Computational Study of the Effects of Particle Size, Particle Injection Configuration, and Operating Pressure Gradient on Turbulent Dispersion of Spherical Micron-Sized Particles in a Generic Mockup Aircraft Cabin

2012 ◽  
Author(s):  
Khosrow Ebrahimi ◽  
Zhongquan C. Zheng ◽  
Mohammad H. Hosni
Keyword(s):  
Particle Concentration ◽  
Particle Distribution ◽  
Computational Study ◽  
Turbulent Dispersion ◽  
Optimum Number ◽  
Airflow Velocity ◽  
Particle Injection ◽  
Aircraft Cabin ◽  
Gauge Pressure ◽  
Turbulent Airflow

Computational study of dispersion of particles is one way to evaluate the spread of contaminants and viruses amongst occupants of an enclosure, such as an aircraft cabin. In this investigation, the turbulent dispersion of particles in a ventilated generic cabin is studied. The generic cabin resembles one-half of a Boeing 767-300 aircraft cabin. In the first phase, the turbulent dispersion of particles injected through stainless steel straight vertical tube is simulated. A Lagrangian approach is used to predict the particle concentration in specified monitoring location inside the cabin. The steady RANS solutions for the airflow velocity data are used to initialize the particle-tracking calculations through the Discrete Phase Model (DPM). To calculate the effects of turbulence on the dispersion behavior of particles, a Discrete Random Walk (DRW) model is employed. The particle concentration field under steady-state, zero-gauge-pressure conditions for 3 μm and 10 μm spherical liquid particles are calculated. Through the comparisons between the measured and the calculated particle concentration data for the two examined sizes of mono-disperse particles, the effect of particle size on distribution behavior of micron-sized particles is investigated and discussed. In the second phase, in order to reduce the effect of initial injection velocity for 10 μm particles on their distribution, the straight injection tube is replaced by a cone diffuser while maintaining the upstream primary flow conditions. Using the same RANS model and under the new particle injection configuration, the characteristics of turbulent airflow in the cabin are found to be very similar to those of turbulent airflow without particle injection. A grid independency study is performed for the airflow velocity data prior to validation of the particle distribution results. The steady-state DPM simulations are performed initially for the zero-gauge-pressure condition and then the effect of pressurizing the cabin on particle distribution is investigated by increasing the gauge-pressure up to 0.025 inches of water. Through a detailed study, carried out to obtain an optimum number for the number of tries in the DRW, it is realized that the optimum number of tries is 175 for both cases of pressurized and non-pressurized cabin.

A Computational Study of Turbulent Airflow and Tracer Gas Diffusion in a Generic Aircraft Cabin Model

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Khosrow Ebrahimi ◽  
Zhongquan C. Zheng ◽  
Mohammad H. Hosni
Keyword(s):  
Transport Model ◽  
Computational Study ◽  
Flow Behavior ◽  
Gas Diffusion ◽  
Wall Function ◽  
Tracer Gas ◽  
Airflow Velocity ◽  
Aircraft Cabin ◽  
Cfd Models ◽  
Turbulent Airflow

In order to study the capability of computational methods in investigating the mechanisms associated with disease and contaminants transmission in aircraft cabins, the computational fluid dynamics (CFD) models are used for the simulation of turbulent airflow and tracer gas diffusion in a generic aircraft cabin mockup. The CFD models are validated through the comparisons of the CFD predictions with corresponding experimental measurements. It is found that using large eddy simulation (LES) with the Werner-Wengle wall function, one can predict unsteady airflow velocity field with relatively high accuracy. However in the middle region of the cabin mockup, where the recirculation of airflow takes place, the accuracy is not as good as that in other locations. By examining different k-ε models, the current study recommends the use of the RNG k-ε model with the nonequilibrium wall function as an Reynolds averaged Navier-Stokes model for predicting the steady-state airflow velocity. It is also found that changing the nozzle height has a significant effect on the flow behavior in the middle and upper part of the cabin, while the flow pattern in the lower part is not affected as much. Through the use of LES and species transport model in simulating tracer gas diffusion, a very good agreement between predicted and measured tracer gas concentration is achieved for some monitoring locations, but the agreement level is not uniform for all the locations. The reasons for the deviations between prediction and measurement for those locations are discussed.

