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Fluids, Volume 11, Issue 8 (August 2026) – 23 articles

Cover Story (view full-size image): Wall-flow filters are used in exhaust gas aftertreatment systems to reduce particulate matter emissions from internal combustion engines. Filter regeneration may cause particle structure fragments to rearrange within individual filter channels, leading to particulate structure deposits that modify the filter’s pressure drop, loading behavior, and separation efficiency. This study advances resolved-particle lattice Boltzmann simulations toward realistic operating conditions by including high-velocity flow, turbulence modeling, and temperature-dependent reaction. The approach provides numerical insight into particle rearrangement mechanisms that are difficult to access experimentally. View this paper
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53 pages, 12851 KB  
Article
Internal Flow Analysis of a Dual-Swirl Dryer for Zingiberaceous Root Drying Through Numerical Simulation with Experimental Validation
by Raziel Enrique Chumacero, Yanis Alexis Oblitas and Julio Román Ronceros
Fluids 2026, 11(8), 207; https://doi.org/10.3390/fluids11080207 - 21 Aug 2026
Viewed by 260
Abstract
Convective drying of Zingiberaceous roots, particularly ginger (Zingiber officinale), requires a uniform distribution of airflow and temperature to ensure energy efficiency and product quality. However, many drying systems exhibit aerothermal limitations that produce temperature gradients and non-uniform drying conditions. To address [...] Read more.
Convective drying of Zingiberaceous roots, particularly ginger (Zingiber officinale), requires a uniform distribution of airflow and temperature to ensure energy efficiency and product quality. However, many drying systems exhibit aerothermal limitations that produce temperature gradients and non-uniform drying conditions. To address this issue, this study proposes a dual-swirl dryer featuring two air inlets: an upper helical inlet and a lower tangential inlet. Both inlet configurations generate swirling airflow patterns that enhance thermal uniformity and increase the residence time of hot air within the drying chamber. The internal flow behavior was investigated using Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent2025 R1 version. A three-dimensional polyhedral mesh was generated to improve computational efficiency and numerical accuracy. Turbulence and recirculation phenomena were modeled using the Realizable k–ϵ turbulence model, while temperature distribution was analyzed through the energy conservation equation. Numerical predictions were experimentally validated using temperature sensors integrated into an automatic control system. The comparison between numerical and experimental results demonstrated that the dual-swirl configuration improves airflow redistribution, reduces thermal stagnation zones, and promotes a more homogeneous temperature field throughout the drying chamber. These findings confirm that the proposed system is an efficient alternative for agro-industrial drying applications. Full article
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15 pages, 4333 KB  
Article
Investigating the Effect of UV Light on Marangoni Flow and Drainage of Aqueous Photoswitchable Microscale Foams
by Nastaran Rezaee, John Aunna and Jamal Naser
Fluids 2026, 11(8), 206; https://doi.org/10.3390/fluids11080206 - 21 Aug 2026
Viewed by 239
Abstract
Exposing foams stabilized by photoswitchable surfactants to UV light induces changes in surface surfactant concentration, leading to significant alterations in foam behaviour such as the generation of Marangoni flow and change in foam drainage patterns. The occurrence of Marangoni flow can be observed [...] Read more.
Exposing foams stabilized by photoswitchable surfactants to UV light induces changes in surface surfactant concentration, leading to significant alterations in foam behaviour such as the generation of Marangoni flow and change in foam drainage patterns. The occurrence of Marangoni flow can be observed when either all elements of the foam or only their films are exposed to UV light. Conversely, changes in foam drainage occur when a macroscale portion of a foam column is exposed to UV light. To explore these phenomena, numerical models are developed and validated using experimental data. These models simulate the scale and profile of Marangoni flow from foam networks to films, as well as the drainage flow within the foam network. Microscale findings demonstrate that Marangoni flow can be controlled by adjusting the intensity and duration of UV light exposure. Macroscopically, the drainage profile in exposed foam regions undergoes significant changes with varying UV intensity. Furthermore, beyond a certain threshold, the foam drainage reverses direction, contrary to gravity. The effect of foam interfacial mobility on the reversed drainage of both interior and exterior foams is analyzed. The findings provide a potential tool to control foam drainage behaviour without the need to modify other variables. Full article
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26 pages, 10110 KB  
Article
A Numerical Investigation on the Influence of a Combined Desk Local Exhaust Ventilation System on COVID-19 Dispersion and Indoor Thermal Comfort in Classrooms
by Ahmed Qasim Ahmed, Hayder M. B. Obaida, Aldo Rona and Ahmed Jawad Khaleel
Fluids 2026, 11(8), 205; https://doi.org/10.3390/fluids11080205 - 20 Aug 2026
Viewed by 269
Abstract
Providing a healthy environment in schools, particularly during a global pandemic, is crucial to saving occupants’ lives and reducing infection rates. This paper proposes a novel desk local exhaust ventilation (DLEV) system that uses a local exhaust diffuser integrated into a classroom desk. [...] Read more.
