Добірка наукової літератури з теми "Oscillating Drop"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Oscillating Drop".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Статті в журналах з теми "Oscillating Drop":
1
Szakáll, Miklós, Karoline Diehl, Subir K. Mitra, and Stephan Borrmann. "A Wind Tunnel Study on the Shape, Oscillation, and Internal Circulation of Large Raindrops with Sizes between 2.5 and 7.5 mm." Journal of the Atmospheric Sciences 66, no. 3 (March 1, 2009): 755–65. http://dx.doi.org/10.1175/2008jas2777.1.
Анотація:
Abstract Precipitation prediction using weather radars requires detailed knowledge of the shape parameters of raindrops falling at their terminal velocities in air. Because the raindrops undergo oscillation, the most important shape parameters from the radar prediction point of view are the equilibrium drop shape, the time-averaged axis ratio, and the oscillation frequency. These parameters for individual water drops with equivalent diameter from 2.5 to 7.5 mm were investigated in a vertical wind tunnel using high-speed video imaging. A very good agreement was found between the measured and the theoretically determined raindrop shape calculated by a force balance model. A new method was developed to determine the equivalent drop diameter with the help of the oscillation frequency. The drop size determination by means of the frequency method was found to be three times more precise than by volumetric methods. The time-averaged axis ratio was found to be equal to the equilibrium axis ratio in the investigated raindrop size range. The analysis of the oscillation frequency of the raindrops revealed that the drops undergo multimode oscillations and are oscillating in a transverse mode in addition to an axisymmetric oblate–prolate mode. Experiments are included in which the internal circulation associated with drop oscillation was investigated and compared to theory.
2
Thurai, M., V. N. Bringi, M. Szakáll, S. K. Mitra, K. V. Beard, and S. Borrmann. "Drop Shapes and Axis Ratio Distributions: Comparison between 2D Video Disdrometer and Wind-Tunnel Measurements." Journal of Atmospheric and Oceanic Technology 26, no. 7 (July 1, 2009): 1427–32. http://dx.doi.org/10.1175/2009jtecha1244.1.
Анотація:
Abstract Comparisons of drop shapes between measurements made using 2D video disdrometer (2DVD) and wind-tunnel experiments are presented. Comparisons are made in terms of the mean drop shapes and the axis ratio distributions. Very close agreement of the mean shapes is seen between the two sets of measurements; the same applies to the mean axis ratio versus drop diameter. Also, in both sets of measurements, an increase in the oscillation amplitudes with increasing drop diameter is observed. In the case of the 2DVD, a small increase in the skewness was also detected. Given that the two sets of measurements were conducted in very different conditions, the agreement between the two sets of data implies a certain “robustness” in the mean shape of oscillating drops that may be extended to natural raindrop oscillations, at least in steady rainfall and above the surface layer.
3
Khaibullina, A. I., A. R. Khayrullin, and V. K. Ilyin. "Experimental study of oscillating flow in tube bundle." Vestnik IGEU, no. 6 (December 28, 2023): 29–37. http://dx.doi.org/10.17588/2072-2672.2023.6.029-037.
Анотація:
Oscillating reciprocating flows are found in a variety of engineering applications. The mechanisms of oscillating flows have not been sufficiently studied. Oscillating flows can be created artificially to increase heat transfer equipment by intensifying heat transfer. Thus, this paper studies the flow and heat transfer characteristics of a tube bundle under the influence of oscillating flow. The assessment of heat transfer and the hydrodynamic flow pattern in a tube bundle during flow oscillations is carried out on the basis of experimental studies. Flow oscillations have been created by a pneumatic system that drove a pulsator. The time characteristic of the pressure drop of the tube bundle has been recorded using an oscilloscope and pressure drop sensors. To assess the dynamics of flow velocity, the high-speed shooting method is used. The heat exchange of a tube bundle has been determined by the electrical power expended to maintain a constant temperature on the tube side of the bundle. For the first time, heat transfer and the hydrodynamic flow pattern with asymmetrical flow oscillations in an inline tube bundle are studied experimentally. It is shown that the shape of oscillations of flow velocity and pressure drop depend on frequency. It has been found that with increasing frequency there is an increase in the values of flow velocity and pressure drop. It has been determined that for certain moments of time, the flow velocity and pressure drop during asymmetrical oscillations exceed symmetrical ones. It has been established that the heat transfer rate of a bundle increases by 1,7 times with an increase in frequency. It has been shown that asymmetrical oscillations are more effective in intensifying heat transfer than symmetrical ones by an average of 1,1 times. Analysis of the results obtained has showed the possibility of intensifying heat transfer in a tube bundle using oscillating flows. Thus, oscillating flows can be used to increase the efficiency of heat exchange equipment. The results obtained on the hydrodynamic flow pattern can be used in mathematical modeling of oscillating flows, which are necessary to expand the operating parameters of the study and determine the most effective ones.
4
Sterlyadkin, Victor V. "Some Aspects of the Scattering of Light and Microwaves on Non-Spherical Raindrops." Atmosphere 11, no. 5 (May 21, 2020): 531. http://dx.doi.org/10.3390/atmos11050531.
Анотація:
A review of the author’s work on the study of the microphysics of rain is carried out. The effect of an anomalously high modulation of light scattered by oscillating drops of water, which consists in the formation of powerful pulses of light when illuminating an oscillating drop with continuous light and observation at scattering angles near a first-order rainbow, is described and explained. The anomalous scattering tracks obtained in the photographs provide information on the mass, average shape, mode, and amplitude of oscillations for each drop, by analogy with the Wilson camera. In field measurements, spatial selection of droplets by size was detected, when droplets of different sizes were grouped in different parts of space. The theoretical substantiation of the grouping of rain particles in space under the influence of wind gusts is carried out. It has been shown that the grouping and clustering of raindrops affects the relationship between radar reflectivity Z and rain intensity R. The influence of non-sphericity and oscillation of raindrops on the scattering of microwave radiation is studied. Polarization methods are proposed for enhancing or sharply reducing the contributions of the asphericity of raindrops to reflected radar signals.
5
Barrabino, Albert, Torleif Holt, Bård Bjørkvik, and Erik Lindeberg. "First Approach to Measure Interfacial Rheology at High-Pressure Conditions by the Oscillating Drop Technique." Colloids and Interfaces 5, no. 2 (April 13, 2021): 23. http://dx.doi.org/10.3390/colloids5020023.
