Heterogeneous Regime Research Articles

Gaming the mobility regimes during COVID-19: border-making and crossing between China and Africa

ABSTRACT Transnational border crossing presented new complexities during the COVID-19 pandemic due to a series of emergency measures. Based on in-depth interviews and analysis of policy documents and social media posts, this article examines the border logics and mobility patterns between China and Africa during the pandemic. First, we propose a five-fold typology to map themobility regimes governing Sino-African cross-border travel. Using the ‘medical-political-logistical complex’ as an analytical framework, we then explain how the emergency border apparatus generated new logics of control, coordination, and negotiation in shaping travellers’ (im)mobility. The three-dimensional complex indicates three types of power – medical, political, and logistical, which may cooperate, collude, or conflict with each other in different scenarios. Being deeply politicized and medicalized under the zero-COVID policy, China’s border measures involved large-scale logistical (re)arrangements across multiple destinations. We contend that logistical power was initially dominated by the state but increasingly decentralized by non-state actors with the rise of intermediaries. This intensified the externalization of border control and the commercialization of mobility infrastructures, thereby widening mobility inequality on the one hand while creating space for various actors, including travelers, to game the mobility regimes on the other. Empirically, this study expands the literature on COVID-19 mobilities by presenting new evidence on the heterogeneous transcontinental mobility regimes. Theoretically, it adds a logistical perspective to understand the matrix of power underlying the emergency border apparatus. We also discuss the malleable nature of pandemic borders, which shall hold implications for future research on borders and epidemics.

Global knowledge flows and the psychiatric encounter in Indonesia.

In this article, we examine the clinical encounters of people diagnosed with a severe mental illness (SMI). Drawing on more than 1-year of ethnographic research and interviews in Indonesia, we show that instances of moral self-reflection occurring in the process of acquiring and appropriating clinical insight emerge at the intersection of heterogeneous discursive regimes. When biomedical notions of health and illness dominate these discourses, they reimagine pre-existing notions about spirituality and religion. Furthermore, consenting to psychiatric notions of health and illness can create common ground and a sense of shared experience, leading to grassroots movements for the empowerment of the mentally ill, self-help groups, and other support structures. At the same time, these processes can increase uncertainty and be generative of a culture of blame, as individuals are caught in overlapping and at times contradictory moral systems that each have the potential to strip patients of their moral status.

Experimental study of hydrodynamic characteristics in three-phase coarse particle fluidized flotation column

Understanding multiphase flow regimes and hydrodynamic characteristics in the three-phase coarse particle fluidized flotation column (TFC) is crucial in mineral processing. This study systematically investigated the influence of gas velocity (Ug) and water velocity (Uw) on the flow regimes in TFC, focusing on the identification and hydrodynamic characteristics of different flow regimes in the freeboard and bulk fluidized bed regions. Three distinct flow regimes (heterogeneous flow, pseudo-homogeneous flow and mono-homogeneous flow) and two transition water velocities (transitions from a heterogeneous flow regime to a pseudo-homogeneous flow (Ut1) and transitions from a pseudo-homogeneous flow to a mono-disperse homogeneous flow regime (Ut2)) were identified in the freeboard region based on the visual observation and bubble characteristic parameter acquisition system (BVW-2) monitoring the variations in the bubble size distribution. Visual observation combined with electrical resistance tomography (ERT) monitoring the solid concentration variations facilitated accurate determination of three flow regimes (fixed bed regime, agitated bed regime, and complete fluidization regime) and two transition points (minimum agitation water velocity (ULma) and minimum fluidization water velocity (ULmf)) in the bulk fluidized bed region. Furthermore, statistical and spectral methods were used to analyze pressure fluctuation signals and characterize fluidization behavior across different flow regimes, including the average pressure fluctuation (ΔP¯), the probability density function (PDF), normalized standard deviation (δ), kurtosis (K), skewness (S), autocorrelation function (ACF), power spectral density (PSD) and average cycle frequency (fc). The results indicated that it is the changes in dominant flow structures within the three-phase fluidized bed, such as variations in bubble behavior and particle movement under different Ug and Uw, that lead to differences in flow characteristics, thereby forming distinct flow regimes.

