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Fedina, Olga V., Arthur R. Zakinyan e Irina M. Agibova. "Design of science laboratory sessions with magnetic fluids". International Journal of Mechanical Engineering Education 45, n. 4 (26 maggio 2017): 349–59. http://dx.doi.org/10.1177/0306419017708644.
Testo completoAbstract (sommario):
Application of new achievements in science and technology to the physics laboratory sessions can ensure the advancement of physics education. One particular example of the technologies giving new opportunities in the design of physics laboratory works is the magnetic fluid. We describe the laboratory works within the scope of the general physic course for the undergraduate students. Principal feature of the laboratories presented is the use of magnetic fluids. It makes possible to design some creative laboratory works, which can help to develop skills in performing scientific experiments and to increase the understanding of the physical concepts. The sample consists of 120 third-grade university students from the Department of General and Theoretical Physics in the North Caucasus Federal University in Stavropol, Russia. These laboratories arouse students’ interest and contribute to the achievement of high quality of learning outcomes. We also show that such laboratories engage students’ interest in the scientific research work.
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Yue, Peng, Jinghui Zhang e Sibei Wei. "Mathematical Model for Excited State Fluid Dynamics". Journal of Physics: Conference Series 2650, n. 1 (1 novembre 2023): 012031. http://dx.doi.org/10.1088/1742-6596/2650/1/012031.
Testo completoAbstract (sommario):
Abstract The rational mechanic’s research method is synthesized with the help of mathematical means such as generalized function analysis and tensor analysis. The basic definition of the fluctuation velocity generation is based on phenomenological physics in this article. The basic control equations of general excited state fluid dynamics applicable to the flowfield are obtained based on the basic principles of quantum mechanical superposition states. The simplified basic equations of the excited State are finally obtained through time and space discretization. The basic theory of excited state fluid dynamics is established, providing new ideas for the innovation and application of flow control, fluid mechanical engineering design, and other aspects of research work.
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Saravanakumar, Sri Manikandan, e Paul-Vahe Cicek. "Microfluidic Mixing: A Physics-Oriented Review". Micromachines 14, n. 10 (25 settembre 2023): 1827. http://dx.doi.org/10.3390/mi14101827.
Testo completoAbstract (sommario):
This comprehensive review paper focuses on the intricate physics of microfluidics and their application in micromixing techniques. Various methods for enhancing mixing in microchannels are explored, with a keen emphasis on the underlying fluid dynamics principles. Geometrical micromixers employ complex channel designs to induce fluid–fluid interface distortions, yielding efficient mixing while retaining manufacturing simplicity. These methods synergize effectively with external techniques, showcasing promising potential. Electrohydrodynamics harnesses electrokinetic phenomena like electroosmosis, electrophoresis, and electrothermal effects. These methods offer dynamic control over mixing parameters via applied voltage, frequency, and electrode positioning, although power consumption and heating can be drawbacks. Acoustofluidics leverages acoustic waves to drive microstreaming, offering localized yet far-reaching effects. Magnetohydrodynamics, though limited in applicability to certain fluids, showcases potential by utilizing magnetic fields to propel mixing. Selecting an approach hinges on trade-offs among complexity, efficiency, and compatibility with fluid properties. Understanding the physics of fluid behavior and rationalizing these techniques aids in tailoring the most suitable micromixing solution. In a rapidly advancing field, this paper provides a consolidated understanding of these techniques, facilitating the informed choice of approach for specific microfluidic mixing needs.
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Elsaady, Wael, S. Olutunde Oyadiji e Adel Nasser. "A review on multi-physics numerical modelling in different applications of magnetorheological fluids". Journal of Intelligent Material Systems and Structures 31, n. 16 (7 luglio 2020): 1855–97. http://dx.doi.org/10.1177/1045389x20935632.
Testo completoAbstract (sommario):
Magnetorheological fluids involve multi-physics phenomena which are manifested by interactions between structural mechanics, electromagnetism and rheological fluid flow. In comparison with analytical models, numerical models employed for magnetorheological fluid applications are thought to be more advantageous, as they can predict more phenomena, more parameters of design, and involve fewer model assumptions. On that basis, the state-of-the-art numerical methods that investigate the multi-physics behaviour of magnetorheological fluids in different applications are reviewed in this article. Theories, characteristics, limitations and considerations employed in numerical models are discussed. Modelling of magnetic field has been found to be rather an uncomplicated affair in comparison to modelling of fluid flow field which is rather complicated. This is because, the former involves essentially one phenomenon/mechanism, whereas the latter involves a plethora of phenomena/mechanisms such as laminar versus turbulent rheological flow, incompressible versus compressible flow, and single- versus two-phase flow. Moreover, some models are shown to be still incapable of predicting the rheological nonlinear behaviour of magnetorheological fluids although they can predict the dynamic characteristics of the system.
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Papanastasiou, Tasos C., Dionissios G. Kiriakidis e Theodore G. Nikoleris. "Extrudate Swelling: Physics, Models, and Computations". Applied Mechanics Reviews 48, n. 10 (1 ottobre 1995): 689–95. http://dx.doi.org/10.1115/1.3005050.
Testo completoAbstract (sommario):
Viscous, viscoelastic, or elastic normal stresses are superimposed to pressure within flowing fluids. These stresses act normal to the boundaries of the flow that may deform depending on their modulus or viscosity. At absolutely rigid boundaries of infinite modulus of elasticity any boundary deformation and therefore any fluid expansion or swelling is surpressed (eg, flow in rigid pipes, annuli, channels). Elastic boundaries (eg, flow in veins and arteries, flow by membranes, around inflating/deflating balloons) deform under the action of normal stresses, allowing expansion or swelling of fluid. The same mechanism prevails in lubrication, where pressure and superimposed normal viscoelastic stresses keep surfaces in relative motion apart, with simultaneous increase in load capacity. Viscous boundaries (eg, liquid jet in air or in immiscible liquid, slow extrusion of viscoelastic liquids from dies, expanding/collapsing air-bubbles or liquid-droplets) are displaced by flowing adjacent immiscible fluids, allowing swelling or imposing contraction depending on relative rheological characteristics. Thus, the kind of swelling examined here is independent of density, ie, incompressible, and is due to the action of normal stresses against the boundary that is imposed either by adjacent deformable obstacles or else by surface tension. The resulting swelling is dynamic (ie, it initiates, changes and ceases with the flow) and can be made permanent by solidification, crystallization or glassification. The most profound form of incompressible swelling is the extrude swelling that controls the ultimate shape of extruded parts. Incompressible swelling is enhanced by the ability of macromolecules to deform and recover (eg, viscoelastic) and by the design of flow conduits to impose sharp transitions of deformation modes (eg, singular exit flows). The same swelling is reduced by the ability of molecules (or fibers in fiber-suspensions) to align with the flow streamines, as well as any tendency of solid-like structure formulation (eg, viscoplastic).
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Serrano, Jean Carlos, Satish Kumar Gupta, Roger D. Kamm e Ming Guo. "In Pursuit of Designing Multicellular Engineered Living Systems: A Fluid Mechanical Perspective". Annual Review of Fluid Mechanics 53, n. 1 (5 gennaio 2021): 411–37. http://dx.doi.org/10.1146/annurev-fluid-072220-013845.
