scholarly journals Observations and Modeling of Heavy Particle Deposition in a Windbreak Flow

2006 ◽  
Vol 45 (9) ◽  
pp. 1332-1349 ◽  
Author(s):  
T. Bouvet ◽  
J. D. Wilson ◽  
A. Tuzet
Keyword(s):  
Particle Deposition ◽  
Particle Trajectory ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Wind Model ◽  
Heavy Particles ◽  
Model Match ◽  
Wind Statistics ◽  
Particle Trajectory Model ◽  
Peak Value

Abstract This paper presents new observations of deposition of heavy particles (glass beads of gravitational settling velocity 8.7 cm s−1) within an undisturbed flow and within a flow disturbed by a porous windbreak fence. These data are then used to diagnose the capability of a Lagrangian stochastic (LS) particle trajectory model, which simulates heavy particle dispersion. The model is based on existing parameterizations and is coupled to a wind model based on a Reynolds stress turbulence closure that provides computed fields of wind statistics. The deposition rates, as simulated by the model, match the observation within E = 30% of accuracy, with E being the root-mean-square error normalized by the peak value on the deposition swath. These results suggest that the LS model handles properly the heterogeneities of the flow and that the heuristic adjustments made to account for the inertia of heavy particles are useful approximations. The model consequently proves to be a valuable tool to investigate the patterns of dispersion about an obstacle.

Numerical Simulation of Heavy Particle Dispersion—Scale Ratio and Flow Decay Considerations

1994 ◽  
Vol 116 (1) ◽  
pp. 154-163 ◽  
Author(s):  
Lian-Ping Wang ◽  
David E. Stock
Keyword(s):  
Numerical Simulation ◽  
Time Scale ◽  
Dispersion Coefficient ◽  
Fluid Velocity ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Heavy Particles ◽  
Velocity Scale ◽  
Scale Ratio ◽  
Diffusivity Ratio

Lagrangian statistical quantities related to the dispersion of heavy particles were studied numerically by following particle trajectories in a random flow generated by Fourier modes. An experimental fluid velocity correlation was incorporated into the flow. Numerical simulation was performed with the use of nonlinear drag. The simulation results for glass beads in a nondecaying turbulent air showed a difference between the horizontal dispersion coefficient and vertical dispersion coefficient. This difference was related to the differences of both the velocity scale and the time scale between the two direction. It was shown that for relatively small particle sizes the particle time scale ratio dominates the value of the diffusivity ratio. For large particles, the velocity scale ratio reaches a value of 1/2 and thus fully determines the diffusivity ratio. Qualitative explanation was provided to support the numerical findings. The dispersion data for heavy particles in grid-generated turbulences were successfully predicted by the simulation when flow decay was considered. As a result of the reduction in effective inertia and the increase in effective drift caused by the flow decay, the particle dispersion coefficient in decaying flow decreases with downstream location. The particle rms fluctuation velocity has a slower decay rate than the fluid rms velocity if the drift parameter is large. It was also found that the drift may substantially reduce the particle rms velocity.

A Trajectory-Simulation Model for Heavy Particle Motion in Turbulent Flow

1989 ◽  
Vol 111 (4) ◽  
pp. 492-494 ◽  
Author(s):  
Y. Zhuang ◽  
J. D. Wilson ◽  
E. P. Lozowski
Keyword(s):  
Turbulent Flow ◽  
Simulation Model ◽  
Particle Motion ◽  
Simple Procedure ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Fluid Density ◽  
Heavy Particles ◽  
Trajectory Simulation ◽  
Acceptable Agreement

For many purposes it is useful to be able to mimic the paths of heavy particles in a turbulent flow. This paper gives a simple procedure by which this may be achieved, provided particle spin is not important and under the restriction that the ratio of particle to fluid density exceeds about 1000. The procedure is related to the models of Faeth (1986) and Hunt and Nalpanis (1985). Simulation of the experiments of Snyder and Lumley (1971) yielded acceptable agreement with the observed rate of heavy particle dispersion.

