Observations and LDA measurements of confined turbulent vortex flow

1980 ◽  
Vol 98 (1) ◽  
pp. 49-63 ◽  
Author(s):  
M. P. Escudier ◽  
J. Bornstein ◽  
N. Zehnder
Keyword(s):  
Axial Velocity ◽  
Vortex Flow ◽  
Vortex Tube ◽  
Reversed Flow ◽  
Remarkable Change ◽  
Fluid Medium ◽  
Turbulent Vortex ◽  
Average Value ◽  
Annular Jet ◽  
Order Of Magnitude

A series of LDA measurements and visual observations of confined turbulent vortex flow are described. The experiments were performed with water as the fluid medium in a vortex tube of length-to-diameter ratio L/D = 3.8 for a range of exit diameters De between De/D = 1 and 0.18. The experiments reveal a remarkable change in the vortex structure as De is reduced: from a thick core with an axial-velocity defect in the centre, and even reversed flow, to a thin annular jet-like core with a peak axial velocity more than an order of magnitude greater than the average value and again a central velocity deficit. The corresponding swirl profiles are not remarkable and are well-represented under all conditions by the solution of Burgers (1948), albeit with a velocity maximum which is strongly dependent upon De.

Paper 25: Vortex Flow in a Cylinder

1969 ◽  
Vol 184 (7) ◽  
pp. 65-75
Author(s):  
P. L. Betts ◽  
Y-K. Yue
Keyword(s):  
Pressure Drop ◽  
Internal Combustion Engine ◽  
Cross Sections ◽  
Axial Velocity ◽  
Vortex Flow ◽  
Vortex Tube ◽  
Swirling Flow ◽  
Combustion Engine ◽  
Engine Cylinder ◽  
Port Opening

The swirling flow inside certain types of internal combustion engine depends in a complex way on a large number of variables. The steady flow of air through a cylinder, which reproduces the main features of an induction swirl engine cylinder, has been investigated. The pressure drop across the inlet ports, the port inclination, and the port opening were varied independently while other variables were held constant. For each condition, tangential velocities were measured and axial velocity directions observed over cross-sections of the cylinder. The results have been compared with a simplified hypothesis of R. S. Benson and with theories of the Ranque–Hilsch vortex tube.

Seismic wave energy inferred from long-period body wave inversion

1988 ◽  
Vol 78 (5) ◽  
pp. 1707-1724
Author(s):  
Masayuki Kikuchi ◽  
Yoshio Fukao
Keyword(s):  
Seismic Wave ◽  
Wave Energy ◽  
Body Wave ◽  
Empirical Relation ◽  
P Waves ◽  
Average Value ◽  
Long Period ◽  
Wave Inversion ◽  
Moment Ratio ◽  
Order Of Magnitude

Abstract The seismic wave energy is evaluated for 35 large earthquakes by inverting far-field long-period P waves into the multiple-shock sequence. The results show that the seismic wave energy thus obtained is systematically less than that inferred from the Gutenberg-Richter's formula with the seismic magnitude. The difference amounts to one order of magnitude. The results also show that the energy-moment ratio is well confined to a narrow range: 10−6 < ES/Mo < 10−5 with the average of ∼5 × 10−6. This average value is exactly one order of magnitude as small as the energy-moment ratio inferred from the Gutenberg-Richter's formula using the moment magnitude. Comparing the energy-moment ratio with Δσo/2μ, where Δσo and μ are the stress drop and the rigidity, we obtain an empirical relation: ES/Mo ∼ 0.1 × Δσ0/2μ. Such a relation can be interpreted in terms of a subsonic rupture where the energy loss due to cohesion is not negligible to the seismic wave energy.

scholarly journals Tripod-Loop Metasurfaces for Terahertz-Sensing Applications: A Comparison

2020 ◽  
Vol 10 (18) ◽  
pp. 6504
Author(s):  
Irati Jáuregui-López ◽  
Bakhtiyar Orazbayev ◽  
Victor Pacheco-Peña ◽  
Miguel Beruete
Keyword(s):  
Thin Film ◽  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Ring Resonators ◽  
Film Sensor ◽  
Average Value ◽  
Sensing Applications ◽  
Order Of Magnitude ◽  
Hole Arrays

The high electric field intensity achieved on the surface of sensors based on metasurfaces (metasensors) makes them an excellent alternative for sensing applications where the volume of the sample to be identified is tiny (for instance, thin-film sensing devices). Various shapes and geometries have been proposed recently for the design of these metasensors unit-cells (meta-atoms) such as split ring resonators or hole arrays, among others. In this paper, we propose, design, and evaluate two types of tripod metasurfaces with different complexity in their geometry. An in-depth comparison of their performance is presented when using them as thin-film sensor devices. The meta-atoms of the proposed metasensors consist of a simple tripod and a hollow tripod structure. From numerical calculations, it is shown that the best geometry to perform thin-film sensing is the compact hollow tripod (due to the highest electric field on its surface) with a mean sensitivity of 3.72 × 10−5 nm−1. Different modifications are made to this structure to improve this value, such as introducing arms in the design and rotating the metallic pattern 30 degrees. The best sensitivity achieved for extremely thin film analytes (5–25 nm thick) has an average value of 1.42 × 10−4 nm, which translates into an extremely high improvement of 381% with respect to the initial hollow tripod structure. Finally, a comparison with other designs found in the literature shows that our design is at the top of the ranking, improving the overall performance by more than one order of magnitude. These results highlight the importance of using metastructures with more complex geometries so that a higher electric field intensity distribution and, therefore, designs with better performance can be obtained.

