The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Mark L Brusseau - One of the best experts on this subject based on the ideXlab platform.
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non ideal behavior during complete dissolution of organic Immiscible Liquid 2 ideal porous media
Water Air and Soil Pollution, 2010Co-Authors: M K Mahal, Asami Murao, Gwynn R Johnson, A E Russo, Mark L BrusseauAbstract:Column experiments were conducted using ideal natural sands and stainless-steel beads to examine the complete dissolution behavior of an organic Immiscible Liquid. Trichloroethene was used as the representative organic Liquid. The elution curves exhibited multi-step behavior, with multiple extended periods of relatively constant contaminant flux. These secondary steady-state stages occurred at concentrations several orders-of-magnitude below aqueous solubility for the well-sorted sands. In contrast, the secondary steady-state stages occurred within 1 log of aqueous solubility for the poorly sorted sand. The non-ideal behavior is hypothesized to result from constraints to hydraulic accessibility of the organic Liquid to flowing water, which may be expected to be mediated by the pore-scale configuration of the flow field and the fluid phases.
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mass removal and mass flux reduction behavior for idealized source zones with hydraulically poorly accessible Immiscible Liquid
Chemosphere, 2008Co-Authors: Mark L Brusseau, Erica L Difilippo, J Marble, M OostromAbstract:A series of flow-cell experiments was conducted to investigate aqueous dissolution and mass-removal behavior for systems wherein Immiscible Liquid was non-uniformly distributed in physically heterogeneous source zones. The study focused specifically on characterizing the relationship between mass flux reduction and mass removal for systems for which Immiscible Liquid is poorly accessible to flowing water. Two idealized scenarios were examined, one wherein Immiscible Liquid at residual saturation exists within a lower-permeability unit residing in a higher-permeability matrix, and one wherein Immiscible Liquid at higher saturation (a pool) exists within a higher-permeability unit adjacent to a lower-permeability unit. The results showed that significant reductions in mass flux occurred at relatively moderate mass-removal fractions for all systems. Conversely, minimal mass flux reduction occurred until a relatively large fraction of mass (>80%) was removed for the control experiment, which was designed to exhibit ideal mass removal. In general, mass flux reduction was observed to follow an approximately one-to-one relationship with mass removal. Two methods for estimating mass-flux-reduction/mass-removal behavior, one based on system-indicator parameters (ganglia-to-pool ratio) and the other a simple mass-removal function, were used to evaluate the measured data. The results of this study illustrate the impact of poorly accessible Immiscible Liquid on mass-removal and mass-flux processes, and the difficulties posed for estimating mass-flux-reduction/mass-removal behavior.
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source zone characterization of a chlorinated solvent contaminated superfund site in tucson az
Journal of Contaminant Hydrology, 2007Co-Authors: Mark L Brusseau, Nicole T Nelson, Zhihui Zhang, J E Blue, J W Rohrer, T AllenAbstract:An extensive site-characterization project was conducted at a large chlorinated-solvent contaminated Superfund site in Tucson, AZ. The project consisted of several components, including traditional site-characterization activities, tracer tests, laboratory experiments conducted with core material collected from the site, and mathematical modeling. The primary focus of the work presented herein is the analysis of induced-gradient contaminant elution tests conducted in a source zone at the site, investigation of the potential occurrence of Immiscible Liquid in the saturated zone, characterization of the relationship between mass flux reduction and mass removal, and evaluation of the impact of source-zone management on site remediation. The results of the present study, along with those of prior work, indicate that Immiscible Liquid is likely present in the saturated zone at the site source zones. Extensive tailing and rebound was observed for the contaminant-elution tests, indicating nonideal transport and mass-transfer behavior. The elution data were analyzed with a source-zone-scale mathematical model, and the results indicated that nonideal Immiscible-Liquid dissolution was the primary cause of the observed behavior. The time-continuous relationship between mass flux reduction and mass removal associated with the plume-scale pump-and-treat operation exhibited an initial large drop in mass flux with minimal mass removed, followed by a period of minimal mass flux reduction and a second period of large reduction. This behavior reflects the impact of both source-zone and aqueous-plume mass removal dynamics. Ultimately, a greater than 90% reduction in mass flux was achieved for a mass removal of approximately 50%. The influence of source-zone management on site remediation was evaluated by conducting two predictive simulations, one for which the source zones were controlled and one for which they were not. A plume-scale model was used to simulate the composite contaminant concentrations associated with groundwater extracted with the pump-and-treat system, which were compared to measured data. The information generated from this study was used to enhance the site conceptual model, help optimize operation of the pump-and-treat system, and evaluate the utility of source-zone remediation.