Development and validation of a 1D gas–liquid model for dissolved Mn(II) removal by oxidation process in a square bubble column

Modeling multiphase reactors requires an in-depth multidisciplinary analysis of various phenomena including the chemical kinetics, oxygen mass transfer, as well as the simulation of flows within these contactors. In this study, a 1D model of two-phase flow for Mn(II) removal from drinking water by aeration process is developed and validated. This model is based on the Eulerian description of two-phase gas–liquid flow with the comparison between a one-medium bubble size and a two-bubble class description to represent the bubble population in the heterogeneous flow regime. All the relevant chemical species are simulated by coupling hydrodynamics, gas–liquid mass transfer, and reaction kinetic. A pseudo-first-order model accounting for homogeneous and heterogeneous kinetics is considered for Mn(II) oxidation. The performance of the developed 1D model is compared and validated with experimental data. The 1D model was able to predict quantitatively Mn oxidation as a function of pH, initial Mn(II) and initial Mn(IV) concentrations.

Influence of the gas phase on a large-scale bubble column fluid dynamics: Gas holdup, flow regime transitions, and bubble size distributions

We present the results of an experimental study of a large-diameter bubble column operating in batch mode with air or CO2 as the gas phase and water as the liquid phase. The bubble column has an inner diameter of 0.24 m and is 5.3 m in height. The superficial gas velocity varied between 0.0037 m/s and 0.0233 m/s. The experimental investigation consists of gas holdup measurements and image analysis. Flow regime transitions were detected by gas holdup measurements, and image analysis was used to investigate the bubble size distributions. The results suggest that the homogeneous flow regime is stabilized when CO2 is used as the gas phase. The gas holdup is higher for the CO2-water system at fixed superficial gas velocity, especially in the heterogeneous flow regime. In the homogeneous flow regime, the mean bubble diameter and the fraction of large bubbles are lower for the CO2-water system, explaining the higher gas holdup.

Bootstrapped Edge Count Tests for Nonparametric Two-Sample Inference Under Heterogeneity

Nonparametric two-sample testing is a classical problem in inferential statistics. While modern two-sample tests, such as the edge count test and its variants, can handle multivariate and non-Euclidean data, contemporary gargantuan datasets often exhibit heterogeneity due to the presence of latent subpopulations. Direct application of these tests, without regulating for such heterogeneity, may lead to incorrect statistical decisions. We develop a new nonparametric testing procedure that accurately detects differences between the two samples in the presence of unknown heterogeneity in the data generation process. Our framework handles this latent heterogeneity through a composite null that entertains the possibility that the two samples arise from a mixture distribution with identical component distributions but with possibly different mixing weights. In this regime, we study the asymptotic behavior of weighted edge count test statistic and show that it can be effectively recalibrated to detect arbitrary deviations from the composite null. For practical implementation we propose a Bootstrapped Weighted Edge Count test which involves a bootstrap-based calibration procedure that can be easily implemented across a wide range of heterogeneous regimes. A comprehensive simulation study and an application to detecting aberrant user behaviors in online games demonstrates the excellent non-asymptotic performance of the proposed test. Supplementary materials for this article are available online.

3D computational fluid dynamics analysis of natural gas separation efficiency in multiphase pumping wells with heterogeneous flow regime

This research uses 3D Computational Fluid Dynamics (CFD) simulations to investigate the downhole Natural Gas Separation Efficiency (NGSE) for multiphase pumping wells in the heterogeneous churn flow regime. Results explain the effects of key parameters such as liquid viscosity, intake port sizes/diameter, and casing diameter, on the NGSE. Methods are thus suggested to enhance the NGSE in oil field operations, and key improvements to the widely used mathematical formulations for viscous service are proposed. Transient numerical simulations were performed for a section of an experimental flow loop extracted from the literature, and the flow solution was obtained with the Volume of Fluid (VOF) model. For most simulations, turbulence effects were modelled with the k − ϵ turbulence model. The k − ω SST turbulence model was however considered for the sensitivity analysis on liquid viscosity. The final numerical results validated against the corresponding experimental data showed an average error of less than 6%. Combining past literature and current results confirms that (i), the NGSE is affected by the downhole geometry (i.e annulus space and pump intake port flow area geometry) and (ii), current analytical NGSE models are not ideal for multiphase viscous service (high viscosity Newtonian flow) in the heterogeneous flow regime. The widely used steady-state formulations might thus not be adequate for this flow regime.

