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Fluids, Volume 10, Issue 10 (October 2025) – 27 articles

Cover Story (view full-size image): In this study, we simulated aerosol transport in the common area of a real inpatient ward. The risk of airborne transmission of COVID-19 in the ward was evaluated. The results showed that the central-return ventilation system causes directional air flows in the corridors, which enhanced long-distance aerosol transport and were conducive to infection transmission between different rooms. An improved ventilation system was proposed that aimed to reduce air mixing and minimise directional air flows. The improvement involved only rearrangement of air supply and exhaust vents, but led to significant reductions in both particle residence time and travelling distance within the ward, resulting in a 34% reduction in the overall infection probability. View this paper
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31 pages, 11576 KB  
Review
Machine Learning Reshaping Computational Fluid Dynamics: A Paradigm Shift in Accuracy and Speed
by Aly Mousaad Aly
Fluids 2025, 10(10), 275; https://doi.org/10.3390/fluids10100275 - 21 Oct 2025
Viewed by 855
Abstract
Accurate and efficient CFD simulations are essential for a wide range of engineering and scientific applications, from resilient structural design to environmental analysis. Traditional methods such as RANS simulations often face challenges in capturing complex flow phenomena like separation, while high-fidelity approaches including [...] Read more.
Accurate and efficient CFD simulations are essential for a wide range of engineering and scientific applications, from resilient structural design to environmental analysis. Traditional methods such as RANS simulations often face challenges in capturing complex flow phenomena like separation, while high-fidelity approaches including Large Eddy Simulations and Direct Numerical Simulations demand significant computational resources, thereby limiting their practical applicability. This paper provides an in-depth synthesis of recent advancements in integrating artificial intelligence and machine learning techniques with CFD to enhance simulation accuracy, computational efficiency, and modeling capabilities, including data-driven surrogate models, physics-informed methods, and ML-assisted numerical solvers. This integration marks a crucial paradigm shift, transcending incremental improvements to fundamentally redefine the possibilities of fluid dynamics research and engineering design. Key themes discussed include data-driven surrogate models, physics-informed methods, ML-assisted numerical solvers, inverse design, and advanced turbulence modeling. Practical applications, such as wind load design for solar panels and deep learning approaches for eddy viscosity prediction in bluff body flows, illustrate the substantial impact of ML integration. The findings demonstrate that ML techniques can accelerate simulations by up to 10,000 times in certain cases while maintaining or improving the accuracy, particularly in challenging flow regimes. For instance, models employing learned interpolation can achieve 40- to 80-fold computational speedups while matching the accuracy of baseline solvers with a resolution 8 to 10 times finer. Other approaches, like Fourier Neural Operators, can achieve inference times three orders of magnitude faster than conventional PDE solvers for the Navier–Stokes equations. Such advancements not only accelerate critical engineering workflows but also open unprecedented avenues for scientific discovery in complex, nonlinear systems that were previously intractable with traditional computational methods. Furthermore, ML enables unprecedented advances in turbulence modeling, improving predictions within complex separated flow zones. This integration is reshaping fluid mechanics, offering pathways toward more reliable, efficient, and resilient engineering solutions necessary for addressing contemporary challenges. Full article
(This article belongs to the Special Issue Machine Learning and Artificial Intelligence in Fluid Mechanics)
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27 pages, 6242 KB  
Article
Numerical Prediction of the NPSH Characteristics in Centrifugal Pumps
by Matej Štefanič
Fluids 2025, 10(10), 274; https://doi.org/10.3390/fluids10100274 - 21 Oct 2025
Viewed by 304
Abstract
This study focuses on the numerical analysis of a centrifugal pump’s suction capability, aiming to reliably predict its suction performance characteristics. The main emphasis of the research was placed on the influence of different turbulence models, the quality of the computational mesh, and [...] Read more.
This study focuses on the numerical analysis of a centrifugal pump’s suction capability, aiming to reliably predict its suction performance characteristics. The main emphasis of the research was placed on the influence of different turbulence models, the quality of the computational mesh, and the comparison between steady-state and unsteady numerical approaches. The results indicate that steady-state simulations provide an unreliable description of cavitation development, especially at lower flow rates where strong local pressure fluctuations are present. The unsteady k–ω SST model provides the best overall agreement with experimental NPSH3 characteristics, as confirmed by the lowest mean deviation (within the ISO 9906 tolerance band, corresponding to an overall uncertainty of ±5.5%) and by multiple operating points falling entirely within this range. This represents one of the first detailed unsteady CFD verifications of NPSH prediction in centrifugal pumps operating at high rotational speeds (above 2900 rpm), achieving a mean deviation below ±5.5% and demonstrating improved predictive capability compared to conventional steady-state approaches. The analysis also includes an evaluation of the cavitation volume fraction and a depiction of pressure conditions on the impeller as functions of flow rate and inlet pressure. In conclusion, this study highlights the potential of advanced hybrid turbulence models (such as SAS or DES) as a promising direction for future research, which could further improve the prediction of complex cavitation phenomena in centrifugal pumps. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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19 pages, 3911 KB  
Article
Numerical Investigation of Gas Flow Rate Optimization for Enhanced Mixing in RH Degassing
by Nihal Saji, Kiranchandru Lingeswaran, Xipeng Guo, Nicholas J. Walla, Rudolf Moravec and Chenn Zhou
Fluids 2025, 10(10), 273; https://doi.org/10.3390/fluids10100273 - 21 Oct 2025
Viewed by 250
Abstract
Optimizing the operational parameters of an RH degasser is essential for increasing the production of high-quality steel while reducing energy and resource consumption. This paper presents a study on the impact of different injection gas flow rates on the mixing characteristics of an [...] Read more.
