scholarly journals Observation of the Development of Secondary Features in a Richtmyer–Meshkov Instability Driven Flow

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Tennille Bernard ◽  
C. Randall Truman ◽  
Peter Vorobieff ◽  
Clint Corbin ◽  
Patrick J. Wayne ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Vortex Pair ◽  
Shock Acceleration ◽  
Shock Focusing ◽  
Planar Shock ◽  
Gravity Driven ◽  
The Subject ◽  
Counter Rotating Vortex Pair ◽  
Heavy Gas ◽  
Gaseous Tracer

Richtmyer–Meshkov instability (RMI) has long been the subject of interest for analytical, numerical, and experimental studies. In comparing results of experiment with numerics, it is important to understand the limitations of experimental techniques inherent in the chosen method(s) of data acquisition. We discuss results of an experiment where a laminar, gravity-driven column of heavy gas is injected into surrounding light gas and accelerated by a planar shock. A popular and well-studied method of flow visualization (using glycol droplet tracers) does not produce a flow pattern that matches the numerical model of the same conditions, while revealing the primary feature of the flow developing after shock acceleration: the pair of counter-rotating vortex columns. However, visualization using fluorescent gaseous tracer confirms the presence of features suggested by the numerics; in particular, a central spike formed due to shock focusing in the heavy-gas column. Moreover, the streamwise growth rate of the spike appears to exhibit the same scaling with Mach number as that of the counter-rotating vortex pair (CRVP).

On the Evolution of Double Shock-Accelerated Elliptic Gas Cylinders

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Liyong Zou ◽  
Wenbin Huang ◽  
Cangli Liu ◽  
Jun Yu ◽  
Xisheng Luo
Keyword(s):  
Cross Sections ◽  
High Speed ◽  
Vortex Pair ◽  
Elliptic Cylinder ◽  
Planar Shock ◽  
Planar Shock Wave ◽  
Flow Morphology ◽  
Heavy Gas ◽  
Elliptical Cylinders ◽  
Gas Cylinders

The evolution of double elliptic heavy-gas (SF6) cylinders impacted by a planar shock wave is studied by high-speed camera diagnostics. The minor axes (b) of the elliptic cross sections are aligned perpendicular to the shock direction. While the cylinder dimensions are fixed, we adjust the center-to-center separation s between the cylinders. The resulting flow morphologies are visualized and the interaction between double cylinders is analyzed. When s/b = 4.0 or 3.0, the two elliptical cylinders roll up into two counter-rotating vortex pairs and their interaction is weak. When s/b decreases to 2.0 or 1.2, due to strong interaction of the two inner vortices, the inner structure completely disappears and the flow morphology evolves into one counter-vortex pair. Compared with the s/b = 2.0 case, larger amount of baroclinic vorticity is produced in the s/b = 1.2 case, and the morphology is similar to the single elliptic cylinder case, with a second vortex phenomenon occurring at later times. As s/b increases, the extent of cylinder-cylinder interaction becomes weaker, and the integral height of double elliptic cylinders grows while the length decreases.

Experiments on Drop Impact and Coalescence at a Liquid/Liquid Interface

2003 ◽  
Author(s):  
Zulfaa Mohamed-Kassim ◽  
Ellen K. Longmire
Keyword(s):  
High Speed ◽  
Vortex Pair ◽  
Reynolds Numbers ◽  
Video Camera ◽  
Liquid Interface ◽  
Bulk Liquid ◽  
Index Matching ◽  
High Speed Video Camera ◽  
Gravity Driven ◽  
Counter Rotating Vortex Pair

The gravity-driven impact and coalescence of a single drop through a liquid/liquid interface have been investigated experimentally. PIV images were obtained with a high frequency pulsed-laser and a high-speed video camera. Index-matching and a slight camera inclination were employed to eliminate optical distortion. The drop Reynolds numbers based on impact velocity and ambient viscosity were 20 and 68. During the approach towards the interface, viscous stresses generated a vortex ring inside each drop and a wake behind it. The subsequent deformation of the drop and the interface due to impact were observed to be more radical in the higher Re case. Both the wake shearing on the upper drop surface and interfacial deformation were significant in dissipating the vorticity inside the drops. After the vorticity dissipated, an outward flow developed along one radian between the ‘resting’ drop and the interface below generating a counter-rotating vortex pair. The eventual coalescence was typically off axis. During coalescence, a capillary ring wave propagated radially inward enhancing the collapse of the drop fluid into the bulk liquid below.