Providing a healthy environment in schools, particularly during a global pandemic, is crucial to saving occupants’ lives and reducing infection rates. This paper proposes a novel desk local exhaust ventilation (DLEV) system that uses a local exhaust diffuser integrated into a classroom desk. The performance of the system in providing a healthy and comfortable indoor thermal environment and reducing the risk of COVID-19 infection was assessed numerically. The assessment combined indoor thermal comfort indices and the bioaerosol dispersion behavior of airborne particles. The study was completed in a typical classroom layout, in which the results show that the DLEV system meets thermal comfort requirements by maintaining the gradients of vertical temperature within an acceptable range. The DLEV system increases the air motion in the breathing zone while keeping it within the recommended range of <0.25 m/s. The PMV and PPD indices are within recommended comfort levels for all but three occupants. Most notably, the DLEV system substantially reduces the concentration of bioaerosols, especially around the occupants’ head. This system works by capturing and removing the virus-rich aerosols exhaled by infected subjects before they disperse in the classroom. This lowers the risk of infection among healthy subjects. These findings confirm the effectiveness of the DLEV system in enhancing both thermal comfort and indoor air quality, making it suitable for environments where specific goals regarding occupants’ health and thermal management are required, such as in a classroom of healthy and infected subjects. Full article
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35 pages, 12230 KB  
Article
CFD and CHT Methodology for the Thermal Simulation and Validation of a Prismatic LiFePO4 Cell
by Duccio Fedeli, Marco Lagnoni, Claudio Scarpelli, Francesco Giuseppe Quilici, Antonio Bertei, Giovanni Lutzemberger, Filippo Fruzza, Maria Vittoria Salvetti and Alessandro Mariotti
Fluids 2026, 11(8), 204; https://doi.org/10.3390/fluids11080204 - 18 Aug 2026
Viewed by 230
Abstract
A computational fluid dynamics and conjugate heat transfer (CFD+CHT) methodology is developed for the thermal simulation of a commercial prismatic LiFePO4 cell under charging and discharging operating conditions. The approach couples a three-dimensional representation of the battery, including a simplified description of [...] Read more.
A computational fluid dynamics and conjugate heat transfer (CFD+CHT) methodology is developed for the thermal simulation of a commercial prismatic LiFePO4 cell under charging and discharging operating conditions. The approach couples a three-dimensional representation of the battery, including a simplified description of its internal layered structure, with an electrochemical–thermal heat-generation model implemented as a temperature- and time-dependent volumetric source term. The heat source is applied within the active layers of the cell and updated during the transient simulation according to the local thermal state and to the evolution of the state of charge. The methodology is applied to 1C and 2C cycles under natural convection and forced-air cooling at free-stream velocities of 10ms1 and 20ms1. A dedicated wind-tunnel campaign is carried out on the same cell, instrumented with type-K thermocouples distributed over its external surfaces, to provide experimental data for model validation. The results show that the proposed framework accurately reproduces the main wall-temperature trends observed experimentally. Under natural convection, the temperature distribution remains nearly uniform, whereas forced convection produces more pronounced vertical and in-plane gradients. For the charge cycles, the comparison between CFD predictions and end-of-cycle measurements yields a mean absolute error (MAE) of 0.66C and a root-mean-square error (RMSE) of 0.82C over 168 measurement locations. The discharge cycles yield a comparable level of agreement (MAE 0.65C, RMSE 0.81C over 168 probe points), confirming the predictive capability of the methodology for both operating modes. Full article
(This article belongs to the Section Heat and Mass Transfer)
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36 pages, 75905 KB  
Article
Parametric Investigation of Methanol Spray Combustion Under Direct-Injection Conditions
by Kirtan Aryal, Guanxiong Zhai, Ruiyuan Cao, Yijun Lin, Shijie Xu, Kar Mun Pang, Cheng Wang, Guan Heng Yeoh and Qing Nian Chan
Fluids 2026, 11(8), 203; https://doi.org/10.3390/fluids11080203 - 17 Aug 2026
Viewed by 223
Abstract
This study presents a systematic mapping of methanol spray autoignition, lift-off, and flame development across an engine-relevant range of ambient temperatures (1000–1200 K), injection pressures (70–130 MPa), and O2 concentrations (21–15 vol.%), using a single fixed injector and optical configuration. In addition, [...] Read more.
This study presents a systematic mapping of methanol spray autoignition, lift-off, and flame development across an engine-relevant range of ambient temperatures (1000–1200 K), injection pressures (70–130 MPa), and O2 concentrations (21–15 vol.%), using a single fixed injector and optical configuration. In addition, the study reports a dual-fuel strategy to address the low-temperature instability challenges highlighted by the mapping. Within this dataset, ignition delay increases with a lower ambient temperature, reduced injection pressure, or a lower O2 concentration, while the lift-off length increases with a lower temperature and higher injection pressure. Schlieren imaging consistently captures ignition in the mid-axial region of the jet, softening of spray-head gradients before high-temperature ignition, and occasional upstream ignition sites during the diffusion-controlled phase that affect the flame base position. At the lowest tested temperature of 1000 K, methanol autoignites over a wide ignition-delay range (±1.33 ms), with combustion occurring outside the chamber’s field of view. The corresponding heat-release profile cannot be interpreted conclusively under the current test configuration. Introducing a pilot jet at this condition enables methanol to ignite shortly after the start of injection over a much narrower range (∼±0.10 ms). The resulting combustion event remains within the field of view and occurs much closer to the nozzle compared with its autoignition counterpart. Full article
(This article belongs to the Collection Challenges and Advances in Heat and Mass Transfer)
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13 pages, 353 KB  
Article
On the Role of Surface Tension in the Energy Budget of Dispersive Undular Bores
by Samer Israwi, Charbel Aoun, Mahmoud Mehdi and Bassam A. Y. Alqaralleh
Fluids 2026, 11(8), 202; https://doi.org/10.3390/fluids11080202 - 14 Aug 2026
Viewed by 196
Abstract
Undular bores are classical shallow-water phenomena in which a sharp transition between two flow states is replaced, in a dispersive theory, by an oscillatory wave train. In non-dispersive shallow-water theory, the bore is associated with an apparent loss of mechanical energy. In dispersive [...] Read more.
