scholarly journals Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 183
Author(s):  
Francesco Romanò
Keyword(s):  
Particle Trajectory ◽  
Density Ratio ◽  
Particle Interaction ◽  
Stokes Number ◽  
Cavity Wall ◽  
Inertial Particles ◽  
Particle Segregation ◽  
Rigid Particle ◽  
Theoretical Understanding ◽  
First Time

A small spherical rigid particle in a cylindrical cavity is considered. The harmonic rotation of the cavity wall drives the background flow characterized by the Strouhal number Str, assumed as the first parameter of our investigation. The particle immersed in the flow (assumed Stokesian) has a Stokes number St=1 and a particle-to-fluid density ratio ϱ which is assumed as the second parameter of this study. Building on the theoretical understanding of the recently discovered oscillatory switching centrifugation for inertial particles in unbounded flows, we investigate the effect of a confinement. For the first time we study how the presence of a wall affects the particle trajectory in oscillatory switching centrifugation dynamics. The emergence of two qualitatively different particle attractors is characterized for particles centrifuged towards the cavity wall. The implication of two such classes of attractors is discussed focusing on the application to microfluidics. We propose some strategies for exploiting the confined oscillatory switching centrifugation for selective particle segregation and for the enhancement of particle interaction events.

Clustering in Euler–Euler and Euler–Lagrange simulations of unbounded homogeneous particle-laden shear

2018 ◽  
Vol 859 ◽  
pp. 174-203 ◽  
Author(s):  
M. Houssem Kasbaoui ◽  
Donald L. Koch ◽  
Olivier Desjardins
Keyword(s):  
Particle Trajectory ◽  
Density Ratio ◽  
Particle Dispersion ◽  
Solid Particles ◽  
Inertial Particles ◽  
Particle Volume ◽  
Local Dispersion ◽  
Preferential Concentration ◽  
Homogeneous Particle ◽  
Two Fluid

Particle-laden flows of sedimenting solid particles or droplets in a carrier gas have strong inter-phase coupling. Even at low particle volume fractions, the two-way coupling can be significant due to the large particle to gas density ratio. In this semi-dilute regime, the slip velocity between phases leads to sustained clustering that strongly modulates the overall flow. The analysis of perturbations in homogeneous shear reveals the process by which clusters form: (i) the preferential concentration of inertial particles in the stretching regions of the flow leads to the formation of highly concentrated particle sheets, (ii) the thickness of the latter is controlled by particle-trajectory crossing, which causes a local dispersion of particles, (iii) a transverse Rayleigh–Taylor instability, aided by the shear-induced rotation of the particle sheets towards the gravity normal direction, breaks the planar structure into smaller clusters. Simulations in the Euler–Lagrange formalism are compared to Euler–Euler simulations with the two-fluid and anisotropic-Gaussian methods. It is found that the two-fluid method is unable to capture the particle dispersion due to particle-trajectory crossing and leads instead to the formation of discontinuities. These are removed with the anisotropic-Gaussian method which derives from a kinetic approach with particle-trajectory crossing in mind.

“Little Trio” for clarinet, bassoon and piano

2018 ◽  
pp. 75-79
Author(s):  
N. Yakovchuk
Keyword(s):  
Chamber Music ◽  
Instrumental Music ◽  
Instrumental Ensemble ◽  
Interesting Phenomenon ◽  
Theoretical Understanding ◽  
Classical Traditions ◽  
And Performance ◽  
Instrumental Ensembles ◽  
Written Compositions ◽  
First Time

The chamber-instrumental ensemble music in the Ukrainian musical culture of the last third of the 20th and the beginning of the 21st centuries occupies one of the leading places and is characterized by powerful processes in its development. Such circumstances caused the Ukrainian musicologist interests to the problems of chamber-instrumental music creativity and performance. There are appeared researches in the field of theory, history and performance problems covering the most important questions like chamber music definitions, specific genre issues, the growing function of piano in the Ukrainian chamber music, the increasing questions of technique and timbre importance of modern instrumental ensembles. In the significant multifaceted creative work of contemporary Ukrainian composer, Oleksandr Yakovchuk, the genre of chamber instrumental ensemble music represents a complex and interesting phenomenon. Original and skillfully written compositions reflect artistic world of the composer of postmodern time and gained recognition in music life of Ukraine and beyond. These works are highly appreciated in performing practice of our days. The purpose of the article is to analyze the work — “Little Trio” for clarinet, bassoon and piano (1980), which has the signs of neoclassical tendency in the composer’s style. The methodological basis of this research is a comprehensive approach in theoretical understanding of the subject of research (the methods of textology, source study as well as the method of interviewing the author were used). The scientific novelty of this article is in the priority of its main provisions, since the “Little Trio” entered the scientific circulation for the first time. The three-movement “Little Trio” (1980) is notable for the light feeling of timbre colours and the shape clarity. The Ist movement — Allegretto giocoso — is written in a sonata form following all classical traditions. Quite interesting are the two monologues of clarinet and bassoon from the IInd movement, they represent very modern line in Ukrainian chamber music — the possibility of sincere confession which comes through the solo cadence. In the IIIrd movement, the composer took advantage from the folk Ukrainian dance “hopak” using the rhythm of it and creating dance character of the Final.

