Search results for "Vortex"

Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds

2015

Abstract Laboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.

On vortex shape in unbaffled stirred vessels as measured by digital image analysis

2012

In this work, digital image analysis coupled with a suitable shadowgraphy-based technique is employed to investigate the shape of the free-surface vortex that forms in uncovered unbaffled tanks stirred by either a D=T/3 Lightnin A310 or a D=T/3 Rushton turbine. The technique is based on back-lighting the vessel and suitably averaging vortex images over time. Data obtained show that the two different impellers give rise to quite different vortex shapes. A novel 2-parameter model is proposed that successfully describes vortex shapes obtained with both impellers.

Free vortex shape in Uncovered Unbaffled Stirred Tanks (UUST) agitated by Rushton turbines

2012

The main feature of unbaffled stirred tanks is the highly swirling liquid motion, which leads to the formation of a central vortex on the liquid free surface, when the vessel is operated without top-cover (Uncovered Unbaffled Stirred Tanks, UUST). In this work, original data on fluid dynamics characteristics of (UUST) agitated by a Rushton turbine are presented. In particular, digital image analysis is employed to accurately assess vortex shape and validate an original model for its description. The model describes vortex shape in the case of sub-critical systems (when vortex bottom is placed above the impeller plane) as well as in the case of super-critical systems (when vortex bottom fall…

Superconducting properties of in-plane W-C nanowires grown by He+ Focused Ion Beam Induced Deposition

2021

Focused ion beam induced deposition (FIBID) is a nanopatterning technique that uses a focused beam of charged ions to decompose a gaseous precursor. So far, the flexible patterning capabilities of FIBID have been widely exploited in the fabrication of superconducting nanostructures, using the W(CO)6 precursor mostly in combination with a focused beam of Ga+ ions. Here, the fabrication and characterization of superconducting in-plane tungsten-carbon (W-C) nanostructures by He+ FIBID of the W(CO)6 precursor is reported. A patterning resolution of 10 nm has been achieved, which is virtually unattainable for Ga+ FIBID. When the nanowires are patterned with widths of 20 nm and above, the deposit…

HEAT FLUX IN SUPERFLUID TRANSITION AND IN TURBULENT HELIUM COUNTERFLOW

Life Cycle Study of a Diabatic Rossby Wave as a Precursor to Rapid Cyclogenesis in the North Atlantic—Dynamics and Forecast Performance

2011

Monthly Weather Review, 139 (6)

Micro-computed tomographic evaluation of dentinal defects after root canal preparation with hyflex edm and vortex blue rotary systems

2018

Background To evaluate the incidence of dentinal microcracks formation after root canal shaping procedures with HyFlex EDM and Vortex Blue rotary systems comparing with that of hand instrumentation using micro-computed tomography. Material and methods Mandibular first molar teeth (n=60) having 50 to 200mesial root curvature were scanned using high resolution micro-CT imaging before root canal preparation to identify the presence of dentinal defects. Post-instrumentation cross-sectional images were taken and increased number and type of root defects were assessed and recorded. The data was statistically analysed by using chi-square test and McNemar's test at a significance level of 5%. Resul…

Depletion of ozone and reservoir species of chlorine and nitrogen oxide in the lower Antarctic polar vortex measured from aircraft

2017

Novel airborne in situ measurements of inorganic chlorine, nitrogen oxide species, and ozone were performed inside the lower Antarctic polar vortex and at its edge in September 2012. We focus on one flight during the Transport and Composition of the LMS/Earth System Model Validation (TACTS/ESMVal) campaign with the German research aircraft HALO (High-Altitude LOng range research aircraft), reaching latitudes of 65°S and potential temperatures up to 405 K. Using the early winter correlations of reactive trace gases with N2O from the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), we find high depletion of chlorine reservoir gases up to ∼40% (0.8 ppbv) at 12 km to 1…

Direct observation of spin diffusion enhanced nonadiabatic spin torque effects in rare-earth-doped permalloy

2018

The relation between the nonadiabaticity parameter $\ensuremath{\beta}$ and the damping parameter $\ensuremath{\alpha}$ is investigated in permalloy-based microdisks. In order to determine $\ensuremath{\beta}$, high-resolution imaging of the current-induced vortex-core displacement is performed using scanning electron microscopy with polarization analysis. The materials properties of the films are varied via rare-earth Dy doping, leading to a greatly enhanced damping, while retaining the same spin configuration for the confined vortex state. A clear trend to much higher nonadiabaticity values is seen for the higher doping levels and an averaged value of $\ensuremath{\beta}=(0.29\ifmmode\pm\…

Quasiclassical free energy of superconductors : Disorder-driven first-order phase transition in superconductor/ferromagnetic-insulator bilayers

2020

In the seminal work by G. Eilenberger, Z. Phys. 214, 195 (1968), a closed-form expression for the free energy of inhomogeneous spin-singlet superconductor in terms of quasiclassical propagators has been suggested. However, deriving this expression and generalizing it for superconductors or superfluids with general matrix structure, e.g., spin-triplet correlations, has remained problematic. Starting from the Luttinger-Ward formulation, we discuss here the general solution. Besides ordinary superconductors with various scattering mechanisms, the obtained free-energy functional can be used for systems, such as superfluid $^{3}\mathrm{He}$ and superconducting systems with spatially inhomogeneou…