Optimizing the operational parameters of an RH degasser is essential for increasing the production of high-quality steel while reducing energy and resource consumption. This paper presents a study on the impact of different injection gas flow rates on the mixing characteristics of an industrial-scale RH degasser and evaluates the optimal flow rate for achieving the lowest mixing time. A 3D simulation model was developed using a VOF–DPM framework, with gas flow rates being varied from 18 to 72 SCFM to assess mixing time and associated flow behavior. The results indicate that the mixing time has a non-linear relationship with the gas flow rate, and increasing the flow rate does not always lead to a reduced mixing time. A flow rate of 45 SCFM (a 1.5-fold increase from 18 SCFM) provided the best mixing efficiency, reducing the mixing time by 52%. Additionally, beyond 36 SCFM, a saturation limit was observed in the circulation rate, where further increases in the gas flow rate resulted in a less than 5% improvement in steel flowing through the snorkels. These findings highlight the need for careful evaluation of injection gas flow rates in RH operations to identify the optimal value that maximizes mixing efficiency, minimizes resource consumption, and enhances productivity by enabling greater steel output in less time. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics Applied to Transport Phenomena)
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22 pages, 25232 KB  
Article
RIM-PIV Measurements of Solid–Liquid Flow in a Stirred Tank Used for Mesenchymal Stem Cell Culture
by Mohamad Madani, Angélique Delafosse, Sébastien Calvo and Dominique Toye
Fluids 2025, 10(10), 272; https://doi.org/10.3390/fluids10100272 - 20 Oct 2025
Viewed by 287
Abstract
Mesenchymal stem cells are widely cultivated in stirred tank bioreactors. Due to their adhesion properties, they are attached to small spherical spheres called microcarriers. To understand the hydromechanical stresses encountered by the cells, it is essential to characterize the flow using the PIV [...] Read more.
Mesenchymal stem cells are widely cultivated in stirred tank bioreactors. Due to their adhesion properties, they are attached to small spherical spheres called microcarriers. To understand the hydromechanical stresses encountered by the cells, it is essential to characterize the flow using the PIV technique. However, the usual solid–liquid system used in cell cultures has poor optical properties. Thus, shifting to one with better optical properties, while respecting the physical characteristics, is mandatory to achieve a relevant representation. PMMA microparticles suspended with 61 wt% ammonium thiocyanate solution NH4SCN were found to be a robust candidate. The refractive index (RI) of both sides is of the order of 1.491 with a density ratio of ρf/ρp≈ 0.96, and particle size averaged around 168 μm. Using the RIM-PIV (refractive index matched particle image velocimetry) technique for a 0.7 L volume stirred tank equipped with an HTPG down-pumping axial impeller and operating at full homogeneous speed N=150 rpm, mean and turbulence quantities of the liquid phase were measured as a function of PMMA particle volume fractions αp, which ranged from 0.5 to 3 v%. This corresponds to a particle number density of n=12 particles/mm3, which is considered original and challenging for the PIV technique. At 3 v%, the addition of particles dampened the turbulent kinetic energy (TKE) of the liquid phase locally by 20% near the impeller. This impact became trivial (<10%) at the local-average level. The structure and direction of the recirculation loop also shifted. Full article
(This article belongs to the Special Issue Flow Visualization: Experiments and Techniques, 2nd Edition)
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20 pages, 7515 KB  
Article
Numerical Investigation on Flow Separation Control for Aircraft Serpentine Intake with Coanda Injector
by Zhan Fu, Zhixu Jin, Wenqiang Zhang, Tao Yang, Jichao Li and Jun Shen
Fluids 2025, 10(10), 271; https://doi.org/10.3390/fluids10100271 - 20 Oct 2025
Viewed by 293
Abstract
Modern military aircraft integrate a large number of high-power-density electronic devices, which leads to a rapid increase in thermal load and poses significant challenges for heat dissipation. A promising thermal management approach is to intake ram air through a fuselage-mounted S-duct inlet and [...] Read more.
Modern military aircraft integrate a large number of high-power-density electronic devices, which leads to a rapid increase in thermal load and poses significant challenges for heat dissipation. A promising thermal management approach is to intake ram air through a fuselage-mounted S-duct inlet and utilize it as a heat sink for the downstream heat exchanger. However, the S-duct’s geometry can induce significant flow separation and total pressure distortion, thereby limiting the mass flow rate. To address these challenges, this study investigates three flow-control strategies—vortex generators (VGs), Coanda injectors, and their combination—using high-fidelity three-dimensional numerical simulations validated against experimental data. The results indicate that VGs effectively suppress local separation and improve flow uniformity, although additional losses limit pressure recovery. The Coanda injector enhances boundary-layer momentum, substantially increasing mass flow throughput and pressure recovery. The combined VGs and Coanda injector approach achieves a lower distortion coefficient and provides a favorable balance between pressure recovery and flow uniformity. These findings demonstrate the potential of hybrid passive–active flow control in improving inlet aerodynamic quality and supporting integrated thermal management systems for future aircraft. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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15 pages, 3566 KB  
Article
Passive Control of Boundary-Layer Separation on a Wind Turbine Blade Using Varying-Parameter Flow Deflector
by Xin Chen, Jiaqian Qiu, Junwei Zhong, Chaolei Zhang and Yufeng Gan
Fluids 2025, 10(10), 270; https://doi.org/10.3390/fluids10100270 - 16 Oct 2025
Viewed by 230
Abstract
Horizontal-axis wind turbines are widely used for wind energy harvesting, but they often encounter flow separation near the blade root, leading to power loss and structural fatigue. A varying-parameter flow deflector (FD) is proposed as a passive flow control method. The FD adopts [...] Read more.
