strength of Materials and Theory of Structures, no 113 (29 novembre 2024) : 227–40. https://doi.org/10.32347/2410-2547.2024.113.227-240.
Texte intégralRésumé :
The paper uses hyperbolic models for the analysis of heat and moisture exchange in inhomogeneous porous materials in which short heat pulses propagate. The heat transfer in sharply inhomogeneous media at room temperature is not described by Fourier and Cattaneo laws, but is modeled by Guyer-Krumhansl-type equations. The O.V. Lykov system of equations of interrelated heat and mass transfer taking into account the finiteness of heat and mass (moisture) transfer rates is solved using a one-dimensional formulation. However, the heat propagation velocity is of the order of the sound speed, so due to the short relaxation time, the solutions of the hyperbolic equation of thermal conductivity largely coincide with the solutions of the classical parabolic equation, although there are some significant differences. They depend on processes occurring on the surface (in thin layers) of porous bodies. The moisture diffusion rate in capillary-porous materials is approximately 106…107 and more times lower than the heat propagation rate, so, accordingly, the relaxation time of diffusion processes is much longer and should be considered in mass transfer equations. Exact analytical solutions of the one-dimensional Guyer-Krumhansl equation are obtained using the operator method. This equation is also used to study heat pulses of different shapes in the medium with respect to phonon/ballistic methods of heat transfer. The obtained results are used to model the heat and moisture propagation in thin films of capillary-porous bodies with account taken of molecular effects in systems of reduced dimension. The very short heat pulses propagation simulating isolated heat waves is modeled with reference to Knudsen number, as well as the solutions for the periodic initial function. The exact solutions of the above problems in the model of thin films of capillary-porous bodies are obtained.
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Hidayatulloh, Irwan, Nurcahyo Nugroho, Gede Wibawa et Kuswandi Kuswandi. « Liquid-liquid Equilibria for Quaternary System of Eugenol (1) + β-Caryophyllene (2) + 1-Propanol (3) + Water (4) at Temperatures 303.15, 313.15, and 323.15 K ». MATEC Web of Conferences 156 (2018) : 02001. http://dx.doi.org/10.1051/matecconf/201815602001.
Texte intégralRésumé :
In this work, the experimental liquid–liquid equilibrium (LLE) data were measured for quaternary mixtures of eugenol(1) + β–caryophyllene(2) + 1-propanol(3) + water(4) at temperatures 303.15, 313.15, and 323.15 K and at atmospheric pressure. The equilibrium data ware determined by using an equilibrium cell with temperature controlled. Quantitive analysis was performed by using gas chromatography (GC) equipped with thermal conductivity detector and capillary column Rtx-5. The experimental data were then correlated by using the NRTL and the UNIQUAC models. The reliability of these models were tested by compared with the experimental results using a root mean square deviation (RMSD). Based on the RMSD, the NRTL and the UNIQUAC models suited really well and give satisfactory result for the system of eugenol, β–caryophyllene, 1-propanol, and water with the average RMSD of the UNIQUAC and the NRTL models were 0.417% and 0.502%, respectively. Furthermore there was no significant effect of temperatures on the equilibrium composition for the system.
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Czernek, Krystian, et Stanisław Witczak. « Hydrodynamics of Two-Phase Gas-Very Viscous Liquid Flow in Heat Exchange Conditions ». Energies 13, no 21 (31 octobre 2020) : 5709. http://dx.doi.org/10.3390/en13215709.
