Abd Alhamid R Sarhan
@swin.edu.au
Department of Mechanical and Product Design Engineering
Swinburne University of Technology
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
David Dodds, Abd Alhamid Rafea Sarhan, and Jamal Naser
Springer Science and Business Media LLC
AbstractThis paper presents a detailed experimental and numerical analysis of free-falling particle streams impacting a 45° inclined surface of differing materials. The particles used in this study were glass spheres with average diameters of 136 and 342 µm and a density of 2500 kg/m3. The three mass flow rates considered are 50, 150, and 250 grams per minute (gpm). The effect of wall material on the collision process was also analysed. Special attention was paid to the influence of wall roughness. Therefore, a plate of stainless steel with polished surface, an aluminium sheet, and a Perspex plate with similar properties to those of the rest of the wall sections were used. The experimental data were used to improve and validate a wall collision model in the frame of the Lagrangian approach. A new drag force formula that includes the effects of particle concentration as well as particle Reynolds number was implemented into commercially available codes from CFX4-4 package. It was found that the improved CFD model better predicted the experimental measurements for the particle rebound properties. The rough-wall model in these results showed greater effect on smaller particles than on larger particles. The results also showed that the improved CFD model predicted the velocity changes slightly better than the standard model, and this was confirmed by both the quantitative velocity comparisons and the qualitative concentration plots. Finally, the inclusion of the particle-particle collision was shown to be the dominant factor in providing the dispersion of the particles post collision. Without a sufficient particle-particle collision model, the standard model showed all particles behaving virtually identical, with the main particle stream continuing after the collision process.
Fardausur Rahaman, Abd Alhamid Rafea Sarhan, and Jamal Naser
MDPI AG
In this work, a three-dimensional CFD model for the gas–solid flow of two different particle sizes in a CFB riser coupled with a kinetic theory (KT) has been developed. The properties of the solid phases are calculated using the proposed multi-particle kinetic theory. The CFD model is implemented in the commercial CFD software CFX4.4. In the current model, one gas phase and two solid phases are used. However, the model is generalised for one carrier phase and N number of solid phases to enable a realistic particle size distribution in the system. The momentum, volume fraction and granular temperature equations are solved for each individual solid phase and implemented into the CFD model through user-defined functions (UDFs). The k-ε turbulence model is used in simulating the circulating fluidised bed model. For verification, simulation results obtained with the new KT model were compared with experimental data, and then the model was used for further analysis. It was found that the proposed multi-particle model can be used to calculate the properties of gas–solid systems with particles of different sizes and/or densities, removing the assumptions of previous models that required all the particles to be of an equal mass, size and density.
Abd Alhamid R. Sarhan, Melanie Franklyn, and Peter V. S. Lee
Informa UK Limited
While injuries sustained from body armour backface deformation (BFD) have not been well-documented in military injury trauma registries, data from US law enforcement officers, animal tests and currently available data pertaining to military combatants has shown that BFD can not only cause minor injuries, but also result in serious trauma. However, the nature and severity of injuries sustained depends on a multitude of factors including the projectile type, the impact location and velocity, and the specific type of body armour worn. The difficulties involved in current measurement techniques for ballistic testing has led researchers to seek alternative techniques to evaluate the level of protection from body armour, such as the finite element (FE) method. In the current study, a systematic review of the open literature was undertaken using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. The aim was to summarise the literature pertaining to the development and application of FE models to investigate body armour BFD and behind armour blunt trauma (BABT), and included FE models representing the projectile, clay-based mediums, ballistic gelatine and the human torso. Using the keywords 'behind armour*', 'ballistic blunt trauma', 'BABT', 'backface signature', 'backface deformation', 'BFS', 'BFD', 'wound ballistic', 'ballistic impact testing', 'body armour', 'bullet proof vest', 'ballistic vest', 'Finite Element*' and 'FE', an electronic database search of EBSCOhost, Google Scholar, ProQuest, Scopus, Standards, Web of Science and PubMed was conducted, and included peer-reviewed journal articles, review papers, research reports, conference papers, and MSc or PhD theses. While this research demonstrates the potential of FE analysis for recreating realistic blunt impact scenarios and enhancing the current understanding of BABT mechanisms, a common limitation in most studies is the lack of validation. Thus, in order to address this issue, it is proposed that injury predictions from FE models be correlated with trauma data from soldiers who have sustained BABT. Consequently, pressure and energy distributions within the organs can be used to interpret the effects of non-penetrating ballistic impacts on the human torso. Bridging the gap between simulation and real-world data is essential in order to validate FE models and enhance their utility in optimising body armour design and employing injury mitigation strategies.