Planar Shock Focusing Through Perfect Gas Lens: First Experimental Demonstration

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Laurent Biamino ◽  
Christian Mariani ◽  
Georges Jourdan ◽  
Lazhar Houas ◽  
Marc Vandenboomgaerde ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Shock Acceleration ◽  
Perfect Gas ◽  
Shock Focusing ◽  
Planar Case ◽  
Planar Shock ◽  
Planar Shock Wave

When a shock wave crosses an interface between two materials, this interface becomes unstable and the Richtmyer–Meshkov instability develops. Such instability has been extensively studied in the planar case, and numerous results were presented during the previous workshops. But the Richtmyer–Meshkov (Richtmyer, 1960, “Taylor Instability in Shock Acceleration of Compressible Fluids,” Commun. Pure Appl. Math., 13(2), pp. 297–319; Meshkov, 1969, “Interface of Two Gases Accelerated by a Shock Wave,” Fluid Dyn., 4(5), pp. 101–104) instability also occurs in a spherical case where the convergence effects must be taken into account. As far as we know, no conventional (straight section) shock tube facility has been used to experimentally study the Richtmyer–Meshkov instability in spherical geometry. The idea originally proposed by Dimotakis and Samtaney (2006, “Planar Shock Cylindrical Focusing by a Perfect-Gas Lens,” Phys. Fluid., 18(3), pp. 031705–031708) and later generalized by Vandenboomgaerde and Aymard (2011, “Analytical Theory for Planar Shock Focusing Through Perfect Gas Lens and Shock Tube Experiment Designs,” Phys. Fluid., 23(1), pp. 016101–016113) was to retain the flexibility of a conventional shock tube to convert a planar shock wave into a cylindrical one through a perfect gas lens. This can be done when a planar shock wave passes through a shaped interface between two gases. By coupling the shape with the impedance mismatch at the interface, it is possible to generate a circular transmitted shock wave. In order to experimentally check the feasibility of this approach, we have implemented the gas lens technique on a conventional shock tube with the help of a convergent test section, an elliptic stereolithographed grid, and a nitrocellulose membrane. First experimental sequences of schlieren images have been obtained for an incident shock wave Mach number equal to 1.15 and an air/SF6-shaped interface. Experimental results indicate that the shock that moves in the converging part has a circular shape. Moreover, pressure histories that were recorded during the experiments show pressure increase behind the accelerating converging shock wave.

THE INFLUENCE OF AGE ON PERFORMANCE AS SHOWN BY EXERCISE TESTS

PEDIATRICS ◽  
1963 ◽  
Vol 32 (4) ◽  
pp. 737-741
Author(s):  
D. B. Dill
Keyword(s):  
Work Performance ◽  
Experimental Studies ◽  
Business Administration ◽  
Distance Runner ◽  
Indiana University ◽  
Exercise Tests ◽  
The Subject ◽  
To Come ◽  
The Many ◽  
Harvard School