Анотація:
An oscillating drop rheometer capable of operating under conditions of high pressure and high temperature has been built. The oscillating drop mechanism was able to support pressures as high as 1300 bar and successfully performed oscillations at constant pressure. Apparent elastic and viscous complex moduli were measured for a system of CO2 and synthetic seawater containing 100 ppm of a linear alkyl ethoxylate surfactant for different pressures and temperatures. The moduli had strong dependencies on both pressure and temperature. At temperatures of 40 and 80 °C, the apparent elastic modulus passed through a maximum for pressures between 100 and 300 bar. The harmonic distortion of the oscillations was calculated for all measurements, and it was found that drop oscillations below ca. 2.6 µL caused distortions above 10% due to a mechanical backlash of the motor.
6
De Maio, L., and F. Dunlop. "Sessile Drop on Oscillating Incline." Journal of Applied Fluid Mechanics 11, no. 6 (November 1, 2018): 1471–76. http://dx.doi.org/10.29252/jafm.11.06.28380.
7
Egry, I., H. Giffard, and S. Schneider. "The oscillating drop technique revisited." Measurement Science and Technology 16, no. 2 (January 20, 2005): 426–31. http://dx.doi.org/10.1088/0957-0233/16/2/013.
8
Goncalves Dos Santos, Angelica, Francisco Javier Montes-Ruiz Cabello, Fernando Vereda, Miguel A. Cabrerizo-Vilchez, and Miguel A. Rodriguez-Valverde. "Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces." Coatings 9, no. 4 (April 21, 2019): 270. http://dx.doi.org/10.3390/coatings9040270.
Анотація:
Evaluation of superhydrophobic (SH) surfaces based on contact angle measurements is challenging due to the high mobility of drops and the resolution limits of optical goniometry. For this reason, some alternatives to drop-shape methods have been proposed such as the damped-oscillatory motion of ferrofluid sessile drops produced by an external magnetic field. This approach provides information on surface friction (lateral/shear adhesion) from the kinetic energy dissipation of the drop. In this work, we used this method to compare the low adhesion of four commercial SH coatings (Neverwet, WX2100, Ultraever dry, Hydrobead) formed on glass substrates. As ferrofluid, we used a maghemite aqueous suspension (2% v/v) synthesized ad hoc. The rolling magnetic drop is used as a probe to explore shear solid–liquid adhesion. Additionally, drop energy dissipates due to velocity-dependent viscous stresses developed close to the solid–liquid interface. By fitting the damped harmonic oscillations, we estimated the decay time on each coating. The SH coatings were statistically different by using the mean damping time. The differences found between SH coatings could be ascribed to surface–drop adhesion (contact angle hysteresis and apparent contact area). By using this methodology, we were able to grade meaningfully the liquid-repelling properties of superhydrophobic surfaces.
9
Ivantsov, Andrey, Tatyana Lyubimova, Grigoriy Khilko, and Dmitry Lyubimov. "The Shape of a Compressible Drop on a Vibrating Solid Plate." Mathematics 11, no. 21 (November 3, 2023): 4527. http://dx.doi.org/10.3390/math11214527.
Анотація:
The influence of high-frequency vibrations on the shape of a compressible drop placed on an oscillating solid substrate is studied in this paper. Due to the significant difference in characteristic temporal scales, the average and pulsating motions of the drop can be considered separately. For nearly hemispherical drop, the solution to the problem of pulsating motion is found in the form of series in Legendre polynomials. Frequencies of natural sound oscillations of hemispherical axisymmetric drop are obtained. Resonances of the acoustic mode of drop oscillations are found. The problem of forced oscillations of hemispherical drop in the limit of weakly compressible liquid is considered. It is found that drop oscillation amplitude grows with vibration intensity according to quadratic law, which is consistent with the solution of the pulsation problem for finite compressibility assumption. A variational principle for calculation of average drop shape is formulated based on minimization of energy functional for the case, so the compressibility of the liquid should be taken into account. It is shown that the functional (the sum of the kinetic and potential energies of the pulsating flow, the kinetic energy of the averaged flow, and the surface tension energy of the drop) decreases and reaches a minimum value at quasi-equilibrium state, in which the average shape of the drop becomes static. The influence of vibrations on the drop shape is studied for small values of the vibrational parameter. The surface of the drop in the absence of vibrations is assumed to be hemispherical. Calculations showed that under vibrations, drop height decreases, while the area of the base increases.
10
WUNDERLICH, RAINER K., and MARKUS MOHR. "Non-linear effects in the oscillating drop method for viscosity measurements." High Temperatures-High Pressures 48, no. 3 (2020): 253–77. http://dx.doi.org/10.32908/hthp.v48.648.
Анотація:
The contribution of non-linear fluid flow effects to the damping of surface oscillations in the oscillation drop method was investigated in a series of experiments in an electromagnetic levitation device installed on the International Space station, ISS-EML. In order to correctly evaluate the damping time constant from measured surface oscillation decays the effect of a modulated signal response on measured surface oscillation decay curves was investigated. It could be shown that various experimentally observed signal patterns could be well represented by a modulated response. The physical origin of such modulations is seen in rotation and precession. Over a temperature range of 220 K covered by different surface oscillation excitation pulses with an initial sample shape deformation of 5 – 10% the amplitude of surface oscillations as a function of time could be very well represented by a Lamb type damping with a temperature dependent viscosity. A direct comparison of surface oscillation decay times measured in the same temperature range but for different oscillation amplitudes showed no non-linear contribution to the damping time constant with a confidence level better 10%.
Дисертації з теми "Oscillating Drop":
1
Jaber, Ahmad. "Interfacial Viscoelastic moduli of bare, surfactant-laden and nanoparticle-laden interfaces oscillating in a weak gel." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0104.