Horizontal-axis wind turbines are widely used for wind energy harvesting, but they often encounter flow separation near the blade root, leading to power loss and structural fatigue. A varying-parameter flow deflector (FD) is proposed as a passive flow control method. The FD adopts varying parameters along the blade spanwise direction to match the varying local angle of attack. Numerical simulation using the transition SST k-ω turbulence model combined with the response-surface methodology are used to investigate the effect of the varying-parameter FD on the flow structure and aerodynamic performance of the NREL Phase VI wind turbine. The results indicate that optimal performance can be achieved when the normal position of the FD increases from the blade root to the tip, and the install angle of the FD should be greater than 62° at blade section of r/R = 63.1%. Furthermore, response-surface methodology was employed to optimize the deflector parameters, with analysis of variance revealing the relative significance of geometric factors (l1 > l2 > θ1 > θ2). Compared with the original blade, the shaft torque of the controlled blade with the optimal FD is improved by 24.7% at 10 m/s. Full article
(This article belongs to the Special Issue Industrial CFD and Fluid Modelling in Engineering, 3rd Edition)
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15 pages, 2013 KB  
Article
Influence of Bubble Shape on Mass Transfer in Multiphase Media: CFD Analysis of Concentration Gradients
by Irina Nizovtseva, Pavel Mikushin, Ilya Starodumov, Ksenia Makhaeva, Margarita Nikishina, Sergey Vikharev, Olga Averkova, Dmitri Alexandrov, Dmitrii Chernushkin and Sergey Lezhnin
Fluids 2025, 10(10), 269; https://doi.org/10.3390/fluids10100269 - 16 Oct 2025
Viewed by 317
Abstract
Our study investigates how non-spherical bubble shapes influence gas–liquid mass transfer across the bubble interface. An analytical shape descriptor, namely Superformula, is used to parametrically define the bubble interface, enabling efficient CFD simulations over a range of Reynolds (Re) and [...] Read more.
Our study investigates how non-spherical bubble shapes influence gas–liquid mass transfer across the bubble interface. An analytical shape descriptor, namely Superformula, is used to parametrically define the bubble interface, enabling efficient CFD simulations over a range of Reynolds (Re) and Eötvös (Eo) numbers. By prescribing the bubble geometry analytically, we avoid expensive interface-capturing simulations and directly compute the concentration field without transient boundary shape pre-equilibration. The represented approach is computationally efficient and captures the impact of bubble shape and flow parameters on the dissolved gas concentration gradients in the surrounding liquid. Results show that bubble deformation alters the distribution of dissolved gas around the bubble and the overall mass transfer rate, with higher Re enhancing convective transport and higher Eo (more deformed bubbles), leading to anisotropic concentration boundary layers. The developed framework not only advances a fundamental understanding of bubble-driven mass transfer mechanisms but also directly addresses industrial needs, particularly in optimizing oxygen delivery within bioreactors contour and similar aerated processes. The proposed efficient modeling strategy provides a basis for developing fast surrogate tools in hybrid modeling frameworks, where high-fidelity CFD insights are incorporated into larger-scale multiphase process simulations. Full article
(This article belongs to the Special Issue Advances in Multiphase Flow Science and Technology, 2nd Edition)
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13 pages, 1024 KB  
Article
A Verification of the Two-Fluid Model with Interfacial Inertial Coupling
by Raghav Ram, Martín López-de-Bertodano, James A. Howard and Alejandro Clausse
Fluids 2025, 10(10), 268; https://doi.org/10.3390/fluids10100268 - 14 Oct 2025
Viewed by 262
Abstract
The two-fluid model (TFM) has become a foundational tool in numerical codes used for engineering analyses of two-phase flows in energy systems. However, its completeness remains a topic of debate because improper modeling of interfacial inertial coupling can render the momentum conservation equations [...] Read more.
The two-fluid model (TFM) has become a foundational tool in numerical codes used for engineering analyses of two-phase flows in energy systems. However, its completeness remains a topic of debate because improper modeling of interfacial inertial coupling can render the momentum conservation equations elliptic. This issue leads to short wavelength perturbations growing at an infinite rate. This paper demonstrates the practical feasibility of incorporating variational inertial-coupling terms into an industrial CFD TFM code to ensure it is well-posed without the need for regularization. For verification, two special cases with exact analytical solutions of the TFM equations are utilized, exhibiting convergence at a mesh resolution of 1 mm. Full article
(This article belongs to the Special Issue Industrial CFD and Fluid Modelling in Engineering, 3rd Edition)
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17 pages, 5030 KB  
Article
Mitigating Airborne Infection Transmission in the Common Area of Inpatient Wards—A Case Study
by Xiangdong Li, Kevin Kevin, Wai Kit Lam, Andrew Ooi, Cameron Zachreson, Nicholas Geard, Loukas Tsigaras, Samantha Bates, Forbes McGain, Lidia Morawska, Marion Kainer and Jason Monty
Fluids 2025, 10(10), 267; https://doi.org/10.3390/fluids10100267 - 14 Oct 2025
Viewed by 582
Abstract
In a hospital ward, transmission of airborne pathogens can occur in any area where people breathe the same air. These areas include patient rooms and specialised treatment rooms, as well as corridors and common areas. Numerous studies have been conducted to investigate the [...] Read more.