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This paper presents the results of analyses of the impact of heat transfer conditions on the hydrodynamics of downward co-current annular flow in vertical tubes of very viscous liquid and gas. The research was conducted within the range of gas velocities of 0–30.0 m/s and liquid velocities of 0.001–0.254 m/s, while the viscosity was in the unprecedented range of 0.046–3.5 Pas. The research demonstrates that the volume and nature of the liquid waves with various amplitudes and frequencies arising on the surface of the film are relative to the flow rate and viscosity of the gas phase. At the same time, we found that, under the condition of liquid cooling, an increase in viscosity resulted in the formation of a smooth interface whereas, under the conditions where the liquid is heated at the end of the channel section, a greater number of capillary waves were formed. This research resulted in the development of new dependencies which take into account the influence of selected thermal and flow parameters (including mass fraction) on the values of volumes specific to very viscous liquid film flows. These dependencies improve the accuracy of calculation by 8–10% and are fully applicable to the description of the performance of an apparatus with a hydraulically generated liquid film.
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Garcia-Ybarra, P. L., et M. G. Velarde. « Oscillatory Marangoni–Bénard interfacial instability and capillary–gravity waves in single- and two-component liquid layers with or without Soret thermal diffusion ». Physics of Fluids 30, no 6 (1987) : 1649. http://dx.doi.org/10.1063/1.866229.
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AARTS, DIRK G. A. L., et HENK N. W. LEKKERKERKER. « Droplet coalescence : drainage, film rupture and neck growth in ultralow interfacial tension systems ». Journal of Fluid Mechanics 606 (10 juillet 2008) : 275–94. http://dx.doi.org/10.1017/s0022112008001705.
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We study the coalescence of a drop with its bulk phase in fluid–fluid demixing colloid–polymer mixtures. Such mixtures show behaviour analogous to molecular fluid–fluid systems, but the interfacial tension is between 105 to 107 times smaller than in the molecular case. Such an ultralow interfacial tension has several important consequences and offers significant advantages in the study of droplet coalescence. The coalescence process can be divided into three consecutive stages: (i) drainage of the continuous film between droplet and bulk phase, (ii) rupture of the film, and (iii) growth of the connection. These stages can be studied within a single experiment by optical microscopy thanks to the ultralow interfacial tension in colloid–polymer mixtures, which significantly changes the relevant characteristic length and time scales. The first stage is compared with existing theories on drainage, where we show several limiting theoretical cases. The experimental drainage curves of different colloid–polymer mixtures can be scaled and then show very similar behaviour. We observe that drainage becomes very slow and eventually the breakup of the film is induced by thermal capillary waves. The time it takes for a certain height fluctuation of the interface to occur, which turns out to be an important parameter for the kinetics of the process, can be directly obtained from experiment. During the third stage we observe that the radius of the connecting neck grows linearly with time both for gas bubbles and liquid droplets with an order of magnitude that is in good agreement with the capillary velocity. Finally, partially bleaching the fluorescent dye inside the liquid droplet reveals how the surface energy is transformed into kinetic energy upon coalescence. This opens the way for a more complete understanding of the hydrodynamics involved.
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Martínez, Hector, Enrique Chacón, Pedro Tarazona et Fernando Bresme. « The intrinsic interfacial structure of ionic surfactant monolayers at water–oil and water–vapour interfaces ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 467, no 2131 (16 février 2011) : 1939–58. http://dx.doi.org/10.1098/rspa.2010.0516.
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Using computer simulations, we investigate the interfacial structure of sodium dodecyl sulphate (SDS) monolayers adsorbed at the water surface and water–oil interfaces. Using an algorithm that removes the averaging effect of the capillary waves, we obtain a detailed view of the solvation structure of water around the monolayer. We investigate surface concentrations between 45 and 33 Å 2 per surfactant, which are near experimental conditions corresponding to the critical micellar concentration and the formation of Newton black films. The surfactants induce a layering structure in water, which disappears at approximately 1 nm from the monolayer plane. The water molecules exhibit a preferred orientation with the dipoles pointing towards the monolayer. The orientational order decays slowly, but it does not influence the hydrogen bond structure of water, which is significantly disrupted in the interfacial region only. These structural changes are qualitatively the same in SDS–water and oil–SDS–water interfaces. In the latter case, we find a small degree of penetration of oil in the monolayer (between 0.2 and 0.25 molecules per SDS). This small penetration has a measurable effect on the monolayer, which increases its thickness by approximately 10 per cent. The bending modulus of the SDS monolayers is of the order of the thermal energy, k B T .