David Dodds, Abd Alhamid R. Sarhan, and Jamal Naser
MDPI AG
In the simulation of dilute gas-solid flows such as those seen in many industrial applications, the Lagrangian Particle Tracking method is used to track packets of individual particles through a converged fluid field. In the tracking of these particles, the most dominant forces acting upon the particles are those of gravity and drag. In order to accurately predict particle motion, the determination of the aforementioned forces become of the upmost importance, and hence an improved drag force formula was developed to incorporate the effects of particle concentration and particle Reynolds number. The present CFD study examines the individual effects of particles located both perpendicular and parallel to the flow direction, as well as the effect of a particle entrain within an infinite matrix of evenly distributed particles. Results show that neighbouring particles perpendicular to the flow (Model 2) have an effect of increasing the drag force at close separation distances, but this becomes negligible between 5–10 particle diameters depending on particle Reynolds number (Rep). When entrained in an infinite line of particles co-aligned with the flow (Model 1), the drag force is remarkably reduced at close separation distances and increases as the distance increases. The results of the infinite matrix of particles (Model 3) show that, although not apparent in the individual model, the effect of side particles is experienced many particle diameters downstream.
Abd Alhamid R. Sarhan, Parisa Naser, and Jamal Naser
Springer Science and Business Media LLC
Abstract In light of the COVID-19 pandemic, it is becoming extremely necessary to assess respiratory disease transmission in passenger cars. This study numerically investigated the human respiration activities’ effects, such as breathing and speaking, on the transport characteristics of respiratory-induced contaminants in passenger car. The main objective of the present study is to accurately predict when and who will get infected by coronavirus while sharing a passenger car with a patient of COVID-19 or similar viruses. To achieve this goal, transient simulations were conducted in passenger car. We conducted a 3D computational fluid dynamics (CFD)-based investigation of indoor airflow and the associated aerosol transport in a passenger car. The Eulerian-Eulerian flow model coupled with k-ε turbulence approach was used to track respiratory contaminants with diameter ≥ 1 μm that were released by different passengers within the passenger car. The results showed that around 6.38 min, this is all that you need to get infected with COVID-19 when sharing a poorly ventilated car with a driver who got coronavirus. It also has been found that enhancing the ventilation system of the passenger car will reduce the risk of contracting Coronavirus. The predicted results could be useful for future engineering studies aimed at designing public transport and passenger cars to face the spread of droplets that may be contaminated with pathogens.
