The rapid distortion of two-way coupled particle-laden turbulence

2019 ◽  
Vol 877 ◽  
pp. 82-104 ◽  
Author(s):  
M. Houssem Kasbaoui ◽  
Donald L. Koch ◽  
Olivier Desjardins
Keyword(s):  
Single Phase ◽  
Density Fluctuations ◽  
Gravitational Potential Energy ◽  
Inertial Particles ◽  
Mass Loading ◽  
Number Density ◽  
Turbulence Statistics ◽  
Preferential Sampling ◽  
Gravitational Loading ◽  
Two Phases

In this study, we address the modification of sheared turbulence by dispersed inertial particles. The preferential sampling of the straining regions of the flow by inertial particles in turbulence leads to an inhomogeneous distribution of particles. The strong gravitational loading exerted by the highly concentrated regions results in anisotropic alteration of turbulence at small scales in the direction of gravity. These effects are investigated in a rapid distortion theory (RDT) extended for two-way coupled particle-laden flows. To make the analysis tractable, we assume that particles have small but non-zero inertia. In the classical results for single-phase flows, the RDT assumption of fast shearing compared to the turbulence time scales leads to the distortion and shear-induced production of turbulence. In particle-laden turbulence, the coupling between the two phases under rapid shearing induces number density fluctuations that convert gravitational potential energy to turbulent kinetic energy and modulate the turbulence spectrum in a manner that increases with mass loading. Turbulence statistics obtained from RDT are compared with Euler–Lagrange simulations of homogeneously sheared particle-laden turbulence.

Effect of Ferrite Volume Fraction on Mechanical Properties of X80 Pipeline Steel

2014 ◽  
Vol 989-994 ◽  
pp. 212-215
Author(s):  
J. Liu ◽  
G. Zhu ◽  
W. Mao
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Work Hardening ◽  
Single Phase ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
X80 Pipeline Steel ◽  
Hardening Behavior ◽  
Two Phases ◽  
Better Than

The effect of volume fraction of ferrite on the mechanical properties including strength, plasticity and wok hardening was systematically investigated in X80 pipeline steel in order to improve the plasticity. The microstructures with different volume fraction of ferrite and bainite were obtained by heat-treatment processing and the mechanical properties were tested. The work hardening behavior was analyzed by C-J method. The results show that the small amount of ferrite could effectively improve the plasticity. The work hardening ability and the ratio of yield/tensile strength with two phases of ferrite/bainite would be obviously better than that with single phase of bainite. The improvement of plasticity could be attributed to the ferrite in which more plastic deformation was afforded.

scholarly journals Inertial-particle accelerations in turbulence: a Lagrangian closure

2016 ◽  
Vol 798 ◽  
pp. 187-200 ◽  
Author(s):  
S. Vajedi ◽  
K. Gustavsson ◽  
B. Mehlig ◽  
L. Biferale
Keyword(s):  
Numerical Simulations ◽  
Numerical Data ◽  
Direct Numerical Simulations ◽  
Inertial Particles ◽  
Inertial Particle ◽  
Order Unity ◽  
Heavy Particles ◽  
Preferential Sampling ◽  
Closure Scheme ◽  
Light Particles

The distribution of particle accelerations in turbulence is intermittent, with non-Gaussian tails that are quite different for light and heavy particles. In this article we analyse a closure scheme for the acceleration fluctuations of light and heavy inertial particles in turbulence, formulated in terms of Lagrangian correlation functions of fluid tracers. We compute the variance and the flatness of inertial-particle accelerations and we discuss their dependency on the Stokes number. The closure incorporates effects induced by the Lagrangian correlations along the trajectories of fluid tracers, and its predictions agree well with results of direct numerical simulations of inertial particles in turbulence, provided that the effects induced by inertial preferential sampling of heavy/light particles outside/inside vortices are negligible. In particular, the scheme predicts the correct functional behaviour of the acceleration variance, as a function of $St$, as well as the presence of a minimum/maximum for the flatness of the acceleration of heavy/light particles, in good qualitative agreement with numerical data. We also show that the closure works well when applied to the Lagrangian evolution of particles using a stochastic surrogate for the underlying Eulerian velocity field. Our results support the conclusion that there exist important contributions to the statistics of the acceleration of inertial particles independent of the preferential sampling. For heavy particles we observe deviations between the predictions of the closure scheme and direct numerical simulations, at Stokes numbers of order unity. For light particles the deviation occurs for larger Stokes numbers.

scholarly journals A summary of observational records on periodicities above the rotational period in the Jovian magnetosphere

2009 ◽  
Vol 27 (6) ◽  
pp. 2565-2573 ◽  
Author(s):  
E. A. Kronberg ◽  
J. Woch ◽  
N. Krupp ◽  
A. Lagg
Keyword(s):  
Data Sets ◽  
Mass Loading ◽  
Triggering Mechanism ◽  
Release Process ◽  
Jovian Magnetosphere ◽  
Planetary Rotation ◽  
Mass Release ◽  
Two Phases ◽  
Associated Mass

Abstract. The Jovian magnetosphere is a very dynamic system. The plasma mass-loading from the moon Io and the fast planetary rotation lead to regular release of mass from the Jovian magnetosphere and to a change of the magnetic topology. These regular variations, most commonly on several (2.5–4) days scale, were derived from various data sets obtained by different spacecraft missions and instruments ranging from auroral images to in situ measurements of magnetospheric particles. Specifically, ion measurements from the Galileo spacecraft represent the periodicities, very distinctively, namely the periodic thinning of the plasma sheet and subsequent dipolarization, and explosive mass release occurring mainly during the transition between these two phases. We present a review of these periodicities, particularly concentrating on those observed in energetic particle data. The most distinct periodicities are observed for ions of sulfur and oxygen. The periodic topological change of the Jovian magnetosphere, the associated mass-release process and auroral signatures can be interpreted as a global magnetospheric instability with analogies to the two step concept of terrestrial substorms. Different views on the triggering mechanism of this magnetospheric instability are discussed.