scholarly journals The scalar chemical potential in cosmological collider physics

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Arushi Bodas ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Particle Production ◽  
Chemical Potential ◽  
Direct Detection ◽  
Heavy Particle ◽  
Scalar Particle ◽  
Energy Scale ◽  
Fine Tuning ◽  
Tree Level ◽  
Heavy Particles ◽  
Non Gaussian

Abstract Non-analyticity in co-moving momenta within the non-Gaussian bispectrum is a distinctive sign of on-shell particle production during inflation, presenting a unique opportunity for the “direct detection” of particles with masses as large as the inflationary Hubble scale (H). However, the strength of such non-analyticity ordinarily drops exponentially by a Boltzmann-like factor as masses exceed H. In this paper, we study an exception provided by a dimension-5 derivative coupling of the inflaton to heavy-particle currents, applying it specifically to the case of two real scalars. The operator has a “chemical potential” form, which harnesses the large kinetic energy scale of the inflaton, $$ {\overset{\cdot }{\phi}}_0^{1/2}\approx 60H $$ ϕ ⋅ 0 1 / 2 ≈ 60 H , to act as an efficient source of scalar particle production. Derivative couplings of inflaton ensure radiative stability of the slow-roll potential, which in turn maintains (approximate) scale-invariance of the inflationary correlations. We show that a signal not suffering Boltzmann suppression can be obtained in the bispectrum with strength fNL ∼ $$ \mathcal{O} $$ O (0.01–10) for an extended range of scalar masses $$ \lesssim {\overset{\cdot }{\phi}}_0^{1/2} $$ ≲ ϕ ⋅ 0 1 / 2 , potentially as high as 1015 GeV, within the sensitivity of upcoming LSS and more futuristic 21-cm experiments. The mechanism does not invoke any particular fine-tuning of parameters or breakdown of perturbation-theoretic control. The leading contribution appears at tree-level, which makes the calculation analytically tractable and removes the loop-suppression as compared to earlier chemical potential studies of non-zero spins. The steady particle production allows us to infer the effective mass of the heavy particles and the chemical potential from the variation in bispectrum oscillations as a function of co-moving momenta. Our analysis sets the stage for generalization to heavy bosons with non-zero spin.

scholarly journals Marine macro debris transport based on hydrodynamic model before and after reclamation in Jakarta Bay, Indonesia

2020 ◽  
Vol 5 (2) ◽  
pp. 100-111
Author(s):  
Yudi Nurul Ihsan
Keyword(s):  
Eddy Current ◽  
Hydrodynamic Model ◽  
Particle Trajectory ◽  
Surface Current ◽  
Contamination Level ◽  
Model Data ◽  
The World ◽  
Before And After ◽  
Debris Transport ◽  
Particle Trajectory Model

Jakarta Bay as an area with the densest population in Indonesia became one of the highest contamination level waters in the world includes pollution of debris. Reclamation activities in Jakarta Bay will change the water conditions will also affect the distribution of debris at sea. Therefore, this study conducted to determine the movement of the macro debris before and after island reclamation in Jakarta Bay. The method used is a model that simulated by the hydrodynamic model and particle trajectory model. Data needed for the hydrodynamic model were wind, tides, bathymetry, and shoreline, while for the trajectory of the particles using a data type of macro debris, debris weight, and debris flux. Hydrodynamics simulations indicate if a reclamation island formation does not change surface current patterns significantly, but causes a decrease in the flow velocity of ± 0.002 to 0.02 m/s at some point. The trajectory of particles of debris indicate if after reclamation, debris tends to accumulate in the eastern Jakarta Bay in the rainy season (January) as there are anticlockwise eddy current, as well as in the western and eastern regions during the dry season (July), because there is a clockwise eddy current in the eastern Jakarta Bay.