Undular bores are classical shallow-water phenomena in which a sharp transition between two flow states is replaced, in a dispersive theory, by an oscillatory wave train. In non-dispersive shallow-water theory, the bore is associated with an apparent loss of mechanical energy. In dispersive models, this energy can be interpreted as being redistributed into the oscillatory tail. The aim of this short article is to formulate a possible extension of this interpretation when surface tension is included. The capillary contribution modifies the long-wave dispersion coefficient through a Bond-number-dependent term and adds an additional surface energy to the total energy functional. We derive the basic capillary-gravity KdV scaling, identify the modified energy density, and discuss how surface tension may affect the amplitude, wavelength, and energy flux of the trailing oscillations. The proposed direction is relevant for small-scale laboratory bores, tidal-bore fronts, and shallow tidal currents in which a rapid transition generates short dispersive oscillations. Special attention is paid to the critical value Bo=1/3, where the classical KdV dispersion vanishes, and a fifth-order correction is required. Full article
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24 pages, 2850 KB  
Review
A Review of Thermal Management in Modern Data Centres: Water Usage Effectiveness and Heat Transfer Coefficients
by Andre Cooper and Thi Bang Tuyen Nguyen
Fluids 2026, 11(8), 201; https://doi.org/10.3390/fluids11080201 - 14 Aug 2026
Cited by 1 | Viewed by 538
Abstract
Rapid growth in artificial intelligence, machine learning, and high-performance computing has substantially increased data centre rack power densities, resulting in higher heat generation and more demanding cooling requirements. As water remains widely used in many cooling systems, understanding the relationship between cooling technologies [...] Read more.
Rapid growth in artificial intelligence, machine learning, and high-performance computing has substantially increased data centre rack power densities, resulting in higher heat generation and more demanding cooling requirements. As water remains widely used in many cooling systems, understanding the relationship between cooling technologies and water consumption is essential for improving cooling efficiency and sustainability. This paper presents a survey of reported water usage effectiveness (WUE) across 83 data centre entries, providing a combined dataset that links WUE with heat-rejection categories. The reported data shows that 23 of these data centres exceed 0.4 L/kWh, which is a sustainability target specified by the Climate Neutral Data Centre Pact for new data centres in water-stressed regions using potable water. Dry facilities employing closed-loop liquid cooling require essentially no water, while evaporative systems typically report water usage effectiveness values up to 2.5 L/kWh. Reported WUE is a facility-level operational metric, set by the proportion of the IT heat load rejected by evaporation, which depends on the heat-rejection topology, ambient wet-bulb conditions, and operating set points. A higher server-side heat transfer coefficient permits a higher coolant supply temperature for a given chip temperature limit, widening the range of ambient conditions under which heat can be rejected without evaporative assistance. Server-side heat transfer is therefore an enabling condition for low WUE rather than a determinant of it. One-dimensional heat transfer models are developed to estimate heat transfer coefficients for different server-level cooling mechanisms widely used for cooling servers within data centres, including air cooling, single-phase immersion cooling, direct liquid cooling, and two-phase immersion cooling. Air cooling, with the lowest heat transfer coefficient, remains widely used in small-scale facilities, whereas direct liquid cooling and two-phase immersion cooling achieve coefficients up to three orders of magnitude higher and are increasingly deployed in high-density installations. These coefficients are used to derive an equivalent evaporative water demand, an upper-bound estimate of the water that would be evaporated in rejecting the heat each mechanism removes; it shares the units of reported WUE but describes thermal capability rather than facility water consumption. Full article
(This article belongs to the Special Issue Thermal Fluids: Theory and Applications)
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20 pages, 4891 KB  
Article
Construction and Validation of a Dynamics-Driven Boundary-Responsive Model for Sediment Deposition in Pumping Station Forebay
by Chunxun He, Liangliang Du, Hao Wang, Dan Zi, Chaoyue Wang and Fujun Wang
Fluids 2026, 11(8), 200; https://doi.org/10.3390/fluids11080200 - 14 Aug 2026
Viewed by 168
Abstract
Pumping stations serve as critical hydraulic infrastructure for water conveyance and irrigation. Sediment deposition in forebays can deteriorate intake flow conditions, increase hydraulic losses, reduce pumping efficiency, and consequently impair the long-term operational performance of pumping systems. To accurately predict sediment deposition in [...] Read more.
Pumping stations serve as critical hydraulic infrastructure for water conveyance and irrigation. Sediment deposition in forebays can deteriorate intake flow conditions, increase hydraulic losses, reduce pumping efficiency, and consequently impair the long-term operational performance of pumping systems. To accurately predict sediment deposition in complex three-dimensional flow fields, we developed a dynamics-driven boundary-responsive numerical model that integrates sediment particle dynamics with real-time bed evolution. This model adopts the near-bed vertical velocity of sediment particles as the deposition discrimination criterion and dynamically updates bed topography via a mass-conservation-based boundary response strategy. The proposed method was validated against open-channel experimental data. The simulated flow structures, deposition patterns, and temporal variations in deposition thickness agreed well with the measurements, with average deviations below 4%. Compared with conventional static-boundary numerical methods, the proposed model reproduces the coupled evolution of sediment transport, flow redistribution, and bed deformation with higher fidelity. The developed framework provides an effective numerical tool for sediment deposition prediction and offers practical support for hydraulic structure optimization, maintenance scheduling, and energy-efficient operation of pumping stations with sediment-laden flow. Full article
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31 pages, 4581 KB  
Article
A Torque-Balance Model for Predicting Arch Stability and Flow Blockage
by Saule Kazhikenova and Gulnazira Shaikhova
Fluids 2026, 11(8), 199; https://doi.org/10.3390/fluids11080199 - 13 Aug 2026
Viewed by 239
Abstract
Gas-assisted discharge of granular materials plays a critical role in shaft furnaces, moving-bed reactors, and other industrial multiphase systems, where interstitial gas flow strongly influences arch stability and may induce progressive flow blockage. Existing analytical models generally neglect aerodynamic gas–particle interactions, whereas CFD–DEM [...] Read more.