Testo completoAbstract (sommario):
From intracellular protein signaling to embryonic symmetry-breaking, fluid transport ubiquitously drives biological events in living systems. We provide an overview of the fundamental fluid mechanics and transport phenomena across a range of length scales in cellular systems, with emphasis on how cellular functions are influenced by fluid transport. We also highlight how understanding the physical basis of these fluid dynamic phenomena can be implemented to engineer increasingly complex multicellular systems that recapitulate tissue-level functions. Examples discussed include the manipulation of intracellular fluid volume to achieve cell differentiation/dedifferentiation and the use of microfluidic systems to control the spatial and temporal distribution of morphogens and fluid forces to generate vascularized organoids.
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ZHANG, CHENGYUAN, XIAOYAN LIU, DAOYING XI e QUANSHENG LIU. "AN ROCK-PHYSICS-BASED COMPLEX PORE-FLUID-DISTRIBUTION MODEL TO SEISMIC DYNAMICAL RESPONSE". International Journal of Modern Physics B 22, n. 09n11 (30 aprile 2008): 1437–42. http://dx.doi.org/10.1142/s021797920804689x.
Testo completoAbstract (sommario):
It is very important to know how the reservoir rock and its fluid properties are linked to seismic dynamic response. Literatures show that there are a variety of rock-physics models such as the most famous Biot-Gassmann equation aimed at the relationship between seismic velocity and liquid saturation. Most of these models make a fundamental assumption of one fluid phase or homogeneous phase within the pore volume. In this paper, we discuss possible seismic velocities change in a two immiscible pore fluids (i.e. water-gas) saturated reservoir with patchy saturation distribution. It is found that P-wave velocity of a reservoir rock with the same saturation but different pore fluid distribution exhibits noticeable variation and deviate overall from Gassmann's results. We use DEM theory to explain this phenomenon. It belongs to hybrid approach in rock-physics modeling and can handle complex pore-fluid-distribution cases. Based on the modeling study, we found that various fluid-distribution models may significantly affect the modulus and P-wave velocity. The seismic reflection time, amplitude and phase characteristics may change with the choice of pore-fluid-distribution models. Relevant rock mechanical experiments indicate the same trend of seismic responses. It also be proven by seismic reservoir monitoring experiment (time lapse study) that incorrect conclusion may be drawn about the strong seismic reflection in pure Utsira Sand if the microscopic pore-fluid-distribution effects are not taken into account.
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Siagian, Mutiara. "PENGARUH PENGUASAAN HUKUM KEKEKALAN ENERGI MEKANIK TERHADAP HASIL BELAJAR FISIKA MATERI POKOK MEKANIKA FLUIDA DI KELAS XI SMA NEGERI PADANGSIDIMPUAN". JURNAL PhysEdu (PHYSICS EDUCATION) 5, n. 1 (31 marzo 2023): 22–28. http://dx.doi.org/10.37081/physedu.v5i1.4933.
Testo completoAbstract (sommario):
This study aimed to determine a general idea of mastering the law of conservation of mechanical energy and fluid mechanics, and then I see the influence of the law of conservation of mechanical energy mastery of the learning outcomes of the subject matter of physics of fluid mechanics in class XI of SMAN 8 Padangsidimpuan. The research was conducted using descriptive method.The population is all class XI student are 45 students. The sample is 45 students which are taken by total sampling technique. The data is collected by using test as an instrument. The writer uses statistic processes in analyzing data. They are descriptive analysis and inferential analysis by using the formula of “r” Product Moment and the formula of t test. After collecting the data, it is found the average of mastering the law of conservation of mechanical energy,can be categorized “pretty” .While the average value of the subject matter of physics learning outcomes of fluid mechanics 68.17 can be categorized “pretty”. The result of the analyzed data shows the score of ttest > ttable (2,0 > 1,67) . in other words, the score of ttest is bigger than ttable. So, the hypothesis is accepted. It means there is the influence of the law of conservation of mechanical energy mastery of the learning outcomes of the subject matter of physics of fluid mechanics in class XI of SMAN 8 Padangsidimpuan
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Deng, Wubing, e Igor B. Morozov. "Macroscopic mechanical properties of porous rock with one saturating fluid". GEOPHYSICS 84, n. 6 (1 novembre 2019): MR223—MR239. http://dx.doi.org/10.1190/geo2018-0602.1.
Testo completoAbstract (sommario):
Effective frequency-dependent moduli and [Formula: see text]-factors are broadly used for characterizing the behavior of earth media in laboratory and field seismic observations. However, such properties are wavemode- and experiment-dependent and are often incomplete and/or inaccurate for modeling realistic situations. For example, viscoelastic moduli for porous fluid-saturated rock are usually derived for primary waves, but they may not apply to cases in which secondary waves are important, such as reflections in finely layered poroelastic media or quasistatic pore-fluid flows in laboratory experiments. To obtain a model applicable to all cases, equations of mechanics should be used, and mechanical properties of the material must be identified. To reveal and measure such properties for fluid-saturated porous rock, we have developed a Biot-consistent model based on Lagrangian continuum mechanics. The model is “minimal,” purely macroscopic, and independent of the macrostructure or patterns of pore-fluid flows; thus, it could represent many existing wave-induced fluid-flow (WIFF) as well as non-WIFF models. Due to its mechanical definition, the model should be applicable to all rock-physics experiments (linear creep, pore flow, low-frequency, resonant, or ultrasonic), any waves in the field (primary, secondary, standing, surface, etc.) under arbitrary boundary conditions, and also finite-difference and finite-element numerical modeling. When based on this model, numerical simulations require no integral equations, fractional derivatives, memory variables, or additional kinetic equations. We further use the model to invert for detailed elastic and viscous properties of fluid-saturated Berea and Fontainebleau sandstones from recently published low-frequency laboratory experiments. All rock properties inferred in the model are time- and frequency-independent, comparable to other physical observations, and the model closely predicts the data. The model can be approximately pore-fluid independent, which allows performing rigorous fluid substitution with viscous pore fluids. As an illustration, P-wave velocity dispersion and attenuation in water-, oil-, and gas-saturated sandstone are simulated.
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Zhao, Yueqiang, Zhengming Wu e Weiwei Liu. "Statistical mechanical theory of fluid mixtures". Physica A: Statistical Mechanics and its Applications 393 (gennaio 2014): 62–75. http://dx.doi.org/10.1016/j.physa.2013.08.062.
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Jaffrey, Andrew, e Jim Gordon. "Passive well monitoring systems and carbon, capture and storage (CCS) application". Australian Energy Producers Journal 64, n. 2 (16 maggio 2024): S495—S499. http://dx.doi.org/10.1071/ep23222.
Testo completoAbstract (sommario):
With an increasing number of ageing subsea wells and a tightening of global regulations for well management, assuring well integrity is a key feature of risk management for oil and gas operators. Baker Hughes, in collaboration with Sentinel Subsea, has successfully deployed patented passive well monitoring systems able to detect a range of subsea emissions and alert well owners. This early detection and warning technology harnesses the natural forces and processes of chemistry and physics but does not use any electrical power for the monitoring and detection of fluids. Static mechanical structures and the natural buoyancy of escaping fluids of interest are used to gather fluids in the subsea environment where they are detected chemically using specially developed Triggers. By using fluid-specific Triggers, systems respond only to the fluid(s) of interest, not to other fluids typically encountered around subsea assets. When the target fluid has been detected passively, a coded signal beacon (previously dormant) is mechanically released to the ocean surface using self-buoyancy where an alarm is transmitted via satellite and the responsible party alerted. Systems are currently supporting multiple major and independent operators mitigate the risks associated with subsea wells globally. Based on these experiences, this paper discusses the development process of a passive well integrity monitoring system with application for carbon, capture and storage (CCS) sites.