In a hospital ward, transmission of airborne pathogens can occur in any area where people breathe the same air. These areas include patient rooms and specialised treatment rooms, as well as corridors and common areas. Numerous studies have been conducted to investigate the risk of airborne transmission within hospital rooms where patient care activities take place; however, studies assessing the risk of exposure to airborne pathogens in common areas such as nurse stations and corridors, in which healthcare workers spend up to 63% of their time, are very rare. In this study, we addressed this gap by simulating aerosol transport in the common area of a real inpatient ward encompassing different types of patient rooms and equipped with a mixing ventilation system. The risk of airborne transmission of COVID-19 in the ward was evaluated using a spatially resolved risk model, coupled with the clinical and pathological data on SARS-CoV-2 infection. The results showed that the central-return ventilation system causes directional air flows in the corridors, which enhanced long-distance aerosol transport and were conducive to infection transmission between different rooms. An improved ventilation system was proposed that aimed to reduce air mixing and minimise directional air flows. The improvement involved only rearrangement of air supply and exhaust vents, but led to significant reductions in both particle residence time and travelling distance within the ward, contributing to a nearly two-fold increase and 60% decrease in the areas of low-risk and high-risk zones, respectively, resulting in a 34% reduction in the overall infection probability in the studied area. This study demonstrated the potential of preventing hospital-acquired infection (HAI) via engineering controls and provided recommendations for future studies to assess novel ventilation configurations to reduce transmission risk. Full article
(This article belongs to the Special Issue CFD Applications in Environmental Engineering)
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25 pages, 8293 KB  
Article
Prediction of Erosion of a Hydrocyclone Inner Wall Based on CFD-DPM
by Ziyang Wu, Gangfeng Zheng and Shuntang Li
Fluids 2025, 10(10), 266; https://doi.org/10.3390/fluids10100266 - 13 Oct 2025
Viewed by 371
Abstract
The erosion mechanism of hydrocyclones under air column conditions is still unclear. In this paper, Computational Fluid Dynamics–Discrete Phase Model (CFD-DPM) technology is adopted to perform transient simulations of the three-phase flow (liquid–gas–solid) within a hydrocyclone. The Reynolds Stress Model (RSM) and Volume [...] Read more.
The erosion mechanism of hydrocyclones under air column conditions is still unclear. In this paper, Computational Fluid Dynamics–Discrete Phase Model (CFD-DPM) technology is adopted to perform transient simulations of the three-phase flow (liquid–gas–solid) within a hydrocyclone. The Reynolds Stress Model (RSM) and Volume of Fluid (VOF) model are adopted to simulate the continuous phase flow field within the hydrocyclone, while the DPM coupled with the Oka erosion model is used to predict the particle flow and erosion mechanisms on each wall within the hydrocyclone. The particle sizes considered are 15 μm, 30 μm, 60 μm, 100 μm, 150 μm, and 200 μm, respectively, with a density of 2600 kg/m3. The particle velocity is consistent with the fluid velocity at 5 m/s, the total mass flow rate is 6 g/s, and the volume fraction is less than 10%. The results indicate that the cone section suffers the severest erosion, followed by the overflow pipe, column section, infeed section, and roof section. The erosion in the cone section reaches its maximum value near the underflow port, with an erosion rate approximately 6.8 times that of the upper cone section. The erosion distribution in the overflow pipe is uneven. The erosion of the column section exhibits a spiral banded distribution with a relatively large pitch. The erosion rate in the infeed section is approximately 1.47 times that of the roof section. Full article
(This article belongs to the Special Issue Pipe Flow: Research and Applications, 2nd Edition)
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21 pages, 7464 KB  
Article
Suction Flow Measurements in a Twin-Screw Compressor
by Jamshid Malekmohammadi Nouri, Diego Guerrato, Nikola Stosic and Youyou Yan
Fluids 2025, 10(10), 265; https://doi.org/10.3390/fluids10100265 - 11 Oct 2025
Viewed by 219
Abstract
Mean flow velocities and the corresponding turbulence fluctuation velocities were measured within the suction port of a standard twin-screw compressor using LDV and PIV optical techniques. Time-resolved velocity measurements were carried out over a time window of 1° at a rotor speed of [...] Read more.
Mean flow velocities and the corresponding turbulence fluctuation velocities were measured within the suction port of a standard twin-screw compressor using LDV and PIV optical techniques. Time-resolved velocity measurements were carried out over a time window of 1° at a rotor speed of 1000 rpm, a pressure ratio of 1, and an air temperature of 55 °C. Detailed LDV measurements revealed a very stable and slow inflow, with almost no influence from rotor movements except near the rotors, where a more complex flow formed in the suction port. The axial velocity near the rotors exhibited wavy profiles, while the horizontal velocity showed a rotational flow motion around the centre of the port. The turbulence results showed uniform distributions and were independent of the rotors’ motion, even near the rotors. PIV measurements confirmed that there is no rotor movement influence on the inflow structure and revealed complex flow structures, with a crossflow dominated by a main flow stream and two counter-rotating vortices in the X-Y plane; in the Y-Z plane, the presence of a strong horizonal stream was observed away from the suction port, which turned downward vertically near the entrance of the port. The corresponding turbulence results in both planes showed uniform distributions independent of rotor motions that were similar in all directions. Full article
(This article belongs to the Section Turbulence)
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30 pages, 7320 KB  
Article
Micro-Hydropower Generation Using an Archimedes Screw: Parametric Performance Analysis with CFD
by Martha Fernanda Mohedano-Castillo, Carlos Díaz-Delgado, Boris Miguel López-Rebollar, Humberto Salinas-Tapia, Abad Posadas-Bejarano and David Rojas Valdez
Fluids 2025, 10(10), 264; https://doi.org/10.3390/fluids10100264 - 10 Oct 2025
Viewed by 572
Abstract
Micro-hydropower technologies are increasingly attracting attention due to their potential to contribute to sustainable energy generation. With the growing global demand for electricity, it is essential to research and innovate in the development of devices capable of harnessing hydroelectric potential through such technologies. [...] Read more.
