Recent advances in modeling and simulation of nanofluid flows-Part I: Fundamentals and theory

A random flow generation (RFG) technique is presented, which can be used for initial/ inlet boundary generation in LES (Large-Eddy-Simulations) or particle tracking in LES/ RANS (Reynolds-Averaged Navier-Stokes) computations of turbulent flows. The technique is based on previous methods of synthesizing divergence-free vector fields from a sample of Fourier harmonics and allows to generate non-homogeneous anisotropic flow field representing turbulent velocity fluctuations. It was validated on the cases of boundary layer and flat plate flows. Applications of the technique to LES and particle tracking are considered

Random Flow Generation Technique for Large Eddy Simulations and Particle-Dynamics Modeling

Comparison of indoor aerosol particle concentration and deposition in different ventilated rooms by numerical method

Particle deposition in turbulent duct flows—comparisons of different model predictions

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...

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Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer

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.

Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow

Deposition of aerosols on surfaces in a turbulent channel flow

Aerosol particle deposition in an obstructed turbulent duct flow

Dispersion and deposition of particles in a turbulent channel flow with rough walls are studied. A procedure for simulating the deposition of aerosol particles on a rough surface is developed. The instantaneous turbulent flow field is generated as the sum of a mean and a randomly fluctuating Gaussian field. Particle equation of motion including the effects of Brownian diffusion, Saffman lift force, and gravity is solved numerically. Starting with an initially uniform concentration near the wall, ensembles of particle trajectories are generated and statistically analyzed. Several simulations for deposition of aerosol particles of various sizes are performed and the corresponding deposition velocities are evaluated. The results are compared with those obtained by empirical equations and experimental data

Computer Simulation of Deposition of Aerosols in a Turbulent Channel Flow with Rough Walls

A computational model for simulating particle dispersion and deposition in the human tracheobronchial tree is developed. The trachea and the main bronchi are modeled as a two-dimensional duct with two symmetric branches, and a branching angle of 45°. For high inspiratory flow rates, the occurrence of turbulence in the air is considered. Using the thermodynamically consistent rate-dependent anisotropic turbulence model, the mean velocity, as well as the root-mean-square fluctuation velocity fields in the airways are evaluated. The instantaneous turbulence fluctuating velocity is simulated as a continuous Gaussian random vector field. The Brownian motion is modeled as a white noise process. The Stokes drag, the Brownian and the Saffman forces are included in the particle equation of motion. Several digital simulations for particle transport and deposition in the upper tracheobronchial airways for different breathing conditions are performed. For particles in the size range of 0.01 to 20 μm, the corresponding deposition rates on various surfaces are evaluated. The net deposition rates are compared with the available experimental data and earlier digital simulations for bifurcating tubes.

Amy Li

Papers

Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow

Deposition of aerosols on surfaces in a turbulent channel flow

Aerosol particle deposition in an obstructed turbulent duct flow

Computer Simulation of Deposition of Aerosols in a Turbulent Channel Flow with Rough Walls

Computer Simulation of Particle Deposition in the Upper Tracheobronchial Tree