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Poulichet, Vincent, et Valeria Garbin. « Ultrafast desorption of colloidal particles from fluid interfaces ». Proceedings of the National Academy of Sciences 112, no 19 (28 avril 2015) : 5932–37. http://dx.doi.org/10.1073/pnas.1504776112.
Texte intégralRésumé :
The self-assembly of solid particles at fluid–fluid interfaces is widely exploited to stabilize emulsions and foams, and in materials synthesis. The self-assembly mechanism is very robust owing to the large capillary energy associated with particle adsorption, of the order of millions of times the thermal energy for micrometer-sized colloids. The microstructure of the interfacial colloid monolayer can also favor stability, for instance in the case of particle-stabilized bubbles, which can be indefinitely stable against dissolution due to jamming of the colloid monolayer. As a result, significant challenges arise when destabilization and particle removal are a requirement. Here we demonstrate ultrafast desorption of colloid monolayers from the interface of particle-stabilized bubbles. We drive the bubbles into periodic compression–expansion using ultrasound waves, causing significant deformation and microstructural changes in the particle monolayer. Using high-speed microscopy we uncover different particle expulsion scenarios depending on the mode of bubble deformation, including highly directional patterns of particle release during shape oscillations. Complete removal of colloid monolayers from bubbles is achieved in under a millisecond. Our method should find a broad range of applications, from nanoparticle recycling in sustainable processes to programmable particle delivery in lab-on-a-chip applications.
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Gaillot, S., C. Destouches, G. Cheymol et J. Brinster and Al. « Fuel Irradiation Devices Test of Feedthroughs Equipped With Optical Fibers in support of the development of innovative instrumentation ». EPJ Web of Conferences 288 (2023) : 04011. http://dx.doi.org/10.1051/epjconf/202328804011.
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As part of the activities for developing experimental devices for research reactors and associated test loops, some concern the development and qualification of instrumentation. The on-board instrumentation makes it possible to monitor online the evolution of physical parameters of samples and/or components subjected to different stresses (thermal, hydraulic, chemical and nuclear, etc.). In addition to the so-called “classic” instrumentation implemented in this type of equipment (pressure, temperature, flow, elongation), R&D actions are in progress in order to propose innovative instrumentation, able to improve the experimental offer and describe the physical phenomena with more accuracy. This is the case of optical measurements which present many advantages (compactness, insensitivity to EM waves, complex measurements by optical interrogation of a single fiber). In addition, actions are underway for the selection of optical fibers that can be used for applications in a nuclear reactor (in particular resistance to the irradiation). The tests presented in this paper relate to the behavior of sealed feedthroughs for optical fibers to the thermal hydraulics conditions of light water reactors. These tests are part of the safety demonstration in so-called degraded operating cases i.e. corresponding to a configuration where the optical fiber is placed directly in the process fluid (pressurized water). One note that in normal operation, the optical fiber is isolated from the process fluid by a jacket consisting of a metal capillary. After an introduction and a brief presentation of the use of optical fibers in experimental equipment, the paper describes the tightness feedthroughs used, the tests carried out, indicate the main results obtained and opens up some perspectives for future development phases.
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Khroustalev, B. M., Liu Tingguo, V. D. Akeliev, Li Zhongyu, H. Yu Aliakseyeu et V. V. Zankаvich. « Heat Resistance and Heat-and-Mass Transfer in Road Pavements ». ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 62, no 6 (29 novembre 2019) : 536–46. http://dx.doi.org/10.21122/1029-7448-2019-62-6-536-546.