Hybrid LES/RANS Model for Simulation of Particle Dispersion and Deposition

2018 ◽  
Author(s):  
H. Sajjadi ◽  
M. Salmanzadeh ◽  
G. Ahmadi ◽  
S. Jafari
Keyword(s):  
Turbulence Model ◽  
Particle Deposition ◽  
Computational Cost ◽  
Particle Dispersion ◽  
Distribution Functions ◽  
Wall Region ◽  
Rans Model ◽  
Turbulence Effects ◽  
Scale Turbulence ◽  
Les Model

Particle dispersion and deposition in a modeled room was investigated using the Lattice Boltzmann method (LBM) in conjunction with the hybrid RANS/LES turbulence model. For this new model a combination of LES and RANS models was used to reduce the computational cost of using the full LES in the entire domain. Here the near wall region was simulated by the RANS model, while the rest of the domain was analyzed using the LES model within the framework of the LBM. The k-ε turbulence model was applied in the RANS region. For using the k-ε model in the LBM framework, two additional distribution functions for k and ε were defined. For the LES region the sub-grid scale turbulence effects were simulated through a Smagorinsky model. To study the particle dispersion and deposition in the modeled room, particles with different sizes (diameters of 10nm to 10 μm) were investigated. The simulated results for particle dispersion and deposition showed that the predictions of the present hybrid method were quite similar to the earlier LES-LBM. In addition, the predictions of the hybrid model for the particle deposition and dispersion were closer to the LES simulation results compared to those of the k-ε model. It was shown that the Brownian excitation is very important for nanoparticles and the number of deposited particles for 10nm particles is higher than those for the larger 100nm and 1μm particles. The deposition rate for 10 μm particles is also high due to the inertial effects.

Particle Dispersion and Deposition in a Curved Duct

2009 ◽  
Author(s):  
C. M. Winkler ◽  
S. P. Vanka
Keyword(s):  
Particle Deposition ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Outer Wall ◽  
Particle Dispersion ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Particle Volume ◽  
Particle Tracking Method ◽  
Dean Vortex

Particle transport in ducts of square cross-section with constant streamwise curvature is studied using numerical simulations. The flow is laminar, with Reynolds numbers of Reτ = 40 and 67, based on the friction velocity and duct width. The corresponding Dean numbers for these cases are 82.45 and 184.5, respectively, where De = Rea/R, a is the duct width and R is the radius of curvature. A Lagrangian particle tracking method is used to account for the particle trajectories, with the particle volume fraction assumed to be low such that inter-particle collisions and two-way coupling effects are negligible. Four particle sizes are studied, τp+ = 0.01, 0.05, 0.1, and 1. Particle dispersion patterns are shown for each Dean number, and the steady-state particle locations are found to be reflective of the Dean vortex structure. Particle deposition on the walls is shown to be dependent upon both the Dean number and particle response time, with the four-cell Dean vortex pattern able to prevent particle deposition along the center of the outer wall.

Effect of Inter-Particle Interaction on Particle Deposition in a Cross-Flow Microfilter

2013 ◽  
Author(s):  
Talukder Z. Jubery ◽  
Shiv G. Kapoor ◽  
John E. Wentz
Keyword(s):  
Surface Properties ◽  
Particle Deposition ◽  
Particle Trajectory ◽  
Particle Interaction ◽  
Cross Flow ◽  
Pore Wall ◽  
Operating Conditions ◽  
Hard Sphere Model ◽  
Wall Surface ◽  
Membrane Pore

Recent studies show that inter-particle interaction can affect particle trajectories and particle deposition causing fouling in the microfilters used for metal working fluids (MWFs). Inter-particle interaction depends on various factors: particle geometry and surface properties, membrane pore geometry and surface properties, MWF’s properties and system operating conditions, etc. A mathematical model with a Langevin equation for particle trajectory and a hard sphere model for particle deposition has been used to study the effect of particle’s size, particle’s surface zeta potential, inter-particle distance, and shape of membrane pore wall surface on particle trajectory and its deposition on membrane pore wall. The study reveals that bigger particles have a lesser tendency to be deposited on membrane pore walls than smaller particles. The shape of the membrane pore wall surface can also affect the particle deposition behavior.

