Effect of Particle Residence Time on Particle Dispersion in a Plane Mixing Layer

1993 ◽  
Vol 115 (4) ◽  
pp. 751-759 ◽  
Author(s):  
Tsuneaki Ishima ◽  
Koichi Hishida ◽  
Masanobu Maeda
Keyword(s):  
Gas Phase ◽  
Residence Time ◽  
Time Scale ◽  
Characteristic Time ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Laser Doppler Velocimeter ◽  
Characteristic Time Scale ◽  
Two Phase ◽  
Particle Residence Time

A particle dispersion has been experimentally investigated in a two-dimensional mixing layer with a large relative velocity between particle and gas-phase in order to clarify the effect of particle residence time on particle dispersion. Spherical glass particles 42, 72, and 135 μm in diameter were loaded directly into the origin of the shear layer. Particle number density and the velocities of both particle and gas phase were measured by a laser Doppler velocimeter with modified signal processing for two-phase flow. The results confirmed that the characteristic time scale of the coherent eddy apparently became equivalent to a shorter characteristic time scale due to a less residence time. The particle dispersion coefficients were well correlated to the extended Stokes number defined as the ratio of the particle relaxation time to the substantial eddy characteristic time scale which was evaluated by taking account of the particle residence time.

scholarly journals Numerical analysis of pulverized biomass combustion

2021 ◽  
Vol 321 ◽  
pp. 01001
Author(s):  
Cansu Deniz Canal ◽  
Erhan Böke ◽  
Ali Cemal Benim
Keyword(s):  
Gas Phase ◽  
Radiative Heat ◽  
Particle Dispersion ◽  
Single Step ◽  
Biomass Combustion ◽  
Phase Conversion ◽  
Two Phase ◽  
Dissipation Model ◽  
Turbulent Particle Dispersion ◽  
Step Mechanism

Combustion of pulverized biomass in a laboratory swirl burner is computationally investigated. The two-phase flow is modelled by an Eulerian-Lagrangian approach. The particle size distribution and turbulent particle dispersion are considered. The radiative heat transfer is modelled by the P1 method. For modelling turbulence, different RANS modelling approaches are applied. The pyrolysis of the solid fuel is modelled by a single step mechanism. For the combustion of the volatiles a two-step reaction mechanism is applied. The gas-phase conversion rate is modelled by the Eddy Dissipation Model, combined with kinetics control. The results are compared with measurements.

UNIVERSAL MULTIFRACTAL CHARACTERIZATION AND SIMULATION OF SPEECH

1992 ◽  
Vol 02 (03) ◽  
pp. 715-719
Author(s):  
CHRIS LARNDER ◽  
NICOLAS DESAULNIERS-SOUCY ◽  
SHAUN LOVEJOY ◽  
DANIEL SCHERTZER ◽  
CLAUDE BRAUN ◽  
...  
Keyword(s):  
Time Scale ◽  
Scale Invariance ◽  
Characteristic Time ◽  
Low Frequency ◽  
Characteristic Time Scale ◽  
Low Frequencies ◽  
Universal Behavior ◽  
Nonlinear Mixing

In the 1970's it was found that; for low frequencies (<10 Hz), speech is scaling: it has no characteristic time scale. Now such scale invariance is associated with multiscaling statistics, and multifractal structures. Just as Gaussian noises frequently arise because they are generically produced by sums of many independent noise processes, scaling noises have an analogous universal behavior arising from nonlinear mixing of processes. We show that low frequency speech is consistent with these ideas, and use the measured parameters to produce stochastic speech simulations which are strikingly similar to real speech.

Daytime efficiency and characteristic time scale of interplanetary electric fields penetration to equatorial latitude ionosphere

2011 ◽  
Vol 73 (11-12) ◽  
pp. 1555-1559 ◽  
Author(s):  
C.M. Denardini ◽  
H.C. Aveiro ◽  
P.D.S.C. Almeida ◽  
L.C.A. Resende ◽  
L.M. Guizelli ◽  
...  
Keyword(s):  
Electric Fields ◽  
Time Scale ◽  
Characteristic Time ◽  
Characteristic Time Scale ◽  
Equatorial Latitude

scholarly journals Radio Flux Flicker of Extragalactic Sources

1982 ◽  
Vol 97 ◽  
pp. 327-328
Author(s):  
D. S. Heeschen
Keyword(s):  
Time Scale ◽  
Characteristic Time ◽  
Characteristic Time Scale ◽  
Radio Flux ◽  
Wavelength Radiation ◽  
Compact Sources

Compact sources (compactness evidenced by flat/complex spectra) display a “flicker” in their intrinsic centimeter wavelength radiation, with an amplitude of about 2% and a characteristic time scale of a few days.