Gas-assisted discharge of granular materials plays a critical role in shaft furnaces, moving-bed reactors, and other industrial multiphase systems, where interstitial gas flow strongly influences arch stability and may induce progressive flow blockage. Existing analytical models generally neglect aerodynamic gas–particle interactions, whereas CFD–DEM simulations provide high predictive accuracy at the expense of substantial computational cost. To bridge this gap, the present study develops and validates a physically based Torque-Balance Model for predicting gas-assisted granular discharge, arch stability, and flow blockage. A comprehensive experimental investigation was performed using a quasi-two-dimensional transparent apparatus and a thermally stabilized shaft model operated under controlled conditions. Gas-assisted discharge was examined for different gas-flow directions, gas properties, outlet geometries, and particulate materials using hydrogen, helium, and air. High-speed imaging together with gravimetric measurements enabled detailed characterization of discharge regimes and arch evolution. The proposed analytical framework explicitly incorporates interparticle mechanical interactions, aerodynamic drag, outlet geometry, and gas-pressure effects within a unified torque-balance formulation. The model describes successive stages of the discharge process, including stable discharge, transition to blockage, and complete flow suppression, while maintaining computational efficiency suitable for engineering calculations. Experimental results demonstrated that gas-flow direction governs arch stability and discharge behavior. Co-current gas flow promoted repeated arch collapse and enhanced discharge, whereas counter-current flow progressively stabilized the granular arch and ultimately produced complete flow blockage. Validation against the complete experimental database demonstrated excellent agreement between theoretical predictions and experimental observations, yielding an average prediction error below 10%, a maximum deviation within ±20%, and a coefficient of determination of R2 = 0.96. The proposed Torque-Balance Model provides a computationally efficient and physically interpretable engineering framework that bridges the gap between simplified empirical correlations and computationally intensive CFD–DEM simulations and can be applied to the prediction and optimization of gas-assisted granular discharge in industrial multiphase systems. Full article
(This article belongs to the Special Issue Granular Flows and Fluid-Particle Systems in Industrial Processes)
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23 pages, 1800 KB  
Review
Effectiveness of Engineered Tsunami Mitigation Measures: A Review of Current Approaches and Research Needs, Part II: Experimental and Numerical Assessment
by Reza Arefi, Ioan Nistor and Abdolmajid Mohammadian
Fluids 2026, 11(8), 198; https://doi.org/10.3390/fluids11080198 - 12 Aug 2026
Viewed by 292
Abstract
Laboratory experiments and numerical modeling are essential tools for understanding the performance of engineered tsunami mitigation measures, enabling controlled investigation of complex hydrodynamic processes that are difficult to capture in real events. This review critically evaluates current research on key structural countermeasures, seawalls, [...] Read more.
Laboratory experiments and numerical modeling are essential tools for understanding the performance of engineered tsunami mitigation measures, enabling controlled investigation of complex hydrodynamic processes that are difficult to capture in real events. This review critically evaluates current research on key structural countermeasures, seawalls, breakwaters, and water-filled canals, focusing on findings from physical modeling and computational simulations. Evidence from numerical and laboratory studies demonstrates that properly designed mitigation structures can reduce tsunami wave energy, delay inland inundation, and decrease forces on downstream infrastructure. The effectiveness of these measures is strongly influenced by structural geometry, placement, and maintenance, as well as by accurate representation of flow dynamics in experiments and simulations. Despite significant advances, important gaps remain, including the validation of numerical models against high-fidelity experiments, the assessment of extreme events, and the evaluation of hybrid or integrated strategies combining multiple mitigation measures. This review identifies these gaps and highlights research priorities aimed at improving predictive capabilities, optimizing structural designs, and supporting the development of reliable, scalable, and context-specific tsunami mitigation solutions. Full article
(This article belongs to the Special Issue Feature Reviews for Fluids 2025–2026)
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31 pages, 7547 KB  
Review
Fluid Application Technologies in Plant Protection and Irrigation: A Review from Droplet Dynamics to Sprayers and Sprinklers
by Si-Liang Sun, Jian-Hui Gui, Kai Dong and Wei Zhang
Fluids 2026, 11(8), 197; https://doi.org/10.3390/fluids11080197 - 11 Aug 2026
Viewed by 253
Abstract
Plant protection and sprinkler irrigation rely on common fluid dynamic processes, including liquid atomization, droplet transport, target interaction, and flow distribution. This review analyses these mechanisms within a multi-scale framework. The analysis starts with droplet–target interactions. It addresses droplet impact and foliar retention [...] Read more.
Plant protection and sprinkler irrigation rely on common fluid dynamic processes, including liquid atomization, droplet transport, target interaction, and flow distribution. This review analyses these mechanisms within a multi-scale framework. The analysis starts with droplet–target interactions. It addresses droplet impact and foliar retention in plant protection, alongside droplet kinetic energy and soil-surface responses in irrigation. The discussion then extends to the spatial transport and distribution of sprays. At the device scale, this work examines nozzles and sprinklers from the perspective of fluid mechanics and structural innovation, detailing how nozzle geometry and flow conditions affect macroscopic application performance. Finally, this review addresses advances at the system scale, with a focus on energy consumption and data-driven performance prediction. By connecting fluid behavior across multiple spatial scales, this work links micro-scale droplet dynamics to whole-system performance and identifies directions for improving agricultural spraying and sprinkler irrigation systems. Full article
(This article belongs to the Special Issue Research on the Formation and Movement of Droplets)
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23 pages, 5550 KB  
Article
Numerical Investigation of Sweeping-Jet Control at the Nose Region of a High-Speed Train
by Tanghong Liu, Wenxuan Yuan, Zhiqi Liu and Xiaodong Chen
Fluids 2026, 11(8), 196; https://doi.org/10.3390/fluids11080196 - 11 Aug 2026
Viewed by 190
Abstract
With the increase in operating speed, aerodynamic drag becomes a major part of the total resistance of high-speed trains. Further drag reduction by only optimizing the streamlined shape is difficult. In this study, a three-car high-speed train model was used to explore active [...] Read more.