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The paper presents a fragment of on-going investigations directed on creation of optimal information environment that ensures an access to the R&D publications from the known scientific journals and other scientific serials which are necessary for qualitative execution of scientific and technological activities on priority areas in highway engineering. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific publications which are necessary for execution of investigations on heat and mass transfer in road dressings. Their deformations occur under various climatic conditions due to heat and mass transfer processes, interaction of transport flows and road surface that leads to crack formation in depth and on the surface of road dressings. Structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-, reinforced concrete, concrete, brick scrap and products of their recycling, various wastes of production etc.) exerts an influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to viscosity, air velocity, geometric characteristics, permeability, capillary pressures in materials. It has been shown that calculations based on principles of complex number usage have specific features in engineering practice: it is required to observe their accuracy in approaches, calculation reduction due to some accuracy degradation as a consequence of transition from complex numbers to their modules with exclusion of phase shift account and related with propagation of thermal waves. In this respect calculations of heat resistance without phase shifts are considered as rather important if they are in agreement with principles based on the fact that a complexity is characterized by thermal absorptivity of the material in a great number of calculations. The investigations have been supported by Henan Center for Outstanding Overseas Scientists, Grant Number GZS 2018006 (People’s Republic of China, Henan Province).
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Horesh, Amihai, William Connacher et James Friend. « Acoustothermal phase change and acoustically driven atomization for cold liquid microthrusters ». Applied Physics Letters 122, no 1 (2 janvier 2023) : 014104. http://dx.doi.org/10.1063/5.0131467.
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Over the years, a diverse range of physical and chemical phenomena have been explored and applied to devise reliable, small thrusters for stationkeeping and orientation of spacecraft. Commercial space flight is accelerating this need. Here, we consider acoustically driven melting of a frozen working fluid in the nozzle of an acoustic device, followed by acoustofluidic atomization from the nozzle to produce thrust. Fifty-five MHz acoustic waves generated by piezoelectric transducers couple into liquid and transfer energy in the form of both acoustic radiation and streaming, producing a directed atomized spray. A challenge in this system, as with most liquid-thrust systems, is the risk of phase change due to the extreme thermal environment in space, particularly in the freezing of the working fluid. Though acoustic energy is known to produce rapid and controllable heating, it so far has not been used to produce phase changes. The atomization produces capillary pressure sufficient to draw in fluid from a reservoir, though we do use a simple pressure-driven pump to support greater atomization rates. We provide a simple energy conservation model to explain the acoustothermal interaction and validate this with experiments. The specific impulse and thrust of this type of thruster are quite modest at 0.1–0.4 s and 12.3 μN, respectively, but the thruster component is small, light, and is without moving parts, a fascinating potential alternative to current technologies.
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Serdyukov, Vladimir, Nikolay Miskiv et Anton Surtaev. « The Simultaneous Analysis of Droplets’ Impacts and Heat Transfer during Water Spray Cooling Using a Transparent Heater ». Water 13, no 19 (2 octobre 2021) : 2730. http://dx.doi.org/10.3390/w13192730.
Texte intégralRésumé :
This paper demonstrates the advantages and prospects of transparent design of the heating surface for the simultaneous study of the hydrodynamic and thermal characteristics of spray cooling. It was shown that the high-speed recording from the reverse side of such heater allows to identify individual droplets before their impact on the forming liquid film, which makes it possible to measure their sizes with high spatial resolution. In addition, such format enables one to estimate the number of droplets falling onto the impact surface and to study the features of the interface evolution during the droplets’ impacts. In particular, the experiments showed various possible scenarios for this interaction, such as the formation of small-scale capillary waves during impacts of small droplets, as well as the appearance of “craters” and splashing crowns in the case of large ones. Moreover, the unsteady temperature field during spray cooling in regimes without boiling was investigated using high-speed infrared thermography. Based on the obtained data, the intensity of heat transfer during spray cooling for various liquid flow rates and heat fluxes was analyzed. It was shown that, for the studied regimes, the heat transfer coefficient weakly depends on the heat flux density and is primarily determined by the flow rate. In addition, the comparison of the processes of spray cooling and nucleate boiling was made, and an analogy was shown in the mechanisms that determine their intensity of heat transfer.