scholarly journals Numerical Simulations of a Gas–Solid Two-Phase Impinging Stream Reactor with Dynamic Inlet Flow

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1913 ◽  
Author(s):  
Xueqing Liu ◽  
Song Yue ◽  
Luyi Lu ◽  
Wei Gao ◽  
Jianlan Li
Keyword(s):  
Residence Time ◽  
Single Particle ◽  
Particle Motion ◽  
Oscillatory Motion ◽  
Two Phase ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Particle Residence Time ◽  
The Mean ◽  
Inlet Conditions

Fluid flow characteristics and particle motion behavior of an impinging stream reactor with dynamic inlet flow (both inlet velocity patterns exhibit step variation) are investigated and discussed with the computational fluid dynamics–discrete element method (CFD–DEM). The effect of T (variation period of the dynamic inlet flow) and ∆u (inlet velocity difference) on the motion characteristics of single and multiple particles, as well as the mean particle residence time, are studied and discussed. The research results indicate that, compared with the traditional impinging stream reactor (both inlet velocities are equal and constant) with equal mean inlet velocity (um) within one period, the impinging surface is instantaneously moving and the flow regime is varied with time in the impinging stream reactor with dynamic inlet flow. The impinging stream reactor with dynamic inlet flow provides higher cost performance over the traditional impinging stream reactor, under equal um, in terms of single-particle residence time. Moreover, three new particle motion modes exist in multi-particle motions of the impinging stream reactor with dynamic inlet flow; particles are accelerated by the original or reverse fluid and perform oscillatory motion at least once after an interparticle collision. Whether it is a single particle or multi-particles, the mean particle residence time reaches a maximum value when T/2 is approximately equal to the first particle acceleration time, since the maximum axial kinetic energy increases in every oscillatory motion compared with traditional impinging stream, and the number of oscillatory motions is increasing. The mean residence time of a particle in the impinging stream reactor with a dynamic inlet flow increases with increasing ∆u, since the dynamic inlet conditions and increasing ∆u can continuously supply more energy to particles and thus cause more particles to enter one of the three new modes of particle motion.

scholarly journals Does the Radio Luminosity of Pulsar Grow up in its Later Stage?

1987 ◽  
Vol 125 ◽  
pp. 50-50
Author(s):  
T. Lu ◽  
P. C. Zhu ◽  
J. S. Kui
Keyword(s):  
Time Scale ◽  
Characteristic Time ◽  
Statistical Analyses ◽  
Striking Feature ◽  
Characteristic Time Scale ◽  
Radio Luminosity ◽  
Mean Values ◽  
The Mean

In usual statistical analyses, because of diversities of proper parameters of pulsars, some interesting features might be smeared. In order to remove these diversities, we use the mean values for all quantities of pulsars, instead of values of individual pulsar, to do statistical analyses. logP/P3 - log τ and logL - logτ have been plotted, here τ P/2P and L denote the characteristic time scale and the radio luminosity of pulsars respectively. The most striking feature is that after its initial dropping to a dip at about τ∼106 yrs, the radio luminosity of pulsar appears to grow up evidently and then redrop again. This feature is difficult to be understood in usual models. However, two tentative interpretations have been given in this paper.

The characteristic time scale for basin hydrological response using radar data

2001 ◽  
Vol 252 (1-4) ◽  
pp. 85-99 ◽  
Author(s):  
Efrat Morin ◽  
Yehouda Enzel ◽  
Uri Shamir ◽  
Rami Garti
Keyword(s):  
Time Scale ◽  
Characteristic Time ◽  
Radar Data ◽  
Characteristic Time Scale ◽  
Hydrological Response

Role of thermal conduction in the expansion of a plasma from a vacuum interface

1988 ◽  
Vol 66 (8) ◽  
pp. 662-673 ◽  
Author(s):  
D. Parfeniuk ◽  
A. Ng ◽  
P. Celliers
Keyword(s):  
Time Scale ◽  
Thermal Conduction ◽  
Characteristic Time ◽  
Characteristic Time Scale ◽  
Rarefaction Waves ◽  
Vacuum Interface ◽  
Aluminum Plasma ◽  
Self Similar ◽  
Expansion Model ◽  
Isotropic Expansion

The effects of thermal conduction are examined for the expansion of a plasma from a vacuum interface using an analytic model based on well-known self-similar models of rarefaction waves. Conventional analysis of shock-unloading experiments uses an isotropic expansion model. However, thermal conduction introduces a characteristic time scale during which the flow is not self-similar. The significance of this time scale for experimental measurements is also discussed. The characteristic time is calculated for an aluminum plasma using theoretical equation-of-state and conductivity models.

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