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characterizing pore scale dissolution of organic Immiscible Liquid in natural porous media using synchrotron x ray microtomography
AGU Fall Meeting Abstracts, 2006Co-Authors: G Schnaar, Mark L BrusseauAbstract:The objective of this study was to characterize the pore-scale dissolution of organic Immiscible-Liquid blobs residing within natural porous media. Synchrotron X-ray microtomography was used to obtain high-resolution, three-dimensional images of the aqueous, organic-Liquid, and solid phases residing in columns packed with one of two porous media. Images of the packed columns were obtained after a stable, discontinuous distribution (e.g., residual saturation) of the organic Liquid (trichloroethene) had been established, and three subsequent times during column flushing. These data were used to characterize the morphology of the organic-Liquid blobs as a function of dissolution, and to quantify changes in total organic-Liquid volume, surface area, and water-organic Liquid interfacial area. The dissolution dynamics of individual blobs appeared to be influenced by the local pore configuration. In addition to dissolution-induced shrinkage, some blobs were observed to separate into multiple distinct subunits. The median blob size decreased by approximately a factor of 2 at the point where approximately 90% of the initial organic-Liquid volume had been removed. The ratio of capillary associated interfacial area to total water-organic Liquid interfacial area increased by 50% at the point where approximately 95% of the initial mass had been removed. A nearly linear relationship was observed between both total and capillary associated interfacial area and organic Liquid volumetric fraction. Changes in the measured aqueous-phase trichloroethene effluent concentrations were well correlated with changes in the volume, surface area, and number of blobs. The effluent concentration data were adequately described by a first-order mass transfer expression employing a constant value of the mass-transfer coefficient, with values for the water-organic Liquid interfacial area obtained independently from the microtomography data.
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characterizing pore scale configuration of organic Immiscible Liquid in multiphase systems with synchrotron x ray microtomography
Vadose Zone Journal, 2006Co-Authors: G Schnaar, Mark L BrusseauAbstract:The objective of this study was to examine the pore-scale distribution and morphology of organic Immiscible Liquid in natural porous media containing three Immiscible fluids. High-resolution, three-dimensional images of an organic Liquid (tetrachloroethene) in both three-phase (water–air–organic Liquid) and two-phase (water–organic Liquid) systems were obtained using synchrotron X-ray microtomography. These data were used to quantitatively characterize the morphology of the organic Liquid residing within columns packed with one of three natural, sandy porous media. Organic-Liquid blobs varied greatly in both size and shape, ranging from small, single spheres (≥0.03 mm in diameter) to large, amorphous ganglia with mean lengths of 4 to 5 mm. Singlets comprised the greatest number of blobs, whereas the large ganglia, while much fewer in number, comprised the majority of the organic-Liquid surface area and volume. A significant portion of the organic Liquid in the three-phase systems was observed to exist as lenses and films in contact with air. These features were not observed in the two-phase water–organic Liquid systems. The median of the blob-frequency distributions was smaller and the variance larger for the three-phase systems. In addition, the global specific surface areas of the organic Liquid were greater for the three-phase systems. These differences are attributed to the presence of the organic-Liquid lenses and films for the three-phase systems.
Zhihui Zhang - One of the best experts on this subject based on the ideXlab platform.
