Turbulent deposition and trapping of aerosols at a wall

Brooke, John W.; Kontomaris, K.; Hanratty, Thomas J.; McLaughlin, John B.

doi:10.1063/1.858299

Cited by 140 publications

(60 citation statements)

References 13 publications

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“…3(b), we observe that particle number density profile has developed a maximum well into the near-wall region (0 < z + < 20). This behavior can be viewed as the consequence of the turbulence non-homogeneity [50], and has been observed in a number of previous works [5,36,41].…”

Section: Introductionmentioning

confidence: 98%

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Particles turbulence interactions in boundary layers

Soldati

2005

Z Angew Math Mech

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Turbulent dispersed flows in boundary layers are crucial in a number of industrial and environmental applications. In most applications, the key information is space distribution of particles which is known to be strongly non-homogeneous. Specifically, inertial particles distribute preferentially avoiding strong vortical regions and segregating into straining regions. The vortical boundary layer structures control momentum, mass, heat, and particle transfer. Coherent structures bring particles toward the wall and away from the wall and favour particle segregation in the viscous region giving rise to nonuniform particle distribution profiles which peak close to the wall. The reason for this behavior is particle inertia, which filters the high frequency turbulence fluctuations. The object of this work is to review the current understanding of turbulent boundary layer dynamics and to examine the mechanisms for particle transfer, segregation, and preferential distribution. The physical mechanisms discussed and proposed are based on Direct Numerical Simulations of turbulence and Lagrangian tracking of inertial particles.

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Section: Introductionmentioning

confidence: 98%

“…There is experimental and numerical evidence that heavy particles in turbulent boundary layer have a tendency to migrate toward the wall under the turbophoretic drift [5,8,39,50,67]. Fig.…”

Section: Particle Dynamicsmentioning

confidence: 99%

Particles turbulence interactions in boundary layers

Soldati

2005

Z Angew Math Mech

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Section: 56b Lagrangian Simulations With Turbulent Flow From Les mentioning

confidence: 99%

“…Brooke et al (1992) and Brooke et al (1994) conducted Lagrangian particle tracking in a DNS-generated vertical channel flow with particles in the diffusion-impaction regime considering only the drag force. The paper by Brooke et al (1992) contains observations similar to those reported in other simulation work. These include the accumulation of particles in the diffusion-impaction regime near the vertical wall and their segregation into the low-speed streaks, the violation of the particle Reynolds number criteria for drag calculation, the importance of near-wall vortices in causing particle deposition and impact velocities of depositing particles on the same order as the friction velocity.…”

Section: 56b Lagrangian Simulations With Turbulent Flow From Les mentioning

confidence: 99%

Particle deposition in ventilation ducts

Sippola¹

2002

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Exposure to airborne particles is detrimental to human health and indoor exposures dominate total exposures for most people. The accidental or intentional release of aerosolized chemical and biological agents within or near a building can lead to exposures of building occupants to hazardous agents and costly building remediation.Particle deposition in heating, ventilation and air-conditioning (HVAC) systems may significantly influence exposures to particles indoors, diminish HVAC performance and lead to secondary pollutant release within buildings. This dissertation advances the understanding of particle behavior in HVAC systems and the fates of indoor particles by means of experiments and modeling.Laboratory experiments were conducted to quantify particle deposition rates in horizontal ventilation ducts using real HVAC materials. Particle deposition experiments were conducted in steel and internally insulated ducts at air speeds typically found in ventilation ducts, 2-9 m/s. Behaviors of monodisperse particles with diameters in the size range 1-16 µm were investigated. Deposition rates were measured in straight ducts with 1 2 a fully developed turbulent flow profile, straight ducts with a developing turbulent flow profile, in duct bends and at S-connector pieces located at duct junctions. In straight ducts with fully developed turbulence, experiments showed deposition rates to be highest at duct floors, intermediate at duct walls, and lowest at duct ceilings. Deposition rates to a given surface increased with an increase in particle size or air speed. Deposition was much higher in internally insulated ducts than in uninsulated steel ducts. In most cases, deposition in straight ducts with developing turbulence, in duct bends and at S-connectors at duct junctions was higher than in straight ducts with fully developed turbulence.Measured deposition rates were generally higher than predicted by published models.A model incorporating empirical equations based on the experimental measurements was applied to evaluate particle losses in supply and return duct runs. Model results suggest that duct losses are negligible for particle sizes less than 1 µm and complete for particle sizes greater than 50 µm. Deposition to insulated ducts, horizontal duct floors and bends are predicted to control losses in duct systems. When combined with models for HVAC filtration and deposition to indoor surfaces to predict the ultimate fates of particles within buildings, these results suggest that ventilation ducts play only a small role in determining indoor particle concentrations, especially when HVAC filtration is present.However, the measured and modeled particle deposition rates are expected to be important for ventilation system contamination. ChairDate

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“…A computational proce-dure for analyzing particle transport and deposition in complex passages was described by Li et al (1994). Using a direct numerical simulation procedure via a pseudospe ctral code, McLaughlin (1989), Ounis et al (1991bOunis et al ( , 1993, Brook et al (1992), Pedinotti et al (1992), and Squire s and Eaton (1991) analyzed the aerosol particle deposition in a turbulent channel¯ow. Soldati et al (1993) used a direct numerical simulation to study the particle transport in electrostatic precipitators.…”

Section: Introductionmentioning

confidence: 99%

Charged Particle Trajectory Statistics and Deposition in a Turbulent Channel Flow

Soltani¹,

Ahmadi²

1999

Aerosol Science and Technology

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ABSTRACT. The statistical properties of charged particles and their wall deposition in a turbulent channel¯ow in the presence of an electrostatic ® eld is studied in this paper. For a dilute concentration, the in¯uence of small particles on the¯uid motion is neglected. The instantaneous velocity ® eld is generated by a direct numerical simulation of the Navier± Stokes equation via a pseudospectral method. The case in which each particle carries a single unit of charge and the case in which the particles h ave a saturation charge distribution are analyzed. Ensembles of 8192 p article tr ajectories are used for evaluating various statistics. Effects of size and electric ® eld intensity on particle trajectory statistics and wall deposition rate are studied. RMS p article velocities and p article concentrations at different distances from the wall are evaluated and discussed. The results for deposition rates are compared with those obtained from empirical equations.

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Turbulent deposition and trapping of aerosols at a wall

Cited by 140 publications

References 13 publications

Particles turbulence interactions in boundary layers

Particles turbulence interactions in boundary layers

Particle deposition in ventilation ducts

Charged Particle Trajectory Statistics and Deposition in a Turbulent Channel Flow

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