Motion of a spherical solid particle in thermal counterflow turbulence

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Abstract

With numerical methods, we formulate and solve a mathematical model of solid-particle motion in thermal counterflow turbulence. We find a direct link between the intensity of vortex-particle collision induced Kelvin waves (vortex-gas "temperature") and the intensity of the particle-velocity fluctuations around its mean value. The latter mean value is determined by three factors: (a) the frequency of head-on particle-vortex collisions, (b) the formation of a vortex-tail behind the particle, and (c) the viscous drag. The frequency of head-on particle-vortex collisions depends on (a) the vortex line density, (b) the average tangle drift relative to the particle, and (c) the degree of tangle stratification normal to the counterflow direction. A higher stratification degree reduces the frequency of head-on collisions and allows the vortex-tail effect to dominate. At T=1.3 K, vortex voids in the tangle act like barriers to particle motion; the particle-velocity fluctuations are comparable to its mean value and, thus, the particle's direction of motion is sporadically reversed.
LanguageEnglish
Article number174508
Number of pages5
JournalPhysical Review B: Condensed Matter and Materials Physics
Volume77
Issue number17
DOIs
Publication statusPublished - 12 May 2008

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counterflow
Vortex flow
Turbulence
turbulence
vortices
particle motion
stratification
collisions
Kelvin waves
viscous drag
particle collisions
Hot Temperature
gas temperature
Drag
voids
Numerical methods
mathematical models
Gases
Mathematical models

Keywords

  • mathematical models
  • thermal counterflow turbulence

Cite this

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title = "Motion of a spherical solid particle in thermal counterflow turbulence",
abstract = "With numerical methods, we formulate and solve a mathematical model of solid-particle motion in thermal counterflow turbulence. We find a direct link between the intensity of vortex-particle collision induced Kelvin waves (vortex-gas {"}temperature{"}) and the intensity of the particle-velocity fluctuations around its mean value. The latter mean value is determined by three factors: (a) the frequency of head-on particle-vortex collisions, (b) the formation of a vortex-tail behind the particle, and (c) the viscous drag. The frequency of head-on particle-vortex collisions depends on (a) the vortex line density, (b) the average tangle drift relative to the particle, and (c) the degree of tangle stratification normal to the counterflow direction. A higher stratification degree reduces the frequency of head-on collisions and allows the vortex-tail effect to dominate. At T=1.3 K, vortex voids in the tangle act like barriers to particle motion; the particle-velocity fluctuations are comparable to its mean value and, thus, the particle's direction of motion is sporadically reversed.",
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AB - With numerical methods, we formulate and solve a mathematical model of solid-particle motion in thermal counterflow turbulence. We find a direct link between the intensity of vortex-particle collision induced Kelvin waves (vortex-gas "temperature") and the intensity of the particle-velocity fluctuations around its mean value. The latter mean value is determined by three factors: (a) the frequency of head-on particle-vortex collisions, (b) the formation of a vortex-tail behind the particle, and (c) the viscous drag. The frequency of head-on particle-vortex collisions depends on (a) the vortex line density, (b) the average tangle drift relative to the particle, and (c) the degree of tangle stratification normal to the counterflow direction. A higher stratification degree reduces the frequency of head-on collisions and allows the vortex-tail effect to dominate. At T=1.3 K, vortex voids in the tangle act like barriers to particle motion; the particle-velocity fluctuations are comparable to its mean value and, thus, the particle's direction of motion is sporadically reversed.

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