Effect of spatial inhomogeneity and temporal fluctuation of particle distributions on interparticle collision rate in particulate flows

2007 ◽  
Vol 172 (3) ◽  
pp. 188-192 ◽  
Author(s):  
Changfu You ◽  
Hailiang Zhao ◽  
Xuchang Xu ◽  
Delong Xu
Keyword(s):  
Spatial Inhomogeneity ◽  
Collision Rate ◽  
Particulate Flows ◽  
Temporal Fluctuation ◽  
Particle Distributions ◽  
Interparticle Collision

scholarly journals DSMC Prediction of Particle Behavior in Gas-Particle Two-Phase Impinging Streams

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Min Du ◽  
Changsui Zhao ◽  
Bin Zhou ◽  
Yingli Hao
Keyword(s):  
Particle Concentration ◽  
Chemical Engineering ◽  
Lagrangian Approach ◽  
Particle Collision ◽  
Collision Rate ◽  
Two Phase ◽  
Particle Behavior ◽  
Transfer Processes ◽  
Collision Zone ◽  
Interparticle Collision

Devices with impinging streams have been employed in various fields of chemical engineering, as a means of intensifying heat and mass transfer processes. The particle behavior in gas-particle two-phase impinging streams (GPISs), which is of essential importance for the research of transfer processes, was simulated by an Eulerian-Lagrangian approach in this paper. Collisional interaction of particles was taken into account by means of a modified direct simulation Monte Carlo (DSMC) method based on a Lagrangian approach and the modified Nanbu method. A quantitative agreement was obtained between the predicted results and the experimental data in the literature. The particle motion behavior and the distributions of particle concentration and particle collision positions were presented reasonably. The results indicate that the particle distribution in GPIS can be divided into three zones: particle-collision zone, particle-jetting zone, and particle-scattering zone. Particle collisions occur mainly in the particle-collision zone, which obviously results in a few particles penetrating into the opposite stream. The interparticle collision rate and the particle concentration reach their maximum values in the particle-collision zone, respectively. The maximum value of the particle concentration increases with the increasing inlet particle concentration according to a logarithmic function. The interparticle collision rate is directly proportional to the square of local particle concentration.

Experimental investigation of interparticle collision rate in particulate flow

2004 ◽  
Vol 30 (9) ◽  
pp. 1121-1138 ◽  
Author(s):  
Changfu You ◽  
Hailiang Zhao ◽  
Yi Cai ◽  
Haiying Qi ◽  
Xuchang Xu
Keyword(s):  
Experimental Investigation ◽  
Particulate Flow ◽  
Collision Rate ◽  
Interparticle Collision

The use of particle monitoring in the performance optimisation of conventional clarification and filtration processes

1997 ◽  
Vol 36 (4) ◽  
pp. 191-198
Author(s):  
G. Standen ◽  
P. J. Insole ◽  
K. J. Shek ◽  
R. A. Irwin
Keyword(s):  
Activated Carbon ◽  
Water Supply ◽  
Laser Diffraction ◽  
Raw Water ◽  
Particle Distributions ◽  
Upper Limit ◽  
Start Up ◽  
On Line ◽  
Particulates Removal ◽  
Particle Monitoring

The application of laser diffraction particle monitoring to the performance optimisation of a pilot clarifier and full-scale rapid gravity filters (RGF), operating on water supply works in Hampshire, is described. Furthermore the dosing of powdered activated carbon (PAC) into the works' clarifiers has been evaluated in terms of RGF performance. A costly proposal to install a third filter medium was subsequently abandoned when it was found that particle numbers in the filtered water were consistently below 1×102/ml. Various combinations and doses of coagulants and flocculant aids, shown to give optimum particulates removal during intensive jar testing trials, were transferred to the pilot clarifier. Particle monitoring enabled a more accurate derivation of suitable blanket chemistry and optimum blanket heights than turbidity changes. Raw water turbidities were 10-15 NTU at start-up with corresponding counts beyond the upper limit of the particle monitor. An on-line dilution system was developed to overcome this problem. Latex bead (4.33 μm) and Lycopodium spore (4-5 μm) suspensions (about 1 × 109 particles) were injected into the pilot clarifier to assess the removal efficiency of Cryptosporidium-sized particles. Reductions of about 1.7 log and 2.6 log were achieved for the beads and spores, respectively. Particle distributions of various PAC's and a bentonite were obtained in order to assess their potential effects on the coagulation process during clarification. Bentonite was also beneficial as an on-line means of checking particle monitor response and calibration. The works' filters achieved 1.5 to 2.0 log removals of 2-5 μm particles without media addition or operational changes. Combined clarification and filtration gave better particulates removal than two-stage microfiltration.