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Yen, Jeannette, Marc J. Weissburg e Michael H. Doall. "The fluid physics of signal perception by mate-tracking copepods". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353, n. 1369 (29 maggio 1998): 787–804. http://dx.doi.org/10.1098/rstb.1998.0243.
Testo completoAbstract (sommario):
Within laboratory–induced swarms of the marine copepod Temora longicornis , the male exhibits chemically mediated trail–following behaviour, concluding with fluid mechanical provocation of the mate–capture response. The location and structure of the invisible trail were determined by examining the specific behaviour of the female copepods creating the signal, the response of the male to her signal, and the fluid physics of signal persistence. Using the distance of the mate–tracking male from the ageing trail of the female, we estimated that the molecular diffusion coefficient of the putative pheromonal stimulant was 2.7 times –5 cm 2 s –1 , or 1000 times slower than the diffusion of momentum. Estimates of signal strength levels, using calculations of diffusive properties of odour trails and attenuation rates of fluid mechanical signals, were compared to the physiological and behavioural threshold detection levels. Males find trails because of strong across–plume chemical gradients; males sometimes go the wrong way because of weak along–plume gradients; males lose the trail when the female hops because of signal dilution; and mate–capture behaviour is elicited by suprathreshold flow signals. The male is stimulated by the female odour to accelerate along the trail to catch up with her, and the boundary layer separating the signal from the chemosensitive receptors along the copepod antennule thins. Diffusion times, and hence reaction times, shorten and behavioural orientation responses can proceed more quickly. While ‘perceptive’ distance to the odour signal in the trail or the fluid mechanical signal from the female remains within 1 to 2 body lengths (< 5 mm), the ‘reactive’ distance between males and females was an order of magnitude larger. Therefore, when nearest–neighbour distances are 5 cm or less, as in swarms of 10 4 copepods m –3 , mating events are facilitated. The strong similarity in the structure of mating trails and vortex tubes (isotropic, millimetre—centimetre scale, 10:1 aspect ratio, 10 s persistence), indicates that these trails are constrained by the same physical forces that influence water motion in a low Reynolds number fluid regime, where viscosity limits forces to the molecular scale. The exploratory reaches of mating trails appear inscribed within Kolmogorov eddies and may represent a measure of eddy size. Biologically formed mating trails, however, are distinct in their flow velocity and chemical composition from common small–scale turbulent features; and mechanoreceptive and chemoreceptive copepods use their senses to discriminate these differences. Zooplankton are not aimless wanderers in a featureless environment. Their ambit is replete with clues that guide them in their efforts for survival in the ocean.
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Kondic, Lou, Alejandro G. González, Javier A. Diez, Jason D. Fowlkes e Philip Rack. "Liquid-State Dewetting of Pulsed-Laser-Heated Nanoscale Metal Films and Other Geometries". Annual Review of Fluid Mechanics 52, n. 1 (5 gennaio 2020): 235–62. http://dx.doi.org/10.1146/annurev-fluid-010719-060340.
Testo completoAbstract (sommario):
Metal films of nanoscale thickness, deposited on substrates and exposed to laser heating, provide systems that involve several interesting multiphysics effects. In addition to fluid mechanical aspects associated with a free boundary setup, other relevant physical effects include phase change, thermal flow, and liquid–solid interactions. Such films are challenging to model, in particular because inertial effects may be relevant, and large contact angles require care when considering the long-wave formulation. Applications of nanoscale metal films are numerous, and the materials science community is actively pursuing more complex setups involving templated films and substrates, bimetallic films and alloys, and a variety of elemental film geometries. The goal of this review is to discuss our current understanding of thin metal film systems, while also providing an overview of the challenges in this research area, which stands at the intersection of fluid mechanics, materials science, and thermal physics.
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Yoshizawa,, A., S.-I. Itoh ,, K. Itoh, e Toshi Tajima,. "Plasma and Fluid Turbulence: Theory and Modelling. Series in Plasma Physics". Applied Mechanics Reviews 57, n. 1 (1 gennaio 2004): B5—B6. http://dx.doi.org/10.1115/1.1641779.
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Christov, Ivan C. "Soft hydraulics: from Newtonian to complex fluid flows through compliant conduits". Journal of Physics: Condensed Matter 34, n. 6 (18 novembre 2021): 063001. http://dx.doi.org/10.1088/1361-648x/ac327d.
Testo completoAbstract (sommario):
Abstract Microfluidic devices manufactured from soft polymeric materials have emerged as a paradigm for cheap, disposable and easy-to-prototype fluidic platforms for integrating chemical and biological assays and analyses. The interplay between the flow forces and the inherently compliant conduits of such microfluidic devices requires careful consideration. While mechanical compliance was initially a side-effect of the manufacturing process and materials used, compliance has now become a paradigm, enabling new approaches to microrheological measurements, new modalities of micromixing, and improved sieving of micro- and nano-particles, to name a few applications. This topical review provides an introduction to the physics of these systems. Specifically, the goal of this review is to summarize the recent progress towards a mechanistic understanding of the interaction between non-Newtonian (complex) fluid flows and their deformable confining boundaries. In this context, key experimental results and relevant applications are also explored, hand-in-hand with the fundamental principles for their physics-based modeling. The key topics covered include shear-dependent viscosity of non-Newtonian fluids, hydrodynamic pressure gradients during flow, the elastic response (deformation and bulging) of soft conduits due to flow within, the effect of cross-sectional conduit geometry on the resulting fluid–structure interaction, and key dimensionless groups describing the coupled physics. Open problems and future directions in this nascent field of soft hydraulics, at the intersection of non-Newtonian fluid mechanics, soft matter physics, and microfluidics, are noted.
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Bernard, Peter S., e Robert A. Handler. "Reynolds stress and the physics of turbulent momentum transport". Journal of Fluid Mechanics 220 (novembre 1990): 99–124. http://dx.doi.org/10.1017/s0022112090003202.
Testo completoAbstract (sommario):
The nature of the momentum transport processes responsible for the Reynolds shear stress is investigated using several ensembles of fluid particle paths obtained from a direct numerical simulation of turbulent channel flow. It is found that the Reynolds stress can be viewed as arising from two fundamentally different mechanisms. The more significant entails transport in the manner described by Prandtl in which momentum is carried unchanged from one point to another by the random displacement of fluid particles. One-point models, such as the gradient law are found to be inherently unsuitable for representing this process. However, a potentially useful non-local approximation to displacement transport, depending on the global distribution of the mean velocity gradient, may be developed as a natural consequence of its definition. A second important transport mechanism involves fluid particles experiencing systematic accelerations and decelerations. Close to the wall this results in a reduction in Reynolds stress due to the slowing of sweep-type motions. Further away Reynolds stress is produced in spiralling motions, where particles accelerate or decelerate while changing direction. Both transport mechanisms appear to be closely associated with the dynamics of vortical structures in the wall region.
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Vanorio, Tiziana, Amos Nur e Yael Ebert. "Rock physics analysis and time-lapse rock imaging of geochemical effects due to the injection of CO2 into reservoir rocks". GEOPHYSICS 76, n. 5 (settembre 2011): O23—O33. http://dx.doi.org/10.1190/geo2010-0390.1.
