Importance of Initial Particle Distribution in Modeling Dam Break Analysis with SPH

Mahyar Pourlak,Hassan Akbari,Ehsan Jabbari 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1

Smoothed-Particle Hydrodynamics (SPH) has drawn a great deal of attention in recent years to model various phenomena in engineering and science. SPH is a Lagrangian model in which moving particles represent the fluid body during simulation. Therefore, the initial distribution of particles may affect the model results along with the simulation, and a good initial condition can minimize numerical errors or increase the computational efficiency. Since SPH model particle distributions need a flow pattern, the dam break flow as a classic benchmark SPH problem is selected in this study, and the best initial particle distribution for this case has to be found. Different results, including the mean density of particles, hydrostatic and dynamic pressures and surge front position, are considered the main model results for the adequacy of different initial particle distributions to be discussed. All models are verified at first by simulating different test cases and comparing the results with analytical and experimental data. Acceptable agreements between these data show the model's capability in well predicting the dam break flows. Then, the effects of initial particle distribution on the results are investigated by considering five different particle distributions. For this purpose, Body-Centered Cubic (BCC), Simple Cubic (SC), Greedy, Voronoi Tessellation and Fibonacci algorithms for particle distributions have been modeled. To get reliable conclusions, these distributions have been utilized in models with different kernel functions as well as with different particle spacings. Based on the results, irregular arrangements such as Greedy distribution perform better than regular SC and BCC distributions in modeling dam-break flow. In addition, both Voronoi and Fibonacci distributions perform almost the same with a moderate level of accuracy. Regarding mentioned arrangements, the main outcome of this study, is that the initial particle distribution is an important issue in SPH models, which clearly affects the results.

Uneven distribution of particle flow in RFCC reactor riser

Cho, Hyungtae,Kim, Junghwan,Park, Chanho,Lee, Kwanghee,Kim, Myungjun,Moon, Il Elsevier Sequoia 2017 Powder technology Vol.312 No.-

<P><B>Abstract</B></P> <P>The uneven distribution of particle flow, i.e., a different particle mass flow rate in each outlet of the riser in residue fluidized catalytic cracking (RFCC) processes, is one major problem associated with commercial RFCC processes. This problem affects the formation of carbonaceous deposits in the secondary reactor cyclone, which incurs serious catalyst carryover in the fractionators. This study analyzes particle-fluid flow patterns in the riser, and diagnoses the uneven distribution of particle flow using a computational particle fluid dynamics (CPFD) method to solve this real industrial problem. Through this analysis, the effect of the number of feed injectors is investigated. The CPFD method, which has been developed to complement the Eulerian-Eulerian and Eulerian-Lagrangian methods, applies the Navier-Stokes equation for fluid phase and multi-phase-particle-in-cell (MP-PIC) models for particle phase. The particle flow distribution was found to vary by 15.5–18.7% at different outlets in the 1 injector case, which implies that the solid loading ratio in each cyclone is different, thereby affecting the separation efficiency of the cyclone and the formation of carbonaceous deposits. The uneven distribution of particle flow phenomena was identified, and the standard deviations of particle mass flow rates were evaluated for the cases of 1, 2, 4, 6, 8 and 12 injectors, and were found to be 7.52, 4.07, 2.66, 1.78, 2.85 and 3.82, respectively. From these results, the 6 injectors case was found to have a largely even particle flow distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We develop CPFD model of the riser of RFCC under commercial operation conditions. </LI> <LI> This CPFD model was verified by comparing it with the commercial plant data. </LI> <LI> The uneven distribution of particle flow affecting a turnaround period is ascertained. </LI> <LI> We solve the industrial problem by investigating the effect of the feed injector. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Aerosol size distributions observed at the Seoul National University campus in Korea during the Asian dust and non-Asian dust periods

