A large eddy simulation of turbulent particle-laden flow inside a cubical differentially heated cavity

Abdel Dehbi (Corresponding Author), Jarmo Kalilainen, Terttaliisa Lind, Ari Auvinen

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

Large Eddy Simulations (LES) have been conducted to investigate turbulent air flow and particulate depletion inside a cubical cavity of length 0.7 m and temperature difference of 39 K between the hot and cold opposing vertical walls, thus resulting in a Rayleigh number of 109. Initial confrontation of the idealized flow field against experimental data (Kalilainen, Rantanen, Lind, Auvinen, & Dehbi, 2016) revealed that wall to wall radiation needs to be taken into account in order to reproduce the enhanced turbulence levels and reduced thermal stratification observed in the experiment. We introduce thereafter radiation effects indirectly by specifying measured temperatures rather than zero convective heat flux on the adiabatic walls. The LES predictions with realistic boundary conditions are in very good overall agreement with the measured velocity fields and temperature profiles. This accurate flow field is used to perform Lagrangian tracking simulations for spherical SiO2 particles with aerodynamic diameters of 1.4 µm and 3.5 µm. Here too, the computed particle depletion rates are in excellent agreement with the experimental data. Further Euler/Lagrange simulations are conducted for particles with hypothetical diameters in the range of 0.5 µm to 10 µm. Particles with diameters larger than 3 µm are removed at rates comparable to those predicted by the simple "stirred settling" model. However, as particle diameters decrease, the deposition rates are increasingly faster than predicted by stirred settling, and the decay constants tend towards an asymptotic value that is independent of particle size. Additionally, sensitivity computations show that thermophoresis has little effect on the removal rates of particles, but the inclusion of the thermophoretic force modifies the deposition pattern of sub-micron aerosols. The strong turbulent diffusion is thus the overriding cause for the significant deposition rates of smaller particles.
Original languageEnglish
Pages (from-to)67-82
Number of pages16
JournalJournal of Aerosol Science
Volume103
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

Fingerprint

large eddy simulation
Large eddy simulation
cavity
Deposition rates
Flow fields
Thermophoresis
Thermal stratification
Radiation effects
Aerosols
Temperature
Heat flux
Aerodynamics
Turbulence
flow field
Particle size
Boundary conditions
Radiation
Rayleigh number
Air
turbulent diffusion

Keywords

  • air
  • deposition
  • deposition rates
  • elementary particles
  • flow fields
  • heat flux
  • particle size
  • radiation effects
  • velocity

Cite this

Dehbi, Abdel ; Kalilainen, Jarmo ; Lind, Terttaliisa ; Auvinen, Ari. / A large eddy simulation of turbulent particle-laden flow inside a cubical differentially heated cavity. In: Journal of Aerosol Science. 2017 ; Vol. 103. pp. 67-82.
@article{f94bb48a93b444ffbf627112451d7ce6,
title = "A large eddy simulation of turbulent particle-laden flow inside a cubical differentially heated cavity",
abstract = "Large Eddy Simulations (LES) have been conducted to investigate turbulent air flow and particulate depletion inside a cubical cavity of length 0.7 m and temperature difference of 39 K between the hot and cold opposing vertical walls, thus resulting in a Rayleigh number of 109. Initial confrontation of the idealized flow field against experimental data (Kalilainen, Rantanen, Lind, Auvinen, & Dehbi, 2016) revealed that wall to wall radiation needs to be taken into account in order to reproduce the enhanced turbulence levels and reduced thermal stratification observed in the experiment. We introduce thereafter radiation effects indirectly by specifying measured temperatures rather than zero convective heat flux on the adiabatic walls. The LES predictions with realistic boundary conditions are in very good overall agreement with the measured velocity fields and temperature profiles. This accurate flow field is used to perform Lagrangian tracking simulations for spherical SiO2 particles with aerodynamic diameters of 1.4 µm and 3.5 µm. Here too, the computed particle depletion rates are in excellent agreement with the experimental data. Further Euler/Lagrange simulations are conducted for particles with hypothetical diameters in the range of 0.5 µm to 10 µm. Particles with diameters larger than 3 µm are removed at rates comparable to those predicted by the simple {"}stirred settling{"} model. However, as particle diameters decrease, the deposition rates are increasingly faster than predicted by stirred settling, and the decay constants tend towards an asymptotic value that is independent of particle size. Additionally, sensitivity computations show that thermophoresis has little effect on the removal rates of particles, but the inclusion of the thermophoretic force modifies the deposition pattern of sub-micron aerosols. The strong turbulent diffusion is thus the overriding cause for the significant deposition rates of smaller particles.",
keywords = "air, deposition, deposition rates, elementary particles, flow fields, heat flux, particle size, radiation effects, velocity",
author = "Abdel Dehbi and Jarmo Kalilainen and Terttaliisa Lind and Ari Auvinen",
note = "ISI: ENGINEERING, CHEMICAL",
year = "2017",
doi = "10.1016/j.jaerosci.2016.10.003",
language = "English",
volume = "103",
pages = "67--82",
journal = "Journal of Aerosol Science",
issn = "0021-8502",
publisher = "Elsevier",

}

A large eddy simulation of turbulent particle-laden flow inside a cubical differentially heated cavity. / Dehbi, Abdel (Corresponding Author); Kalilainen, Jarmo; Lind, Terttaliisa; Auvinen, Ari.