With the increase in operating speed, aerodynamic drag becomes a major part of the total resistance of high-speed trains. Further drag reduction by only optimizing the streamlined shape is difficult. In this study, a three-car high-speed train model was used to explore active drag reduction by sweeping jets. The improved delayed detached-eddy simulation (IDDES) method based on the SST k-ω turbulence model was adopted. An equivalent sweeping-jet model was used to reduce the computational cost. Three important parameters were considered: the outlet width of the sweeping-jet model, the jet angle, and the jet velocity. The results show that a larger jet outlet gives a stronger drag-reduction effect. When the ratio between the jet outlet width and the train width is 5:50, the total drag reduction in the three-car train reaches about 1.5%. When the jet angle is 120°, the total drag reduction reaches about 2.84%, and the middle car has the largest drag reduction of 6.19%. When the jet velocity is 0.30 times the incoming flow velocity, the total drag reduction reaches about 4.0%. The main flow-control mechanism is that the sweeping jet forms a low-speed recirculation region near the train surface. This region lifts the incoming flow, weakens its direct impact on the train body, and reduces the surface pressure in the controlled region. The results provide a useful basis for applying sweeping jets to aerodynamic drag reduction in high-speed trains. Full article
(This article belongs to the Special Issue Open and Closed-Loop Control Systems for Active Flow Control)
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18 pages, 6999 KB  
Article
A Computational Study of the Efficiency of Using Low-Concentration Nanoemulsions with Diesel Fuel to Enhance Oil Recovery
by Dmitriy Guzei, Sofia Ivanova, Angelica Skorobogatova, Vladimir Zhigarev and Andrey Minakov
Fluids 2026, 11(8), 195; https://doi.org/10.3390/fluids11080195 - 10 Aug 2026
Viewed by 290
Abstract
The article presents the results of systematic numerical studies on the efficacy of low-concentration nanoemulsions for enhanced oil recovery. A series of computational investigations was conducted to examine the displacement regimes of oil from digital core models with varying permeability using the developed [...] Read more.
The article presents the results of systematic numerical studies on the efficacy of low-concentration nanoemulsions for enhanced oil recovery. A series of computational investigations was conducted to examine the displacement regimes of oil from digital core models with varying permeability using the developed low-concentration diesel fuel-based nanoemulsions. The volume fraction of diesel fuel in the emulsions was 1 vol.%. The volume fraction of the emulsifier ranged from 0.05% to 0.4%. The nanoemulsions demonstrated high efficiency across the entire range of permeabilities considered. It was shown that the behavior of the displacement front for water and for emulsions differs fundamentally. The waterflood front for emulsions is significantly more uniform and exhibits more complete cross-sectional saturation of pore channels compared to water flooding. With an increase in the capillary number, the oil displacement coefficient achieved by nanoemulsions increases. However, the maximum incremental effect from the use of nanoemulsions is observed at the minimum values of the capillary number. This finding indicates that the primary mechanisms underlying the positive impact of emulsions on oil displacement are the reduction in interfacial tension and the improvement of wettability. Full article
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17 pages, 5512 KB  
Article
Simulation of Particle Structure Rearrangement and Reaction in Wall-Flow Filters at High Flow Velocities with Lattice Boltzmann Methods
by Christoph Gaul, Ole Desens, Pascal Ernst, Andreas Nettekoven, Achim Dittler and Mathias J. Krause
Fluids 2026, 11(8), 194; https://doi.org/10.3390/fluids11080194 - 5 Aug 2026
Viewed by 586
Abstract
Wall-flow filters are used in exhaust gas after treatment systems to reduce particulate matter emissions from internal combustion engines. The particles accumulate on the filter surface during operation, forming a layer that progressively increases the flow resistance and thus the pressure drop. This [...] Read more.
Wall-flow filters are used in exhaust gas after treatment systems to reduce particulate matter emissions from internal combustion engines. The particles accumulate on the filter surface during operation, forming a layer that progressively increases the flow resistance and thus the pressure drop. This layer consists mostly of combustible materials but also contains inert ash parts. The pressure drop increase leads to the necessity of regenerating the filter. Filter regeneration may cause particle structure fragments to rearrange within single-filter channels, leading to specific ash deposition patterns that modify the filter’s pressure drop, loading behavior, and separation efficiency. This work advances previous investigations toward application-relevant temperature and inflow-velocity conditions by extending the existing resolved-particle methodology with turbulence and reaction models, enabling temperature-dependent effects on particle-structure fragments to be considered. The rearrangement process is studied in detail. It can be shown that at high velocity, most gas crosses into the outlet channel at the end of the inflow channel, leading to a pressure spike. A fragment-local reaction model was introduced and shows qualitative agreement with the experimental results. These simulations also showed a temperature difference of about 15 K between particles at the beginning and end of the inlet channel, leading to faster oxidation close to the inlet. The presented modeling approach helps to assess the formation of deposition patterns and their influence on filter behavior, engine efficiency, fuel consumption, and long-term filter durability. Full article
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23 pages, 7794 KB  
Article
Catalytic Combustion Enhancement of Cottonseed Biodiesel-Based Nanofuel Containing MgCO3 Nanoparticles in a Diesel Engine: Experimental Investigation and RSM Optimization
by Arif Savaş, Samet Uslu, Oğuzhan Der and Ramazan Şener
Fluids 2026, 11(8), 193; https://doi.org/10.3390/fluids11080193 - 3 Aug 2026
Viewed by 547
Abstract
This study investigates the effects of magnesium carbonate (MgCO3) nanoparticles in addition to cottonseed biodiesel/diesel blends on diesel engine performance and emission characteristics. Experiments were conducted under various engine loads, and Response Surface Methodology (RSM) was employed for modeling and multi-objective [...] Read more.