Testo completoAbstract (sommario):
The fundamental concept of time-lapse seismic monitoring is that changes in physical parameters—such as saturation, pore fluid pressure, temperature, and stress—affect rock and fluid properties, which in turn alter the seismic velocity and density. Increasingly, however, time-lapse seismic monitoring is called upon to quantify subsurface changes due in part to chemical reactions between injected fluids and the host rocks. This study springs from a series of laboratory experiments and high-resolution images assessing the changes in microstructure, transport, and seismic properties of fluid-saturated sandstones and carbonates injected with [Formula: see text]. Results show that injecting [Formula: see text] into a brine-rock system induces chemo-mechanical mechanisms that permanently change the rock frame. Injecting [Formula: see text] into brine-saturated-sandstones induces salt precipitation primarily at grain contacts and within small pore throats. In rocks with porosity lower than 10%, salt precipitation reduces permeability and increases P- and S-wave velocities of the dry rock frame. On the other hand, injecting [Formula: see text]-rich water into micritic carbonates induces dissolution of the microcrystalline matrix, leading to porosity enhancement and chemo-mechanical compaction under pressure. In this situation, the elastic moduli of the dry rock frame decrease. The results in these two scenarios illustrate that the time-lapse seismic response of chemically stimulated systems cannot be modeled as a pure fluid-substitution problem. A first set of empirical relationships links the time-variant effects of injection to the elastic properties of the rock frame using laboratory velocity measurements and advanced imaging.
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Moore, Nicholas J., Jake Cherry, Shang-Huan Chiu e Bryan D. Quaife. "How fluid-mechanical erosion creates anisotropic porous media". Physica D: Nonlinear Phenomena 445 (marzo 2023): 133634. http://dx.doi.org/10.1016/j.physd.2022.133634.
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LIU, TIANSHU, e LIXIN SHEN. "Fluid flow and optical flow". Journal of Fluid Mechanics 614 (16 ottobre 2008): 253–91. http://dx.doi.org/10.1017/s0022112008003273.
Testo completoAbstract (sommario):
The connection between fluid flow and optical flow is explored in typical flow visualizations to provide a rational foundation for application of the optical flow method to image-based fluid velocity measurements. The projected-motion equations are derived, and the physics-based optical flow equation is given. In general, the optical flow is proportional to the path-averaged velocity of fluid or particles weighted with a relevant field quantity. The variational formulation and the corresponding Euler–Lagrange equation are given for optical flow computation. An error analysis for optical flow computation is provided, which is quantitatively examined by simulations on synthetic grid images. Direct comparisons between the optical flow method and the correlation-based method are made in simulations on synthetic particle images and experiments in a strongly excited turbulent jet.
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Roper, Marcus, e Agnese Seminara. "Mycofluidics: The Fluid Mechanics of Fungal Adaptation". Annual Review of Fluid Mechanics 51, n. 1 (5 gennaio 2019): 511–38. http://dx.doi.org/10.1146/annurev-fluid-122316-045308.
Testo completoAbstract (sommario):
Fungi are the dark matter of biology, typically leading cryptic lives, buried in soil or inside of plants or other organisms, and emerging into the light only when they build their elegantly engineered fruiting bodies. Ecological success across so many niches has required that they solve many challenging fluid mechanical problems of growth, dispersal, and transport of fluids across networks. Study of fungal life histories by fluid mechanicians has shown their exquisite capability for engineering and revealed new organizing ideas for understanding fungal diversity.
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Voigt, A. "Fluid deformable surfaces". Journal of Fluid Mechanics 878 (4 settembre 2019): 1–4. http://dx.doi.org/10.1017/jfm.2019.549.
Testo completoAbstract (sommario):
Lipid membranes are examples of fluid deformable surfaces, which can be viewed as two-dimensional viscous fluids with bending elasticity. With this solid–fluid duality any shape change contributes to tangential flow and vice versa any tangential flow on a curved surface induces shape deformations. This tight coupling between shape and flow makes curvature a natural element of the governing equations. The modelling and numerical tools outlined in Torres-Sánchez et al. (J. Fluid Mech., vol. 872, 2019, pp. 218–271) open a new field of study by enabling the exploration of the role of curvature in this context.
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YOKOYAMA, Hiroshi, e Chisachi KATO. "Fluid-Acoustic Interactions in Acoustic Radiation in Turbulent Cavity Flows : Fluid-Dynamic Oscillations(Fluids Engineering)". Transactions of the Japan Society of Mechanical Engineers Series B 75, n. 760 (2009): 2369–78. http://dx.doi.org/10.1299/kikaib.75.760_2369.
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Letelier, Mario F., Dennis A. Siginer e Cristian Barrera Hinojosa. "On the physics of viscoplastic fluid flow in non-circular tubes". International Journal of Non-Linear Mechanics 88 (gennaio 2017): 1–10. http://dx.doi.org/10.1016/j.ijnonlinmec.2016.09.012.
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Gagnon, D. A., e P. E. Arratia. "The cost of swimming in generalized Newtonian fluids: experiments with C. elegans". Journal of Fluid Mechanics 800 (14 luglio 2016): 753–65. http://dx.doi.org/10.1017/jfm.2016.420.
Testo completoAbstract (sommario):
Numerous natural processes are contingent on microorganisms’ ability to swim through fluids with non-Newtonian rheology. Here, we use the model organism Caenorhabditis elegans and tracking methods to experimentally investigate the dynamics of undulatory swimming in shear-thinning fluids. Theory and simulation have proposed that the cost of swimming, or mechanical power, should be lower in a shear-thinning fluid compared to a Newtonian fluid of the same zero-shear viscosity. We aim to provide an experimental investigation into the cost of swimming in a shear-thinning fluid from (i) an estimate of the mechanical power of the swimmer and (ii) the viscous dissipation rate of the flow field, which should yield equivalent results for a self-propelled low Reynolds number swimmer. We find the cost of swimming in shear-thinning fluids is less than or equal to the cost of swimming in Newtonian fluids of the same zero-shear viscosity; furthermore, the cost of swimming in shear-thinning fluids scales with a fluid’s effective viscosity and can be predicted using fluid rheology and simple swimming kinematics. Our results agree reasonably well with previous theoretical predictions and provide a framework for understanding the cost of swimming in generalized Newtonian fluids.
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Yang, Qingda, Paul Kobrin, Charles Seabury, Sridhar Narayanaswamy e William Christian. "Mechanical modeling of fluid-driven polymer lenses". Applied Optics 47, n. 20 (9 luglio 2008): 3658. http://dx.doi.org/10.1364/ao.47.003658.
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Photiadis, Douglas M. "Fluid Loaded Structures With One Dimensional Disorder". Applied Mechanics Reviews 49, n. 2 (1 febbraio 1996): 100–125. http://dx.doi.org/10.1115/1.3101885.
Testo completoAbstract (sommario):
This paper reviews the problem of the vibration of fluid loaded structures with one dimensional disorder. There are two aspects which are important in understanding the behavior of such systems: the nature of the fluid loading and the effects arising from irregularity. These two areas of investigation have been pursued simultaneously by the structural acoustics and condensed matter physics communities, and only recently have attempts been made to use the results from both fields. The key results from these areas which have been employed in the analysis of disordered fluid loaded structures are reviewed, and the recent research results in this area are described.
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Adcock, Thomas A. A., Scott Draper, Richard H. J. Willden e Christopher R. Vogel. "The Fluid Mechanics of Tidal Stream Energy Conversion". Annual Review of Fluid Mechanics 53, n. 1 (5 gennaio 2021): 287–310. http://dx.doi.org/10.1146/annurev-fluid-010719-060207.