scholarly journals Influence of a Standing Wave Flow-Field on the Dynamics of a Spray Diffusion Flame

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
J. Barry Greenberg ◽  
David Katoshevski
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Standing Wave ◽  
Diffusion Flame ◽  
Stokes Number ◽  
Flame Height ◽  
Wave Flow ◽  
Two Dimensional ◽  
Governing Equations ◽  
First Time

A theoretical investigation of the influence of a standing wave flow-field on the dynamics of a laminar two-dimensional spray diffusion flame is presented for the first time. The mathematical analysis permits mild slip between the droplets and their host surroundings. For the liquid phase, the use of a small Stokes number as the perturbation parameater enables a solution of the governing equations to be developed. Influence of the standing wave flow-field on droplet grouping is described by a specially constructed modification of the vaporization Damkohler number. Instantaneous flame front shapes are found via a solution for the usual Schwab–Zeldovitch parameter. Numerical results obtained from the analytical solution uncover the strong bearing that droplet grouping, induced by the standing wave flow-field, can have on flame height, shape, and type (over- or under-ventilated) and on the existence of multiple flame fronts.

Snowflakes in the atmospheric surface layer: observation of particle–turbulence dynamics

2017 ◽  
Vol 814 ◽  
pp. 592-613 ◽  
Author(s):  
Andras Nemes ◽  
Teja Dasari ◽  
Jiarong Hong ◽  
Michele Guala ◽  
Filippo Coletti
Keyword(s):  
Large Scale ◽  
Isotropic Turbulence ◽  
Volume Fraction ◽  
Response Times ◽  
Field Measurements ◽  
Stokes Number ◽  
Inertial Particles ◽  
Natural Setting ◽  
Scale Particle ◽  
Particle Imaging

We report on optical field measurements of snow settling in atmospheric turbulence at $Re_{\unicode[STIX]{x1D706}}=940$. It is found that the snowflakes exhibit hallmark features of inertial particles in turbulence. The snow motion is analysed in both Eulerian and Lagrangian frameworks by large-scale particle imaging, while sonic anemometry is used to characterize the flow field. Additionally, the snowflake size and morphology are assessed by digital in-line holography. The low volume fraction and mass loading imply a one-way interaction with the turbulent air. Acceleration probability density functions show wide exponential tails consistent with laboratory and numerical studies of homogeneous isotropic turbulence. Invoking the assumption that the particle acceleration has a stronger dependence on the Stokes number than on the specific features of the turbulence (e.g. precise Reynolds number and large-scale anisotropy), we make inferences on the snowflakes’ aerodynamic response time. In particular, we observe that their acceleration distribution is consistent with that of particles of Stokes number in the range $St=0.1{-}0.4$ based on the Kolmogorov time scale. The still-air terminal velocities estimated for the resulting range of aerodynamic response times are significantly smaller than the measured snow particle fall speed. This is interpreted as a manifestation of settling enhancement by turbulence, which is observed here for the first time in a natural setting.

Orientation Specific Thermal Properties of Polyimide Film

2000 ◽  
Vol 123 (3) ◽  
pp. 273-277 ◽  
Author(s):  
Robert J. Samuels ◽  
Nancy E. Mathis
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Polyimide Film ◽  
New Materials ◽  
Polyimide Films ◽  
Nondestructive Technique ◽  
Theoretical Understanding ◽  
First Time ◽  
The Relationship ◽  
Transfer Mechanisms

The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.

scholarly journals N.G. JUSOITY AS A THEORETIC AND PRACTICE OF ART TRANSLATION

Kavkaz-forum ◽  
2020 ◽  
Author(s):  
Л.Б. ДЗАПАРОВА
Keyword(s):  
Research Field ◽  
Theory And Practice ◽  
Literary Translation ◽  
Theoretical Understanding ◽  
Semantic Level ◽  
Literary Journals ◽  
Poetic Translation ◽  
Problems Of Translation ◽  
First Time