Park, Soon-Ung,Kim, Jong-Won Elsevier 2006 Atmospheric environment Vol.40 No.9

<P><B>Abstract</B></P><P>Aerosol size distributions of observed mass concentration and number concentration at the Seoul National University (SNU) campus site in Korea during the non-Asian dust and the Asian dust (Hwangsa) periods have been examined using the 8-stage cascade impactor and the 8-channel airborne particle counting system, respectively. The particle size distribution of the observed mass concentration during the Asian dust period at the SNU site is compared with that observed at the Asian dust source site of Duolun in Inner Mongolia, China. The results indicate that the size distribution of both the mass concentration and the number concentration shows a bi-modal distribution that can be regressed optimally with two log-normal distribution functions. It is found that the optimally regressed probability density function of the mass concentration distribution during the non-Asian dust period at the SNU site shows two log-normal distributions with the particle mean diameters of 0.66 and 8.51μm and the standard deviations of 1.78 and 2.14μm, respectively. The probability density of the small size mode is slightly smaller than that of the large size mode. During the Asian dust period at the SNU site the estimated probability density function of the mass concentration also composes of two log-normal distributions with the particle mean diameters of 0.89 and 9.12μm and the standard deviations of 2.40 and 2.14μm, respectively. However, the high probability density is greatly shifted to the large size mode. The probability density of the small size mode is only 6% of that of the large size mode. A quite similar size distribution pattern is found in the Asian dust source region of Duolun, suggesting the high probability density at the large particle-size mode during the Asian dust period being mainly attributed to long-range transport of particles from the Asian dust source region. It is also found that the estimated probability density function of the number concentration distribution observed at the SNU site during the non-Asian dust period has a bi-modal distribution with the particle mean diameters of 0.36 and 1.12μm and the mean standard deviations of 1.48 and 1.91μm, respectively. Much higher probability density is found in the small size mode in contrast to that of the mass concentration distribution where the probability density of both modes is almost the same.</P>

Gerdien 이온측정기를 이용한 에어로졸의 하전 특성 분석에 관한 연구

조윤행,심준목,신일경,육세진,박현설,Joe, Yun-Haeng,Shim, Joonmok,Shin, Il-Kyoung,Yook, Se-Jin,Park, Hyun-Seol 한국입자에어로졸학회 2018 Particle and Aerosol Research Vol.14 No.1

Since the motion of the charged particle strongly depends on its charge characteristics, information on charge distributions of target particles is one of the important variables in aerosol research. In this study, charged distribution of atomized NaCl particles were measured using a Gerdien type ion counter. Two kinds of particle charging conditions were used in this study. First, atomized NaCl particles were passed through an aerosol neutralizer to have a Boltzmann charge distribution, and then its charge distribution was measured. In this case, the portion of uncharged particles was compared with the portion obtained from the Boltzmann charge distribution for verifying the suggested experimental method. Second, same experiment was conducted without the aerosol neutralizer to measure the charge distribution of atomized and un-neutralized NaCl particles. In the conclusion, the portion of uncharged, negatively charged and positively charged particles were 19%, 62% and 20%, respectively, for neutralized particles. The atomized particles, which was generated without the aerosol neutralizer, also had almost a zero charge state, but the standard deviation in charge distribution was larger than that of neutralized particles. The test method proposed in this study is expected to be used in various aerosol research fields because it can obtain simple information on the particle charge characteristics more easily and quickly than the existing test methods.

Aerosol particle mixing state, refractory particle number size distributions and emission factors in a polluted urban environment: Case study of Metro Manila, Philippines

Kecorius, S.,Madueno, L.,Vallar, E.,Alas, H.,Betito, G.,Birmili, W.,Cambaliza, M.O.,Catipay, G.,Gonzaga-Cayetano, M.,Galvez, M.C.,Lorenzo, G.,Muller, T.,Simpas, J.B.,Tamayo, E.G.,Wiedensohler, A. Pergamon Press ; Elsevier [distribution] 2017 Atmospheric environment Vol.170 No.-