Анотація:
Nous présentons une étude mettant en œuvre la méthode de la goutte oscillante pour sonder l'interface huile/eau, modifiable par ajout de tensioactifs ou des nanoparticules, entourée d'une phase continue de rhéologie contrôlable. La question clé posée dans ce travail porte sur l'effet des propriétés rhéologiques de la phase continue sur les mesures des modules viscoélastiques interfaciaux déduits à partir de la compression/dilatation d'une goutte oscillante. Dans cette optique, la phase continue est constituée d'un hydrogel thermoréversible K-carraghénane, sélectionné pour son inactivité interfaciale mais également pour son hystérèse en transition sol/gel qui permet en effet d'avoir un gel ou un liquide à la même température selon l'histoire thermique.Dans le cas d'une interface nue huile/eau et dans les conditions où la solution de KC est liquide, le module élastique de l'interface reste faible. Quand la solution de KC devient un gel, même si ce dernier est faible au point que la solution s'écoule sous son propre poids, nous assistons à l'apparition d'une signature élastique des meures viscoélastiques interfaciales attestant que la contribution de la rhéologie de la phase continue est non négligeable. La présence d'un tensioactif à l'interface huile/eau, génèrent un module élastique interfacial qui augmente avec la concentration en tensioactif dans le cas d'un milieu environnant liquide. En présence d'un gel faible, le module interracial s'effondre à force que le module du gel KC augmente attribuer à une pseudo-localisation de déformation à l'interface. Ce phénomène disparaît dans le cas d'une interface dense en nanoparticules solides (effet Pickering).L'ensemble de ce travail révèle l'importance de la déconvolution des contributions interfaciale et de volume dans des essais de rhéologie interfaciale avec la goutte pendanteWe present a study implementing the oscillating drop method to probe the oil/water interface, modifiable by surfactants or nanoparticles, while surrounded by a continuous phase of controllable rheology. The key question posed in this work concerns the effect of the rheological properties of the continuous phase on the measurements of interfacial viscoelastic moduli extracted from the compression/expansion of an oscillating drop. With this in mind, the continuous phase consists of a thermo-reversible hydrogel K-carrageenan, selected for its interfacial inactivity but also for its hysteresis after the sol/gel transition which allows to have a gel or liquid at the same temperature according to the thermal history.In the case of a pure oil/water interface and under conditions where the KC solution is liquid, the elastic modulus of the interface remains weak. When the KC solution becomes a gel, even if it is weak to the point that the solution flows under its own weight, we witness the appearance of an elastic signature in interfacial viscoelastic measures attesting to the contribution of the rheology of the continuous phase being not negligible.The presence of a surfactant at the oil/water interface, generating an interfacial elastic modulus that increases with the concentration of surfactant in the case of a liquid surrounding medium. In the presence of a weak gel, the interfacial modulus decreases by despite that the modulus of the KC gel increases, this is attributed to a pseudo-localization of deformation at the interface. This phenomenon disappears in the case of an interface laden with solid nanoparticles (Pickering effect).All of this work reveals the importance of deconvoluting interfacial and volume contributions in an interfacial viscoelasticity test of the pendant drop
2
Al-Faize, Mustafa M. "Mass transfer characteristics of large oscillating drops." Thesis, Aston University, 1986. http://publications.aston.ac.uk/10193/.
3
Ertl, Moritz [Verfasser]. "Direct Numerical Investigations of Non-Newtonian Drop Oscillations and Jet Breakup / Moritz Ertl." München : Verlag Dr. Hut, 2020. http://d-nb.info/121960609X/34.
4
Ertl, Moritz [Verfasser], and Bernhard [Akademischer Betreuer] Weigand. "Direct numerical investigations of non-Newtonian drop oscillations and jet breakup / Moritz Ertl ; Betreuer: Bernhard Weigand." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1205737022/34.
5
Abi, Chebel Nicolas. "Dynamique et rhéologie interfaciales à haute fréquence d'une goutte oscillante." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT043G/document.
Анотація:
Ce travail présente une étude de la dynamique interfaciale de gouttes oscillantes dans une plage étendue de fréquences, en particulier dans le domaine des hautes fréquences. Nous avons développé une méthode de caractérisation de la dynamique des oscillations de gouttes, en présence d’un forçage externe imposé, sous la forme de variations de volume périodiques de faible amplitude sur une goutte attachée à l’extrémité d’un capillaire. Cette méthode permet d’identifier les modes d’oscillation des gouttes et d’en mesurer les fréquences et les taux d’amortissement. Cette méthode a été appliquée à différents systèmes liquide-liquide, en l’absence ou en présence de surfactants. Dans ce dernier cas, elle permet d’évaluer l’effet du comportement viscoélastique des interfaces sur la dynamique des oscillations. Ainsi 3 types d’interfaces ont été identifiés. Pour les interfaces de premier type (heptane/eau sans ajout de surfactant), chaque mode propre est modélisé par un oscillateur linéaire peu amorti. Les fréquences propres et les taux d’amortissement sont bien prédits par la théorie linéaire. Les interfaces de types 2 et 3 sont obtenues en ajoutant du pétrole brut à la phase dispersée. Les surfactants naturellement présents dans le pétrole (asphaltènes, résines) s’adsorbent à l’interface et lui confèrent des propriétés viscoélastiques. Pour les interfaces jeunes (type 2, moins de 20 minutes de vieillissement), les fréquences propres mesurées restent bien prédites par la théorie, qui considère des interfaces non contaminées, tandis que les taux d’amortissement sont de loin supérieurs aux valeurs théoriques. D’autre part, les interfaces vieillies (type 3) présentent des modes propres différents avec des fréquences de résonance supérieures à celles des interfaces jeunes. Dans ce cas, la dynamique de l’interface à haute fréquence est régie par l’élasticité du réseau formé par les espèces amphiphiles du pétrole brut. Les oscillations libres d’une goutte en ascension dans une phase externe stagnante, pour un système liquide-liquide sans ajout de surfactants, ont été étudiées. Les valeurs mesurées de la fréquence d’oscillation des 4 premiers modes sont en adéquation avec la théorie linéaire. Cependant les valeurs mesurées du taux d’amortissement sont très élevées par rapport aux valeurs théoriques, pour une interface non contaminée. En effet, des espèces résiduelles adsorbées à l’interface provoquent l’apparition d’un gradient de tension interfaciale par effet Marangoni et par suite une production de vorticité plus intense dans les couches-limites, ce qui conduit à l’augmentation de l’amortissement des oscillationsWe present an experimental study of oscillating drop interfacial dynamics at a wide frequency range, especially at high frequency. A characterization method of drops oscillation dynamics has been developed. The oscillations are generated by imposing low amplitude periodic variation of volume to a drop which is attached to a capillary tip. The present method is based on the identification of the drop eigenmodes and the determination of their frequencies and damping rates. It has been applied to characterize several liquid-liquid systems. Three types of interface have been identified. For interfaces of type 1 (heptane/water without added surfactant), each eigenmode is modelled by a weakly damped linear oscillator. Eigenfrequencies and damping rates are well predicted by the linear theory. Interfaces of Types 2 and 3 are obtained by adding crude oil to the disperse phase. Oil native surfactants (asphaltenes, resins) adsorb on the drop interface and provide the latter with viscoelastic behaviour. For young interfaces (type 2 with aging time below 20 minutes), eigenfrequencies remain well predicted by the theory, which deals with non contaminated interfaces, whereas the measured damping rates are significantly higher than the theoretical values. On the other hand, aged interfaces (type 3) exhibit different eigenmodes, of which eigenfrequencies are much higher than the resonance frequencies measured for the young interfaces. At high frequency, the dynamics of aged interfaces are governed by the elasticity of the network constituted by the crude oil amphiphilic species, while the dynamics of young interfaces are governed by interfacial tension. Freely decaying oscillations of a rising drop in a liquid at rest without added surfactant were also considered. Measured frequencies for the first four eigenmodes are in good agreement with the linear theory. However, measured damping rates are much higher than the theoretical rates for non contaminated interfaces. In fact, residual adsorbed species at the heptane/water interface induce Marangoni effects and thus gradients of interfacial tension. Therefore, vorticity production within the boundary layers is enhanced, which explains the observed increase of the oscillation damping rates
6
Ullah, Asmat. "Separation of oil drops from produced water using a slotted pore membrane." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/15687.