The dynamics of confined vortices

1982 ◽  
Vol 382 (1783) ◽  
pp. 335-360 ◽  
Keyword(s):  
Vortex Core ◽  
Axial Velocity ◽  
Vortex Tube ◽  
Vortex Breakdown ◽  
Laser Doppler Anemometer ◽  
Present Evidence ◽  
Cylindrical Vortex ◽  
Breakdown Phenomenon ◽  
Similarities And Differences ◽  
Independent Parameters

Referring to flow-visualization and laser-Doppler anemometer measurements of swirl and axial velocity profiles, we discuss the physics of the flow in a cylindrical vortex tube as various independent parameters are varied. Three main classes of flow occur, depending upon the location of a vortex jump within the vortex tube. We present evidence to suggest a connection between vortex breakdown and the criticality and stability of the vortex core upon which it occurs and attempt to reconcile the various explanations that have been proposed for the breakdown phenomenon. Similarities and differences between the present experiments and those of previous investigators are also pointed out. Finally, as an Appendix, we present the results of a hydraulic analogue of our vortex experiment.

Validation of the framycetin sulfate determination technique by HPLC in a Framidex medicinal preparation

2020 ◽  
Vol 86 (6) ◽  
pp. 73-78
Author(s):  
D. D. Gapparov ◽  
Z. A. Smanova ◽  
Y. V. Timchenko ◽  
A. V. Pirogov
Keyword(s):  
Medicinal Preparation ◽  
Good Manufacturing Practice ◽  
Variation Coefficient ◽  
Intermediate Precision ◽  
Average Value ◽  
Limit Of Determination ◽  
Validation Criteria ◽  
Derivatizing Agent ◽  
Order Of Magnitude

A method for determination of framycetin sulfate in a Framidex preparation (eye and ear drops) by HPLC-UV (λ = 365 nm) using 2, 4-dinitrofluorobenzene as a derivatizing agent has been developed The characteristics of analytical methods determined for the purpose of their validation and relevant criteria for the validity of validated methods with the goal of the quality control of drugs (pharmaceutical substances and drugs) are presented. According to the results of an intralaboratory experiment on the validation assessment of the method by the parameters of the specificity, limit of determination (LOD), linearity, precision and laboratory accuracy, it is shown that the LOD decreases by an order of magnitude, the correlation coefficient is not less than 0.99 correctness (average value — 97.5 – 102.5%; variation coefficient — not more than 2.0%; the confidence range should include 100% of values), convergence (variation coefficient — not more than 1.5%), intermediate precision (variation coefficient — not more than 1.5%). It is shown that the obtained values of metrological characteristics do not exceed the validation criteria and the developed method matches all the well-known requirements of GMP (Good Manufacturing Practice).

Spin-up of a magnetically driven tornado-like vortex

2013 ◽  
Vol 736 ◽  
pp. 641-662 ◽  
Author(s):  
Tobias Vogt ◽  
Ilmārs Grants ◽  
Sven Eckert ◽  
Gunter Gerbeth
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Driving Forces ◽  
Axisymmetric Flow ◽  
Rotating Magnetic Field ◽  
Turbulent Vortex ◽  
Force Magnitude ◽  
Order Of Magnitude ◽  
Converging Flow ◽  
Concentration Condition

AbstractThe spin-up of a concentrated vortex in a liquid metal cylinder with a free surface is considered experimentally and numerically. The vortex is driven by two flow-independent magnetic body forces. A continuously applied rotating magnetic field provides the source of the angular momentum. A pulse of about one order of magnitude stronger travelling magnetic field drives a converging flow that temporarily focuses this angular momentum towards the axis of the container. A highly concentrated vortex forms that produces a funnel-shaped surface depression. We explore experimentally the duration, the depth and the conditions of formation of this funnel. Additionally, we measure the axial velocity and calculate the axisymmetric flow field of this transient vortex at a lower force magnitude. The spin-up vortex is similar to the corresponding developed time-averaged turbulent vortex driven by the same magnetic forces (Grants et al., J. Fluid Mech., vol. 616, 2008, pp. 135–152). There are two main differences. First, the maximum swirl concentration condition cannot be expressed as a constant ratio of the two driving forces. Second, a much higher degree of swirl concentration is feasible. We explain these differences as due to a much lower turbulence during the spin-up.

Area-varying waves on curved vortex tubes with application to vortex breakdown

1989 ◽  
Vol 200 ◽  
pp. 283-307 ◽  
Author(s):  
T. S. Lundgren ◽  
W. T. Ashurst
Keyword(s):  
Shallow Water ◽  
Axial Velocity ◽  
Vortex Tube ◽  
Vortex Breakdown ◽  
Axial Pressure ◽  
Cross Section Area ◽  
Section Area ◽  
Axial Pressure Gradient ◽  
Vortex Tubes ◽  
Axial Waves

Equations which modify those derived by Widnall & Bliss (1971) and Moore & Saffman (1972) are presented in which jet-like flow along the axis of a vortex tube interacts with the motion of the tube. The equations describe two major effects. The first is the propagation of axial waves along the vortex tube which is similar to the flow of shallow water. A local decrease in cross-section area of the vortex tube produces higher swirling velocity and lower pressure. The resulting axial pressure gradient causes a propagating wave of area and axial velocity in order to move fluid into the region of smaller area. The second effect is instability to helical disturbances when the jet-like axial velocity is high enough to overcome the stabilizing effect of the swirling motion. An elementary nonlinear theory of vortex breakdown is presented which has an analogy with the formation of bores in shallow-water theory. A numerical example shows the growth of a helical disturbance behind a vortex breakdown front.

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