Testo completoAbstract (sommario):
Placing mechanical devices into fast-moving tidal streams to generate clean and predictable electricity is a developing technology. This review covers the fundamental fluid mechanics of this application, which is important for understanding how such devices work and how they interact with the tidal stream resource. We focus on how tidal stream turbines and energy generation are modeled analytically, numerically, and experimentally. Owing to the nature of the problem, our review is split into different scales—from turbine to array and regional—and we examine each in turn.
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Wang, Weicheng, Yiping Luo e Meng Ji. "Experimental study on tensile mechanical properties of magnetorheological fluid". International Journal of Modern Physics B 34, n. 08 (27 marzo 2020): 2050070. http://dx.doi.org/10.1142/s0217979220500708.
Testo completoAbstract (sommario):
Magnetorheological fluid (MRF) is a kind of suspension composed of a nonconducting magnetic liquid and small soft magnetic particles with high permeability and low hysteresis. The tensile mechanical properties of MRF reflect its important mechanical properties. In this study, a testing device is designed to investigate the tensile mechanical properties of MRF in accordance with the plate method theory. First, the magnetic field is selected to analyze the influence of different gap sizes on the magnetic field. The magnetic field strength decreases as the gap increases. Second, a testing platform for tensile mechanical properties is built, and the tensile mechanical properties of MRF are experimentally studied under different magnetic field strengths, tensile speeds and surface characteristics. Experimental results show that the stronger the magnetic field, the greater the tensile yield stress. The maximum tensile stress at different velocities is nearly the same. Different surface characteristics affect tensile stress.
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Zhao, Heping, Zhengyou Liu, Jiarui Shen e Youyan Liu. "Mechanical properties of an ideal electrorheological fluid". Solid State Communications 108, n. 12 (novembre 1998): 989–92. http://dx.doi.org/10.1016/s0038-1098(98)00480-3.
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Lotfian, Ali, e Ehsan Roohi. "Radiometric flow in periodically patterned channels: fluid physics and improved configurations". Journal of Fluid Mechanics 860 (7 dicembre 2018): 544–76. http://dx.doi.org/10.1017/jfm.2018.880.
Testo completoAbstract (sommario):
With the aid of direct simulation Monte Carlo (DSMC), we conduct a detailed investigation pertaining to the fluid and thermal characteristics of rarefied gas flow with regard to various arrangements for radiometric pumps featuring vane and ratchet structures. For the same, we consider three categories of radiometric pumps consisting of channels with their bottom or top surfaces periodically patterned with different structures. The structures in the design of the first category are assumed to be on the bottom wall and consist of either a simple vane, a right-angled triangular fin or an isosceles triangular fin. The arrangements on the second category of radiometric pumps consist of an alternating diffuse–specular right-angled fin and an alternating diffuse–specular isosceles fin on the bottom wall. The third category contains either a channel with double isosceles triangular fins on its lowermost surface or a zigzag channel with double isosceles triangular fins on both walls. In the first and the third categories, the surfaces of the channel and its structures are considered as diffuse reflectors. The temperature is kept steady on the horizontal walls of the channel; thus, radiometric flow is created by subjecting the adjacent sides of the vane/ratchet to constant but unequal temperatures. On the other hand, for the second category, radiometric flow is introduced by specifying different top/bottom channel wall temperatures. The DSMC simulations are performed at a Knudsen number based on the vane/ratchet height of approximately one. The dominant mechanism in the radiometric force production is clarified for the examined configurations. Our results demonstrate that, at the investigated Knudsen number, the zigzag channel experiences maximum induced velocity with a parabolic velocity profile, whereas its net radiometric force vanishes. In the case of all other configurations, the flow pattern resembles a Couette flow in the open section of the channel situated above the vane/ratchet. To further enhance the simulations, the predictions of the finite volume discretization of the Boltzmann Bhatnagar–Gross–Krook (BGK)–Shakhov equation for the mass flux dependence on temperature difference and Knudsen number are also reported for typical test cases.
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Sheng, Yu. "Discretization Analysis of Fluid Mechanical Flow Field Grid". Journal of Physics: Conference Series 2292, n. 1 (1 giugno 2022): 012005. http://dx.doi.org/10.1088/1742-6596/2292/1/012005.
Testo completoAbstract (sommario):
Abstract The design basis of the performance of special industrial fluid machinery is to obtain the distribution of air flow parameters through the solution of flow field. In the numerical solution of flow field, the discretization of computational domain grid is the key factor affecting the calculation results. In this paper, the two-dimensional axisymmetric flow field analysis model were adopted. By establishing the software interface and automatic execution script file, the grid discreteness analysis process was established. The Richardson extrapolation method was used to infer the accurate solution of the flow field, and the grid independence and convergence analysis and the grid spacing analysis of the first layer of the wall were carried out. The results showed that the numerical results gradually approached the exact solution with the increase of the total number of grids, but the correlation between the numerical results and the total number of grids decreased in this process; By changing the normal spacing of the first layer of grid on each wall and making mathematical statistical analysis, the sensitive area of grid spacing could be determined. The method established in this paper could significantly improve the overall efficiency of the fluid mechanical mesh discreteness analysis and flow field analysis, and recommended the configuration of the optimal mesh discretization mode for the subsequent simulation calculation, which was conducive to further improve the calculation accuracy and efficiency of the flow field.
32
Greenhow, R. C. "A mechanical resonance experiment with fluid dynamic undercurrents". American Journal of Physics 56, n. 4 (aprile 1988): 352–57. http://dx.doi.org/10.1119/1.15638.
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Banerjee, Sourav, Tribikram Kundu e Dominique Placko. "Ultrasonic Field Modeling in Multilayered Fluid Structures Using the Distributed Point Source Method Technique". Journal of Applied Mechanics 73, n. 4 (20 ottobre 2005): 598–609. http://dx.doi.org/10.1115/1.2164516.
Testo completoAbstract (sommario):
In the field of nondestructive evaluation (NDE), the newly developed distributed point source method (DPSM) is gradually gaining popularity. DPSM is a semi-analytical technique used to calculate the ultrasonic field (pressure and velocity fields) generated by ultrasonic transducers. This technique is extended in this paper to model the ultrasonic field generated in multilayered nonhomogeneous fluid systems when the ultrasonic transducers are placed on both sides of the layered fluid structure. Two different cases have been analyzed. In the first case, three layers of nonhomogeneous fluids constitute the problem geometry; the higher density fluid is sandwiched between two identical fluid half-spaces. In the second case, four layers of nonhomogeneous fluids have been considered with the fluid density monotonically increasing from the bottom to the top layer. In both cases, analyses have been carried out for two different frequencies of excitation with various orientations of the transducers. As expected, the results show that the ultrasonic field is very sensitive to the fluid properties, the orientation of the fluid layers, and the frequency of excitation. The interaction effect between the transducers is also visible in the computed results. In the pictorial view of the resulting ultrasonic field, the interface between two fluid layers can easily be seen.
34
FONTELOS, M. A., e F. DE LA HOZ. "Singularities in water waves and the Rayleigh–Taylor problem". Journal of Fluid Mechanics 651 (30 aprile 2010): 211–39. http://dx.doi.org/10.1017/s0022112009992710.