Abd Alhamid R. Sarhan, Parisa Naser, and Jamal Naser
MDPI AG
The COVID-19 pandemic has caused panic and chaos that modern society has never seen before. Despite their paramount importance, the transmission routes of coronavirus SARS-CoV-2 remain unclear and a point of contention between the various sectors. Recent studies strongly suggest that COVID-19 could be transmitted via air in inadequately ventilated environments. The present study investigates the possibility of the aerosol transmission of coronavirus SARS-CoV-2 and illustrates the associated environmental conditions. The main objective of the current work is to accurately predict the time duration of getting an infection while sharing an indoor space with a patient of COVID-19 or similar viruses. We conducted a 3D computational fluid dynamics (CFD)-based investigation of indoor airflow and the associated aerosol transport in a restaurant setting, where likely cases of airflow-induced infection of COVID-19 caused by asymptomatic individuals were reported in Guangzhou, China. The Eulerian–Eulerian flow model coupled with the k-Ɛ turbulence approach was employed to resolve complex indoor processes, including human respiration activities, such as breathing, speaking, and sneezing. The predicted results suggest that 10 minutes are enough to become infected with COVID-19 when sharing a Table with coronavirus patients. The results also showed that although changing the ventilation rate will improve the quality of air within closed spaces, it will not be enough to protect a person from COVID-19. This model may be suitable for future engineering analyses aimed at reshaping public spaces and indoor common areas to face the spread of aerosols and droplets that may contain pathogens.
A. R. Sarhan, P. Naser, and J. Naser
Springer Science and Business Media LLC
Many countries worldwide have taken early measures to combat the spread of coronavirus SARS-CoV-2 by implementing social distancing measures. The main aim of the present work is to examine the feasibility of social distancing (i.e. 1.5 m) in closed spaces taking into account the possibility for airborne transmission of SARS-CoV-2. A 3D numerical model of human respiration activities, such as breathing and speaking within indoor environments has been simulated with CFD software AVL FIRE R2020. The Eulerian-Eulerian flow model coupled with k-Ɛ approach were employed. With regard to breathing mode, the infected individual is modelled to be breathing 10 times per minute with a pulmonary rate of 6 L/min with a sinusoidal cycle. The present investigation considered air and droplets/particles as separate phases. The predicted results suggested that the social distancing (i.e. 1.5 m) is not adequate to reduce the risk of contracting diseases like COVID-19, especially when staying for a longer period in an indoor environment. The person directly facing the infected person inhaled more than 1000 aerosol droplets within 30 min. The results also showed approximately 65 % decrease in the number of inhaled droplets the room is well ventilated. Within an indoor environment, 1.5 m distance will not be enough to protect the healthy individuals from the droplets coming from an infected person. Also, the situation may become worse with the change of the air ventilation system.
Dhefaf Raisan Faisal, John Aunna, Abd Alhamid Sarhan, and Jamal Naser
Langmuir American Chemical Society (ACS)
We present a numerical simulation using three-dimensional microscale models to illustrate flow dynamics through different foam geometries. These were designed to represent the flow with various liquid volume fractions throughout the Plateau border (PB) and node system within the "dry" limit and throughout the two nodes and PB system within the "wet" limit. Most surfaces in the models involve a gas-liquid interface. Here, the stress-balance boundary condition was applied to achieve coupling between the surface and bulk. The three-dimensional Navier-Stokes equation along with the continuity equation was solved using the finite volume approach, and a qualitative evaluation of flow velocities in different foam geometries was obtained. The numerical results were validated against the available experimental results for foam permeabilities in the nodes and PBs. Discrepancies were expected between the simulated and empirical values as the latter values were obtained by considering only the viscous losses in the PBs. Furthermore, the scaled resistance to flow for varying gas-liquid interface mobilities and liquid fractions was studied. The individual geometrical characteristics of the node and PB components were compared to investigate the PB- and node-dominated flow regimes numerically. Additionally, more accurate information was obtained for comparing the average flow velocities within the node-PB and the two-node-PB systems, providing a better understanding of the effect of a gas-liquid interface on foam flow. We eventually show that when the foam geometry is correctly described, the relative effect of the geometrical factors of the PB and node components of system models can be evaluated, allowing a numerical flow simulation with a unique parameter-the Boussinesq number (Bo).