Анотація:
Microfiltration is one of the most important processes in membrane sciences that can be used for separating drops/particles above 1 ??m. Depth microfiltration membranes retain drops/particles inside the surface of the membrane, the process is expensive and membranes quickly become fouled. On the other hand, surface microfiltration membranes stop drops/particles on the surface of the membrane and the process is less fouling. Higher permeate flux and lower trans-membrane pressure is obtained with a shear enhanced microfiltration technique. Production of specific size of drops and stability of the drops are very important in testing the microfiltration of crude oil drops/water emulsions. Oil drops from 1-15 ??m were produced with a food blender, operated at its highest speed for the duration of 12 mins. In addition, vegetable oil drops were stabilised with 1% polyvinyl alcohol (PVA), Tween 20 and gum Arabic, stability was assessed on the basis of consistency in the size distribution and number of drops in each sample analysed at 30 mins interval. A slotted pore Nickel membrane with the slot width and slot length of 4 and 400 ??m respectively has been used in the filtration experiments. The slot width to the slot length ratio (aspect ratio) of the used membrane is 100. Vibrating the membrane at various frequencies created shear rates of different intensities on the surface of the membrane. Membrane with a tubular configuration is preferred over the flat sheet because it is easy to control in-case of membrane oscillations both at lab and industrial scale. Besides this, a tubular membrane configuration provides a smaller footprint as compared to the flat sheet. The influence of applied shear rate on slots/pore blocking has been studied. Applying shear rate to the membrane reduced the blocking of the slots of the membrane; and reduction of slots blocking is a function of the applied shear rate. At higher shear rate, lower blocking of the slots of the membrane was verified by obtaining lower trans-membrane pressure for constant rate filtration. The experiments are in reasonable agreement with the theoretical blocking model. Divergence of the experimental data from the theory may be due to involvement of deforming drops in the process. During microfiltration of oil drops, the drops deform when passing through the slots or pores of the membrane. Different surfactants provided different interfacial tensions between the oil and water interface. The influence of interfacial tension on deformation of drops through the slots was studied. The higher the interfacial tension then the lower would be the deformation of drops through the slots. A mathematical model was developed based on static and drag forces acting on the drops while passing the membrane. The model predicts 100% cut-off of drops through the membrane. Satisfactory agreement of the model with the experiments shows that the concept of static and drag force can be successfully applied to the filtration of deformable drops through the slotted pore membranes. Due to the applied shear rate, inertial lift migration velocities of the drops away from the surface of the membrane were created. Inertial lift velocities are linear functions of the applied shear rate. A mathematical model was modified based on inertial lift migration velocities. The critical radius of the drops is the one above which drops cannot pass through the surface of the membrane into the permeate due to the applied shear rate and back transport. The model is used as a starting point and is an acceptable agreement with the experiment. The model can be used to predict the 100% cut-off value for oil drops filtration and a linear fit between this value and the origin on a graph of grade (or rejection) efficiency and drop size to slot width ratio was used to predict the total concentration of dispersed oil left after filtration. Hence, it is shown how it is possible to predict oil discharge concentrations when using slotted filters.
7
Scofield, Christopher D. "Oscillating microbubbles created by water drops falling on fresh and salt water : amplitude, damping and the effects of temperature and salinity." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24000.
8
Sartori, Paolo. "The Role of Interfaces in Microfluidic Systems: Oscillating Sessile Droplets and Confined Bacterial Suspensions." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3423250.
Анотація:
This PhD thesis is focused on the role of interfaces that characterize microfluidic systems, such as
the free air/liquid interface of drops or the liquid/solid interface of fluids enclosed in microchannels.
This work has a twofold character: on one side, we studied the dynamics of sessile drops subject to oscillations of the substrate; on the other, we investigated the spatial concentration distribution of suspensions of motile bacteria, as a model system for active collids, tuned by geometrical confinement.
Dynamics of sessile drops. The first topic is related to the field of wetting phenomena and
open microfluidics, which deals with the behaviour of drops, typically in the nano-/microliter range,
deposited on open surfaces. At such length scale, these systems are dominated by capillarity and may give rise to unexpected effects, not commonly observed at the larger scale we are used to. Our studies aim to the achievement of an active control on the motion and shape of drops by means of vibration of the substrates, for chemical or biological applications.
In particular, the motion of liquid drops on an inclined substrate subject to vertical harmonic
oscillations have been considered. Typically, small droplets on inclined surfaces remain pinned because of contact angle hysteresis. When vertical oscillations are applied the droplets unpin and slide down. Surprisingly, for sufficiently large oscillation amplitude the droplets move upward against gravity. The systematical investigation of the response of drops on varying peak acceleration and frequency of oscillations, for fluids with different surface tensions and viscosity, allowed the control of the unidimensional motion along the substrate.
Then, we have studied the interfacial morphologies of water drops confined on the hydrophilic top
face of rectangular posts of width 0.5 mm and various length. For small volumes, the liquid film adopts the shape of a homogeneous filament with a uniform cross section close to a circular segment. For larger volumes, the water interface forms a central bulge, which grows with the volume. In the case of posts longer than a characteristic length, the transition between the two film shapes on varying the volume is discontinuous and exhibits the bistability of the two morphologic states associated with a hysteresis phenomenon. Vertically oscillating the post, with fixed water volume corresponding to the bistability, at certain frequencies induces an irreversible transition from the filament to the bulge state.