Проблемы теории и практики художественного перевода как феномена межкультурной коммуникации в наше время актуализируются в современной филологической науке. Расширяется исследовательское поле в этой области научного знания для переводоведов и всех, кто интересуется проблемами диалога культур. Выбор темы исследования обусловлен и прошедшим в этом году 95-летим юбилеем известного осетинского поэта, драматурга, литературоведа Нафи Григорьевича Джусойты. В статье рассматривается вклад народного писателя Осетии в теоретическое осмысление проблем художественного перевода; впер­вые анализируется одно из самых сложных для перевода стихотворений А.С. Пушкина «Пророк» в интерпретации Н. Джусойты. В частности, автором в статье представлен анализ опубликованных Джусойты на страницах центральных литературных журналов дискуссионных работ по наиболее актуальным проблемам переводоведения. В них Джусойты фокусирует внимание на вопросах верности перевода оригиналу, повышения качества подстрочников, новаторства и модер­низации классических произведений; обуславливает важность переводческого чтения в процессе постижения оригинала; определяет специфику поэтического перевода; выступает против украшательства в переводе, демонстрации на всесоюзном уровне слабых оригиналов и несовершенных переводов. В целом, Джусойты, полемизируя с известными теоретиками, предлагает свою концепцию перевода, начиная от выбора произведения и до конечного результата – текста на другом языке. Перед нами круг проблем, которые до сих пор волнуют специалистов по художественно­му переводу. Автором статьи также представлен сравнительно-сопоставительный анализ стихотворения А. Пушкина в оригинале и в переводческой интерпретации Н.Г. Джусойты. Сличение текстов на смысловом уровне показало стремление Джусойты найти художественные средства, которые помогают раскрыть основной образ. Но не везде раскрыт двуплановый смысл, запечатленный в лексических единицах исходного языка. The problems of the theory and practice of literary translation as a phenomenon of intercultural communication are still actualized in modern philological science. The research field in this area of scientific knowledge is expanding for translators and those interested in the problems of the dialogue of cultures. The choice of the research topic was also conditioned by the 95th anniversary of the famous Ossetian poet, playwright, literary critic Nafi Grigorievich Jusoyty, celebrated this year. The article examines the contribution of the people’s writer of Ossetia to the theoretical understanding of the problems of literary translation; for the first time one of the most difficult poems for translation by A.S. Pushkin’s «Prophet» in the interpretation of N. Jusoyty is reviewed. In particular, the author in the article presents an analysis of the discussion papers published by Jusoyty on the pages of central literary journals on the most pressing problems of translation studies. In them, Jusoyty focuses on the issues of closeness to the original, improving the quality of interlinear translations, innovation and modernization of classical works; determines the importance of translation reading in the process of comprehending the original; determines the specifics of poetic translation; opposes embellishment in translation, the demonstration of weak originals and imperfect translations at the all-Union level. In general, Jusoyty, arguing with well-known theorists, offers his own concept of translation, starting from the choice of a work and up to the final result – a text in another language. We are faced with a range of problems that still concern specialists in literary translation. The author of the article also presents a comparative analysis of A. Pushkin’s poem in the original and in t/he translation interpretation of N.G. Jusoyty. Comparison of the texts at the semantic level showed Jusoyty’s desire to find close artistic means that help to reveal the main image. But not everywhere is disclosed the two-dimensional meaning embodied in the lexical units of the source language.

scholarly journals Concentration and velocity statistics of inertial particles in upward and downward pipe flow

2017 ◽  
Vol 822 ◽  
pp. 640-663 ◽  
Author(s):  
J. L. G. Oliveira ◽  
C. W. M. van der Geld ◽  
J. G. M. Kuerten
Keyword(s):  
Liquid Velocity ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Stokes Number ◽  
Terminal Velocity ◽  
Point Particle ◽  
Inertial Particles ◽  
Carrier Fluid ◽  
Velocity Statistics ◽  
The Difference

Three-dimensional particle tracking velocimetry is applied to particle-laden turbulent pipe flows at a Reynolds number of 10 300, based on the bulk velocity and the pipe diameter, for developed fluid flow and not fully developed flow of inertial particles, which favours assessment of the radial migration of the inertial particles. Inertial particles with Stokes number ranging from 0.35 to 1.11, based on the particle relaxation time and the radial-dependent Kolmogorov time scale, and a ratio of the root-mean-square fluid velocity to the terminal velocity of order 1 have been used. Core peaking of the concentration of inertial particles in up-flow and wall peaking in down-flow have been found. The difference in mean particle and Eulerian mean liquid velocity is found to decrease to approximately zero near the wall in both flow directions. Although the carrier fluid has all of the characteristics of the corresponding turbulent single-phase flow, the Reynolds stress of the inertial particles is different near the wall in up-flow. These findings are explained from the preferential location of the inertial particles with the aid of direct numerical simulations with the point-particle approach.