Testo completoAbstract (sommario):
We describe, by means of asymptotic methods and direct numerical simulation, the structure of singularities developing at the interface between two perfect, inviscid and irrotational fluids of different densities ρ1 and ρ2 and under the action of gravity. When the lighter fluid is on top of the heavier fluid, one encounters the water-wave problem for fluids of different densities. In the limit when the density of the lighter fluid is zero, one encounters the classical water-wave problem. Analogously, when the heavier fluid is on top of the lighter fluid, one encounters the Rayleigh–Taylor problem for fluids of different densities, with this being the case when one of the densities is zero for the classical Rayleigh–Taylor problem. We will show that both water-wave and Rayleigh–Taylor problems develop singularities of the Moore-type (singularities in the curvature) when both fluid densities are non-zero. For the classical water-wave problem, we propose and provide evidence of the development of a singularity in the form of a logarithmic spiral, and for the classical Rayleigh–Taylor problem no singularities were found. The regularizing effects of surface tension are also discussed, and estimates of the size and wavelength of the capillary waves, bubbles or blobs that are produced are provided.
35
Drikakis, Dimitris, Michael Frank e Gavin Tabor. "Multiscale Computational Fluid Dynamics". Energies 12, n. 17 (25 agosto 2019): 3272. http://dx.doi.org/10.3390/en12173272.
Testo completoAbstract (sommario):
Computational Fluid Dynamics (CFD) has numerous applications in the field of energy research, in modelling the basic physics of combustion, multiphase flow and heat transfer; and in the simulation of mechanical devices such as turbines, wind wave and tidal devices, and other devices for energy generation. With the constant increase in available computing power, the fidelity and accuracy of CFD simulations have constantly improved, and the technique is now an integral part of research and development. In the past few years, the development of multiscale methods has emerged as a topic of intensive research. The variable scales may be associated with scales of turbulence, or other physical processes which operate across a range of different scales, and often lead to spatial and temporal scales crossing the boundaries of continuum and molecular mechanics. In this paper, we present a short review of multiscale CFD frameworks with potential applications to energy problems.
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Szulczewski, M. L., e R. Juanes. "The evolution of miscible gravity currents in horizontal porous layers". Journal of Fluid Mechanics 719 (19 febbraio 2013): 82–96. http://dx.doi.org/10.1017/jfm.2012.631.
Testo completoAbstract (sommario):
AbstractGravity currents of miscible fluids in porous media are important to understand because they occur in important engineering projects, such as enhanced oil recovery and geologic CO2 sequestration. These flows are often modelled based on two simplifying assumptions: vertical velocities are negligible compared with horizontal velocities, and diffusion is negligible compared with advection. In many cases, however, these assumptions limit the validity of the models to a finite, intermediate time interval during the flow, making prediction of the flow at early and late times difficult. Here, we consider the effects of vertical flow and diffusion to develop a set of models for the entire evolution of a miscible gravity current. To gain physical insight, we study a simple system: lock exchange of equal-viscosity fluids in a horizontal, vertically confined layer of permeable rock. We show that the flow exhibits five regimes: (i) an early diffusion regime, in which the fluids diffuse across the initially sharp fluid–fluid interface; (ii) an S-slumping regime, in which the fluid–fluid interface tilts in an S-shape; (iii) a straight-line slumping regime, in which the fluid–fluid interface tilts as a straight line; (iv) a Taylor-slumping regime, in which Taylor dispersion at the aquifer scale enhances mixing between the fluids and causes the flow to continuously decelerate; and (v) a late diffusion regime, in which the flow becomes so slow that mass transfer again occurs dominantly though diffusion.
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Singh, Kiran, John R. Lister e Dominic Vella. "A fluid-mechanical model of elastocapillary coalescence". Journal of Fluid Mechanics 745 (25 marzo 2014): 621–46. http://dx.doi.org/10.1017/jfm.2014.102.
Testo completoAbstract (sommario):
AbstractWe present a fluid-mechanical model of the coalescence of a number of elastic objects due to surface tension. We consider an array of spring–block elements separated by thin liquid films, whose dynamics are modelled using lubrication theory. With this simplified model of elastocapillary coalescence, we present the results of numerical simulations for a large number of elements, $N=O(10^4)$. A linear stability analysis shows that pairwise coalescence is always the most unstable mode of deformation. However, the numerical simulations show that the cluster sizes actually produced by coalescence from a small white-noise perturbation have a distribution that depends on the relative strength of surface tension and elasticity, as measured by an elastocapillary number $K$. Both the maximum cluster size and the mean cluster size scale like $K^{-1/2}$ for small $K$. An analytical solution for the response of the system to a localized perturbation shows that such perturbations generate propagating disturbance fronts, which leave behind ‘frozen-in’ clusters of a predictable size that also depends on $K$. A good quantitative comparison between the cluster-size statistics from noisy perturbations and this ‘frozen-in’ cluster size suggests that propagating fronts may play a crucial role in the dynamics of coalescence.
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Li, Lei, Carlos F. Lange e Yongsheng Ma. "Association of design and computational fluid dynamics simulation intent in flow control product optimization". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, n. 13 (14 marzo 2017): 2309–22. http://dx.doi.org/10.1177/0954405417697352.
Testo completoAbstract (sommario):
Computational fluid dynamics has been extensively used for fluid flow simulation and thus guiding the flow control device design. However, computational fluid dynamics simulation requires explicit geometry input and complicated solver setup, which is a barrier in case of the cyclic computer-aided design/computational fluid dynamics integrated design process. Tedious human interventions are inevitable to make up the gap. To fix this issue, this work proposed a theoretical framework where the computational fluid dynamics solver setup can be intelligently assisted by the simulation intent capture. Two feature concepts, the fluid physics feature and the dynamic physics feature, have been defined to support the simulation intent capture. A prototype has been developed for the computer-aided design/computational fluid dynamics integrated design implementation without the need of human intervention, where the design intent and computational fluid dynamics simulation intent are associated seamlessly. An outflow control device used in the steam-assisted gravity drainage process is studied using this prototype, and the target performance of the device is effectively optimized.
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ALBAALBAKI, BASHAR, e ROGER E. KHAYAT. "Pattern selection in the thermal convection of non-Newtonian fluids". Journal of Fluid Mechanics 668 (5 gennaio 2011): 500–550. http://dx.doi.org/10.1017/s0022112010004775.
Testo completoAbstract (sommario):
The thermogravitational instability in a fluid layer of a non-Newtonian medium heated from below is investigated. Linear and weakly nonlinear analyses are successively presented. The fluid is assumed to obey the Carreau–Bird model. Although the critical threshold is the same as for a Newtonian fluid, it is found that non-Newtonian fluids can convect in the form of rolls, squares or hexagons, depending on the shear-thinning level. Similar to Newtonian fluids, shear-thickening fluids convect only in the form of rolls. The stability of the convective steady branches is carried out to determine under which specific conditions a pattern is preferred. The influence of the rheological and physical parameters is examined and discussed in detail.
40
Ezzat, Mohamed, Benjamin M. Adams, Martin O. Saar e Daniel Vogler. "Numerical Modeling of the Effects of Pore Characteristics on the Electric Breakdown of Rock for Plasma Pulse Geo Drilling". Energies 15, n. 1 (30 dicembre 2021): 250. http://dx.doi.org/10.3390/en15010250.