Self-propelled particles under geometrical confinement. The second topic deals with the
behaviour of active fluids, i.e. self-propelled colloid suspensions which are intrinsically out of equilibrium systems (Active Matter). In particular, in the presence of geometrical structures, such systems behave in a very different way with respect to equilibrium Browinan colloids. We have analyzed the role of different swimming patterns on the concentration distribution of bacterial suspensions confined between two flat walls, by considering wild-type E. coli and P. aeruginosa, which perform Run and Tumble and Run and Reverse patterns, respectively. The concentration profiles have been obtained by counting motile bacteria at different distances from the bottom wall. In agreement with previous studies, an accumulation of motile bacteria close to the walls was observed. Different fraction of motile bacteria and different wall separations, ranging from 100 μm to 250 μm, have been tested. The concentration profiles resulted to be independent on the walls separation and on the different kind of motility and to scale with the motile fraction. These results are confirmed by numerical simulations, based on a collection of self-propelled rod-like particles interacting only through steric interactions.Questa tesi di dottorato prende in esame il ruolo delle interfacce che caratterizzano i sistemi microfluidici, come ad esempio l’interfaccia libera aria/acqua delle gocce o l’interfaccia liquido/solido di fluidi racchiusi in microcanali. Questo lavoro ha un duplice carattere: da una parte, abbiamo studiato la dinamica di gocce sessili soggette ad oscillazioni del substrato; dall’altra, abbiamo investigato come la distribuzione spaziale della concentrazione in sospensioni batteriche, prese come sistema modello per colloidi attivi, venga alterata da un confinamento geometrico. Dinamica di gocce sessili. Il primo argomento rientra nel campo dei fenomeni di bagnabilità e della microfluidica aperta, che tratta il comportamento di gocce, tipicamente nel range dei nano- /microlitri, depositate su superfici aperte. A tali scale di lunghezza, questi sistemi sono dominati dalla capillarità a possono produrre effetti inaspettati che non vengono comunemente osservati alle scale macroscopiche a cui siamo abituati. I nostri studi sono volti al raggiungimento del controllo attivo del moto e della forma delle gocce per mezzo di vibrazioni del substrato, con applicazioni dalla Chimica alla Biologia. In particolare, è stato considerato il moto di gocce su in substrato inclinato sottoposto ad oscillazioni armoniche verticali. Normalmente, su superfici inclinate le goccioline rimangono ferme a causa dell’isteresi dell’angolo di contatto. Quando vengono applicate oscillazioni verticali le goccioline si sbloccano e scivolano giù. Sorprendentemente, per ampiezze di oscillazioni sufficientemente grandi le goccioline si muovono verso l’atro contro la forza di gravità. Un’analisi della risposta delle gocce al variare dell’accelerazione di picco e della frequenza di oscillazione, prendendo in esame fluidi con diverse tensioni superficiali e viscosità, ha permesso il controllo del moto unidimensionale lungo il pianoinclinato. Inoltre, abbiamo studiato le morfologie interfacciali di gocce d’acqua confinate sulla faccia superiore idrofilica di post rettangolari con larghezza 0.5 mm e varie lunghezze. Per piccoli volumi, il film liquido prende la forma di un filamento omogeneo con una cross-section uniforme simile ad un segmento circolare. Per volumi più grandi, l’interfaccia acqua/aria forma un rigonfiamento centrale, che cresce con il volume. Nel caso di post più lunghi di una lunghezza caratteristica, la transizione tra le due forme al variare del volume discontinua e mostra la bistabilità dei due stati morfologici associata ad un fenomeno di isteresi. Applicando al post, con volume d’acqua fissato corrispondente alla bistabilità, vibrazioni verticali con determinate frequenze si più indurre una transizione irreversibile dallo stato di filamento omogeneo a quello rigonfiato. Particelle auto-propulse sotto confinamento geometrico. Il secondo argomento riguarda il comportamento di fluidi attivi, cioè sospensioni di colloidi auto-propulsi che costituiscono sistemi intrinsecamente fuori equilibrio (Materia Attiva). In particolare, in presenza di strutture geometriche, tali sistemi si comportano in modo molto differente rispetto a colloidi Browniani all’equilibrio. Abbiamo analizzato il ruolo di diversi schemi di motilità sulla distribuzione di concentrazione di sospensioni batteriche confinate tra due pareti solide. considerando E. coli a P. aeruginosa wild-type, che si muovono secondo gli schemi Run and Tumble e Run and Reverse, rispettivamente. I profili di concentrazione sono tati ottenuti contando i batteri motili a diverse distanze dalle pareti. In accordo con studi precedenti, si osservato un accumulo di batteri motili in prossimit delle pareti. Sono state testate diverse frazioni di batteri motili e diverse distanze di separazione tra le pareti, nel range tra 100μm e 250 μm. I profili di concentrazione risultano indipendenti dalla distanza tra le pareti e dai differenti schemi di motilità e scalano con la frazione di batteri motili. Questi risultati sono confermati da simulazioni numeriche, basate su una collezione di particelle allungate auto-propulse che interagiscono solo tramite interazioni steriche.
9
Boichon, Christelle. "Oscillations d'une masse fluide en lévitation aérodynamique." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0076.
Анотація:
L'objectif de ce travail est la modelisation des modes d'oscillations axisymetriques d'une goutte fluide en levitation aerodynamique au dessus d'une paroi poreuse plane. En premier lieu, le travail a porte sur la modelisation de la forme stationnaire de la goutte levitee a l'aide de la methode des elements de frontiere appliquee a la resolution des equations de stokes stationnaires. En particulier, les champs de vitesse interne et externe a la goutte ont ete calcules. Pour la modelisation des oscillations de la goutte en levitation, la methode des elements de frontiere a egalement ete retenue pour resoudre les equations de stokes instationnaires dans le domaine frequentiel. Avant d'aborder le cas de la goutte en levitation, cette methode a ete mise au point sur le probleme plus simple des modes d'oscillations axisymetriques d'une goutte dans un milieu infini en l'absence de gravite. Une validation a ete realisee avec succes grace aux nombreux resultats de la litterature. Dans le cas de la goutte en levitation aerodynamique, la mise en oeuvre de cette methode a conduit a la mise au point d'un outil numerique qui calcule les frequences et les formes d'oscillations des modes propres axisymetriques de la goutte. Une analyse de sensibilite a conduit au choix optimal des parametres numeriques de ce programme. Par ailleurs, l'etude de l'influence des differents parametres physiques a permis de constater la pertinence des resultats. Enfin, une comparaison avec des resultats experimentaux s'est averee tout a fait satisfaisante.
10
Bouillant, Ambre. "Dynamiques spontanées en caléfaction." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX015.