THE STUDY of work performance as related to age began in this country when Sid Robinson joined the group at the Fatigue Laboratory of the Harvard School of Business Administration. In the winter of 1936-7, he persuaded five champion milers who were in Boston for indoor meets to run on the Laboratory's treadmill on week-ends. Simultaneously, he was chiefly engaged in studying treadmill performance as related to age. This was the subject of his doctorate thesis published later under the title: "Experimental Studies of Physical Fitness as Related to Age". The 91 subjects ranged in age from boys 6 years of age to one man of 91. There were eight 6-year-olds, 10 between 8 and 13 and 20 between 48 and 76. Robinson's background as an Olympic middle-distance runner and as an assistant track coach at Indiana University gave him skill in dealing with the many diverse problems that confronted him. Often he was faced with sociological-psychological problems more difficult to solve than the physiological problems. Indicative of his success is the fact that the subjects were volunteers—no money was offered as an inducement to come to the laboratory. Also worthy of note is that there was no untoward incident throughout the study. Robinson's plan included respiratory, circulatory and metabolic observations in the basal state and in two grades of exercise. He describes the work experiments as follows: (pp. 251-3, reference 2) "After the above observations were completed, the subject performed two grades of work on a motor-driven treadmill, set at an angle of 8.6% in all experiments. Each subject below 73 years of age first walked at 5.6 km per hour for 15 minutes; this raises the oxygen consumption 7 or 8 times the basal level. After resting 10 minutes, he ran or in some cases, walked, at a rate which exhausted him in 2 to 5 minutes.

Evolution and Turbulence Properties of Self-Sustained Transversely Oscillating Flow Induced by Fluidic Oscillator

2007 ◽  
Vol 129 (8) ◽  
pp. 1038-1047 ◽  
Author(s):  
Rong Fung Huang ◽  
Kuo Tong Chang
Keyword(s):  
Stagnation Point ◽  
Vortex Pair ◽  
Transverse Oscillation ◽  
Oscillating Flow ◽  
Near Wake ◽  
Fluidic Oscillator ◽  
Planar Jet ◽  
Oscillation Process ◽  
Gravity Driven ◽  
Flow Evolution

The evolution process and turbulence properties of a transversely oscillating flow induced by a fluidic oscillator are studied in a gravity-driven water tunnel. A planar jet is guided to impinge a specially designed crescent surface of a target blockage that is enclosed in a cavity of a fluidic oscillator. The geometric configuration of the cavity transforms the inherent stability characteristics of the jet from convective instability to absolute instability, so that the jet precedes the persistent back and forth swinging in the cavity. The swinging jet is subsequently directed through two passages and issued alternatively out of the fluidic oscillator. Two short plates are installed near the exits of the alternatively issuing pulsatile jets to deflect the jets toward the central axis. The deflected jets impinge with each other and form a pair of counter-rotating vortices in the near wake of the oscillator with a stagnation point at the impingement point. The stagnation point of the counter-rotating vortex pair moves back and forth transversely because of the phase difference existing between the two issued jets. The merged flow evolving from the counter-rotating vortices formed by the impingement of the two pulsatile jets therefore presents complex behavior of transverse oscillation. The topological models corresponding to the flow evolution are constructed to illustrate the oscillation process of the oscillating flow. Significant momentum dispersion and large turbulence intensity are induced by the transverse oscillation of the merged flow. The statistical turbulence properties show that the Lagrangian integral time and length scales of the turbulence eddies (the fine-scale structure) produced in the oscillating flow are drastically reduced.

scholarly journals Температурные зависимости электропроводности и магнитной восприимчивости кристаллов твердых растворов Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=--Bi-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-

2021 ◽  
Vol 55 (12) ◽  
pp. 1162
Author(s):  
Н.П. Степанов ◽  
В.Ю. Наливкин ◽  
А.К. Гильфанов ◽  
А.А. Калашников ◽  
Е.Н. Трубицына
Keyword(s):  
Electrical Conductivity ◽  
Magnetic Susceptibility ◽  
Solid Solutions ◽  
Thermoelectric Materials ◽  
Materials Science ◽  
Practical Importance ◽  
Experimental Studies ◽  
Electronic System ◽  
Temperature Dependences ◽  
The Subject