A Novel Simulation Approach for Particulate Flows during Filtration

AIChE Journal ◽  
2020 ◽  
Author(s):  
Minhui Qi ◽  
Mingzhong Li ◽  
Rouzbeh G. Moghanloo ◽  
Tiankui Guo
Keyword(s):  
Simulation Approach ◽  
Particulate Flows

scholarly journals Modelling combustion in spark ignition engines with special emphasis on near wall flame quenching

2020 ◽  
pp. 146808742097290
Author(s):  
CP Ranasinghe ◽  
W Malalasekera
Keyword(s):  
Combustion Rate ◽  
Fractal Theory ◽  
Pressure Rise ◽  
Spark Ignition ◽  
Spatial Inhomogeneity ◽  
Combustion Model ◽  
Spark Ignition Engines ◽  
Flame Acceleration ◽  
Flame Quenching ◽  
Near Wall

A flame front is quenched when approaching a cold wall due to excessive heat loss. Accurate computation of combustion rate in such situations requires accounting for near wall flame quenching. Combustion models, developed without considering wall effects, cannot be used for wall bounded combustion modelling, as it leads to wall flame acceleration problem. In this work, a new model was developed to estimate the near wall combustion rate, accommodating quenching effects. The developed correlation was then applied to predict the combustion in two spark ignition engines in combination with the famous Bray–Moss–Libby (BML) combustion model. BML model normally fails when applied to wall bounded combustion due to flame wall acceleration. Results show that the proposed quenching correlation has significantly improved the performance of BML model in wall bounded combustion. As a second step, in order to further enhance the performance, the BML model was modified with the use of Kolmogorov–Petrovski–Piskunov analysis and fractal theory. In which, a new dynamic formulation is proposed to evaluate the mean flame wrinkling scale, there by accounting for spatial inhomogeneity of turbulence. Results indicate that the combination of the quenching correlation and the modified BML model has been successful in eliminating wall flame acceleration problem, while accurately predicting in-cylinder pressure rise, mass burn rates and heat release rates.

scholarly journals Spatiotemporal Variability of Mesoscale Eddies in the Indonesian Seas

2021 ◽  
Vol 13 (5) ◽  
pp. 1017
Author(s):  
Zhanjiu Hao ◽  
Zhenhua Xu ◽  
Ming Feng ◽  
Qun Li ◽  
Baoshu Yin
Keyword(s):  
World Ocean ◽  
Mesoscale Eddies ◽  
Spatial Inhomogeneity ◽  
Spatiotemporal Variability ◽  
Identification Algorithm ◽  
Mean Flow ◽  
Sulu Sea ◽  
Indonesian Seas ◽  
Highly Nonlinear ◽  
Eddy Generation

Mesoscale eddies are ubiquitous in the world ocean and well researched both globally and regionally, while their properties and distributions across the whole Indonesian Seas are not yet fully understood. This study investigates for the first time the spatiotemporal variations and generation mechanisms of mesoscale eddies across the whole Indonesian Seas. Eddies are detected from altimetry sea level anomalies by an automatic identification algorithm. The Sulu Sea, Sulawesi Sea, Maluku Sea and Banda Sea are the main eddy generation regions. More than 80% of eddies are short-lived with a lifetime below 30 days. The properties of eddies exhibit high spatial inhomogeneity, with the typical amplitudes and radiuses of 2–6 cm and 50–160 km, respectively. The most energetic eddies are observed in the Sulawesi Sea and Seram Sea. Eddies feature different seasonal cycles between anticyclonic and cyclonic eddies in each basin, especially given that the average latitude of the eddy centroid has inverse seasonal variations. About 48% of eddies in the Sulawesi Sea are highly nonlinear, which is the case for less than 30% in the Sulu Sea and Banda Sea. Instability analysis is performed using high-resolution model outputs from Bluelink Reanalysis to assess mechanisms of eddy generation. Barotropic instability of the mean flow dominates eddy generation in the Sulu Sea and Sulawesi Sea, while baroclinic instability is slightly more in the Maluku Sea and Banda Sea.

Ultrafast magnetization dynamics of Mn-doped L10 FePt with spatial inhomogeneity

2020 ◽  
Vol 502 ◽  
pp. 166477
Author(s):  
Yuting Liu ◽  
Ute Bierbrauer ◽  
Cinja Seick ◽  
Sebastian T. Weber ◽  
Moritz Hofherr ◽  
...  
Keyword(s):  
Spatial Inhomogeneity ◽  
Magnetization Dynamics ◽  
Ultrafast Magnetization ◽  
Mn Doped

scholarly journals Physical Processes in Nebular Shells and the Interpretation of Nebular Spectra

1983 ◽  
Vol 103 ◽  
pp. 219-227
Author(s):  
J. Patrick Harrington
Keyword(s):  
Charge Transfer ◽  
Simple Model ◽  
Stellar Wind ◽  
High Velocity ◽  
Planetary Nebulae ◽  
Geometrical Parameters ◽  
Stellar Winds ◽  
Physical Processes ◽  
Rapid Cooling ◽  
Particle Distributions

Computed models are now recognized as useful tools for interpretation of the spectra of planetary nebulae. However, even the most detailed models need geometrical parameters such as filling factors which are poorly determined by observations. Some effects may be seen more clearly by modeling the stratification than by just using total fluxes. A simple model for NGC 6720 is presented which reproduces the behavior of (Ne III) λ3869 observed by Hawley and Miller (1977), clearly showing the effects of charge transfer. The behavior of C II λ4267 remains puzzling. Finally, we comment on the interaction of high velocity stellar winds with nebular shells. Non-equilibrium particle distributions at the contact between the shocked stellar wind and the nebula may result in the rapid cooling of the shocked gas.

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