Анотація:
Cette thèse s'intéresse à la caléfaction, ou l'effet Leidenfrost. Une goutte d'eau placée sur un substrat chaud lévite sur un film mince de vapeur. Cette couche intercalaire de gaz, continûment renouvelée, isole mécaniquement et thermiquement la goutte, limitant ainsi son évaporation et supprimant l’ébullition. L'état de lévitation a d'autres conséquences sur le liquide, comme de lui empêcher de mouiller son substrat, donnant à la goutte une forme de perle, et de produire une situation exempte de friction, lui conférant sa grande mobilité.Nous discutons dans premier temps les conditions qui permettent à une goutte de léviter sur sa propre vapeur et la température seuil au delà de laquelle ce phénomène apparaît. Dans un deuxième temps, nous envisageons cette situation d’un point de vue dynamique en détaillant trois phases de la vie d’une goutte. Au-dessus d’une certaine taille, la vapeur s’accumule et érige un dôme liquide. Un film de liquide pur très mince se forme, doté d’une stabilité remarquable. Des différences de température induisent des écoulements superficiels ascensionnels qui sélectionnent son épaisseur et s’opposent à son amincissement, expliquant qu’il subsiste quelques secondes. Pour des rayons plus raisonnables de flaque, des oscillations intermittentes apparaissent, donnant au liquide la forme d'étoile. L’origine de ce phénomène est élucidée : le coussin de vapeur possède une fréquence propre. Ses oscillations excitent le liquide qu’il supporte. La goutte, qui agit comme une cavité résonante, répond pour certains rayons quantifiés en oscillant spontanément suivant le mode accroché par le forçage intrinsèque. En réduisant encore de taille, le liquide acquiert une mobilité spectaculaire. Une goutte caléfiée est le siège d’écoulements internes très rapides, dont la symétrie est dictée par le confinement. En s’évaporant, on assiste à une changement de morphologie qui induit une brisure de symétrie. La gouttelette se met à rouler de manière asymétrique, rectifie et incline sa base, ce qui la propulse. Deux stratégies de contrôle de ces globules fugaces et insaisissables sont finalement proposées, inspirées des travaux relatifs à l'autopropulsion sur des surfaces couvertes de dents asymétriques. Le mouvement directionnel est forcé par l'application d'un gradient de température et par la texturation graduelle de la surface. Ces dynamiques, orchestrées par le confinement, illustrent la richesse de ce système où changements de phase, effets thermiques, aérodynamiques et hydrodynamiquesThis work focuses on the Leidenfrost effect. A water drop placed on a hot substrate levitates on a cushion of its own vapor. This vapor layer, continuously renewed, insulates the liquid both mechanically and thermally : it limits evaporation and suppresses boiling. Levitation has other consequences on the liquid. It prevents the liquid from wetting its substrate, giving it the appearance of a liquid pearl, while producing a frictionless situation and giving ii a high mobility.We first discuss the conditions that allow a drop to levitate above a hot substrate, in particular the threshold in temperature. Then, we adopt a dynamic point of view by detailing the three phases of the life of a Leidenfrost drop. Above a certain size, vapor accumulates and forms a thin liquid dome with remarkable stability. Temperature differences on that pure liquid film induce upward surface flows that select the thickness and oppose the film thinning.For smaller volume, liquid oscillations spontaneously and sporadically appear. The mechanism leading to the liquid stars is elucidated: the vapor film has it natural frequency. The vapor cushion oscillations excite the overlying liquid. The drop acts as a resonant cavity and thus responds for some quantified radius by oscillating according to the mode locked by the intrinsic forcing. By further reducing the radius, the liquid acquires spectacular mobility. A Leidenfrost drop hosts strong internal flows, whose symmetry is selected by confinement. Evaporation induces morphological changes and triggers a symmetry breaking. A droplet rolls asymmetrically, which rectifies and tilts its base. This leads to motion and contributes to the spectacular mobility of Leidenfrost droplets. Two strategies to control these elusive globules are eventually proposed, inspired by the work on self-propulsion on surfaces covered with asymmetric teeth. Directional movement is forced by applying a temperature gradient and by gradually texturing the substrate.The evaporation-driven confinement induces various dynamics that illustrate the richness of this system, where phase changes as well as thermal, aerodynamic and hydrodynamic effects conspire to generate new and exploitable properties
Книги з теми "Oscillating Drop":
1
Al-Faize, Mustafa M. Mass transfer characteristics of large oscillating drops. Birmingham: Aston University. Department of Chemical Engineering, 1986.
2
Scofield, Christopher D. Oscillating microbubbles created by water drops falling on fresh and salt water: Amplitude, damping and the effects of temperature and salinity. Monterey, Calif: Naval Postgraduate School, 1992.
3
Description of an oscillating flow pressure drop test rig. [Washington, DC]: National Aeronautics and Space Administration, 1988.
4
Description of an oscillating flow pressure drop test rig. [Washington, DC]: National Aeronautics and Space Administration, 1988.
Частини книг з теми "Oscillating Drop":
1
Helvensteijn, B. P. M., A. Kashani, A. L. Spivak, P. R. Roach, J. M. Lee, and P. Kittel. "Pressure Drop over Regenerators in Oscillating Flow." In Advances in Cryogenic Engineering, 1619–26. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4757-9047-4_203.
2
Flores Galicia, Fátima, Flor Guadalupe Haro Velázquez, Gerardo Rangel Paredes, David Porta Zepeda, Carlos Echeverría Arjonilla, and Catalina Stern Forgach. "Dynamic Behavior of a Drop on a Vertically Oscillating Surface." In Selected Topics of Computational and Experimental Fluid Mechanics, 489–96. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-11487-3_39.
3
Ryder, Peter L., and Nils Warncke. "Measurement of the Surface Tension of Undercooled Melts by the Oscillating Drop Method in An Electrostatic Levitator." In Solidification and Crystallization, 103–9. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527603506.ch12.
4
Brenn, Günter. "Drop Shape Oscillations." In Fluid Mechanics and Its Applications, 239–49. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33338-6_19.
5
Shchur, Lev, and Maria Guskova. "Drop Oscillation Modeling." In Communications in Computer and Information Science, 198–206. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-64616-5_17.
6
Troconis, Jorge, Armando Blanco, Dominique Legendre, Leonardo Trujillo, and Leonardo Di G. Sigalotti. "Numerical Simulations of Freely Oscillating Drops." In Computational and Experimental Fluid Mechanics with Applications to Physics, Engineering and the Environment, 335–43. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-00191-3_20.
7
Guskova, Maria S., and Lev N. Shchur. "Simulation of the Drops Oscillations in the Channel." In Smart Modelling for Engineering Systems, 275–82. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4619-2_21.
8
Hirata, Yoshinori, K. Tsujimura, B. Y. B. Yudodibroto, M. J. M. Hermans, and I. M. Richardson. "Modeling of Molten Drop Oscillation in Gas Shielded Metal Arc Welding." In THERMEC 2006, 3973–78. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-428-6.3973.
9
Kuzmin, Igor, and Leonid Tonkov. "Component-Based Software Model for Numerical Simulation of Constrained Oscillations of Liquid Drops and Layers." In Lecture Notes in Computational Science and Engineering, 261–71. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-87809-2_20.
10
Cherepanov, Аnatoliy N., and Vera K. Cherepanova. "To the Analytical Solution of the Problem of the Oscillations of a Drop on a Solid Substrate After Impact." In Springer Proceedings in Physics, 41–48. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1872-6_7.
Тези доповідей конференцій з теми "Oscillating Drop":
1
Rangel Paredes, Gerardo, David Porta Zepeda, Carlos Echeverria Arjonilla, and Catalina Stern. "Video: Visualization of currents inside an oscillating water drop." In 67th Annual Meeting of the APS Division of Fluid Dynamics. American Physical Society, 2014. http://dx.doi.org/10.1103/aps.dfd.2014.gfm.v0033.