This study investigates the effects of magnesium carbonate (MgCO3) nanoparticles in addition to cottonseed biodiesel/diesel blends on diesel engine performance and emission characteristics. Experiments were conducted under various engine loads, and Response Surface Methodology (RSM) was employed for modeling and multi-objective optimization of operating parameters. Results showed that biodiesel blends increased brake-specific fuel consumption (BSFC) by up to 16.11% and reduced brake thermal efficiency (BTE) by up to 13.53% compared to diesel fuel, mainly due to lower calorific value and higher viscosity. However, the addition of MgCO3 nanoparticles improved combustion performance, reducing BSFC by up to 5.25% and increasing BTE by up to 5.87% under optimal conditions. Emission analysis revealed that nitrogen oxide (NOx) emissions increased by up to 49.06%, while hydrocarbon (HC) and carbon monoxide (CO) emissions decreased by up to 42.44% and 51.93%, respectively, indicating enhanced combustion efficiency. Carbon dioxide (CO2) emissions increased by up to 17.67% due to improved oxidation reactions. RSM analysis confirmed the statistical significance of the developed models with high coefficients of determination (R2 = 0.9178–0.9921). The optimal operating condition was determined to be 52.30 ppm MgCO3 and 1.51 kW engine load. Validation experiments showed good agreement between predicted and experimental results, with errors ranging from 0.71% to 8.83%, all within acceptable limits. Overall, the study demonstrates that MgCO3 nanoparticles can partially mitigate the performance drawbacks of biodiesel while improving combustion quality, and RSM is an effective tool for optimizing engine operating conditions. Full article
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36 pages, 41555 KB  
Article
3D Numerical Study of Wave–Current-Induced Hydrodynamic and Seabed Dynamic Responses Around a Twin-Pile Group with Various Flow Skew Angles
by Ziheng Huang, Zichen Su, Wei Zhang, Xiaonan Tang, Chenxin Wan and Ming Li
Fluids 2026, 11(8), 192; https://doi.org/10.3390/fluids11080192 - 31 Jul 2026
Viewed by 466
Abstract
This paper systematically investigates the hydrodynamic and seabed dynamic responses around twin-pile groups under various wave–current combinations (current velocity Uc=±1.0,±0.8,±0.6,±0.4,±0.2, 0 m/s) and flow skew [...] Read more.
This paper systematically investigates the hydrodynamic and seabed dynamic responses around twin-pile groups under various wave–current combinations (current velocity Uc=±1.0,±0.8,±0.6,±0.4,±0.2, 0 m/s) and flow skew angles (θ=0°,30°,60°,90°) using a 3D coupled model developed in OpenFOAM. Hydrodynamic results indicate that water surface profiles and gap vortex shedding are heavily modulated by wave–current superposition and pile arrangements. Specifically, strong following currents elongate separated shear layers and amplify gap vorticity, whereas increasing the flow skew angle (θ60°) effectively mitigates upstream wake interference. Furthermore, pore water pressure escalates sharply from strong opposing to strong following currents, exhibiting significant attenuation with depth. Strong opposing currents drastically intensify lateral liquefaction risks around the upstream pile, while strong following currents induce irregular liquefaction distribution. Especially, the maximum pore water pressure and maximum liquefaction depths are induced under strong currents (Uc=±1.0 m/s) at a 60° staggered arrangement. These findings highlight the vulnerability of the lateral seabed regions, indicating that targeted asymmetric reinforcement strategies offer an effective approach for mitigating liquefaction risks in offshore twin-pile foundation designs. Full article
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30 pages, 3254 KB  
Article
Study of the Synergistic Flowback Technology of Fracturing-Fluid Self-Flow and CO2 Gas Lift in Shale Reservoirs of the Lianggaoshan Formation, Sichuan Basin
by Shibin Li and Jinyan Li
Fluids 2026, 11(8), 191; https://doi.org/10.3390/fluids11080191 - 31 Jul 2026
Viewed by 338
Abstract
Severe fracturing-fluid retention and low post-fracturing flowback efficiency are common in the Lianggaoshan shale reservoirs of the Sichuan Basin. Liquid loading may also occur during late production. To address these problems, this study investigates a synergistic flowback technology that combines natural fracturing-fluid flowback [...] Read more.