Micro-hydropower technologies are increasingly attracting attention due to their potential to contribute to sustainable energy generation. With the growing global demand for electricity, it is essential to research and innovate in the development of devices capable of harnessing hydroelectric potential through such technologies. In this context, the Archimedes screw generator (ASG) stands out as a device that potentially offers significant advantages for micro-hydropower generation. This study aimed, through a simplified yet effective method, to analyze and determine the simultaneous effects of the number of blades, inclination angle, and flow rate on the torque, mechanical power, and efficiency of an ASG. Computational Fluid Dynamics (CFD) was employed to obtain the torque and perform the hydrodynamic analysis of the devices, in order to compare the results of the optimal geometric and operational characteristics with previous studies. This proposal also helps guide future work in the preliminary design and evaluation of ASGs, considering the geometric and flow conditions that take full advantage of the available water resources. Under the specific conditions analyzed, the most efficient generator featured three blades, a 20° inclination, and an inlet flow rate of 24.5 L/s, achieving a mechanical power output of 117 W with an efficiency of 71%. Full article
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24 pages, 5200 KB  
Article
Numerical Investigation of Particle Behavior Under Electrostatic Effect in Bifurcated Tubes
by Yanlin Zhao, Haowen Liu, Yonghui Ma and Jun Yao
Fluids 2025, 10(10), 263; https://doi.org/10.3390/fluids10100263 - 10 Oct 2025
Viewed by 274
Abstract
As the prevalence of respiratory diseases continues to rise, inhalation therapy has emerged as a crucial method for their treatment. The effective transmission of medications within the respiratory tract is vital to achieve therapeutic outcomes. Given that most inhaled particles carry electrostatic charges, [...] Read more.
As the prevalence of respiratory diseases continues to rise, inhalation therapy has emerged as a crucial method for their treatment. The effective transmission of medications within the respiratory tract is vital to achieve therapeutic outcomes. Given that most inhaled particles carry electrostatic charges, understanding the electrostatic effect on particle behavior in bifurcated tubes is of significant importance. This work combined Large Eddy Simulation-Lagrangian particle tracking (LES-LPT) technology to simulate particle behavior with three particle sizes (10, 20, and 50 μm) from G2 to G3 (“G” stands for generation) in bifurcated tubes, either with or without electrostatics, under typical human physiological conditions (Re = 1036). The results indicate that the electrostatic force has a significant effect on particle behavior in bifurcated tubes, which increases with particle size. Within the bifurcated tubes, the electrostatic force enhances particle movement in alignment with the secondary flow as well as intensifies the interaction of particles with local turbulent vortices and promotes particle dispersion rather than agglomeration. On the other hand, the distribution of the electrostatic field is influenced by particle behavior. Higher particle concentration presents stronger electrostatic strength, which increases with particle size. Therefore, it can be concluded that the electrostatic interactions among particles can prevent particles from aggregating and enhance the efficiency of inhalation therapy. Full article
(This article belongs to the Special Issue Research on the Formation and Movement of Droplets)
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15 pages, 3314 KB  
Article
Numerical Investigation of the Pneumatic Performance of Vacuum-Assisted Biopsy
by Chu Li, Ziying Zhang, Echuan Yang, Jiongxin Wang and Shuai Ma
Fluids 2025, 10(10), 262; https://doi.org/10.3390/fluids10100262 - 10 Oct 2025
Viewed by 294
Abstract
Vacuum-assisted biopsy needle is an important tool for minimally invasive tissue sampling. Its procedural efficiency is largely compromised by the limited pneumatic efficiency and the recurrent tissue winding problem. In this study, a fluid dynamics model of vacuum-assisted biopsy is established, and its [...] Read more.
Vacuum-assisted biopsy needle is an important tool for minimally invasive tissue sampling. Its procedural efficiency is largely compromised by the limited pneumatic efficiency and the recurrent tissue winding problem. In this study, a fluid dynamics model of vacuum-assisted biopsy is established, and its pneumatic performance is investigated. The analysis focuses on the interplay between pneumatic efficiency and structural design, particularly examining how geometric parameters influence the internal flow dynamics. The results demonstrate that the vacuum pressure applied linearly increases the flow rate. The main energy loss is located at the inlet area. Key findings reveal trade-offs between flow enhancement and winding risks, where anti-winding structures improve tissue winding but impair the pneumatic efficiency. The study can provide guidance for the structural optimization design of vacuum-assisted biopsy needles. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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14 pages, 577 KB  
Article
The Effect of Random Roughness for Fully Developed Forced Flow in Square Microchannels
by Michele Celli, Leandro Alcoforado Sphaier, Gabriele Volpi, Antonio Barletta and Pedro Vayssière Brandão
Fluids 2025, 10(10), 261; https://doi.org/10.3390/fluids10100261 - 9 Oct 2025
Viewed by 396
Abstract
The role of wall roughness in heat and mass transfer for fully developed viscous flows in square microchannels is investigated here. Since the roughness, which is the key geometrical feature to be investigated, introduces high velocity gradients at the wall, the effect of [...] Read more.