Column flotation hydrodynamics operating in the heterogeneous regime estimated by electrical resistance tomography and multi-phase CFD model

ABSTRACT This paper investigates the two-phase flow hydrodynamics of a column flotation operated from a homogeneous to a heterogeneous flow regimes using experimental and computational fluid dynamics (CFD) techniques. Experiments were conducted in a lab scale column flotation of 0.1 m internal diameter and 2.5 m length at various superficial gas velocities using a dual plane electrical resistance tomography (ERT). The mean gas holdup increased from 2 to 18% with the increase in superficial gas velocity from 0.6 to 7.2 cm/s. The gas holdup-based bubble swarm velocity method identified four distinct flow regimes, i.e. homogeneous bubbling regime, narrow discrete bubbling regime, a sustained helical flow regime and churn turbulent flow regime in the column. Further, transient simulations were conducted using a two-fluid model coupled with a population balance model to assess the flow behavior inside the column. Virtual mass, lift and drag forces were incorporated into the model to account for the interphase forces. Numerical simulations predicted mean gas holdup was matching with the experimental data at low gas velocities (<2.4 cm/s), and a marginal deviation was noted at higher gas velocities (>2.4 cm/s). The predicted radial gas holdup profiles were found to change from flatter to parabolic with the increase in gas velocities, i.e. similar to the experiments. The effect of particle size on the rate constant and recovery was estimated with Luttrell and Yoon’s performance model using the particle floatability input data and the two-phase experimental data. The developed CFD model can be useful to optimize the operating and design parameters for efficient operation of the column flotation process.

Effect of corporate governance and enforcement on fair value accounting in Brazil

PurposeThis paper aims to investigate whether Brazilian firms that legally bond to stricter enforcement and commit to stringent corporate governance requirements experience increased value relevance of discretionary fair value measurements (Levels 2 and 3), and how different measurement levels are associated with firms’ systematic risk.Design/methodology/approachThe Brazilian data’s distinctive feature helps in analyzing fair value’s relevance in an emerging market with heterogeneous enforcement regimes. Given the inherent self-selection in corporate governance levels and cross-listing decisions, the authors use a two-step generalized method of moments approach. Building upon Song et al.’s (2010) framework, the authors carefully address potential selection biases. Furthermore, the authors expand Riedl and Serafeim’s (2011) model, based on Ohlson’s (1995) model, to explore whether the negative correlation between Level 1 net assets (assets minus liabilities) and firms’ beta is more pronounced compared to Levels 2 or 3 net assets. Additionally, the authors investigate whether this relationship intensifies when firms align themselves with enhanced governance structures and stricter enforcement regimes.FindingsFair value measurements which require more judgment (Levels 2 and 3) are more value-relevant when a firm is legally bonded to higher enforcement and better corporate governance. Level 1 fair values of these firms’ net assets are associated with lower systematic risk, while Levels 2 and 3 fair values (high subjectivity valuation) are not.Originality/valueThe authors show that firms that bond to better corporate governance and stricter enforcement regimes mitigate the information risk involved in subjective fair-value measurements.

Gas-liquid mass transfer in microbubble column reactors

Microbubble column reactors (MBCRs) present great potential in gas-liquid reactions due to their superior mass transfer efficiency. In this work, an automated platform was built to investigate the effect of gas/liquid superficial velocity, and liquid viscosity on mass transfer performance. Compared to conventional bubble column reactors, MBCRs exhibit significantly enhanced mass transfer efficiency. The findings show that kLa initially increases, followed by a subsequent decrease with the increase of gas superficial velocity. This behavior is attributed to transitioning from a homogeneous to a heterogeneous regime as gas superficial velocity increases. The liquid viscosity has a dual effect on kLa within a homogeneous regime. However, the kL in MBCRs is smaller than that in conventional bubble column reactors due to the movement of large bubbles enhancing liquid turbulence. Moreover, a dimensionless correlation was developed integrating the Weber number to predict the mass transfer coefficient.

Computational fluid dynamics modelling of large-scale bubble columns: from the mono-dispersed to the pure heterogeneous flow regime

This study proposes a CFD model to simulate large-scale bubble columns operating in different flow regimes. Transient 3-D simulations were performed employing a commercial code (ANSYS Fluent), and the numerical results were compared with available experimental data. The superficial gas velocity ranges between 0.0037 m/s and 0.2 m/s, covering both the mono-dispersed and pure-heterogenous flow regimes, where bubbles coalescence and breakup were modelled. The results have been critically analysed, and the discrepancies between the numerical and experimental results have been deeply commented on, setting the stage for future improvements.

