Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow
TL;DR: In this paper, the dispersion and deposition of aerosol particles from a point source in a turbulent channel flow are studied, and an empirical mean velocity profile and experimental data for turbulent intensities are used in the analysis.
Abstract: The dispersion and deposition of particles from a point source in a turbulent channel flow are studied. An empirical mean velocity profile and the experimental data for turbulent intensities are used in the analysis. The instantaneous turbulence fluctuation is simulated as a continuous Gaussian random field, and an ensemble of particle trajectories is generated and statistically analyzed. A series of digital simulations for dispersion and deposition of aerosol particles of various sizes from point sources at different positions from the wall is performed. Effects of Brownian diffusion on particle dispersion are studied. The effects of variation in particle density and particle-surface interaction are also discussed.
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King Mongkut's University of Technology Thonburi1, Xi'an Jiaotong University2, Ferdowsi University of Mashhad3, University of Monastir4, Shahid Beheshti University5, University of Rennes6, Clarkson University7, North Carolina State University8, University of Vermont9, Iran University of Science and Technology10, University of New South Wales11, Royal Society12, Quaid-i-Azam University13, King Abdulaziz University14, University of Tehran15, Babeș-Bolyai University16
TL;DR: A review of the latest developments in modeling of nanofluid flows and heat transfer with an emphasis on 3D simulations can be found in this paper, where the main models used to calculate the thermophysical properties of Nanofluids are reviewed.
659 citations
TL;DR: In this article, the air movement and aerosol particle concentration and deposition in displacement and mixing ventilation rooms are studied numerically and the discrete trajectory model is adopted to simulate particle tracks while the Eulerian method for solving the continuous fluid flow is combined and validated by the case from literature.
352 citations
TL;DR: In this article, a series of numerical simulations were conducted to study the transport and deposition of nano- and micro-particles in a turbulent duct flow using different turbulence models, and the importance of turbulence model, boundary conditions, and turbulence fluctuation particularly near wall on particle transport, deposition, and particle trajectory analysis were performed with the in-house PARTICLE (object-oriented C++) code, as well as with FLUENTTM code with and the use of user's defined subroutines.
324 citations
TL;DR: In this paper, the size-dependent particle transmission efficiency of the aerodynamic lens system used in the Aerodyne Aerosol Mass Spectrometer (AMS) was investigated with computational fluid dynamics calculations and experimental measurements.
Abstract: The size-dependent particle transmission efficiency of the aerodynamic lens system used in the Aerodyne Aerosol Mass Spectrometer (AMS) was investigated with computational fluid dynamics (CFD) calculations and experimental measurements. The CFD calculations revealed that the entire lens system, including the aerodynamic lens itself, the critical orifice which defines the operating lens pressure, and a valve assembly, needs to be considered. Previous calculations considered only the aerodynamic lens. The calculations also investigated the effect of operating the lens system at two different sampling pressures, 7.8 × 104 Pa (585 torr) and 1.0 × 105 Pa (760 torr). Experimental measurements of transmission efficiency were performed with size-selected diethyl hexyl sebacate (DEHS), NH4NO3, and NaNO3 particles on three different AMS instruments at two different ambient sampling pressures (7.8 × 104 Pa, 585 torr and 1.0 × 105 Pa, 760 torr). Comparisons of the measurements and the calculations show qualitative ag...
317 citations
Cites background or methods from "Dispersion and Deposition of Spheri..."
...Several experimental evaluations of a closely related aerodynamic lens designed by Liu et al. (1995a) have been published previously (Jayne et al....
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...[7] Fbi can be calculated from Li and Ahmadi (1992) Fbi = Gi √ π S0 t , [8] where Gi are zero-mean, unit-variance, independent Gaussian random numbers, t is the time step used in the simulation, and S0 = 216 µkT π2d5pρ 2 pCc ....
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...Fbi can be calculated from Li and Ahmadi (1992)...
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TL;DR: In this paper, the authors used a CFD program with a Lagrangian particle tracking method to predict particle dispersion and concentration distribution in ventilated rooms, and the particle size distribution was monodisperse, and particle diameter ranged from 0.31 to 4.5 μm.
316 citations
Cites background from "Dispersion and Deposition of Spheri..."
...However, some of these forces may occasionally become comparable in magnitude to the Stokesian drag force within the turbulent boundary layer (Li and Ahmadi, 1992)....
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6,674 citations
TL;DR: In this paper, the mean values of all the powers of the velocity $u$ and the displacement $s$ of a free particle in Brownian motion are calculated and the exact expressions for the square of the deviation of a harmonically bound particle in the Fokker-Planck partial differential equation as a function of the time and the initial deviation are obtained.
Abstract: With a method first indicated by Ornstein the mean values of all the powers of the velocity $u$ and the displacement $s$ of a free particle in Brownian motion are calculated It is shown that $u\ensuremath{-}{u}_{0}\mathrm{exp}(\ensuremath{-}\ensuremath{\beta}t)$ and $s\ensuremath{-}\frac{{u}_{0}}{\ensuremath{\beta}[1\ensuremath{-}\mathrm{exp}(\ensuremath{-}\ensuremath{\beta}t)]}$ where ${u}_{0}$ is the initial velocity and $\ensuremath{\beta}$ the friction coefficient divided by the mass of the particle, follow the normal Gaussian distribution law For $s$ this gives the exact frequency distribution corresponding to the exact formula for ${s}^{2}$ of Ornstein and F\"urth Discussion is given of the connection with the Fokker-Planck partial differential equation By the same method exact expressions are obtained for the square of the deviation of a harmonically bound particle in Brownian motion as a function of the time and the initial deviation Here the periodic, aperiodic and overdamped cases have to be treated separately In the last case, when $\ensuremath{\beta}$ is much larger than the frequency and for values of $t\ensuremath{\gg}{\ensuremath{\beta}}^{\ensuremath{-}1}$, the formula takes the form of that previously given by Smoluchowski
3,394 citations
TL;DR: In this paper, the forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen's equation and the subsequent modified versions that have since appeared.
Abstract: The forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen’s equation and the subsequent modified versions that have since appeared. Forces from the undisturbed flow and the disturbance flow created by the presence of the sphere are treated separately. Proper account is taken of the effect of spatial variations of the undisturbed flow on both forces. In particular the appropriate Faxen correction for unsteady Stokes flow is derived and included as part of the consistent approximation for the equation of motion.
3,130 citations
TL;DR: In this article, it was shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamline moving in the direction opposite to V.
Abstract: It is shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to the streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamlines moving in the direction opposite to V. Here, a denotes the radius of the sphere, κ the magnitude of the velocity gradient, and μ and v the viscosity and kinematic viscosity, respectively. The relevance of the result to the observations by Segree & Silberberg (1962) of small spheres in Poiseuille flow is discussed briefly. Comments are also made about the problem of a sphere in a parabolic velocity profile and the functional dependence of the lift upon the parameters is obtained.
2,912 citations