Past, Present and Future of Analytical Stems

2001 ◽  
Vol 7 (S2) ◽  
pp. 182-183
Author(s):  
C. Colliex
Keyword(s):  
Analytical Electron Microscopy ◽  
Quantitative Information ◽  
General Level ◽  
Chemical Mapping ◽  
Theoretical Understanding ◽  
Fundamental Limits ◽  
Cornell University ◽  
Resolution Imaging ◽  
First Time ◽  
Major Emphasis

Twenty five years ago, in august 1976, a specialist workshop gathered in Cornell University, at John Silcox's invitation, scientists covering a broad spectrum of interests to assess the potential of analytical electron microscopy, as to instrumentation, fundamental limits, general level of data processing and current theoretical understanding. If the STEM instrument had already been existing for a few years in Crewe's laboratory, its major emphasis, in spite of the existence of an EELS spectrometer, had focused on new modes of high resolution imaging. At the first Cornell workshop, the STEM instrument was for the first time recognized as a potentially formidable analytical instrument because of the possibility of extracting all available signals simultaneously. Furthermore it was directly suitable for digital computer processing and therefore for providing quantitative information. It was also pointed out that a major advantage of the STEM would be its potential to record EELS spectra from every point in the field of view as one scans an area to form an image, thus offering the capability of "chemical" mapping beyond "elemental" mapping.

scholarly journals On the transition between turbulence regimes in particle-laden channel flows

2018 ◽  
Vol 845 ◽  
pp. 499-519 ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins ◽  
Rodney O. Fox
Keyword(s):  
Reynolds Number ◽  
Fluid Phase ◽  
Stokes Number ◽  
Channel Flows ◽  
High Mass ◽  
Inertial Particles ◽  
Mass Loading ◽  
Two Phase ◽  
Phase Dynamics ◽  
Wide Range

Turbulent wall-bounded flows exhibit a wide range of regimes with significant interaction between scales. The fluid dynamics associated with single-phase channel flows is predominantly characterized by the Reynolds number. Meanwhile, vastly different behaviour exists in particle-laden channel flows, even at a fixed Reynolds number. Vertical turbulent channel flows seeded with a low concentration of inertial particles are known to exhibit segregation in the particle distribution without significant modification to the underlying turbulent kinetic energy (TKE). At moderate (but still low) concentrations, enhancement or attenuation of fluid-phase TKE results from increased dissipation and wakes past individual particles. Recent studies have shown that denser suspensions significantly alter the two-phase dynamics, where the majority of TKE is generated by interphase coupling (i.e.  drag) between the carrier gas and clusters of particles that fall near the channel wall. In the present study, a series of simulations of vertical particle-laden channel flows with increasing mass loading is conducted to analyse the transition from the dilute limit where classical mean-shear production is primarily responsible for generating fluid-phase TKE to high-mass-loading suspensions dominated by drag production. Eulerian–Lagrangian simulations are performed for a wide range of particle loadings at two values of the Stokes number, and the corresponding two-phase energy balances are reported to identify the mechanisms responsible for the observed transition.

An Investigation of Crossing Trajectory Effects in Turbulent Shear Flow (Keynote)

2005 ◽  
Author(s):  
Lionel Thomas ◽  
Benoiˆt Oesterle´
Keyword(s):  
Shear Flow ◽  
Isotropic Turbulence ◽  
Fluid Velocity ◽  
Stokes Number ◽  
Turbulent Shear ◽  
Inertial Particles ◽  
Turbulent Shear Flow ◽  
Velocity Magnitude ◽  
Dispersed Particles ◽  
Lagrangian Tracking

The dispersion of small inertial particles moving in a homogeneous, hypothetically stationary, shear flow is investigated using both theoretical analysis and numerical simulation, under one-way coupling approximation. In the theoretical approach, the previous studies are extended to the case of homogeneous shear flow with a corresponding anisotropic spectrum. As it is impossible to obtain a closed theoretical solution without some drastic simplifications, the motion of dispersed particles is also investigated using kinematic simulation where random Fourier modes are generated according to a prescribed anisotropic spectrum with a superimposed linear mean fluid velocity profile. The combined effects of particle Stokes number and dimensionless drift velocity (magnitude and direction) are investigated by computing the statistics from Lagrangian tracking of a large number of particles in many flow field realizations, and comparison is made between the observed effects in shear flow and in isotropic turbulence.

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