Ultrafine soot particles (black carbon, BC) in urban environments are related to adverse respiratory and cardiovascular effects, increased cases of asthma and premature deaths. These problems are especially pronounced in developing megacities in South-East Asia, Latin America, and Africa, where unsustainable urbanization ant outdated environmental protection legislation resulted in severe degradation of urban air quality in terms of black carbon emission. Since ultrafine soot particles do often not lead to enhanced PM<SUB>10</SUB> and PM<SUB>2.5</SUB> mass concentration, the risks related to ultrafine particle pollution may therefore be significantly underestimated compared to the contribution of secondary aerosol constituents. To increase the awareness of the potential toxicological relevant problems of ultrafine black carbon particles, we conducted a case study in Metro Manila, the capital of the Philippines. Here, we present a part of the results from a detailed field campaign, called Manila Aerosol Characterization Experiment (MACE, 2015). Measurements took place from May to June 2015 with the focus on the state of mixing of aerosol particles. The results were alarming, showing the abundance of externally mixed refractory particles (soot proxy) at street site with a maximum daily number concentration of approximately 15000 #/cm<SUP>3</SUP>. That is up to 10 times higher than in cities of Western countries. We also found that the soot particle mass contributed from 55 to 75% of total street site PM<SUB>2.5</SUB>. The retrieved refractory particle number size distribution appeared to be a superposition of 2 ultrafine modes at 20 and 80 nm with a corresponding contribution to the total refractory particle number of 45 and 55%, respectively. The particles in the 20 nm mode were most likely ash from metallic additives in lubricating oil, tiny carbonaceous particles and/or nucleated and oxidized organic polymers, while bigger ones (80 nm) were soot agglomerates. To the best of the authors' knowledge, no other studies reported such high number concentration of ultrafine refractory particles under ambient conditions. Inverse modeling of emission factors of refractory particle number size distributions revealed that diesel-fed public utility Jeepneys, commonly used for public transportation, are responsible for 94% of total roadside emitted refractory particle mass. The observed results showed that the majority of urban pollution in Metro Manila is dominated by carbonaceous aerosol. This suggests that PM<SUB>10</SUB> or PM<SUB>2.5</SUB> metrics do not fully describe possible health related effects in this kind of urban environments. Extremely high concentrations of ultrafine particles have been and will continue to induce adverse health related effects, because of their potential toxicity. We imply that in megacities, where the major fraction of particulates originates from the transport sector, PM<SUB>10</SUB> or PM<SUB>2.5</SUB> mass concentration should be complemented by legislative measurements of equivalent black carbon mass concentration.

Comparisons of particle size measurement method for colloidal silica

Dong-Hyun Lee 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.2

Several methods have been used to measure the particle size and distribution of colloidal silica. It is an important parameter governing the proper function of many industrial products, for example, organic-inorganic hybrid coatings, ceramic coatings, paints, and inks, etc. Particle size distribution of commercial colloidal silica of eight was measured by TEM (transmission electron microscopy) or DLS (dynamic light scattering). The accuracy of the particle distribution is decreased when the colloidal silica is a mixture of approximately 50 nm particles and 100 nm particles. The particles less than ~50 nm may not be detected by DLS analyzer in the case of mixture sample. In order to investigate the difference in particle size distribution among measurement methods, we have compared and discussed particle size results measured from DLS, TEM, and BET (Brunauer-Emmett-Teller) analysis. In the TEM observation, 16 TEM images from one grid were compared and found out that the particle size distribution may vary based on the positions from which the particles are observed either scattered or agglomerated. We suggest combination of DLS, TEM and BET method to obtain the particle size distribution reflecting the dispersion, which represents the surface properties and aggregation state.

TEOS/O₂플라즈마 반응기에서 미립자 성장에 대한 실험적 분석

김동주,김교선 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

A study on the particle growth in TEOS/O2 plasma was performed, and particle size and its distribution was measured by the electrical aerosol analyzer (EAA), light scattering particle size analyzer and the particle size was also determined by SEM, the effects of process variables such as total gas flow rate, reactor pressure, supplied power and initial reactant concentration on the particle growth were investigated. From the EAA results, the particle size distribution is divided into three groups of the cluster size and the small and large size particles. The particle size distribution measured by the light scattering particle size analyzer becomes bimodal, because the cluster size particles smaller than 20nm in diameter cannot be detected by the light scattering particle size analyzer. The size of particles measured by the light scattering particle size analyzer is in good agreements with those by the SEM. Also we could understand that the particle formation is very sensitive to the changes of reactor pressure and reactant concentration. As the total gas flow rate increases, the particle size deceases because of the shorter residence time. As the reactor pressure, or the reactant concentration increases, the particle concentration increases and the particles grow more quickly by the faster coagulation between particles.