scholarly journals ANALYTICAL AND CFD INVESTIGATION OF TURBULENT DIFFUSION MODEL FOR PARTICLE DISPERSION AND DEPOSITION

1970 ◽  
Vol 40 (1) ◽  
pp. 39-53
Author(s):  
Alamgir Hossain ◽  
Jamal Naser
Keyword(s):  
Diffusion Model ◽  
Turbulent Diffusion ◽  
Particle Deposition ◽  
Fluid Velocity ◽  
Particle Diameter ◽  
Particle Dispersion ◽  
Homogeneous Distribution ◽  
Lower Velocity ◽  
Different Depths ◽  
Diffusion Particle

A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights across the pipe flow and circumferential deposition has been developed. This liquid-solid turbulent diffusion model presented in this paper has emanated from an existing gas-liquid turbulent diffusion model. Simultaneously a comprehensive 3D numerical investigation has been carried out to study the above making of multiphase mixture model available in Fluent 6.1. In both studies different particles sizes and densities were used. The deposition was studied as a function of particle diameter, density and fluid velocity. The deposition of particles, along the periphery of the wall and at different depths, was also investigated. Both studies showed that the deposition of heavier particles at the bottom of the pipe wall was found to be higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration near the bottom of the wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. The larger particles clearly showed deposition near the bottom of the wall. These analogies of particles are well discussed with the ratio between free flight velocity and the gravitational settling velocity. Key Words: Multiphase flow, turbulence diffusion, particle deposition, horizontal flow.   doi: 10.3329/jme.v40i1.3472 Journal of Mechanical Engineering, Vol. ME40, No. 1, June 2009 39-53

scholarly journals Airflow and Particle Deposition in Acinar Models with Interalveolar Septal Walls and Different Alveolar Numbers

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Jinxiang Xi ◽  
Mohamed Talaat ◽  
Hesham Tanbour ◽  
Khaled Talaat
Keyword(s):  
Deposition Rate ◽  
Particle Deposition ◽  
Orientation Angle ◽  
Structural Complexity ◽  
Particle Dispersion ◽  
Breath Holding ◽  
Complex Models ◽  
Tracking Model ◽  
Lagrangian Tracking ◽  
Collateral Ventilation

Unique features exist in acinar units such as multiple alveoli, interalveolar septal walls, and pores of Kohn. However, the effects of such features on airflow and particle deposition remain not well quantified due to their structural complexity. This study aims to numerically investigate particle dynamics in acinar models with interalveolar septal walls and pores of Kohn. A simplified 4-alveoli model with well-defined geometries and a physiologically realistic 45-alveoli model was developed. A well-validated Lagrangian tracking model was used to simulate particle trajectories in the acinar models with rhythmically expanding and contracting wall motions. Both spatial and temporal dosimetries in the acinar models were analyzed. Results show that collateral ventilation exists among alveoli due to pressure imbalance. The size of interalveolar septal aperture significantly alters the spatial deposition pattern, while it has an insignificant effect on the total deposition rate. Surprisingly, the deposition rate in the 45-alveoli model is lower than that in the 4-alveoli model, indicating a stronger particle dispersion in more complex models. The gravity orientation angle has a decreasing effect on acinar deposition rates with an increasing number of alveoli retained in the model; such an effect is nearly negligible in the 45-alveoli model. Breath-holding increased particle deposition in the acinar region, which was most significant in the alveoli proximal to the duct. Increasing inhalation depth only slightly increases the fraction of deposited particles over particles entering the alveolar model but has a large influence on dispensing particles to the peripheral alveoli. Results of this study indicate that an empirical correlation for acinar deposition can be developed based on alveolar models with reduced complexity; however, what level of geometry complexity would be sufficient is yet to be determined.

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