The role of wall roughness in heat and mass transfer for fully developed viscous flows in square microchannels is investigated here. Since the roughness, which is the key geometrical feature to be investigated, introduces high velocity gradients at the wall, the effect of the viscous dissipation is considered. A fully developed flow in the forced convection regime is assumed. This assumption allows the two-dimensional treatment of the problem; thus, the velocity and temperature fields are simulated on the microchannel cross-section. The boundary roughness is modeled by randomly throwing points around the nominal square cross-section perimeter and by connecting those points to generate a simple polygon. This modification of the nominal square shape of the cross-section influences the velocity and temperature fields, which are computed by employing a finite element method solver. The heat and mass transfer is studied by calculating the Nusselt and the Poiseuille numbers as a function of roughness amplitude at the boundary. Each Nusselt and Poiseuille number is obtained by employing an averaging procedure over a sample of a thousand cases. Full article
(This article belongs to the Special Issue Physics and Applications of Microfluidics)
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15 pages, 3156 KB  
Article
Numerical Investigation of NASA SC (2)-0714 Airfoil Icing in a Supersonic Flow
by Andrey Kozelkov, Nikolay Galanov and Andrey Kurkin
Fluids 2025, 10(10), 260; https://doi.org/10.3390/fluids10100260 - 5 Oct 2025
Viewed by 357
Abstract
Modern software systems have implemented calculation techniques that allow numerical modeling of the icing of various aerodynamic objects and show themselves well when modeling the icing of objects at subsonic speeds. This paper describes a technique that is used to solve the problem [...] Read more.
Modern software systems have implemented calculation techniques that allow numerical modeling of the icing of various aerodynamic objects and show themselves well when modeling the icing of objects at subsonic speeds. This paper describes a technique that is used to solve the problem of icing the profile of a NASA SC (2)-0714 airfoil streamlined by a supersonic gas stream. A feature of modeling this class of problems is the consideration of factors that arise when moving at high speeds: at supersonic flight speed, aerodynamic heating of the surface above 0 °C is observed, which is accompanied by a high intensity of impinging supercooled water droplets on this surface. The results of the numerical solution of the NASA SC (2)-0714 airfoil icing problem showed that even at a positive airfoil surface temperature, ice shapes can grow at the leading edge due to intense deposition of supercooled droplets. Full article
(This article belongs to the Special Issue High-Speed Processes in Continuous Media)
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22 pages, 2544 KB  
Article
Pressure Drops for Turbulent Liquid Single-Phase and Gas–Liquid Two-Phase Flows in Komax Triple Action Static Mixer
by Youcef Zenati, M’hamed Hammoudi, Abderraouf Arabi, Jack Legrand and El-Khider Si-Ahmed
Fluids 2025, 10(10), 259; https://doi.org/10.3390/fluids10100259 - 4 Oct 2025
Viewed by 417
Abstract
Static mixers are commonly used for process intensification in a wide range of industrial applications. For the design and selection of a static mixer, an accurate prediction of the hydraulic performance, particularly the pressure drop, is essential. This experimental study examines the pressure [...] Read more.
Static mixers are commonly used for process intensification in a wide range of industrial applications. For the design and selection of a static mixer, an accurate prediction of the hydraulic performance, particularly the pressure drop, is essential. This experimental study examines the pressure drop for turbulent single-phase and gas–liquid two-phase flows through a Komax triple-action static mixer placed on a horizontal pipeline. New values of friction factor and z-factor are reported for fully turbulent liquid single-phase flow (11,700 ≤ ReL ≤ 18,700). For two-phase flow, the pressure drop for stratified and intermittent flows (0.07 m/s ≤ UL ≤ 0.28 m/s and 0.46 m/s ≤ UG ≤ 3.05 m/s) is modeled using the Lockhart–Martinelli approach, with a coefficient, C, correlated to the homogenous void fraction. Conversely, the analysis of power dissipation reveals a dependence on both liquid and gas superficial velocities. For conditions corresponding to intermittent flow upstream of the mixer, flow visualization revealed the emergence of a swirling flow in the Komax static mixer. It is interesting to note that an increase in slug frequency leads to an increase, followed by stabilization of the pressure drop. The results offer valuable insights for improving the design and optimization of Komax static mixers operating under single-phase and two-phase flow conditions. In particular, the reported correlations can serve as practical tools for predicting hydraulic losses during the design and scale-up. Moreover, the observed influence of the slug frequency on the pressure drop provides guidance for selecting operating conditions that minimize energy consumption while ensuring efficient mixing. Full article
(This article belongs to the Special Issue Pipe Flow: Research and Applications, 2nd Edition)
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15 pages, 1942 KB  
Article
Predictive URANS/PDF Modeling of Unsteady-State Phenomena in Turbulent Hydrogen–Air Flames
by Mohamed Boukhelef, Mohammed Senouci, Mounir Alliche, Habib Merouane and Abdelhamid Bounif
Fluids 2025, 10(10), 258; https://doi.org/10.3390/fluids10100258 - 29 Sep 2025
Viewed by 391
Abstract
The escalating global demand for primary energy—still predominantly met by conventional carbon-based fuels—has led to increased atmospheric pollution. This underscores the urgent need for alternative energy strategies capable of reducing carbon emissions while meeting global energy requirements. Hydrogen, as a clean combustible fuel, [...] Read more.