Numerical study on the particle distribution of coal for recovery of critical metals

Jha Vandana Kumari 한국자원공학회 2023 Geosystem engineering Vol.26 No.5

Coal is considered to be a significant resource of critical metals and minerals. Recovery of these critical metals is considered to be highly important in terms of advancement and technology. This paper presents a numerical study of the particle size distribution of coal and its impact on the recovery of critical metals. This study uses the computational fluid dynamics (CFD) model to simulate the transport and deposition of coal particles inside a helical domain, which can be used as a device for separating particles. The numerical study , based on the particle tracing model for fluid flow and particle tracing, is used to simulate the behavior of coal particles in a slurry under different flow conditions. The transient study for a six-turn helical coil domain is analyzed for different flow velocities ranging from 4000 � Re � 8000. The simulation results show that the particle size distribution of coal plays a crucial role in the recovery of critical metals. Additionally, the distribution of critical metals inside the domain varies with the size and density of the particles. It is observed that increasing the fluid velocity can significantly increase the recovery of critical metals. Finally, the transmission probability of particles remaining trapped inside the domain is also calculated, which could help in optimizing the helical geometry so that all the particles could come out of the flowing conduit. The number of particles coming out of the helical domain increases with the increase in flow rate. The results of the study show that the particle size distribution of coal plays a significant role in the recovery of critical metals. The findings can help guide the development of more efficient and cost-effective methods for extracting critical metals from coal.

실시간 에어로졸 측정장비를 이용한 대기 중 입자상 물질의 무게 농도 분포의 추정

지준호,배귀남 한국입자에어로졸학회 2013 Particle and Aerosol Research Vol.9 No.2

Real-time aerosol measuring instruments have been widely used for the measurement of atmospheric aerosol, diesel particulate matter, or material synthesis. A scanning mobility particle sizer (SMPS) measures the number size distribution of particles using electrical mobility detection technique. An aerodynamic particle sizer (APS) is used to determine the number concentration and the mean aerodynamic diameter of test particles. An electrical low-pressure impactor (ELPI) is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. In this study, the performance of these instruments were evaluated to assess their ability to obtain mass concentrations from particle number concentration measurements made as a function of particle size. The effect of determination of particle density on the measurement of mass concentration was investigated for the three instruments.

THE DISTRIBUTION OF DIGESTA PARTICLES AND MEAN PARTICLE SIZE OF DIGESTA OBTAINED FROM THE DIVERSE PARTS OF THE GASTROINTESTINAL TRACT OF RUMINANTS

Sekine, J.,Fujikura, T.,Oura, R.,Asahida, Y. Asian Australasian Association of Animal Productio 1992 Animal Bioscience Vol.5 No.1

Three cattle, a sheep and a goat were slaughtered to determine the distribution of digesta particles and mean size of digesta particles. Aliquot samples of digesta in the diverse sites of the digestive tracts were fractionated by a wet sieving technique. Fractionated particles were analyzed by the magnetic grid analyzer system constructed by authors. Results showed that the proportion of particles in digesta was similar among the omasum, abomasums cecum, colon and rectum, but that for the reticulo-ruminal digesta was different from the others. The pattern of the mass base frequency distribution of particles was also similar in the post-ruminal digesta. Average Heywood's diameter (the diameter equivalent to that of a circle with equal area to a projected area of a given particle) was about 1.2 mm in the reticulo-ruminal digesta and decreased to 0.65 mm for cattle or to about 0.35 mm for sheep and goat in the omasal digesta. Average Heywood's diameter was about the same in the post-ruminal digesta. It is concluded that mean particle size and particle distribution in digesta of the rectum or feces reflect those in digesta of the omasum.