Severe fracturing-fluid retention and low post-fracturing flowback efficiency are common in the Lianggaoshan shale reservoirs of the Sichuan Basin. Liquid loading may also occur during late production. To address these problems, this study investigates a synergistic flowback technology that combines natural fracturing-fluid flowback with CO2 gas lift. First, based on the complex fracture network characteristics of the Lianggaoshan shale reservoir, the interaction mechanisms between hydraulic fractures and natural fractures were investigated. An energy model for fracturing-fluid flowback under natural flowback conditions was established, revealing that reservoir gas expansion energy, hydromechanical energy, and rock elastic energy are the primary driving forces for fracturing-fluid flowback. Furthermore, considering fracture closure behavior, fluid leakoff, and wellbore flow dynamics, a calculation model for the natural flowback of fracturing fluid was developed, and a staged pressure-controlled flowback strategy was proposed. Subsequently, to address the decline in liquid unloading capacity caused by formation-energy depletion during the late stage of natural flowback, a gas-lift-assisted flowback multiphase flow model for the wellbore was established. The effects of the gas injection pressure, gas injection rate, and wellhead pressure on liquid unloading efficiency were systematically investigated. The results indicate that the liquid unloading rate increases with an increasing gas injection pressure and gas injection rate; however, a pronounced diminishing marginal effect is observed. For the Well H1 reference case, the central recommended gas injection pressure was 12 MPa, the gas injection rate was 8 × 104–10 × 104 m3/d, and the wellhead backpressure was maintained below 0.5 MPa. Furthermore, the CO2-assisted flowback mechanisms were evaluated by distinguishing between the effects explicitly represented in the model and the potential reservoir-scale physicochemical effects. The reduction in wellbore mixture density and bottomhole flowing pressure was simulated directly, whereas CO2–oil mass transfer, viscosity reduction, mineral dissolution, and changes in water-blocking behavior were interpreted with reference to published experimental studies. Based on these mechanisms, a three-stage synergistic optimized flowback scheme, consisting of “CO2 soaking–natural flowback–CO2 gas lift,” was established. A sequence of stagewise quasi-steady PIPESIM calculations was subsequently performed over the 30-day operating schedule. Under the adopted simulation conditions, the recommended soaking period is 5–7 days. The operation should be switched to gas lift when the wellhead pressure falls below 1.5 MPa or when daily liquid production declines continuously by more than 20%. Under the synergistic scheme, the 30-day cumulative flowback volume was predicted to reach 3492 m3. This value was substantially higher than those obtained by conventional natural flowback and standalone gas-lift processes. Moreover, the flowback curve exhibits a distinct “secondary surge” characteristic. These findings provide a theoretical basis and technical support for efficient fracturing-fluid flowback and stable long-term production in the Lianggaoshan Formation. They may also be applicable to other shale oil reservoirs with low porosity and ultra-low permeability. Full article
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4 pages, 176 KB  
Editorial
Computational Fluid Dynamics Applied to Transport Phenomena: From Fundamental Modeling to Engineering Design
by Liércio André Isoldi, Luiz Alberto Oliveira Rocha and Elizaldo Domingues Dos Santos
Fluids 2026, 11(8), 190; https://doi.org/10.3390/fluids11080190 - 31 Jul 2026
Viewed by 349
Abstract
Transport phenomena, which involve the transfer of momentum, energy, and mass, underlie a wide range of problems in numerous engineering fields, including environmental, civil, mechanical, chemical, energy, and aerospace engineering [...] Full article
(This article belongs to the Special Issue Computational Fluid Dynamics Applied to Transport Phenomena)
22 pages, 11421 KB  
Article
Mechanism of the Influence of Design Parameters on the Power Characteristics of a Multi-Stage Cup-Shaped Paddle Agitator Based on CFD Simulation
by Jingmu Bai, Jian Sun, Yunfei Li, Hailun Ren, Qingzhao Liu, Wenhui Shen, Lu Wang, Weihong Li, Bingxin Zhu, Zheng Wang and Yang Liu
Fluids 2026, 11(8), 189; https://doi.org/10.3390/fluids11080189 - 30 Jul 2026
Viewed by 227
Abstract
Agitator reactors are widely used in chemical production processes, and their structural design has a significant impact on power consumption. Therefore, this study performs numerical simulations of multi-stage cup-shaped paddle agitators with different geometric parameters, and discusses in detail the effects of the [...] Read more.
Agitator reactors are widely used in chemical production processes, and their structural design has a significant impact on power consumption. Therefore, this study performs numerical simulations of multi-stage cup-shaped paddle agitators with different geometric parameters, and discusses in detail the effects of the paddle spacing (S/H), the ratio of the upper paddle length to the reactor radius (Ls/R), the ratio of the lower paddle length to the reactor radius (Lx/R), and the ratio of the upper to lower paddle lengths (Ls/Lx) on the reactor’s power characteristics and internal flow field. Equations were derived to relate the power number (Np) to parameters such as Re, Ls/R, and Lx/R. The study found that, at the same Reynolds number, torque exhibits a slight upward trend as the paddle spacing increases; the best mixing effect is achieved when S/H is 0.333. Based on this pitch, when Ls/R, and Lx/R exceed 0.67, the mixing process fails to form a stable and complete radial circulation; when Ls/R and Lx/R are less than 0.53, the high-velocity zone in the flow field decreases, leading to the formation of dead zones. Therefore, selecting a multi-stage cup-shaped impeller with an Ls/R value of 0.53, an Lx/R value of 0.53, and Ls/Lx of 1 can achieve better mixing results with lower power consumption. These findings provide a reference for the energy-efficient optimization design of multi-stage cup-shaped impeller mixers in industrial applications. Full article
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18 pages, 3027 KB  
Review
Effectiveness of Engineered Tsunami Mitigation Measures: A Review of Current Approaches and Research Needs, Part I: Field Surveys
by Reza Arefi, Ioan Nistor and Abdolmajid Mohammadian
Fluids 2026, 11(8), 188; https://doi.org/10.3390/fluids11080188 - 30 Jul 2026
Cited by 1 | Viewed by 417
Abstract
Tsunamis, though infrequent, pose catastrophic threats to coastal communities and infrastructure, underscoring the urgent need for effective mitigation strategies. This review provides a comprehensive evaluation of current engineered countermeasures, specifically seawalls, breakwaters, and water-filled canals, by synthesizing findings from post-tsunami field surveys. Evidence [...] Read more.