Abd Alhamid Rafea Sarhan, M. Rezwanul Karim, and Jamal Naser
Wiley
D. Dodds, A.R. Sarhan, and J. Naser
Chemical Engineering Research and Design Elsevier BV
Abstract The influence of particle concentration on the drag force of a particle deserves attention when using the Lagrangian Particle Tracking methods for the prediction of industrial type gas-solid flows. The Lagrangian approach is best suited to applications where the solids volume fraction is low, and the effect of particle concentration can be ignored. In the present work, a 3D time dependent numerical analysis is performed to study the effect of Lagrangian model improvements to replicate experimental studies of straight horizontal pipe flow and flow through a 90° horizontal-to-vertical bend. The present predictions are compared with published experimental data of Tsuji and Morikawa (1982) , and Yilmaz (1997) . Special attention is paid to influence of particle mass-flow rates and conveying velocity on the particle motion within the system. This study used a CFX-4 package, where the ability to modify the code was necessary to include particle model improvements. These improvements included implementing a newly drag force model developed as a part of this research work. Particle-wall collision and particle-particle collision models developed by Sommerfeld (1992) , and Sommerfeld (2001) are also implemented in the CFD model. The standard k–e dispersed turbulence model was utilized as the predictions for the gas phase only gave similar predicted axial velocity compared to the more computationally demanding Reynolds stress model. The results showed that the inclusion of the various improvements lead to reasonable predicted particle velocities in both the upper and lower regions of the straight horizontal pipe which denote the dilute and dense regions respectively. It was also found that the inclusion of the rough-wall particle wall collision model decreases the axial particle velocity in the lower region where the bulk of the particle wall collisions occur. While the inclusion of the particle collision models tends to disperse the particles away from the lower region resulting in a less dense lower section and a distinctly more homogenous particle distribution compared with the standard model predictions. Further, the increase in particle concentration leads to a reduction in axial velocity due to a loss of momentum through particle-wall and particle-particle collisions. Finally, the improved CFD model best predicted both the reduction and increase in the particle velocities in the different regions.
D. Dodds, A.R. Sarhan, and J. Naser
Powder Technology Elsevier BV
Abstract The influence of particle concentration on the drag force of a particle deserves attention when using the Lagrangian particle tracking methods for the prediction of industrial type gas-solid flows. The Lagrangian approach is best suited to applications where the solids volume fraction is low and the effect of particle concentration can be ignored. The paper successfully predicted the available experimental findings on the effects of particle arrangements on drag force. These successful predictions lead to the development of a new coefficient of drag for particles in cluster. Then a combined experimental and numerical study of free-falling particles was carried out in this study to investigate the behaviour of particles in cluster. The new coefficient of drag proposed in this study was used in the numerical simulations. The study highlighted the increase in terminal velocities of particles within cluster streams. The numerical simulations, obtained with the newly proposed coefficient of drag, showed improved results for the average size particles used. The improvements obtained for larger particle size particles were not as impressive.
A.R. Sarhan, A.M. Homadi, and J. Naser
Separation and Purification Technology Elsevier BV
Abstract In the current study, computational fluid dynamics (CFD) simulations were used to investigate the detachment rate of hydrophobic particles in the froth phase of a flotation column reactor. A stable froth was formed by injecting the air through a slurry of water at 20 °C and silica (SiO2) solid particles. The slurry inside pulp zone was assumed to be perfectly mixed. A number of sub models representing various processes of the bubble-bubble interaction and bubble-particle interaction in the pulp and froth zones were included in the present work through user defined subroutines coupled to commercial CFD software AVL FIRE v2017. Modelling calculations were conducted using a Eulerian–Eulerian multiphase approach to solve multiphase flow equations for the conservation of mass, momentum and turbulence quantities. The standard k–e dispersed turbulence model was used in the present study for its accuracy. The effect of solid concentration and gas flow rate on the detachment of hydrophobic particles from the froth was studied. The predicted results were in reasonable agreement with experimental observations and available literature results. It was found that the froth height increased with the increase of gas flow rate, and decreased with the increasing of solid concentration. The dynamic froth stability factor was observed to decrease by 16–35 % with the increase of gas flow rate. Depending on the operating conditions, the increase in the detachment rate was in the 25–225% range as Q was increased from 1.4 L/min to 2.1 L/min. The main observation of the present study was that the increase of solid concentration and gas flow rate have a significant effect on the detachment rate of hydrophobic particles in froth layer and thus its stability.