2
Plohl, Gregor, and Günter Brenn. "Measurement of polymeric time scales from linear drop oscillations." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4686.
Анотація:
The oscillating drop method allows material properties of liquids to be measured from damped drop oscillations. Theliterature discusses, e.g., the measurement of the liquid dynamic viscosity and the surface tension against the ambient medium, predominantly for Newtonian liquids. We use this method for measuring pairs of material properties of polymeric liquids. Pairs of properties may be measured, since the quantity measured is a complex frequency with a real and an imaginary part. For the measurements, individual drops are levitated in air by an ultrasonic levitator and imaged with a high-speed camera. Amplitude modulation of the ultrasound drives shape oscillations of the levitated drop. When the modulation is switched off, with the levitating force maintained, the drop performs free oscillations which are damped due to the liquid viscosity. The data acquired from the images recorded are the angular frequency and the damping rate which are used as an input into the characteristic equation of the oscillating drop. Our measurements intend to yield either two viscoelastic time scales with the zero-shear viscosity known, or one time scale and the zero-shear viscosity, with the other time scale known. The two time scales are the stress relaxation and the deformation retardation times. The latter is difficult to get for polymer solutions.The present contribution presents results from a large set of measurements of the deformation retardation time. Liquids studied are aqueous solutions of poly(acryl-amides) at varying concentration. The corresponding values of the zero-shear viscosity agree well with the values from shear rheometry. Values of the deformation retardation time differ substantially from the values commonly used in viscoelastic flow simulations. Furthermore, the measured values disagree with the predictions from the viscous-elastic stress splitting approach in linear viscoelasticity. With our study we will provide a consistent set of material properties for the Oldroyd-B model in linear viscoelasticity. This will beimportant for material modelling in viscoelastic spray simulations.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4686
3
Awazu, Shigeru, Satoshi Matsumoto, and Yutaka Abe. "Study on Nonlinear Deformation Behaviors of Electrostatic Levitating Liquid Drop." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37193.
Анотація:
Under the micro-gravity environment in space, it is possible to hold a liquid drop without using container. The electrostatic levitation is one of the containerless processing techniques. Using this technique, thermo-physical properties of extreme high temperature molten metals have been measured. For example, the surface tension and viscosity have been estimated from the resonance frequency and the damping constant respectively with an oscillating drop method. This method is based on theoretical equations derived under linear approximations. However, an actual levitating drop includes nonlinear effects. Nonlinear effects should be taken into account for highly precise measurements of physical properties, but it is unknown experimentally. The purpose of the present study is to investigate nonlinear effects of a levitating liquid drop from fluid-dynamic point of view. In the present study, at first, axisymmetric oscillation was applied to a liquid drop levitated by electrostatic force and the oscillation frequency was related to the oscillation amplitude. Next, the rotation in the horizontal direction was applied. The drop deformation and the dependence of resonance frequency on rotational angular velocity were investigated. These experimental results agreed with theoretical predictions.
4
Olayiwola, Bolaji O., and Peter Walzel. "Efficient Heat Transfer in a Laminar Flow System by Hydrodynamic Manipulation." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11187.
Анотація:
The effects of flow manipulation on the heat transfer performance of a laminar flow system were investigated. The combination of series of fins and oscillating flow was used due to its inherent advantage of triggering very complex transient interaction of eddies and flow deflection within the system. The investigations were performed with fluids providing Prandtl numbers Pr > 10. Steady Reynolds number in the range of 50 < Re < 1200 were studied. The duct with a hydraulic diameter Dh = 15 mm contains series of non-conducting fins. All geometrical parameters remain constant. Low frequency oscillation f < 100 Hz was used in order to obtain oscillation effects mainly dominated by oscillation velocity, and to avoid attenuation of the oscillation amplitude A in the device. Based on the experimental data, a correlation equation was developed. The energy dissipation as a result of applied oscillation was also determined by phase resolved measurements of the pressure difference and liquid displacement. The heat transfer coefficients were found to be dynamically controlled by the oscillations. The results show efficient heat transfer within the system due to the applied oscillation especially at low flow rates. At higher flow rates, the effect of the flow oscillation on the heat transfer performance of the system diminishes. With oscillating finned flow, the influence of the geometrical parameter Dh/L is not significant due to enhanced fluid mixing and repeated thermal boundary layer rearrangement as a result of the flow oscillation. The predictions of the correlation are reasonable. The results of the CFD show that for the fin spacing to be significant on the effectiveness of the finned system, the oscillating flow velocity must be higher than the mean flow velocity. Enhanced heat transfer performance is possible with increasing fin height but theoretically, this yields high pressure drop and increased pumping power. The calculated power input due to oscillation is comparatively low and decreases towards increasing net flow rates where the pulsating flow has a diminishing effect and the system approaches non-pulsating flow behaviour.
5
He, Ya-Ling, and Wen-Quan Tao. "EXPERIMENTAL STUDY ON PRESSURE DROP THROUGH A WOVEN SCREEN SUBJECTED TO AN OSCILLATING FLOW." In Compact Heat Exchangers and Enhancement Technology for the Process Industries - 2003. Connecticut: Begellhouse, 2023. http://dx.doi.org/10.1615/978-1-56700-195-2.60.
6
Pasumarthi, Kasyap S., and Ajay K. Agrawal. "Schlieren Measurements of Buoyancy Effects on Flow Transition in Low-Density Gas Jets." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56810.
Анотація:
The transition from laminar to turbulent flow in helium jets discharged into air was studied using Rainbow Schlieren Deflectometry technique. In particular, the effects of buoyancy on jet oscillations and flow transition length were considered. Experiments to simulate microgravity were conducted in the 2.2s drop tower at NASA Glenn Research Center. The jet Reynolds numbers varied from 800 to 1200 and the jet Richardson numbers ranged between 0.01 and 0.004. Schlieren images revealed substantial variations in the flow structure during the drop. Fast Fourier Transform (FFT) analysis of the data obtained in Earth gravity experiments revealed the existence of a discrete oscillating frequency in the transition region, which matched the frequency in the upstream laminar regime. In microgravity, the transition occurred farther downstream indicating laminarization of the jet in the absence of buoyancy. The amplitude of jet oscillations was reduced by up to an order of magnitude in microgravity. Results suggest that jet oscillations were buoyancy induced and that the brief microgravity period may not be sufficient for the oscillations to completely subside.
7
McCullough, Charles R., Scott M. Thompson, and Heejin Cho. "Heat Recovery With Oscillating Heat Pipes." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66241.