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source zone characterization of a chlorinated solvent contaminated superfund site in tucson az
Journal of Contaminant Hydrology, 2007Co-Authors: Mark L Brusseau, Nicole T Nelson, Zhihui Zhang, J E Blue, J W Rohrer, T AllenAbstract:An extensive site-characterization project was conducted at a large chlorinated-solvent contaminated Superfund site in Tucson, AZ. The project consisted of several components, including traditional site-characterization activities, tracer tests, laboratory experiments conducted with core material collected from the site, and mathematical modeling. The primary focus of the work presented herein is the analysis of induced-gradient contaminant elution tests conducted in a source zone at the site, investigation of the potential occurrence of Immiscible Liquid in the saturated zone, characterization of the relationship between mass flux reduction and mass removal, and evaluation of the impact of source-zone management on site remediation. The results of the present study, along with those of prior work, indicate that Immiscible Liquid is likely present in the saturated zone at the site source zones. Extensive tailing and rebound was observed for the contaminant-elution tests, indicating nonideal transport and mass-transfer behavior. The elution data were analyzed with a source-zone-scale mathematical model, and the results indicated that nonideal Immiscible-Liquid dissolution was the primary cause of the observed behavior. The time-continuous relationship between mass flux reduction and mass removal associated with the plume-scale pump-and-treat operation exhibited an initial large drop in mass flux with minimal mass removed, followed by a period of minimal mass flux reduction and a second period of large reduction. This behavior reflects the impact of both source-zone and aqueous-plume mass removal dynamics. Ultimately, a greater than 90% reduction in mass flux was achieved for a mass removal of approximately 50%. The influence of source-zone management on site remediation was evaluated by conducting two predictive simulations, one for which the source zones were controlled and one for which they were not. A plume-scale model was used to simulate the composite contaminant concentrations associated with groundwater extracted with the pump-and-treat system, which were compared to measured data. The information generated from this study was used to enhance the site conceptual model, help optimize operation of the pump-and-treat system, and evaluate the utility of source-zone remediation.
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nonideal transport of reactive contaminants in heterogeneous porous media 7 distributed domain model incorporating Immiscible Liquid dissolution and rate limited sorption desorption
Journal of Contaminant Hydrology, 2004Co-Authors: Zhihui Zhang, Mark L BrusseauAbstract:The purpose of this work is to present a distributed-domain mathematical model incorporating the primary mass-transfer processes that mediate the transport of Immiscible organic Liquid constituents in water-saturated, locally heterogeneous porous media. Specifically, the impact of grain/pore-scale heterogeneity on Immiscible-Liquid dissolution and sorption/desorption is represented in the model by describing the system as comprising a continuous distribution of mass-transfer domains. With this conceptualization, the distributions of the initial dissolution rate coefficient and the sorption/desorption rate coefficient are represented as probability density functions. Several sets of numerical experiments are conducted to examine the effects of heterogeneous dissolution and sorption/desorption on contaminant transport and elution. Four scenarios with different combinations of uniform/heterogeneous rate-limited dissolution and uniform/heterogeneous rate-limited sorption/desorption are evaluated. The results show that both heterogeneous rate-limited sorption/desorption and heterogeneous rate-limited dissolution can significantly increase the time or pore volumes required to elute Immiscible-Liquid constituents from a contaminated porous medium. However, sorption/desorption has minimal influence on elution behavior until essentially all of the Immiscible Liquid has been removed. For typical Immiscible-Liquid constituents that have relatively low sorption, the asymptotic elution tailing produced by heterogeneous rate-limited sorption/desorption begins at effluent concentrations that are several orders of magnitude below the initial steady-state concentrations associated with dissolution of the Immiscible Liquid. Conversely, the enhanced elution tailing associated with heterogeneous rate-limited dissolution begins at concentrations that are approximately one-tenth of the initial steady-state concentrations. Hence, dissolution may generally control elution behavior of Immiscible-Liquid constituents in cases wherein grain/pore-scale heterogeneity significantly influences both dissolution and sorption/desorption.