Md Rezwanul Karim, Arafat Ahmed Bhuiyan, Abd Alhamid Rafea Sarhan, and Jamal Naser
Elsevier BV
A comprehensive 3D CFD model has been developed for analyzing thermal conversion of woody biomass fuel in a large reciprocating grate boiler under air/oxy-fuel condition. A number of sub-models representing solid conversion processes such as drying, devolatilisation and char combustion, gas phase flow and chemical reactions, solid and gas phase interaction through heat and mass transfer and bed movement is included in the model by user defined subroutines. The model has been validated by simulating a moving grate furnace from literature and comparing results with this reference experimental study. In this work, wet woody biomass fuel combustion is investigated under different oxy-fuel condition. Three different oxy-fuel cases have been investigated with 25% O2 (OF 25), 27% O2 (OF 27) and 30% O2 (OF 30) concentration by volume in the feed oxidizer gas with CO2 as recycled flue gas. Furnace operating condition is varied by changing air mass flow and inlet oxidizer gas composition, but all other operating conditions and furnace thermal load were kept constant. The effect of O2/recycled flue gas (CO2) ratios on flame temperature distribution, species concentration, char burnout and fuel consumption have been studied in detail and substantial differences were noticed comparing with the air-fired case. The numerical prediction showed that, gas temperature profile OF 25 case is closer to the referenced air fired combustion. The gas flame temperature has increased with O2 concentration rise, reaching maximum temperature at OF 30 case. CO2 concentration was increased to almost three times than air fired case due to use of CO2 in the feed gas. Increased CO2 concentration in the furnace has augmented char combustion rate and fuel consumption. Maximum fuel consumption was observed for OF 30 case where the fuel bed distribution over the grate was found minimum. Therefore, biomass bed combustion under oxy-fuel condition can provide better flame temperature and char burning to improve combustion condition.
M.F. Rahaman, A.R. Sarhan, and J. Naser
Powder Technology Elsevier BV
Abstract In this paper, the kinetic Theory (KT) for multi-particulate flow has been further extended by incorporating contributions from the rotary movement of particles on key flow parameters. The balance laws and constitutive relations for granular mixtures have been re-derived to incorporate contributions from both linear and angular movement of particles in determining the flow parameters. The computed results show similar trend with the existing KT based on equal granular temperature assumption. However, with different granular temperature, the change in flow parameters shows dissimilar trend compared with the previous KT. Flow properties like collisional stress, bulk viscosity of phase i decreases with the increase of the granular temperature of species j and shear viscosity and dilute viscosity increases with the increase of granular temperature of species j. A detail comparison of the computed results for a range of flow properties, based on both equal and unequal granular temperature has been presented in this paper.