In: Journal of Aerosol Science, Vol. 103, 2017, p. 67-82.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - A large eddy simulation of turbulent particle-laden flow inside a cubical differentially heated cavity

AU - Dehbi, Abdel

AU - Kalilainen, Jarmo

AU - Lind, Terttaliisa

AU - Auvinen, Ari

N1 - ISI: ENGINEERING, CHEMICAL

PY - 2017

Y1 - 2017

N2 - Large Eddy Simulations (LES) have been conducted to investigate turbulent air flow and particulate depletion inside a cubical cavity of length 0.7 m and temperature difference of 39 K between the hot and cold opposing vertical walls, thus resulting in a Rayleigh number of 109. Initial confrontation of the idealized flow field against experimental data (Kalilainen, Rantanen, Lind, Auvinen, & Dehbi, 2016) revealed that wall to wall radiation needs to be taken into account in order to reproduce the enhanced turbulence levels and reduced thermal stratification observed in the experiment. We introduce thereafter radiation effects indirectly by specifying measured temperatures rather than zero convective heat flux on the adiabatic walls. The LES predictions with realistic boundary conditions are in very good overall agreement with the measured velocity fields and temperature profiles. This accurate flow field is used to perform Lagrangian tracking simulations for spherical SiO2 particles with aerodynamic diameters of 1.4 µm and 3.5 µm. Here too, the computed particle depletion rates are in excellent agreement with the experimental data. Further Euler/Lagrange simulations are conducted for particles with hypothetical diameters in the range of 0.5 µm to 10 µm. Particles with diameters larger than 3 µm are removed at rates comparable to those predicted by the simple "stirred settling" model. However, as particle diameters decrease, the deposition rates are increasingly faster than predicted by stirred settling, and the decay constants tend towards an asymptotic value that is independent of particle size. Additionally, sensitivity computations show that thermophoresis has little effect on the removal rates of particles, but the inclusion of the thermophoretic force modifies the deposition pattern of sub-micron aerosols. The strong turbulent diffusion is thus the overriding cause for the significant deposition rates of smaller particles.

AB - Large Eddy Simulations (LES) have been conducted to investigate turbulent air flow and particulate depletion inside a cubical cavity of length 0.7 m and temperature difference of 39 K between the hot and cold opposing vertical walls, thus resulting in a Rayleigh number of 109. Initial confrontation of the idealized flow field against experimental data (Kalilainen, Rantanen, Lind, Auvinen, & Dehbi, 2016) revealed that wall to wall radiation needs to be taken into account in order to reproduce the enhanced turbulence levels and reduced thermal stratification observed in the experiment. We introduce thereafter radiation effects indirectly by specifying measured temperatures rather than zero convective heat flux on the adiabatic walls. The LES predictions with realistic boundary conditions are in very good overall agreement with the measured velocity fields and temperature profiles. This accurate flow field is used to perform Lagrangian tracking simulations for spherical SiO2 particles with aerodynamic diameters of 1.4 µm and 3.5 µm. Here too, the computed particle depletion rates are in excellent agreement with the experimental data. Further Euler/Lagrange simulations are conducted for particles with hypothetical diameters in the range of 0.5 µm to 10 µm. Particles with diameters larger than 3 µm are removed at rates comparable to those predicted by the simple "stirred settling" model. However, as particle diameters decrease, the deposition rates are increasingly faster than predicted by stirred settling, and the decay constants tend towards an asymptotic value that is independent of particle size. Additionally, sensitivity computations show that thermophoresis has little effect on the removal rates of particles, but the inclusion of the thermophoretic force modifies the deposition pattern of sub-micron aerosols. The strong turbulent diffusion is thus the overriding cause for the significant deposition rates of smaller particles.

KW - air

KW - deposition

KW - deposition rates

KW - elementary particles

KW - flow fields

KW - heat flux

KW - particle size

KW - radiation effects

KW - velocity

UR - http://www.scopus.com/inward/record.url?scp=84994213372&partnerID=8YFLogxK

U2 - 10.1016/j.jaerosci.2016.10.003

DO - 10.1016/j.jaerosci.2016.10.003

M3 - Article

VL - 103

SP - 67

EP - 82

JO - Journal of Aerosol Science

JF - Journal of Aerosol Science

SN - 0021-8502

ER -