Анотація:
Waste-heat recovery applied in HVAC air systems is of interest to increase the energy efficiency of residential, commercial and industrial buildings. In this study, the feasibility of using tubular-shaped oscillating heat pipes (OHPs), which are two-phase heat transfer devices with ultra-high thermal conductivity, for heat exchange between counter-flowing air streams (i.e., outdoor and exhaust air flows) was investigated. For a prescribed volumetric flow rate of air and duct geometry, four different OHP Heat Exchangers (OHP-HEs) were sized via the ε-NTU method for the task of sub-cooling intake air 5.5 °C (10 °F). The OHP-HE tubes were assumed to have a static thermal conductivity of 50,000 W/m·K and only operate upon a minimum temperature difference in order to simulate their inherent heat transport capability and start-up behavior. Using acetone as the working fluid, it was found that for a maximum temperature difference of 7°C or more, the OHP-HE can operate and provide for an effectiveness of 0.36. Pressure drop analysis indicates the presented OHP-HE design configurations provide for a minimum of 5 kPa. The current work provides a necessary step for quantifying and designing the OHP for waste heat recovery in AC systems.
8
Song, Jinkwan, and Jong Guen Lee. "Characterization of Spray Formed by Liquid Jet Injected Into Oscillating Air Crossflow." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43726.
Анотація:
This paper presents experimental results on the characteristics of spray formed by a liquid (Jet-A) jet injected into an oscillating air crossflow. Ambient air pressure is raised up to 15.86 bar, and the corresponding aerodynamic Weber number and liquid-air momentum flux ratio are up to 1000 and 25, respectively. The level of modulated crossflow velocity is kept up to 20% of its mean value. For limited cases, the air crossflow is preheated. Planar Mie-scattering measurements are utilized to visualize changes of the spray penetration and cross-sectional spray area in the oscillating air crossflow, and PDPA measurements are used to measure the mean drop size and drop size distribution. Phase-synchronized PDPA measurement of droplet size under the modulation of crossflow shows that the modulating crossflow results in preferentially larger amount of smaller and bigger droplets than average-sized droplets. Global spray response of spray to modulating crossflow is characterized by using proper orthogonal decomposition (POD) analysis of Mie-scattering images and collecting (and hence determining gain of) Mie-scattering intensity of droplets at a fixed downstream distance. It is found that the dominant behavior of the spray is convective oscillation in the axial direction and the change of vertical penetration of the spray is almost negligible for the level of crossflow velocity modulation up to 20%. The gain of Mie-scattering intensity with respect to crossflow velocity modulation level gradually decreases as liquid-air momentum flux ratio increases. Also, per given momentum flux ratio and Weber number, the gain hardly varies with respect to crossflow modulation level, suggesting the response of spray increases in proportion to crossflow velocity modulation level.
9
Tregde, Vidar. "Compressible Air Effects in CFD Simulations of Free Fall Lifeboat Drop." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41049.
Анотація:
A free fall lifeboat is typically dropped from heights between 30 and 40m, but during full scale testing, drop heights have been exceeding 60 m. During a drop, the free fall lifeboat is going through several phases; sliding on the skid, rotation on skid, free fall, water entry, ventilation, maximum submergence, resurfacing and the sailing phase. During impact and submergence the lifeboat will go through a ventilation phase. In this phase the lifeboat creates an air cavity behind the pilot house and a larger one behind the stern. The air cavity formed on top of canopy, aft of the pilot house is compressed and then starts to oscillate in time giving rise to large oscillating pressures. Computational Fluid Dynamics (CFD) simulations with compressible air flow model are compared with full scale experimental results. The results compare very well, both in oscillating frequency and amplitude. Later in the ventilation phase, an air bubble aft of the vessel will be drawn down several meters below the water surface. This bubble collapses in an imploding manner and slams with large pressures on the aft bulkhead of the lifeboat. This is simulated in CFD with compressible air model and compares very well to the full scale experimental results. Using incompressible air flow will not capture these effects, and the calculated pressures on the aft bulkhead are a fraction of the real pressures. The water surface in the cavity eventually hits the aft bulkhead with a high slamming velocity. The structure of the air pocket does not have any symmetry, and seem to be chaotic in nature. The local pressures can be very high and distributed over a small area. The effects of the air cavity also influence the motion and acceleration of the lifeboat in the ventilation phase; this is shown and compared to full scale experimental results.
10
Pannell, James, and D. Keith Walters. "Numerical Investigation and Performance Characterization of Oscillating Foil Energy Harvesting." In ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20375.
Анотація:
Abstract Oscillating foil energy harvesting devices are increasingly being considered as a sustainable energy alternative, especially in rivers and tidal areas. This paper applies CFD to an oscillating foil power generation device in order to explore the effects of pitching amplitude, the ratio of heaving amplitude to chord length, and the reduced frequency to the energy harvesting efficiency. Ansys Fluent 17.2 was used for this study, and the results are compared to experimental results that have been previously documented in the open literature. Configurations examined included pitching amplitudes of 65, 70, 75, and 80 degrees; heaving ratios of 0.4, 0.6, and 0.8; and reduced frequencies of 0.1, 0.12, 0.14, and 0.16. Results seems to indicate that the optimal reduced frequency is related to the heaving ratio, with the pitching amplitude only creating slight variations in the power produced by the foil. In the data, configurations with a heaving ratio of 0.4 have highest efficiency at reduced frequencies of either 0.14 or 0.16, but efficiency remains high at both points, which indicates the possibility of a peak in between the two points. Configurations with heaving ratio of 0.6 peak at reduced frequency 0.14 with a significant drop off at reduced frequency of 0.16. Finally, configurations with a heaving ratio of 0.8 show a peak at 0.12 reduced frequency and a significant drop at 0.14 and 0.16. These results suggest that OFEH devices can be effectively optimized for different and potentially varying operating conditions that may be encountered during practical implementation of OFEH technology.
Звіти організацій з теми "Oscillating Drop":
1
Carleson, T. E. Drop oscillation and mass transfer in alternating electric fields. Office of Scientific and Technical Information (OSTI), June 1992. http://dx.doi.org/10.2172/6974824.
2
Carleson, T. E., and W. Yang. Drop oscillation and mass transfer in alternating electric fields. Office of Scientific and Technical Information (OSTI), May 1991. http://dx.doi.org/10.2172/6977832.
3
Carleson, T. E., and W. Yang. Drop oscillation and mass transfer in alternating electric fields. Progress report. Office of Scientific and Technical Information (OSTI), May 1991. http://dx.doi.org/10.2172/10182154.
4
Yang, Wenrui, and T. E. Carleson. Linear oscillations of a drop in uniform alternating electric fields. [Annual report, 1989]. Office of Scientific and Technical Information (OSTI), October 1990. http://dx.doi.org/10.2172/10180141.
5
Carleson, T. E. Drop oscillation and mass transfer in alternating electric fields. Progress report, May 30, 1991--June 1, 1992. Office of Scientific and Technical Information (OSTI), June 1992. http://dx.doi.org/10.2172/10188178.