Solid solutions Bi2Te3-Sb2Te3 continue to be the subject of numerous and versatile experimental studies due to their practical importance for thermoelectric materials science. In this regard, the problem of studying the regularities of changes in the state of the electronic system of these semiconductors from composition and temperature remains urgent. This paper presents the results of studying the temperature dependences of the magnetic susceptibility of Bi2Te3-Sb2Te3 crystals containing 10, 25, 40, 50, 60 mol. % Sb2Te3. The correlation of the behavior of the temperature dependences of the magnetic susceptibility and electrical conductivity is analyzed.

scholarly journals O2 State in 18 O by using Core – Polarization effects

2008 ◽  
pp. 66-72
Keyword(s):  
Perturbation Theory ◽  
Experimental Studies ◽  
Form Factors ◽  
Wave Model ◽  
Collective Model ◽  
Core Polarization ◽  
Polarization Effects ◽  
The Core ◽  
The Subject ◽  
Space Wave

Coulomb form factors for E0 transition in 18O are discussed taking into account core-polarization effects. These effects are taken into account through the collective model of Tassie and also through a microscopic perturbation theory including excitations up to 2p1f shell. Space wave model functions defined for the orbits 1 and 2125O nucleus has been the subject of extensive theoretical and experimental studies, which received much attention in last decade [Alex Brown et.al.2005]. The 18O system contains two neutrons in addition to the16O core distributed in the sd – shell. d1 are obtained from the diagonalization of the interaction Hamilonian of Wildenthal. The calculations include the 0 2state with excitation energies3.6337MeV. The core – polarization effects which incorporate the ollective model of Tassei describe the data very well for this state.

scholarly journals Brazilian Scientific Research about Acupuncture in Dentistry: Bibliometric Analysis of the Papers Presented at SBPqO Meetings

2019 ◽  
Vol 21 (4) ◽  
pp. 348
Author(s):  
José De Alencar Fernandes Neto ◽  
Pettely Thaise De Souza Santos Palmeira ◽  
Jhonatan Thiago Lacerda-Santos ◽  
Ana Luzia Araújo Batista ◽  
Thamyres Maria Silva Simões ◽  
...  
Keyword(s):  
Complementary Therapies ◽  
Experimental Studies ◽  
Secondary Data ◽  
Cross Sectional Study ◽  
Public Institutions ◽  
Cross Sectional ◽  
Dental Research ◽  
Keywords Acupuncture ◽  
The Subject ◽  
Type Of Institution

AbstractThe aim of this study was to investigate the Brazilian scientific production about acupuncture in dentistry, outlining the profile of the works about the subject presented at the Meetings of the Brazilian Society of Dental Research (SBPqO). It was a cross-sectional study, with a quantitative approach, based on secondary data. An analysis of all abstracts presented in the last ten SBPqO Meetings (2009-2018) published in the annals of the event was carried out. For the research the location of the term "acupuntura" or "acupuncture" among the abstracts was realized and the following information was collected: type of institution that carried out the research (public or private), Brazilian region where it was realized, area or specialty of dentistry and whether it involved humans or animals. Of the 26,514 dental research abstracts published in the annals, only 27 papers were experimental studies or systematic reviews about the subject. Of the total, 23 (85.2%) were developed in public institutions, 15 (55.6%) did not receive financial support 20 (74.1%) were carried out in humans and 13 (48.2%) were developed in the Southeast region. Regarding the dental specialty, the majority (70.4%) investigated acupuncture in "Temporomandibular Dysfunction and Orofacial Pain". Therefore, it can be concluded that few acupuncture studies in dentistry have been developed in the last ten years in Brazil, according to the papers presented at the SBPqO Meetings. Thus, it is suggested that research on the subject be carried out and widely disseminated between the academic and professional milieu. Keywords: Acupuncture Therapy. Dental Research. Complementary Therapies. ResumoO objetivo desse estudo foi investigar a produção científica brasileira sobre a acupuntura na odontologia, traçando o perfil dos trabalhos sobre a temática apresentados nas Reuniões da Sociedade Brasileira de Pesquisa Odontológica (SBPqO). Tratou-se de um estudo transversal, com abordagem quantitativa, a partir de dados secundários.  Realizou-se uma análise de todos os resumos apresentados nas últimas dez Reuniões da SBPqO (2009-2018) publicados nos anais do evento. Para pesquisa procedeu-se a localização do termo “acupuntura” ou “acupuncture” entre os resumos e foram colhidas as seguintes informações: tipo de instituição que realizou a pesquisa (pública ou privada), região brasileira onde foi realizada, recebimento de auxílio financeiro, área ou especialidade da odontologia e se envolvia humanos ou animais. Dos 26.514 resumos de pesquisa odontológica publicados em anais, apenas 27 trabalhos tratavam de estudos experimentais ou revisões sistemáticas sobre a temática. Do total, 23 (85,2%) foram desenvolvidos em instituições públicas, 15 (55,6%) não receberam auxílio financeiro, 20 (74,1%) foram realizados em humanos e 13 (48,2%) desenvolvidos na região Sudeste do Brasil. Com relação a especialidade odontológica, a maioria (70,4%) pesquisou sobre a acupuntura na “Disfunção Temporomandibular e Dor Orofacial”. Os achados do presente estudo indicam que poucas pesquisas abordando a acupuntura na odontologia foram desenvolvidas nos últimos dez anos no Brasil, de acordo com os trabalhos apresentados nas Reuniões da SBPqO. Diante disso, sugere-se que pesquisas sobre o tema sejam realizadas e amplamente divulgadas entre o meio acadêmico e profissionais. Palavras-chave: Terapia por Acupuntura. Pesquisa em Odontologia. Terapias Complementares.