A. R. Sarhan, Md. Abdul Karim Miah, and J. Naser
AIP Publishing
A.R. Sarhan, M.R. Karim, Z.K. Kadhim, and J. Naser
Elsevier BV
Abstract Vibration effects on thermal performances of the rectangular flat plate under natural convection condition are experimentally investigated in both horizontal and slightly inclined from horizontal orientations in multiple angles. The effects of Rayleigh number and vibrational Reynolds number on the average heat-transfer coefficient are also examined. The Aluminium made plate was subjected to sinusoidal vibration in the vertical plane. The test sample was heated under a constant heat flux. The amplitude of vibration was varied from 1.5 to 7.5 mm and the frequency of vibration from 0 to 16 Hz. From the results of the experiments, it is observed that the average heat-transfer coefficient increases linearly with increasing Rayleigh number for different orientation angles. It was also found that the average heat-transfer coefficient is much higher for the cases when the plate is horizontal, and it decreases when the orientation angle value was increased. Such as the average heat-transfer coefficient decreased by approximately 13% for 30° orientation case. The measured result further showed that the average heat-transfer coefficient in the vertical position is lower than the average heat-transfer coefficient in the horizontal position and slightly higher than the other orientation angles (i.e. 30°, 45° and 60°). Finally, it was found that the increases in oscillation frequencies lead to an increase in the average heat-transfer coefficient and the maximum increase was obtained in the horizontal position and higher frequencies. However, the average heat-transfer coefficient decreases with increasing the vibration frequencies when the plate was in the vertical position.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract Bubble surface area flux (Sb) is one of the main design parameter in flotation column that typically employed to describe the gas dispersion properties, and it has a strong correlation with the flotation rate constant. There is a limited information available in the literature regarding the effect of particle type, density, wettability and concentration on Sb. In this paper, computational fluid dynamics (CFD) simulations are performed to study the gas–liquid–solid three-phase flow dynamics in flotation column by employing the Eulerian–Eulerian formulation with k-e turbulence model. The model is developed by writing Fortran subroutine and incorporating then into the commercial CFD code AVL FIRE, v.2014. This paper studies the effects of superficial gas velocities and particle type, density, wettability and concentration on Sb and bubble concentration in the flotation column. The model has been validated against published experimental data. It was found that the CFD model was able to predict, where the response variable as indicated by R-Square value of 0.98. These results suggest that the developed CFD model is reasonable to describe the flotation column reactor. From the CFD results, it is also found that Sb decreased with increasing solid concentration and hydrophobicity, but increased with increasing superficial gas velocity. For example, approximately 28% reduction in the surface area flux is observed when coal concentration is increased from 0 to 10%, by volume. While for the same solid concentration and gas flow rate, the bubble surface area flux is approximately increased by 7% in the presences of sphalerite. A possible explanation for this might be that increasing solid concentration and hydrophobicity promotes the bubble coalescence rate leading to the increase in bubble size. Also, it was found that the bubble concentration would decrease with addition of hydrophobic particle (i.e., coal). For instance, under the same operating conditions, approximately 23% reduction in the bubble concentration is predicted when the system was working with hydrophobic particles. The results presented are useful for understanding flow dynamics of three-phase system and provide a basis for further development of CFD model for flotation column.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract Computational fluid dynamics (CFD) has been widely used to study the hydrodynamics of bubble column reactors. However, the interaction between the different phases, which are in fact intimately linked, and the effect of their physical properties on the dynamics of the bubbles are still not well understood. In this study, the population balance equation (PBE) is coupled with CFD model to investigate the effect of liquid and gas phases physico-chemical properties on bubbles formation and the hydrodynamic characteristics in bubble column reactors. The coupling is realized using AVL FIRE v.2017 software, and the predicted results are validated against published experimental data. User subroutines are written using FORTRAN to incorporate the scalar transport equation source term for bubble break-up and coalescence. The predicted results were in reasonable agreement with experimental observations and available literature results, since the model has been able to predict the effect of gas flow rate on the gas holdup in bubble column within the range of ±7%. The simulations showed that the average gas holdup increase with the increase in superficial gas velocity and gas phase density, and decrease with the increase in liquid phase density. It was also found that Sauter mean bubble diameter increases with the increase in liquid density and decreases with the increase in gas density. Finally, the bubble rise velocity increased when water was used as a continuous phase. On the other hand, the increase in gas density causes a decrease in the bubble rise velocity.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract A new approach for simulating the formation of a froth layer in a slurry bubble column is proposed. Froth is considered a separate phase, comprised of a mixture of gas, liquid, and solid. The simulation was carried out using commercial flow simulation software (FIRE v2014) for particle sizes of 60–150 μm at solid concentrations of 0–40 vol%, and superficial gas velocities of 0.02–0.034 m/s in a slurry bubble column with a hydraulic diameter of 0.2 m and height of 1.2 m. Modelling calculations were conducted using a Eulerian–Eulerian multiphase approach with k–e turbulence. The population balance equations for bubble breakup, bubble coalescence rate, and the interfacial exchange of mass and momentum were included in the computational fluid dynamics code by writing subroutines in Fortran to track the number density of different bubble sizes. Flow structure, radial gas holdup, and Sauter mean bubble diameter distributions at different column heights were predicted in the pulp zone, while froth volume fraction and density were predicted in the froth zone. The model was validated using available experimental data, and the predicted and experimental results showed reasonable agreement. To demonstrate the effect of increasing solid concentration on the coalescence rate, a solid-effect multiplier in the coalescence efficiency equation was used. The solid-effect multiplier decreased with increasing slurry concentration, causing an increase in bubble coalescence efficiency. A slight decrease in the coalescence efficiency was also observed owing to increasing particle size, which led to a decrease in Sauter mean bubble diameter. The froth volume fraction increased with solid concentration. These results provide an improved understanding of the dynamics of slurry bubble reactors in the presence of hydrophilic particles.