The escalating global demand for primary energy—still predominantly met by conventional carbon-based fuels—has led to increased atmospheric pollution. This underscores the urgent need for alternative energy strategies capable of reducing carbon emissions while meeting global energy requirements. Hydrogen, as a clean combustible fuel, offers a promising alternative to hydrocarbons, producing neither soot, CO2, nor unburned hydrocarbons. Although nitrogen oxides (NOx) are the primary combustion by-products, their formation can be mitigated by controlling flame temperature. This study investigates the viability of hydrogen as a clean energy vector by simulating an unsteady, turbulent, non-premixed hydrogen jet flame interacting with an air co-flow. The numerical simulations employ the Unsteady Reynolds-Averaged Navier–Stokes (URANS) framework for efficient and accurate prediction of transient flow behavior. Turbulence is modeled using the Shear Stress Transport (SST k-ω) model, which enhances accuracy in high Reynolds number reactive flows. The combustion process is described using a presumed Probability Density Function (PDF) model, allowing for a statistical representation of turbulent mixing and chemical reaction. The simulation results are validated by comparison with experimental temperature and mixture fraction data, demonstrating the reliability and predictive capability of the proposed numerical approach. Full article
(This article belongs to the Special Issue Turbulence and Combustion)
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13 pages, 2543 KB  
Article
Experimental Study on the Time Response of the Microstructure of a Bentonite Suspension
by Hozman Butaybi-Mohamed, Pablo Fatuarte-Gutiérrez, David Gómez-Landero-López, Nicolás Reyes-Clemente, Juan I. Ros-Ruiz and Francisco J. Rubio-Hernández
Fluids 2025, 10(10), 257; https://doi.org/10.3390/fluids10100257 - 28 Sep 2025
Viewed by 271
Abstract
To obtain deeper information on the role played by microstructure evolution with time of particle suspensions specifically used in drilling processes, two representative time scales of a bentonite suspension were proposed. On one hand, a thixotropic time, which represents how fast the microstructure [...] Read more.
To obtain deeper information on the role played by microstructure evolution with time of particle suspensions specifically used in drilling processes, two representative time scales of a bentonite suspension were proposed. On one hand, a thixotropic time, which represents how fast the microstructure of the suspensions reaches equilibrium between build-up and break-down under shear, was obtained from hysteresis loop tests. On the other hand, a representative relaxation time, which refers to the time it takes to dissipate the stresses developed in the microstructure returning to the original free-stress state after some disturbance of the microstructure, was obtained from frequency sweep tests in the linear viscoelastic region using the Generalized Maxwell Model. The ratio of the relaxation time to the thixotropic time, named the thixo-elastic parameter, was lower than unity. Therefore, bentonite suspensions reach an equilibrium state resulting from equality of break and build processes after a long time of rest, while returning very fast to their original free-stress state, enabling the microstructure to rebuild mainly through a thixotropic phenomenon, which was almost not affected by internal stresses, and which facilitates the entrapping of rock cuttings generated during drilling processes. Full article
(This article belongs to the Special Issue IBERHEO 2024—Iberian Rheology)
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24 pages, 6138 KB  
Article
Research on Liquid Flow Pulsation Reduction in Microchannel of Pneumatic Microfluidic Chip Based on Membrane Microvalve
by Xuling Liu, Le Bo, Yusong Zhang, Chaofeng Peng, Kaiyi Zhang, Shaobo Jin, Guoyong Ye and Jinggan Shao
Fluids 2025, 10(10), 256; https://doi.org/10.3390/fluids10100256 - 28 Sep 2025
Viewed by 434
Abstract
The unsteady and discontinuous liquid flow in the microchannel affects the efficiency of sample mixing, molecular detection, target acquisition, and biochemical reaction. In this work, an active method of reducing the flow pulsation in the microchannel of a pneumatic microfluidic chip is proposed [...] Read more.
The unsteady and discontinuous liquid flow in the microchannel affects the efficiency of sample mixing, molecular detection, target acquisition, and biochemical reaction. In this work, an active method of reducing the flow pulsation in the microchannel of a pneumatic microfluidic chip is proposed by using an on-chip membrane microvalve as a valve chamber damping hole or a valve chamber accumulator. The structure, working principle, and multi-physical model of the reducing element of reducing the flow pulsation in a microchannel are presented. When the flow pulsation in the microchannel is sinusoidal, square wave, or pulse, the simulation effect of flow pulsation reduction is given when the membrane valve has different permutations and combinations. The experimental results show that the inlet flow of the reducing element is a square wave pulsation with an amplitude of 0.1 mL/s and a period of 2 s, the outlet flow of the reducing element is assisted by 0.017 and the fluctuation frequency is accompanied by a decrease. The test data and simulation results verify the rationality of the flow reduction element in the membrane valve microchannel, the correctness of the theoretical model, and the practicability of the specific application, which provides a higher precision automatic control technology for the microfluidic chip with high integration and complex reaction function. Full article
(This article belongs to the Special Issue Flow Control Across Varying Length Scales: Nanofluidics, Microfluidics and Millifluidics)
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18 pages, 17796 KB  
Article
Geometric Optimization of a Tesla Valve Through Machine Learning to Develop Fluid Pressure Drop Devices
by Andrew Sparrow, Jett Isley, Walter Smith and Anthony Gannon
Fluids 2025, 10(10), 255; https://doi.org/10.3390/fluids10100255 - 27 Sep 2025
Viewed by 394
Abstract
Thorough investigation into Tesla valve (TV) design was conducted across a large design of experiments (DOE) consisting of four varying geometric parameters and six different Reynolds number regimes in order to develop an optimized pressure drop device utilizing machine learning (ML) methods. A [...] Read more.