A Source and Ground Motion Study of the Veracruz Earthquakes of 29 October 2009 (Mw5.7) and 4 August 2021 (Mw4.8): Evidence of Strong Azimuthal Variation of Attenuation

We study two moderate earthquakes that occurred offshore the State of Veracruz, in the southwestern Gulf of Mexico, on 29 October 2009 (Mw 5.7) and 4 August 2021 (Mw 4.8). The former was located near the town of Alvarado and latter near the city of Veracruz. The events were well recorded by accelerographs and seismographs at local and regional distances. W-phase regional centroid moment tensor inversion reveals that they had reverse-faulting mechanism, similar to several other earthquakes in the southwestern Gulf of Mexico. Of the seven focal mechanisms now available along the southwestern margin, two are strike slip and the rest are of thrust type, suggesting a heterogeneous stress regime. We take advantage of local and regional recordings produced by these two earthquakes to study the characteristics of the ground motion. Source spectra computed at each station separately (without correcting for the site effect), assuming a reasonable geometrical spreading and Q = 141f 0.63, show remarkably high variability due to difference in path and local site effects. The geometric mean apparent source spectrum (source spectrum including site effects) of both earthquakes may be modeled by an ω2 -Brune source model with a stress drop, Δσ, of 40 MPa. These source spectra, along with the application of stochastic method, yield peak ground acceleration (PGA) and velocity (PGV) as a function of distance in general agreement with the observations. Of greater practical importance is the ground motion at sedimentary sites in the city of Veracruz and at the Laguna Verde Nuclear Power Plant (LVNPP) site, especially from a postulated Mw 6.5 earthquake which is a reasonable scenario event for the region. For the city of Veracruz and LVNPP we estimate site effect with respect to the ω2 -Brune source with Δσ of 2 MPa. There is some support for this Δσ. We apply both stochastic and empirical Green’s functions (EGF) techniques in the estimation of the ground motion. The recording of the 2021 earthquake is taken as the EGF, and Δσ of the EGF and the target event are assumed to be the same and equal to 2 MPa. The predicted PGA and PGV at sedimentary sites in the city of Veracruz and LVNPP above the hypocenter (depth = 20 km) from the postulated Mw 6.5 earthquake are 0.2 g and 10 cm/s and 0.18 g and 3 cm/s, respectively. These results are preliminary as they are based on several assumptions.

Study on flow characteristics and phase holdup in a slurry bubble column coupled with mild agitation

A pilot-scale experimental setup was constructed to investigate the effect of mild agitation on the bubble characteristics and phase holdup in a slurry bubble column. Mild agitation positively impacts the axial uniform distribution of solid holdup, though it shows insignificant influence on the radial distribution. In homogenous regime, mild agitation promotes the coalescence of bubbles, and the effect becomes stronger with increasing agitator speed. The mild agitation contributes to a decrease in bubble size in heterogeneous flow regime. Mild agitation presents a significant effect on the gas holdup by adjusting the bubble size and bubble motion trajectory. The modification was introduced to predict the gas holdup considering the effects of mild agitation, a necessary consideration for applications requiring mild agitation. This adapted model predicts gas holdup with a maximum error of 12.9%.

Fire regimes and management options in mixed grassland-fynbos vegetation, South Africa

BackgroundFire regimes in South African fynbos shrublands have been quantified in the western (winter rainfall) and central (aseasonal rainfall) parts. They have not been quantified at their eastern extremity (summer rainfall), where fynbos transitions to grassland and is embedded in other fire-resistant vegetation types. We assessed fire regimes at the eastern extremity of the fynbos biome and discussed the ecological and management implications of our findings.ResultsUsing remote sensing, we assessed fires over 21 years in a 350,000-ha study area at the eastern edge of the fynbos biome. Only 9% of the study area burned, almost exclusively in mixed grassland-fynbos vegetation. The largest proportion (44% of the total area burnt) burnt in late winter and early spring, but fires occurred throughout the year. Fires only occurred in 39% of the mixed grassland-fynbos vegetation. Of the mixed grassland-fynbos vegetation that did burn, 44%, 11%, 26%, and 19% experienced one, two, three, and four fires, respectively. Areas with multiple fires had return intervals ranging from 3 to 15 years, with 76% of the area with multiple fires burning every 4 to 6 years. Most large fires were preceded by two relatively dry months, when fuels were drier and more flammable.ConclusionsThe mixed grassland-fynbos vegetation at the eastern extremity of the fynbos biome is surrounded by fire-resistant vegetation and exhibits a varied fire regime, with different parts experiencing frequent, infrequent, or no fire over 21 years. Fires were largely aseasonal, occurring throughout the year, although data over more years may reveal that a greater proportion of fires will occur in winter, when grasses are cured and rainfall is low, as well as after relatively long (> 2 months) periods of below-average rainfall. As most fires would burn out safely against fire-resistant vegetation, we conclude that lightning-ignited fires should be allowed to spread unhindered to approximate a natural and heterogeneous fire regime, provided that no neighboring properties or infrastructure are threatened. The response of the biota to fires is not well understood for this transition area, and further research is needed.