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.

scholarly journals Growth and Characterization of BxGa1−xN on 6H-SiC (0001) by Movpe

1999 ◽  
Vol 4 (S1) ◽  
pp. 429-434 ◽  
Author(s):  
C. H. Wei ◽  
Z. Y. Xie ◽  
J. H. Edgar ◽  
K. C. Zeng ◽  
J. Y. Lin ◽  
...  
Keyword(s):  
Single Phase ◽  
Band Edge Emission ◽  
Reactant Ratio ◽  
X Ray Diffraction ◽  
Structural And Optical Properties ◽  
Edge Emission ◽  
X Ray ◽  
Two Phases

Boron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. BxGa1−xN films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and BxGa1−xN alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no BxGa1−xN was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of BxGa1−xN varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.

An STATCOM-based Hybrid Shunt Compensation Scheme Capable of Damping Subsynchronous Resonance

2017 ◽  
Vol 6 (3) ◽  
pp. 150
Author(s):  
F. Reyhaneh Mehdizadeh ◽  
Daryoush Nazarpour
Keyword(s):  
Single Phase ◽  
Simulation Analysis ◽  
Static Synchronous Compensator ◽  
Control Loops ◽  
Subsynchronous Resonance ◽  
Three Phase ◽  
Two Phases ◽  
Shunt Compensation ◽  
Shunt Capacitor ◽  
Potential Use

The paper presents the potential use of supplemental control of a new economical phase imbalanced shunt compensation concept for damping sub synchronous resonance (SSR) oscillations. In this scheme, the shunt capacitive compensation in one phase is created by using a Single-Phase Static Synchronous Compensator (STATCOM) in parallel with a fixed capacitor (Cc), and the other two phases are compensated by fixed shunt capacitor (C). The proposed arrangement would, certainly, be economically attractive when compared with a full three-phase STATCOM which have been used/proposed for power swings and SSR damping. SSR mitigation is achieved by introducing a supplemental signal into the control loops of single phase STATCOM. The validity and effectiveness of the proposed structure and supplemental control are demonstrated on a modified version of the IEEE second benchmark model for computer simulation of sub synchronous resonance by means of time domain simulation analysis using the Matlab program.

scholarly journals Prediction of Strength and Ductility in Partially Recrystallized CoCrFeNiTi0.2 High-Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 389 ◽  
Author(s):  
Hanwen Zhang ◽  
Peizhi Liu ◽  
Jinxiong Hou ◽  
Junwei Qiao ◽  
Yucheng Wu
Keyword(s):  
Tensile Strength ◽  
Single Phase ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Number Density ◽  
High Entropy ◽  
Average Size ◽  
Strength And Ductility

The mechanical behavior of a partially recrystallized fcc-CoCrFeNiTi0.2 high entropy alloys (HEA) is investigated. Temporal evolutions of the morphology, size, and volume fraction of the nanoscaled L12-(Ni,Co)3Ti precipitates at 800 °C with various aging time were quantitatively evaluated. The ultimate tensile strength can be greatly improved to ~1200 MPa, accompanied with a tensile elongation of ~20% after precipitation. The temporal exponents for the average size and number density of precipitates reasonably conform the predictions by the PV model. A composite model was proposed to describe the plastic strain of the current HEA. As a consequence, the tensile strength and tensile elongation are well predicted, which is in accord with the experimental results. The present experiment provides a theoretical reference for the strengthening of partially recrystallized single-phase HEAs in the future.

scholarly journals An extremely high ‘Q’ueue value applied to seismological meetings

1988 ◽  
Vol 123 ◽  
pp. 585-585
Author(s):  
Keyword(s):  
Density Fluctuations ◽  
Number Density ◽  
Oscillation Spectrum ◽  
Resonant Cavities ◽  
Future Studies ◽  
High Q ◽  
Long Period ◽  
Fabry Perot ◽  
Solar Type ◽  
Propagation Velocities

Recent observations of the mysterious astronomical body IAU 123 indicate that the ‘Q’ueue value for astronomy symposia can approach 100–120, with very rapid growth and slow exponential decay. Number density fluctuations, with a frequency of 11.56 μHz and extreme phase coherence have been detected outside the main cafeteria. The long period and high ‘Q’ suggest that this may be represented by a g-mode of low radial order.A stabilized Fabry-Perot etalon has been used to measure the low-level motions, with propagation velocities of order 0.01 cm s−1. Although this is well below the local Alfvén speed, there can still arise significant shock effects (e.g. upon discovery of liver loaf as the main course).The observed cafeteria oscillation spectrum is still incomplete. For instance, if ice cream were offered at the end of the line, we would expect to detect the well-known ‘a la’-mode predicted by Baskin and Robbins.We hope that future studies of astronomical Q's may lead to a better understanding of solar-type astronomers' resonant cavities.

Growth and Characterization of BxGal-xN on 6H-SiC (0001) by MOVPE

1998 ◽  
Vol 537 ◽  
Author(s):  
C. H. Wei ◽  
Z. Y. Xie ◽  
J. H. Edgar ◽  
K. C. Zeng ◽  
J. Y. Lin ◽  
...  
Keyword(s):  
Single Phase ◽  
Band Edge Emission ◽  
Reactant Ratio ◽  
X Ray Diffraction ◽  
Structural And Optical Properties ◽  
Edge Emission ◽  
X Ray ◽  
Two Phases

AbstractBoron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. BxGal-xN films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and BxGal-xN alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no BxGal-xN was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of BxGal-xN varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.

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