Tsunamis, though infrequent, pose catastrophic threats to coastal communities and infrastructure, underscoring the urgent need for effective mitigation strategies. This review provides a comprehensive evaluation of current engineered countermeasures, specifically seawalls, breakwaters, and water-filled canals, by synthesizing findings from post-tsunami field surveys. Evidence from major events, such as the 2011 Tohoku Tsunami, indicates that well-designed structural measures can substantially reduce tsunami wave energy and delay inland inundation, thereby improving the resilience of coastal infrastructure. However, their effectiveness depends heavily on proper geometric configuration, construction quality, regular maintenance, and integration with non-structural measures such as evacuation planning. Recent experimental and numerical investigations have also highlighted the potential of innovative countermeasures, in attenuating bore forces and protecting critical infrastructure. Despite advancements, significant knowledge gaps remain, particularly concerning the long-term reliability, cost-effectiveness, and adaptability of these systems under diverse tsunami conditions. This critical review aims to identify these gaps and outline key priorities for future research and development. The findings contribute to a deeper understanding of structural tsunami mitigation and support the advancement of integrated, resilient strategies for reducing disaster risk in tsunami-prone regions worldwide. Full article
(This article belongs to the Special Issue Feature Reviews for Fluids 2025–2026)
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21 pages, 10705 KB  
Article
Evaluation of the Gas-Discharge Plasma Characteristics in the Absence and Presence of a Magnetic Field in a High-Speed Flow Based on Experimental Data and Predictive Modeling
by Olga A. Azarova, Tatiana A. Lapushkina, Ekaterina V. Reshetova and Oleg V. Kravchenko
Fluids 2026, 11(8), 187; https://doi.org/10.3390/fluids11080187 - 26 Jul 2026
Viewed by 313
Abstract
The main objective of this study is to obtain the average parameters of gas-discharge plasma when controlling the steady position of the bow shock wave (BSW) using the combined action of a gas discharge initiated by a current from an external source and [...] Read more.
The main objective of this study is to obtain the average parameters of gas-discharge plasma when controlling the steady position of the bow shock wave (BSW) using the combined action of a gas discharge initiated by a current from an external source and a magnetic field near the frontal surface of the model. The studies were carried out using both experimental and numerical methods in xenon and air. A comparison of the numerical and experimental dependences of the relative distance of the steady BSW from the model on the discharge power showed good agreement. Based on the conducted flow modeling, taking into account the dependence of the adiabatic index on the degree of ionization and the degree of nonequilibrium, and using the theory of Burm et al., gas-discharge plasma characteristics were obtained, such as the degree of ionization and the degree of nonequilibrium, the electron density and the electron temperature in the absence and presence of a magnetic field. By this way an integrated experimental–computational system was formed in which the measured characteristics of the discharge and BSW, as well as the numerically obtained averaged plasma parameters in the impact zone, are combined with the theory of Burm et al. to clarify the thermodynamic state of the medium and determine the corresponding characteristics of the gas-discharge plasma. The obtained results can be used for assessing the characteristics of plasma gas dynamic and magnetohydrodynamic phenomena in high-speed flows; for example, in the development of control systems that take into account the influence of plasma parameters and the electric and magnetic fields. Full article
(This article belongs to the Special Issue High-Speed Processes in Continuous Media)
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4 pages, 165 KB  
Editorial
Special Issue Pipe Flow: Research and Applications Second Edition
by Leonardo Di G. Sigalotti
Fluids 2026, 11(8), 186; https://doi.org/10.3390/fluids11080186 - 25 Jul 2026
Viewed by 405
Abstract
This collection features eleven excellent papers that are included in the second edition of the Special Issue, “Pipe Flow: Research and Applications” [...] Full article
(This article belongs to the Special Issue Pipe Flow: Research and Applications, 2nd Edition)
23 pages, 11949 KB  
Article
Numerical Simulations of Incompressible Flows Around a Rotating Circular Cylinder with Convective Heat Transfer Using the Immersed Boundary Method
by Yang Zhang and Yikun Wang
Fluids 2026, 11(8), 185; https://doi.org/10.3390/fluids11080185 - 24 Jul 2026
Viewed by 365
Abstract
An adaptive immersed boundary method (IBM) for simulating non-isothermal incompressible flows with convective heat transfer involving a rotating circular cylinder is developed. Both Dirichlet- (isothermal) and Neumann (zero heat flux)-type temperature boundary conditions are implemented. In addition to the discrete momentum forcing and [...] Read more.
An adaptive immersed boundary method (IBM) for simulating non-isothermal incompressible flows with convective heat transfer involving a rotating circular cylinder is developed. Both Dirichlet- (isothermal) and Neumann (zero heat flux)-type temperature boundary conditions are implemented. In addition to the discrete momentum forcing and energy forcing adopted to effectively satisfy the prescribed velocity and temperature boundary conditions, a mass source/sink term is introduced into the continuity equation to meet the mass conservation at the immersed boundary. The Navier–Stokes equations are solved using the fractional step method implemented on a staggered Cartesian grid system. Time stepping is performed using a second-order Adams–Bashforth/backward-differentiation method, while spatial derivatives are approximated with a second-order centered scheme. Testing of the flow induced by a rotating disk demonstrates that the spatial accuracy of the presented algorithm is second-order. Furthermore, the proposed method is validated by forced convective flow past a rotating isothermal circular cylinder. Finally, mixed Rayleigh–Bénard convection in a square cavity with an embedded adiabatic rotating circular cylinder is simulated, showing that heat transport can be greatly enhanced by increasing the rotating rate and radius of the cylinder at larger Prandtl numbers in the laminar regime. Full article
(This article belongs to the Section Heat and Mass Transfer)
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