Testo completoAbstract (sommario):
Drilling costs can be 80% of geothermal project investment, so decreasing these deep drilling costs substantially reduces overall project costs, contributing to less expensive geothermal electricity or heat generation. Plasma Pulse Geo Drilling (PPGD) is a contactless drilling technique that uses high-voltage pulses to fracture the rock without mechanical abrasion, which may reduce drilling costs by up to 90% of conventional mechanical rotary drilling costs. However, further development of PPGD requires a better understanding of the underlying fundamental physics, specifically the dielectric breakdown of rocks with pore fluids subjected to high-voltage pulses. This paper presents a numerical model to investigate the effects of the pore characteristics (i.e., pore fluid, shape, size, and pressure) on the occurrence of the local electric breakdown (i.e., plasma formation in the pore fluid) inside the granite pores and thus on PPGD efficiency. Investigated are: (i) two pore fluids, consisting of air (gas) or liquid water; (ii) three pore shapes, i.e., ellipses, circles, and squares; (iii) pore sizes ranging from 10 to 150 μm; (iv) pore pressures ranging from 0.1 to 2.5 MPa. The study shows how the investigated pore characteristics affect the local electric breakdown and, consequently, the PPGD process.
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MÄHLMANN, STEFAN, e DEMETRIOS T. PAPAGEORGIOU. "Interfacial instability in electrified plane Couette flow". Journal of Fluid Mechanics 666 (6 gennaio 2011): 155–88. http://dx.doi.org/10.1017/s0022112010004155.
Testo completoAbstract (sommario):
The dynamics of a plane interface separating two sheared, density and viscosity matched fluids in the vertical gap between parallel plate electrodes are studied computationally. A Couette profile is imposed onto the fluids by moving the rigid plates at equal speeds in opposite directions. In addition, a vertical electric field is applied to the shear flow by impressing a constant voltage difference on the electrodes. The stability of the initially flat interface is a very subtle balance between surface tension, inertia, viscosity and electric field effects. Under unstable conditions, the potential difference in the fluid results in an electrostatic pressure that amplifies disturbance waves on the two-fluid interface at characteristic wave lengths. Various mechanisms determining the growth rate of the most unstable mode are addressed in a systematic parameter study. The applied methodology involves a combination of numerical simulation and analytical work. Linear stability theory is employed to identify unstable parametric conditions of the perturbed Couette flow. Particular attention is given to the effect of the applied electric field on the instability of the perturbed two-fluid interface. The normal mode analyses are followed up by numerical simulations. The applied method relies on solving the governing equations for the fluid mechanics and the electrostatics in a one-fluid approximation by using a finite-volume technique combined with explicit tracking of the evolving interface. The numerical results confirm those of linear theory and, furthermore, reveal a rich array of dynamical behaviour. The elementary fluid instabilities are finger-like structures of interpenetrating fluids. For weakly unstable situations a single fingering instability emerges on the interface. Increasing the growth rates causes the finger to form a drop-like tip region connected by a long thinning fluids neck. Even more striking fluid motion occurs at higher values of the electric field parameter for which multiple fluid branches develop on the interface. For a pair of perfect dielectrics the vertical electric field was found to enhance interfacial motion irrespective of the permittivity ratio, while in leaky dielectrics the electric field can either stabilize or destabilize the interface, depending on the conductivity and permittivity ratio between the fluids.
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Schönecker, Clarissa, Tobias Baier e Steffen Hardt. "Influence of the enclosed fluid on the flow over a microstructured surface in the Cassie state". Journal of Fluid Mechanics 740 (6 gennaio 2014): 168–95. http://dx.doi.org/10.1017/jfm.2013.647.
Testo completoAbstract (sommario):
AbstractAnalytical expressions for the flow field as well as for the effective slip length of a shear flow over a surface with periodic rectangular grooves are derived. The primary fluid is in the Cassie state with the grooves being filled with a secondary immiscible fluid. The coupling of the two fluids is reflected in a locally varying slip distribution along the fluid–fluid interface, which models the effect of the secondary fluid on the outer flow. The obtained closed-form analytical expressions for the flow field and effective slip length of the primary fluid explicitly contain the influence of the viscosities of the two fluids as well as the magnitude of the local slip, which is a function of the surface geometry. They agree well with results from numerical computations of the full geometry. The analytical expressions allow an investigation of the influence of the viscous stresses inside the secondary fluid for arbitrary geometries of the rectangular grooves. For classic superhydrophobic surfaces, the deviations in the effective slip length compared to the case of inviscid gas flow are pointed out. Another important finding with respect to an accurate modelling of flow over microstructured surfaces is that not only the effective slip length, but also the local slip length of a grooved surface, is anisotropic.
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Блинков, Юрий Анатольевич, Лев Ильич Могилевич, Виктор Сергеевич Попов e Елизавета Викторовна Попова. "Evolution of solitary hydroelastic strain waves in two coaxial cylindrical shells with the Schamel physical nonlinearity". Computational Continuum Mechanics 16, n. 4 (1 dicembre 2023): 430–44. http://dx.doi.org/10.7242/1999-6691/2023.16.4.36.
Testo completoAbstract (sommario):
The paper considers the formulation and solution of the hydroelasticity problem for studying wave processes in the system of two coaxial shells containing fluids in the annular gap between them and in the inner shell. We investigate the axisymmetric case for Kirchhoff–Lave type shells whose material obeys a physical law with a fractional exponent of the nonlinear term (Schamel nonlinearity). The dynamics of fluids in the shells is considered within the framework of the incompressible viscous Newtonian fluid model. The derivation of the Schamel nonlinear equations of shell dynamics makes it possible to develop a mathematical formulation of the problem, which includes the obtained equations, the dynamics equations of two shells, the fluid dynamics equations and the boundary conditions at the shell-fluid interfaces and at the flow symmetry axis. The asymptotic analysis of the problem is performed using perturbation techniques, and the system of two generalized Schamel equations is obtained. This system describes the evolution of nonlinear solitary hydroelastic strain waves in the coaxial shells filled with viscous fluids, taking into account the inertia of the fluid motion. In order to determine the fluid stress at the shell-fluid interfaces, we perform linearization of the fluid dynamics equations for fluids in the annular gap and in the inner shell. The linearized equations are solved by the iterative method. The inertial terms are excluded from the equations in the first iteration, while, in the second iteration, these are the values found in the first iteration. A numerical solution of the system of nonlinear evolution equations is obtained by applying a new difference scheme developed using the Gröbner basis technique. Computational experiments are performed to investigate the effect of fluid viscosity and the inertia of fluid motion in the shells on the wave process. In the absence of fluids in the inner shell, the results of calculations demonstrate that the strain waves in the shells during elastic interactions do not change their shape and amplitude, i.e., they are solitons. The presence of viscous fluid in the inner shell leads to attenuation of the wave process.
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CAO, LINGFEI, HYUNSEO PARK, GJERGJ DODBIBA e TOYOHISA FUJITA. "SYNTHESIS OF AN IONIC LIQUID-BASED MAGNETORHEOLOGICAL FLUID DISPERSING Fe84Nb3V4B9 NANOCRYSTALLINE POWDERS". International Journal of Modern Physics B 24, n. 10 (20 aprile 2010): 1227–34. http://dx.doi.org/10.1142/s021797921005538x.
Testo completoAbstract (sommario):
A new magnetorheological (MR) fluid was synthesized by dispersing Fe 84 Nb 3 V 4 B 9 nanocrystalline powders in a nonvolatile ionic liquid (N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate), which is stable from 282K to 573K. The structure, morphology, and magnetization of Fe 84 Nb 3 V 4 B 9 nanocrystalline powders prepared by mechanical alloying were analyzed by using an X-ray diffractometer (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscopy (SEM), respectively. The magnetic clusters of the synthesized MR fluid were observed by using a digital microscope, and its MR properties were measured by using a cone-plate type viscometer. The experimental results showed that Fe 84 Nb 3 V 4 B 9 nanocrystalline powders with an average grain size of 10–20 nm can be prepared by mechanical alloying. The MR fluid is magnetic-field-responsive, behaves like non-Newtonian fluids, and its magnetorheological properties are influenced by the applied magnetic flux density and the width of magnetic clusters.