Gastropod Slime-Based Gel as an Adjustable Synthetic Model for Human Airway Mucus.

Airway mucus works as a protective barrier in the human body, as it entraps pathogens that will be later cleared from the airways by ciliary transport or by coughing, thus featuring the rheological properties of a highly stretchable gel. Nonetheless, the study of these physical barrier as well as transport properties remains limited due to the restricted and invasive access to lungs and bronchi to retrieve mucus and to the poor repeatability inherent to native mucus samples. To overcome these limits, we report on a biobased synthetic mucus prepared from snail slime and multibranched thiol cross-linker, which are able to establish disulfide bonds, in analogy with the disulfide bonding of mucins, and therefore build viscoelastoplastic hydrogels. The gel macroscopic properties are tuned by modifying the cross-linker and slime concentrations and can quantitatively match those of native sputum from donors with cystic fibrosis (CF) or non-cystic fibrosis bronchiectasis (NCFB) both in the small- and large-deformation regimes. Heterogeneous regimes were locally found in the mucus model by passive microrheology, in which both diffusive and non-diffusive motion are present, similar to what is observed in sputa. The biobased synthetic approach proposed in the present study thus allows to produce, with commercially available components, a promising model to native respiratory mucus regarding both mechanical and, to a lesser extent, physicochemical aspects.

Mechanical intelligence simplifies control in terrestrial limbless locomotion.

Limbless locomotors, from microscopic worms to macroscopic snakes, traverse complex, heterogeneous natural environments typically using undulatory body wave propagation. Theoretical and robophysical models typically emphasize body kinematics and active neural/electronic control. However, we contend that because such approaches often neglect the role of passive, mechanically controlled processes (those involving "mechanical intelligence"), they fail to reproduce the performance of even the simplest organisms. To uncover principles of how mechanical intelligence aids limbless locomotion in heterogeneous terradynamic regimes, here we conduct a comparative study of locomotion in a model of heterogeneous terrain (lattices of rigid posts). We used a model biological system, the highly studied nematode worm Caenorhabditis elegans, and a robophysical device whose bilateral actuator morphology models that of limbless organisms across scales. The robot's kinematics quantitatively reproduced the performance of the nematodes with purely open-loop control; mechanical intelligence simplified control of obstacle navigation and exploitation by reducing the need for active sensing and feedback. An active behavior observed in C. elegans, undulatory wave reversal upon head collisions, robustified locomotion via exploitation of the systems' mechanical intelligence. Our study provides insights into how neurally simple limbless organisms like nematodes can leverage mechanical intelligence via appropriately tuned bilateral actuation to locomote in complex environments. These principles likely apply to neurally more sophisticated organisms and also provide a design and control paradigm for limbless robots for applications like search and rescue and planetary exploration.

Hydrodynamics and model of gas‐liquid flow in microbubble column reactors

AbstractMicrobubble column reactors (MBCRs) have the significant advantages of high gas holdup, large gas‐liquid interfacial area, and excellent mass transfer performance, making them attractive for applications such as hydrogenation and oxidation. However, there is still a lack of comprehensive understanding of the gas‐liquid flow behavior in MBCRs. In this work, the effects of gas and liquid superficial velocities on flow regimes, residence time distribution, and gas holdup are investigated. The gas holdup increases linearly with the increase of gas superficial velocity, even in heterogeneous regimes, ranging from 0% to 60% at gas superficial velocities of 0–25 mm/s. Additionally, the gas‐liquid interfacial areas in MBCRs are 1–2 orders of magnitude larger than those in traditional bubble column reactors. A prediction model for gas holdup is established, and the predicted values are in good agreement with the experimental values.