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dissolution of nonuniformly distributed Immiscible Liquid intermediate scale experiments and mathematical modeling
Environmental Science & Technology, 2002Co-Authors: Mark L Brusseau, Nicole T Nelson, Zhihui Zhang, Brent R Cain, Geoffrey R Tick, M OostromAbstract:The purpose of this work is to examine the effect of nonuniform distributions of Immiscible organic Liquid on dissolution behavior, with a specific focus on the condition dependency of dissolution (i.e., mass transfer) rate coefficients associated with applying mathematical models of differing complexities to measured data. Dissolution experiments were conducted using intermediate-scale flow cells packed with sand in which well-characterized zones of residual trichloroethene (TCE) and 1,2-dichloroethane (DCA) saturation were emplaced. A dual-energy gamma radiation system was used for in-situ measurement of NAPL saturation. Aqueous concentrations of TCE and DCA measured in the flow-cell effluent were significantly less than solubility, due primarily to dilution associated with the nonuniform Immiscible-Liquid distribution and bypass flow effects associated with physical heterogeneity. A quantitative analysis of flow and transport was conducted using a three-dimensional mathematical model wherein Immiscible-Liquid distribution, permeability variability, and sampling effects were explicitly considered. Independent values for the initial dissolution rate coefficients were obtained from dissolution experiments conducted using homogeneously packed columns. The independent predictions obtained from the model provided good representations of NAPL dissolution behavior and of total TCE/DCA mass removed, signifying model robustness. This indicates that for the complex three-dimensional model, explicit consideration of the larger scale factors that influenced Immiscible-Liquid dissolution in the flow cells allowed the use of a dissolution rate coefficient that represents only local-scale mass transfer processes. Conversely, the use of simpler models that did not explicitly consider the nonuniform Immiscible-Liquid distribution required the use of dissolution rate coefficients that are approximately 3 orders of magnitude smaller than the values obtained from the column experiments. The rate coefficients associated with the simpler models represent composite or lumped coefficients that incorporate the effects of the larger scale dissolution processes associated with the nonuniform Immiscible-Liquid distribution, which are not explicitly represented in the simpler models, as well as local-scale mass transfer. These results demonstrate that local-scale dissolution rate coefficients, such as those obtained from column experiments, can be used in models to successfully predict dissolution and transport of Immiscible-Liquid constituents at larger scales when the larger scale factors influencing dissolution behavior are explicitly accounted for in the model.
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nonideal transport of reactive solutes in heterogeneous porous media 5 simulating regional scale behavior of a trichloroethene plume during pump and treat remediation
Water Resources Research, 1999Co-Authors: Zhihui Zhang, Mark L BrusseauAbstract:“Pump and treat” is widely used for containment and remediation of groundwater contaminant plumes. However, it is commonly observed that pump-and-treat systems begin to exhibit reduced efficiency at some point. A number of factors and processes may contribute to the reduced efficiency, among them being those associated with nonideal transport behavior, such as subsurface heterogeneity, nonlinear, rate-limited sorption/desorption, and rate-limited dissolution of Immiscible Liquid. We use numerical modeling to analyze the regional-scale (∼49 km2) nonideal transport behavior of trichloroethene in a contaminated aquifer undergoing pump and treat remediation. The pump-and-treat system has been in operation for ∼12 years, during which time the composite concentrations of trichloroethene in the treatment plant influent have decreased from >300 to ∼100 μg L−1. However, as is typically observed elsewhere, the system is exhibiting extensive concentration tailing, wherein the concentrations have remained relatively constant at ∼100 μg L−1 for the past 8 years. Various factors that may be contributing to this tailing phenomenon are evaluated using a three-dimensional solute transport model specifically developed for the site, which is located in Tucson, Arizona. The values for almost all of the input parameters of the model were obtained independently of the historic concentration data being simulated. The hydraulic conductivity field was generated using information obtained from borehole logs and pumping tests, the sorption and local-scale mass transfer parameters were obtained from laboratory experiments conducted with aquifer material collected from the site, and the initial Immiscible-Liquid saturations were based on the results of partitioning tracer tests conducted in a representative source zone at the site. On the basis of our analyses we conclude that while rate-limited desorption and large-scale spatial variability of hydraulic conductivity have significant impacts on trichloroethene transport, the dissolution of Immiscible-Liquid saturation associated with the source zones is most likely the primary cause of the extensive concentration tailing observed at the site. The impact of nonlinear sorption and local-scale mass transfer on trichloroethene removal appears to be insignificant.