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GOLDING, MADELEINE J., JEROME A. NEUFELD, MARC A. HESSE e HERBERT E. HUPPERT. "Two-phase gravity currents in porous media". Journal of Fluid Mechanics 678 (26 aprile 2011): 248–70. http://dx.doi.org/10.1017/jfm.2011.110.
Testo completoAbstract (sommario):
We develop a model describing the buoyancy-driven propagation of two-phase gravity currents, motivated by problems in groundwater hydrology and geological storage of carbon dioxide (CO2). In these settings, fluid invades a porous medium saturated with an immiscible second fluid of different density and viscosity. The action of capillary forces in the porous medium results in spatial variations of the saturation of the two fluids. Here, we consider the propagation of fluid in a semi-infinite porous medium across a horizontal, impermeable boundary. In such systems, once the aspect ratio is large, fluid flow is mainly horizontal and the local saturation is determined by the vertical balance between capillary and gravitational forces. Gradients in the hydrostatic pressure along the current drive fluid flow in proportion to the saturation-dependent relative permeabilities, thus determining the shape and dynamics of two-phase currents. The resulting two-phase gravity current model is attractive because the formalism captures the essential macroscopic physics of multiphase flow in porous media. Residual trapping of CO2 by capillary forces is one of the key mechanisms that can permanently immobilize CO2 in the societally important example of geological CO2 sequestration. The magnitude of residual trapping is set by the areal extent and saturation distribution within the current, both of which are predicted by the two-phase gravity current model. Hence the magnitude of residual trapping during the post-injection buoyant rise of CO2 can be estimated quantitatively. We show that residual trapping increases in the presence of a capillary fringe, despite the decrease in average saturation.
46
Zhu, Jian-Zhou, Weihong Yang e Guang-Yu Zhu. "Purely helical absolute equilibria and chirality of (magneto)fluid turbulence". Journal of Fluid Mechanics 739 (2 gennaio 2014): 479–501. http://dx.doi.org/10.1017/jfm.2013.561.
Testo completoAbstract (sommario):
AbstractPurely helical absolute equilibria of incompressible neutral fluids and plasmas (electron, single-fluid and two-fluid magnetohydrodynamics) are systematically studied with the help of helical (wave) representation and truncation, for genericities and specificities about helicity. A unique chirality selection and amplification mechanism and relevant insights, such as the one-chiral-sector-dominated states, among others, about (magneto)fluid turbulence follow.
47
YOKOYAMA, Hiroshi, e Chisachi KATO. "Fluid-Acoustic Interactions in Acoustic Radiation in Turbulent Cavity Flows : 2nd Report, Fluid-Resonant Oscillations(Fluids Engineering)". Transactions of the Japan Society of Mechanical Engineers Series B 76, n. 765 (2010): 804–13. http://dx.doi.org/10.1299/kikaib.76.765_804.
Testo completo
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Manga, Michael, e H. A. Stone. "Low Reynolds number motion of bubbles, drops and rigid spheres through fluid–fluid interfaces". Journal of Fluid Mechanics 287 (25 marzo 1995): 279–98. http://dx.doi.org/10.1017/s0022112095000954.
Testo completoAbstract (sommario):
The low Reynolds number buoyancy-driven translation of a deformable drop towards and through a fluid–fluid interface is studied using boundary integral calculations and laboratory experiments. The Bond numbers characteristic of both the drop and the initially flat fluid–fluid interface are sufficiently large that the drop and interface become highly deformed, substantial volumes of fluid may be entrained across the interface, and breakup of both interfaces may occur. Specifically, drops passing from a higher- to lower-viscosity fluid are extended vertically as they pass through the interface. For sufficiently large drop Bond numbers, the drop may deform continuously, developing either an elongating tail or enlarging cavity at the back of the drop, analogous to the deformation characteristic of a single deformable drop in an unbounded fluid. The film of fluid between the drop and interface thins most rapidly for those cases that the drop enters a more viscous fluid or has a viscosity lower than the surrounding fluids. In the laboratory experiments, bubbles entering a less viscous fluid are extended vertically and may break into smaller bubbles. The column of fluid entrained by particles passing through the interface may also break into drops. Further experiments with many rigid particles indicate that the spatial distribution of particles may change as the particles pass through interfaces: particles tend to form clusters.
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Protière, Suzie. "Particle Rafts and Armored Droplets". Annual Review of Fluid Mechanics 55, n. 1 (19 gennaio 2023): 459–80. http://dx.doi.org/10.1146/annurev-fluid-030322-015150.
Testo completoAbstract (sommario):
Particles floating at interfaces are commonly observed in nature, as well as in industrial processes. When the particles are non-Brownian particles, large deformations of the interface are created that induce long-ranged capillary interactions and lead to the formation of particle rafts with unique characteristics. In this review we discuss recent efforts in investigating particle raft formation and the role of the rafts’ own weight during dynamic clustering. Under specific conditions, these rafts can ultimately collapse and sink. When subjected to external or internal forces, the raft undergoes large deformations that test the mechanical characteristics of this interfacial composite material. It can behave as a continuous elastic sheet under compression, although its discrete nature can also trigger its fragmentation via interparticle interactions. Finally, armored droplets, drops covered by a protective shell of particles, can lose their integrity when submitted to dynamic deformations, resulting in the ejection of particles or the fracturing of the armor. Open questions to understand the properties of this material are highlighted and future research to understand the fundamental physics of particle rafts, the customization of the cluster formation, or the disassembly of this collective material is suggested.
50
VIEIRA, S. L., M. NAKANO, R. OKE e T. NAGATA. "MECHANICAL PROPERTIES OF AN ER FLUID IN TENSILE, COMPRESSION AND OSCILLATORY SQUEEZE TESTS". International Journal of Modern Physics B 15, n. 06n07 (20 marzo 2001): 714–22. http://dx.doi.org/10.1142/s0217979201005192.
Testo completoAbstract (sommario):
In this work, the mechanical properties of an anhydrous electrorheological fluid made of carbonaceous particles dispersed in silicone oil were determined in tensile, compression and oscillatory squeeze tests. The mechanical tests were carried out on a Mechanical Testling Machine and the device developed for measuring the ER properties was composed of two parallel steel electrodes between which the ER fluid was placed. The mechanical properties were measured for different DC electric field strengths, velocity and initial gap between the electrodes, and the ERF was tested in two different ways: (a) the fluid was placed between the electrodes (configuration 1) and (b) the electrodes were immersed inside the ERF (configuration 2). The results showed that the ER fluid is more resistant to compression than to tensile, and that the shape of the tensile stress-strain curve and the tensile strength varies with the electric field strength and the initial gap between the electrodes. The compressive stress increased with the increase of the electric field strength and with the decrease of the gap size and upper electrode velocity. In oscillatory test, for both configurations 1 and 2, increasing the oscillation frequency f and the number of cycles N produced a decrease of the damping performance of the ER fluid. Besides this, the damping force of each cycle in oscillatory tests increased with N. The electric field also played an important role on the shape of the hysteresis loop (stress as a function of fluid strain) for both configurations.