The role of short‐term temperature variability and light in shaping the phenology and characteristics of seagrass beds

AbstractSeagrass beds inhabit highly heterogeneous temperature regimes that characterize the marine nearshore. Temperature directly influences seagrasses and also provides indirect information on other ecologically relevant environmental variables. Multiple temperature processes operate on seasonal and sub‐seasonal timescales (i.e., hours to months) and include variation from seasonal air–sea heat fluxes, advective heat transport from upwelling and tidal circulation, and daily heating and cooling of shallow waters. Despite this, seagrass–temperature studies typically only examine a single isolated temperature process, often seasonal heating/cooling or marine heatwaves. Furthermore, elucidation of relationships between different short‐term temperature processes and seagrass metrics could provide insights into biologically relevant temperature metrics for seagrasses. Here, we examine the effects of multiple short‐term temperature processes on Zostera marina beds in Atlantic Canada, by describing the seasonal phenology of bed characteristics, plant morphology, and physiology across different temperature regimes and by identifying relationships between different temperature and seagrass metrics. We also include water depth as a proxy for light availability. Four distinct short‐term temperature processes (median temperature, growing degree day [heat accumulation], daily temperature range, and time in the optimal temperature range [5–23°C]) were used to categorize temperature regimes across our study sites as warm and highly variable, or cool and less variable. We found that both temperature regime and light availability were important for leaf area index (LAI) and shoot density, which both decreased with increasing depth yet had the strongest seasonal differences and maximum rates of increase (shoot density) or lowest values and maximum rates of decrease (LAI) in warm and highly variable temperature regimes. These temperature regimes were also associated with seasonal patterns in number of leaves, reduced leaf lengths and number of leaves per shoot, and thinner rhizomes with less carbohydrate storage. Generalized additive models (GAMs) for each seagrass metric using the four temperature processes indicated that while median temperature displayed expected relationships with almost every seagrass metric, inclusion of other temperature processes revealed additional insights not evident from median temperature alone. Our study shows that different sources of short‐term temperature variation influence seagrass properties and that accounting for these will improve our understanding of the temperature–seagrass interaction.

Energy-balance modeling of heterogeneous glacio-hydrological regimes at upper Indus

Study regionThe Upper Indus River Basin (UIB). Study focusThe UIB has experienced marked runoff change due to the accelerated glacier melting under climate warming. Nonetheless, the glacio-hydrological regime in the UIB remains unclear due to considerable uncertainties in precipitation data and glacio-hydrology modeling. Here, we used a state-of-the-art water and energy budget-based distributed glacio-hydrology model (WEB-DHM-S) that employed an energy-balance glacier module for both clean and debris-covered glaciers to analyze the hydrological regimes within the UIB during 2001–2020, particularly the spatial heterogeneity among the Himalaya-Karakoram-Hindu-Kush mountains. New hydrological insights for the regionResults indicated that the high-resolution ERA5-Land precipitation data showed the most reliable estimate (∼750 mm/yr) among available products, which was the model’s forcing data. Our results showed that the mean contributions of snow, glaciers, rainfall, and baseflow to total runoff in the UIB were 41.5%, 23.3%, 34.7%, and 0.5%, respectively. Glacial melting made the largest contribution to total runoff in the Karakoram (35.3%), while the smallest contribution was made in the Hindu Kush (15.9%). Further, we showed that glacial melting was highly sensitive to changes in air temperature and solar radiation inputs. In particular, fluctuating solar radiation could change the magnitude and timing of annual flood peaks in ice melting, which emphasized the crucial role of energy-related forcing data (besides the traditional precipitation and air temperature inputs) in glacio-hydrology modeling.

Computational fluid dynamics simulation of the heterogeneous regime in a large-scale bubble column

Bubble columns are used in many industrial applications, but the complex fluid dynamics phenomena has limited their design and optimization processes. Computational Fluid Dynamics (CFD) is a promising tool to investigate the complex multi-scale flow physics characterising multiphase reactors. In this work, a CFD Eulerian-Eulerian modelling approach is developed to describe the hydrodynamics of a large-scale bubble column operated over a wide range of superficial gas velocities (0.0188 – 0.20 m/s). Available experimental results were used for the model validation. A drag law for oblate bubbles was considered and coupled with a drag modification function to include the effects of bubble–bubble interactions. The numerical approach was tested considering a mono-dispersed approximation and including coalescence and breakup by using a Population Balance Model (PBM). The role played by the lift force was investigated and, for the reactor configuration considered, it turned out to be essential in the description of the local flow properties.