Study on flow field of gas–solid two-phase pulsed jet

2019 ◽  
Vol 33 (24) ◽  
pp. 1950279
Author(s):  
Xinhua Song ◽  
Xiaojie Li ◽  
Yang Wang ◽  
Honghao Yan
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Particle Distribution ◽  
Starch Granule ◽  
Injection Pressure ◽  
Two Phase ◽  
Particle Injection ◽  
Pulsed Jet ◽  
Simulation Based ◽  
Simulation Results

In this paper, a computational fluid dynamics–discrete element method (CFD–DEM) coupling method is established to simulate the starch granule injection by coupling CFD and DEM. Then a gas–solid two-phase pulsed jet system is designed to capture the flow field trajectory of particle injection (colored starch with a mean diameter of 10.67 [Formula: see text]m), and the image is processed by color moment and histogram. Finally, the simulation results are compared with the experimental results, and the following conclusions are drawn. The numerical simulation results show that with the increase of injection pressure, the injection height increases gradually. When the injection pressure reaches above 0.4 MPa, the increase of injection height decreases. The experimental images show that the larger the pressure (i.e., the greater the initial velocity), the faster the velocity of particle distribution in the space, and the injection heights with the injection pressures of 0.4 MPa and 0.5 MPa are close, which is consistent with the result from the FLUENT numerical simulation based on CFD–DEM.

Particle Deposition in a Room-Scale Chamber With Particle Injection

2005 ◽  
Author(s):  
N. Zhang ◽  
Z. Charlie Zheng ◽  
L. Glasgow ◽  
B. Braley
Keyword(s):  
Particle Deposition ◽  
Particle Number ◽  
Particle Distribution ◽  
Turbulent Transport ◽  
Distribution Patterns ◽  
Particle Number Density ◽  
Number Density ◽  
Small Particles ◽  
Particle Injection ◽  
Simulation Results

A model simulating the deposition of small particles with turbulent transport, sedimentation, and coagulation, is presented. Experimental measurements were conducted in a room-scale chamber using a specially designed sequential sampler. The measured deposition-rate data are compared with the simulation results. Distributions of particle-number density at different times are plotted in several viewing planes to facilitate discussion of the particle distribution patterns.

Transient Response of Particle Distribution in a Chamber to Transient Particle Injection

2009 ◽  
Vol 26 (4) ◽  
pp. 199-209 ◽  
Author(s):  
Ning Zhang ◽  
Zhongquan Zheng ◽  
Steven Eckels ◽  
Venkata B. Nadella ◽  
Xiaoyang Sun
Keyword(s):  
Transient Response ◽  
Particle Distribution ◽  
Particle Injection

Results of the IES Cleanroom Flow Modeling Exercise

1992 ◽  
Vol 35 (2) ◽  
pp. 37-48
Author(s):  
Thomas Kuehn ◽  
David Pui ◽  
James Gratzek
Keyword(s):  
Experimental Data ◽  
Flow Pattern ◽  
Working Group ◽  
Particle Concentration ◽  
Numerical Models ◽  
Computer Applications ◽  
Flow Modeling ◽  
Airflow Velocity ◽  
Velocity Magnitude ◽  
Good Agreement

Six contributed solutions to the Cleanroom Flow Modeling Exercise sponsored by the IES Computer Applications/ Cleanroom Modeling and Evaluation Working Group are compared with each other and with experimental data obtained in a cleanroom configuration similar to that defined in the exercise. Quantitative comparisons are given for time-averaged airflow velocity magnitude and direction and particle concentration. The good agreement between the measured and computed velocity results shows that numerical models can accurately predict the flow pattern in this configuration. However, the particle concentration agreement is not as good.

Study of the Particle Separation Performance of a Dust-settling Hopper

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Bofu Wu ◽  
Jinlai Men ◽  
Jie Chen
Keyword(s):  
Fluid Dynamics ◽  
Particle Concentration ◽  
Separation Efficiency ◽  
Simulation Analysis ◽  
Numerical Study ◽  
Particle Separation ◽  
Separation Performance ◽  
Particle Removal ◽  
Airflow Velocity ◽  
Calculation Results

This paper presents a numerical study to predict the particle separation performance of a dust-settling hopper using computational fluid dynamics. The Euler-Lagrange approach was employed to analyze the particle separation efficiency and the outflow particle concentration of the dust-settling hopper under different inlet airflow velocities. The calculation results obtained reveal that the overall particle separation efficiency and the outflow particle concentration decrease with the increase of the inlet airflow velocity, and the particle grade efficiency increases with particle size. Since there is a paradox between the particle separation performance and the particle removal performance for a street vacuum sweeper, it is necessary to counter-balance the effects of the inlet airflow velocity on them. According to the simulation analysis, an appropriate inlet airflow velocity is provided for the design of the dust-settling hopper.