T Allen - One of the best experts on this subject based on the ideXlab platform.
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source zone characterization of a chlorinated solvent contaminated superfund site in tucson az
Journal of Contaminant Hydrology, 2007Co-Authors: Mark L Brusseau, Nicole T Nelson, Zhihui Zhang, J E Blue, J W Rohrer, T AllenAbstract:An extensive site-characterization project was conducted at a large chlorinated-solvent contaminated Superfund site in Tucson, AZ. The project consisted of several components, including traditional site-characterization activities, tracer tests, laboratory experiments conducted with core material collected from the site, and mathematical modeling. The primary focus of the work presented herein is the analysis of induced-gradient contaminant elution tests conducted in a source zone at the site, investigation of the potential occurrence of Immiscible Liquid in the saturated zone, characterization of the relationship between mass flux reduction and mass removal, and evaluation of the impact of source-zone management on site remediation. The results of the present study, along with those of prior work, indicate that Immiscible Liquid is likely present in the saturated zone at the site source zones. Extensive tailing and rebound was observed for the contaminant-elution tests, indicating nonideal transport and mass-transfer behavior. The elution data were analyzed with a source-zone-scale mathematical model, and the results indicated that nonideal Immiscible-Liquid dissolution was the primary cause of the observed behavior. The time-continuous relationship between mass flux reduction and mass removal associated with the plume-scale pump-and-treat operation exhibited an initial large drop in mass flux with minimal mass removed, followed by a period of minimal mass flux reduction and a second period of large reduction. This behavior reflects the impact of both source-zone and aqueous-plume mass removal dynamics. Ultimately, a greater than 90% reduction in mass flux was achieved for a mass removal of approximately 50%. The influence of source-zone management on site remediation was evaluated by conducting two predictive simulations, one for which the source zones were controlled and one for which they were not. A plume-scale model was used to simulate the composite contaminant concentrations associated with groundwater extracted with the pump-and-treat system, which were compared to measured data. The information generated from this study was used to enhance the site conceptual model, help optimize operation of the pump-and-treat system, and evaluate the utility of source-zone remediation.
Sehyun Shin - One of the best experts on this subject based on the ideXlab platform.
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centrifugation free extraction of circulating nucleic acids using Immiscible Liquid under vacuum pressure
Scientific Reports, 2018Co-Authors: Wonhwi Na, Chanhee Park, Kyong Hwa Park, Sehyun ShinAbstract:Extraction of cell-free DNA (cfDNA), which exists at an extremely low concentration in plasma, is a critical process for either targeted-sensing or massive sequencing of DNAs. However, such small amount of DNA cannot be fully obtained without high-speed centrifugation (<20,000 g). Here, we developed a centrifugation-free cfDNA extraction method and system that utilizes an Immiscible solvent under single low vacuum pressure throughout the entire process. It has been named Pressure and Immiscibility-Based EXtraction (PIBEX). The amounts of extracted cfDNA by PIBEX were compared with those extracted by the conventional gold standards such as QIAGEN using quantitative PCR (qPCR). The PIBEX system showed equal performance regarding extraction amount and efficiency compared to the existing method. Because the PIBEX eliminates the troublous and repetitive centrifugation processes in DNA extraction, it can be further utilized in microfluidic-sample preparation systems for circulating nucleic acids, which would lead to an integrated sample-to-answer system in Liquid biopsies.
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centrifugation free extraction of circulating nucleic acids using Immiscible Liquid under vacuum pressure
Scientific Reports, 2018Co-Authors: Hoyoon Lee, Chanhee Park, Kyong Hwa Park, Sehyun ShinAbstract:Extraction of cell-free DNA (cfDNA), which exists at an extremely low concentration in plasma, is a critical process for either targeted-sensing or massive sequencing of DNAs. However, such small amount of DNA cannot be fully obtained without high-speed centrifugation (<20,000 g). Here, we developed a centrifugation-free cfDNA extraction method and system that utilizes an Immiscible solvent under single low vacuum pressure throughout the entire process. It has been named Pressure and Immiscibility-Based EXtraction (PIBEX). The amounts of extracted cfDNA by PIBEX were compared with those extracted by the conventional gold standards such as QIAGEN using quantitative PCR (qPCR). The PIBEX system showed equal performance regarding extraction amount and efficiency compared to the existing method. Because the PIBEX eliminates the troublous and repetitive centrifugation processes in DNA extraction, it can be further utilized in microfluidic-sample preparation systems for circulating nucleic acids, which would lead to an integrated sample-to-answer system in Liquid biopsies.