scholarly journals Dynamic simulations of many-body electrostatic self-assembly

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170143 ◽  
Author(s):  
Eric B. Lindgren ◽  
Benjamin Stamm ◽  
Yvon Maday ◽  
Elena Besley ◽  
A. J. Stace
Keyword(s):  
Self Assembly ◽  
Experimental Studies ◽  
Charged Particles ◽  
Theoretical Chemistry ◽  
Many Body ◽  
Single Particles ◽  
Theme Issue ◽  
Dynamic Simulations ◽  
The Subject ◽  
Small Clusters

Two experimental studies relating to electrostatic self-assembly have been the subject of dynamic computer simulations, where the consequences of changing the charge and the dielectric constant of the materials concerned have been explored. One series of calculations relates to experiments on the assembly of polymer particles that have been subjected to tribocharging and the simulations successfully reproduce many of the observed patterns of behaviour. A second study explores events observed following collisions between single particles and small clusters composed of charged particles derived from a metal oxide composite. As before, observations recorded during the course of the experiments are reproduced by the calculations. One study in particular reveals how particle polarizability can influence the assembly process. This article is part of the theme issue ‘Modern theoretical chemistry’.

scholarly journals On the formation of the counter-rotating vortex pair in transverse jets

2001 ◽  
Vol 446 ◽  
pp. 347-373 ◽  
Author(s):  
L. CORTELEZZI ◽  
A. R. KARAGOZIAN
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Transverse Jets ◽  
Vortical Structures ◽  
Jet In Crossflow ◽  
Dynamical Generation ◽  
Counter Rotating Vortex Pair

Among the important physical phenomena associated with the jet in crossflow is the formation and evolution of vortical structures in the flow field, in particular the counter-rotating vortex pair (CVP) associated with the jet cross-section. The present computational study focuses on the mechanisms for the dynamical generation and evolution of these vortical structures. Transient numerical simulations of the flow field are performed using three-dimensional vortex elements. Vortex ring rollup, interactions, tilting, and folding are observed in the near field, consistent with the ideas described in the experimental work of Kelso, Lim & Perry (1996), for example. The time-averaged effect of these jet shear layer vortices, even over a single period of their evolution, is seen to result in initiation of the CVP. Further insight into the topology of the flow field, the formation of wake vortices, the entrainment of crossflow, and the effect of upstream boundary layer thickness is also provided in this study.

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