Localized Particle Concentration Measurement in Slurry Flows Using A-Scan Ultrasound Technique

2009 ◽  
Author(s):  
John M. Furlan ◽  
Venkat Mundla ◽  
Jaikrishnan Kadambi ◽  
Nathaniel Hoyt ◽  
Robert Visintainer ◽  
...  
Keyword(s):  
Solid Particle ◽  
Particle Concentration ◽  
Volume Fraction ◽  
Computational Study ◽  
Solid Particles ◽  
Acoustic Properties ◽  
Imaging Method ◽  
Concentration Profiles ◽  
Calibration Data ◽  
Slurry Flows

In the design of slurry transport equipment, the effects of solid particle concentration on hydraulic performance and wear have to be considered. This study involves examining the acoustic properties of slurry flows such as velocity, backscatter and attenuation as a function of volume fraction of solid particles. Ultrasound A-mode imaging method is developed to obtain particle concentration in a flow of soda lime glass particles (diameter of 200 micron) and water slurry in a 1″ diameter pipe. Based on the acoustic properties of the slurry a technique is developed to measure local solid particle concentrations. The technique is used to obtain concentration profiles in homogeneous (vertical flow) and non-homogeneous (horizontal flow) slurry flows with solid particle concentrations ranging from 1–10% by volume. The algorithm developed utilizes the power spectrum and attenuation measurements obtained from the homogeneous loop as calibration data in order to obtain concentration profiles in other (i.e. non-homogenous) flow regimes. A computational study using FLUENT was performed and a comparison is made with the experimental results. A reasonable agreement between the experimental and computational results is observed.

scholarly journals Numerical investigation of particles turbulent dispersion in channel flow

2012 ◽  
Vol 16 (5) ◽  
pp. 1510-1514
Author(s):  
Tian Li ◽  
Li-Hao Zhao ◽  
Xiao-Ke Ku ◽  
Helge Andersson ◽  
Terese Lovas
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Numerical Investigation ◽  
Channel Flow ◽  
Particle Distribution ◽  
Turbulent Dispersion ◽  
Wall Turbulence ◽  
Navier Stokes ◽  
Reynolds Averaged Navier Stokes ◽  
Over Time

This paper investigates the performance of Reynolds-averaged Navier-Stokes model on dispersion of particles in wall turbulence. A direct numerical simulation of wall-bounded channel flow with particles suspensions was set as a benchmark. The standard k-? model coupled with two different eddy interaction models was used in Reynolds-averaged Navier-Stokes model and compared to the direct numerical simulation. Detailed comparisons between direct numerical simulation and Reynolds-averaged Navier-Stokes model on particle distribution evolving over time were carried out.

Nuclear Magnetiic Resonance Imaging (NMRI) of Flow-Induced Microstructure of Concentratied Suspensions

1992 ◽  
Vol 289 ◽  
Author(s):  
A. W. Chow ◽  
S. W. Sinton ◽  
J. H. Iwamiya
Keyword(s):  
Particle Concentration ◽  
Particle Distribution ◽  
Leading Edge ◽  
Particle Migration ◽  
Fall Velocity ◽  
Resonance Flow ◽  
Liquid Suspensions ◽  
Induced Changes ◽  
Solid Liquid ◽  
Neutrally Buoyant

AbstractThe application of nuclear magnetic resonance flow imaging (NMRI) to the study of Couette and falling-ball viscometry of solid/liquid suspensions is described. The suspension consisted of non-Brownian, monodisperse, neutrally-buoyant spheres of 50 vol%. NMRI data demonstrated flow-induced changes in the particle distribution in the suspension that strongly influence the accuracy in viscosity measurements using these flow geometries. In Couette flow, direct correlation between stress measurements and particle concentrations at various locations in the flow cell as a function of shear strain can be made. Our data directly confitrm the shearinduced particle migration theory proposed by Leighton and Acrivos.[1] In the falling-ball experiments, increased particle concentration at the leading edge and decreased concentration at the trailing edge of the ball was observed when the falling ball is big compared to the cylinder containing the suspension. This change in particle distribution can be directly related to the changes in fall velocity of the ball as a function of position in the cylinder.

scholarly journals Model of a Light Extinction Sensor for Assessing Wear Particle Distribution in a Lubricated Oil System

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4091
Author(s):  
Kevin Krogsøe ◽  
Morten Henneberg ◽  
René Eriksen
Keyword(s):  
Particle Concentration ◽  
Particle Distribution ◽  
Optical Design ◽  
Signal Amplitude ◽  
Wear Particle ◽  
Light Extinction ◽  
Contamination Level ◽  
Special Focus ◽  
Particle Contamination ◽  
Measurement Principle

Light extinction based optical wear particle counters (OPCs) have been widely used in the industry for oil condition monitoring for several years, and while experiments have tested the benefits and drawbacks of the measurement principle, limited research has been conducted regarding a theoretical approach to evaluate opportunities and limitations of the measurement scheme. In this paper, we present a method for theoretically modelling the output of an OPC based on the light extinction principle in the regime of geometrical optics, with a special focus on the influence of sensor optical design, particle concentration and measurement noise. Moreover, we show that, if only signal amplitude is considered, an algorithm for evaluating sensor output can cause an erroneous assessment of particle contamination level.

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