Chao Yang - One of the best experts on this subject based on the ideXlab platform.
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visual study on the interphase mass transfer of Immiscible Liquid Liquid system in a stirred tank
Industrial & Engineering Chemistry Research, 2019Co-Authors: Xiaoxia Duan, Chao YangAbstract:A novel experiment is designed to visually study the interphase mass transfer in an Immiscible Liquid–Liquid system using the planar laser-induced fluorescence method combined with the refractive i...
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Numerical Simulation of Turbulent Flow and Mixing in Gas–Liquid–Liquid Stirred Tanks
2017Co-Authors: Dang Cheng, Chao Yang, Steven Wang, Zai-sha MaoAbstract:The turbulent flow and macro-mixing processes in gas–Liquid–Liquid stirred vessels agitated by a Rushton turbine have been numerically simulated, based on the Eulerian multifluid approach. Both the isotropic k–ε model and anisotropic Reynolds stress model are used for turbulence modeling. The numerical models are validated by comparing simulated flow field of agitated Immiscible Liquid–Liquid dispersions to the corresponding experimental data from the literature. The predicted time traces of normalized concentration of inertial tracer and mixing time in gas–Liquid–Liquid stirred tanks are compared to the experimentally measured ones as well. Both turbulence models correspond reasonably well to the experimental data in Liquid–Liquid and gas–Liquid–Liquid stirred tanks, and the Reynolds stress model produces better results, in terms of flow field, homogenization curve, and mixing time, than the k–ε model. The information reported in this work is useful for chemical/process engineers when undertaking relevant engineering process designs
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numerical simulation of the marangoni effect on transient mass transfer from single moving deformable drops
Aiche Journal, 2011Co-Authors: Jianfeng Wang, Zhihui Wang, Ping Lu, Chao YangAbstract:A level set approach was adopted in numerical simulation of interphase mass transfer from a deformable drop moving in a continuous Immiscible Liquid, and the simulation results on Marangoni effect were presented with respect to three experimental runs in the methyl isobutyl ketone-acetic acid-water system. Experiments showed that when the solute concentration was sufficiently high, the Marangoni effect would occur with the interphase mass transfer enhanced. Numerical results indicated that the mass-transfer coefficient with Marangoni effect was larger than that without Marangoni effect and stronger Marangoni effect made the drop deform more easily. The predictions were qualitatively in accord with the experimental data. Numerical simulation revealed well the transient flow structure of Marangoni effect. (C) 2011 American Institute of Chemical Engineers AIChE J, 57: 2670-2683, 2011
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numerical simulation of Immiscible Liquid Liquid flow in microchannels using lattice boltzmann method
Science China-chemistry, 2011Co-Authors: Yumei Yong, Chao Yang, Yi Jiang, Ameya Joshi, Youchun Shi, Xiaolong YinAbstract:Immiscible kerosene-water two-phase flows in microchannels connected by a T-junction were numerically studied by a Lattice Boltzmann (LB) method based on field mediators. The two-phase flow lattice Boltzmann model was first validated and improved by several test cases of a still droplet. The five distinct flow regimes of the kerosene-water system, previously identified in the experiments from Zhao et al., were reproduced. The quantitative and qualitative agreement between the simulations and the experimental data show the effectiveness of the numerical method. The roles of the interfacial tension and contact angle on the flow patterns and shapes of droplets were discussed and highlighted according to the numerical results based on the improved two-phase LB model. This work demonstrated that the developed LBM simulator is a viable tool to study Immiscible two-phase flows in microchannels, and such a tool could provide tangible guidance for the design of various microfluidic devices that involve Immiscible multi-phase flows.