A. R. Sarhan, J. Naser, and G. Brooks
Informa UK Limited
ABSTRACT The available computational fluid dynamics (CFD) models for multi-phase bubble column ignore the effects of attached particles on the dynamics of the bubbles. Bubbles become heavier with the attachment of solid particles which has significant impact on their buoyancy, and hence their flow dynamics. The present paper endeavours to simulate multi-phase slurry bubble column accounting for the effect of bubble–particle aggregate density on the flow dynamics in a multi-phase slurry bubble column. A CFD model was developed and validated against air–paraffin oil data at ambient conditions to understand the hydrodynamics of a three-phase slurry bubble column.
Abd Alhamid R. Sarhan, M. R. Rezwanul Karim, Jamal Naser, and Geoffrey Brooks
Author(s)
In this study, a numerical investigation has been conducted to describe the pulp zone properties by predicting the local gas holdup and bubble size distribution accounting for the effect of bubble-particle aggregate on the flow dynamic of slurry bubble column. Modelling calculations have been conducted using Eulerian–Eulerian multiphase approach with k-e turbulence for the liquid phase. This work is carried out considering a finite volume method (FVM) tool using AVL FIRE, v.2014 coupled with the user defined subroutines especially for the change in the concentration number of different bubble sizes due to bubble break-up and coalescence. This code is validated comparing the experimental gas holdup with the numerically predicted data and a reasonable agreement has been found. In the current model, the effect of attachment and detachment process was included into the kinetic equation.by transferring the mass of attached particles to the gas bubble-particle aggregate. The results of this study show that the ...
A. R. Sarhan, J. Naser, and G. Brooks
Informa UK Limited
ABSTRACT A computational fluid dynamic (CFD) model has been developed to incorporate pulp and froth zones into one model. In the present research, froth was considered as a separate phase comprised of a mixture of gas, liquid and solids. Considering the froth phase as a separate phase, allowed the incorporation of pulp and froth zones into one model by tracking the formation and destruction of the froth phase due to mass exchange between the pulp and froth. Bubble break-up and coalescence were taken into account in the pulp zone, by employing user functions, written using FORTRAN. The effect of bubble coalescence process due to film rupture was considered in the froth phase. The variation in the concentration of attached particles due to attachment and detachment processes were also taken into account. The CFD model predicted the height of froth layer, the concentration of different bubble sizes in both pulp and froth zones, and finally the multiphase flow phenomena in the slurry column. Froth height was found to increase with the increase of gas flow rate while increasing solid concentration decreased froth height.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract A Computational Fluid Dynamics (CFD) model was developed and validated against published experimental data to understand the effect of slurry concentration on bubbles’ coalescence process in flotation cell. The existing flow field was modelled for two- phase (gas-liquid) and three-phase (gas-liquid-solids). The simulations were carried out using the commercial flow simulation software AVL-FIRE 2009.2 for Jg= 0.94-5.01 cm s-1 Cs= 0-200 kg m-3, respectively. Modelling calculations have been conducted using Eulerian–Eulerian multiphase model with k-ɛ turbulence model for the liquid phase. In the present study, the population balance equation for bubble break-up and bubble coalescence rate and the interfacial exchange of mass and momentum as well as bubble-particles attachment and detachment have been included in the CFD code by writing subroutines in FORTRAN. Comparisons of the predicted results against measured gas holdups and axial pressure profile show reasonable agreement without using any fitting parameter. With the increase of slurry concentration, the gas holdup in a flotation column decreased. These results are in line with those of previous studies. The results also show that the addition of solid particles reduced the size of bubbles in a flotation column.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract A Computational Fluid Dynamics (CFD) model of flotation column was developed and validated against published experimental data. The model is based on an Eulerian multi-fluid formulation with k – ɛ turbulence model and includes three phases: gas bubbles, liquid and solid particle suspended in the liquid. The model is developed by writing FORTRAN subroutine and incorporating then into the commercial CFD code AVL FIRE, v.2014. The gas holdup in flotation column was predicted as a function of superficial gas velocity and solids concentration. The effect of particle type, density, wettability and concentration on gas holdup and bubble hydrodynamics (i.e. bubble size distribution, and attached particle density) were studied. The rate of removal of particles from the pulp zone was obtained with kinetic equations for the three sub-processes: collision, attachment, and detachment involving number density of bubbles and particle concentrations, which were also calculated in this model. As confirmed by the comparisons with available data, the modelling methodology proposed in this work represents the physics of flotation column consistently, since the CFD model correctly predicts the experimental effects of gas flow rate and solid concentration on gas holdup within the range of ±20%. It was found that the addition of hydrophobic particles to the air/water mixture promotes bubble coalescence and, therefore, reduces the gas holdup, while the addition of hydrophilic particles suppresses bubble coalescence and increases the gas holdup. It was also found that the increase of gas flow rate leads to an increase in the attached particle density due to the increase of the concentration number of bubbles that were available for the attachment process. Further, the increase of hydrophobic particles concentration led to an increase in the attached particle density.
A.R. Sarhan, J. Naser, and G. Brooks
Elsevier BV
Abstract A computational fluid dynamics (CFD) model was used to investigate the influence of solid concentration on bubbles' coalescence rate in flotation cell using Eulerian–Eulerian approach. CFD simulations were performed with AVL-FIRE 2009.2, and the existing flow field was modelled for two-phase (gas–liquid) and three-phase (gas–liquid–solids). The liquid phase was treated as a continuum and the gas phase (bubbles) and solid particles were considered as dispersed phases. The population balance equation for bubble break-up and bubble coalescence rate and the interfacial exchange of mass and momentum as well as bubble–particle attachment and detachment have been included in the CFD code by writing subroutines in FORTRAN. This investigation focused on studying the effect of solid particle on bubble break-up and bubble coalescence rate in the flotation cell at different superficial gas velocity values. The results predict that the presence of solid particles reduced the gas holdup in a flotation column. With the increase of the superficial gas velocity the size of gas bubble that were generated inside the cell decreased, leading to increased gas holdup. The result also shows that the Sauter mean diameter of bubbles decreases with the increase of solid concentration. Reasonably good agreement was obtained between simulation and experimental results for the effect of solid concentration on gas hold-up and axial pressure profile. In the current study, the froth zone was neglected, only the pulp zone was simulated. This is a deficiency of the present model, as the pulp is only one part of the flotation process, and it is physically linked to the froth. However, the model is a step towards gaining a complete view to describing the processes within a flotation cell through inspect the impact of presence of solid particles on the bubble coalescence rate under the different operation conditions.