Thorough investigation into Tesla valve (TV) design was conducted across a large design of experiments (DOE) consisting of four varying geometric parameters and six different Reynolds number regimes in order to develop an optimized pressure drop device utilizing machine learning (ML) methods. A non-standard TV design was geometrically parameterized, and an automation suite was created to cycle through numerous combinations of parameters. Data were collected from completed computational fluid dynamics (CFD) simulations. TV designs were tested in the restricted flow direction for overall differential pressure, and overall minimum pressure with consideration to the onset of cavitation. Qualitative observations were made on the effects of each geometric parameter on the overall valve performance, and particular parameters showed greater influence on the pressure drop compared to classically optimized parameters used in previous TV studies. The overall minimum pressure demonstrated required system pressure for a valve to be utilized such that onset to cavitation would not occur. Data were utilized to train an ML model, and an optimized geometry was selected for maximized pressure drop. Multiple optimization efforts were made to meet design pressure drop goals versus traditional diodicity metrics, and two geometries were selected to develop a final design tool for overall pressure drop component development. Future work includes experimental validation of the large dataset, as well as further validation of the design tool for use in industry. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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26 pages, 5646 KB  
Article
Air–Water Dynamic Performance Analysis of a Cross-Medium Foldable-Wing Vehicle
by Jiaqi Cheng, Dazhi Huang, Hongkun He, Feifei Yang, Tiande Lv and Kun Chen
Fluids 2025, 10(10), 254; https://doi.org/10.3390/fluids10100254 - 27 Sep 2025
Viewed by 333
Abstract
Inspired by the free-flight capabilities of the gannet in both aerial and underwater environments, a foldable-wing air–water cross-medium vehicle was designed. To enhance its propulsive performance and transition stability across these two media, aero-hydrodynamic performance analyses were conducted under three representative operating states: [...] Read more.
Inspired by the free-flight capabilities of the gannet in both aerial and underwater environments, a foldable-wing air–water cross-medium vehicle was designed. To enhance its propulsive performance and transition stability across these two media, aero-hydrodynamic performance analyses were conducted under three representative operating states: aerial flight, underwater navigation, and water entry. Numerical simulations were performed in ANSYS Fluent (Version 2022R2) to quantify lift, drag, lift-to-drag ratio (L/D), and tri-axial moment responses in both air and water. The transient multiphase flow characteristics during water entry were captured using the Volume of Fluid (VOF) method. The results indicate that: (1) in the aerial state, the lift coefficient increases almost linearly with the angle of attack, and the L/D ratio peaks within the range of 4–6°; (2) in the folded (underwater) configuration, the fuselage still generates effective lift, with a maximum L/D ratio of approximately 2.67 at a 10° angle of attack; (3) transient water entry exhibits a characteristic two-stage force history (“initial impact” followed by “steady release”), with the peak vertical load increasing significantly with water entry angle and velocity. The maximum vertical force reaches 353.42 N under the 60°, 5 m/s condition, while the recommended compromise scheme of 60°, 3 m/s effectively reduces peak load and improves attitude stability. This study establishes a closed-loop analysis framework from biomimetic design to aero-hydrodynamic modeling and water entry analysis, providing the physical basis and parameter support for subsequent cross-medium attitude control, path planning, and intelligent control system development. Full article
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16 pages, 3517 KB  
Article
Effect of Polymer Concentration on the Rheology and Surface Activity of Cationic Polymer and Anionic Surfactant Mixtures
by Chung-Chi Sun and Rajinder Pal
Fluids 2025, 10(10), 253; https://doi.org/10.3390/fluids10100253 - 27 Sep 2025
Viewed by 448
Abstract
The effects of polymer concentration on rheology, surface tension, and electrical conductivity of polymer–surfactant mixtures are investigated experimentally. The polymer studied is a cationic quaternary ammonium salt of hydroxyethyl cellulose, and the surfactant used is anionic sodium lauryl sulfate. The polymer concentration is [...] Read more.
The effects of polymer concentration on rheology, surface tension, and electrical conductivity of polymer–surfactant mixtures are investigated experimentally. The polymer studied is a cationic quaternary ammonium salt of hydroxyethyl cellulose, and the surfactant used is anionic sodium lauryl sulfate. The polymer concentration is varied from 1000 to 4000 ppm, and the surfactant concentration varied from 0 to 500 ppm. Polymer concentration affects the properties of the mixtures substantially. At a given surfactant concentration, the consistency of the polymer–surfactant mixture rises sharply with the increase in polymer concentration. The mixture also becomes more shear-thinning with the increase in polymer concentration. The surface tension decreases substantially, and the electrical conductivity increases with the increase in polymer concentration at a fixed surfactant concentration. At a given polymer concentration, the consistency index generally exhibits a maximum and the surface tension exhibits a minimum at some intermediate surfactant concentration. With the increase in polymer concentration, the maximum in the consistency index and the minimum in surface tension shift to higher surfactant concentrations. Although the exact mechanisms are not clear at present, a possible explanation for the observed initial changes in rheological and surface-active properties of polymer–surfactant mixtures with the addition of surfactant is charge neutralization and entanglement of polymer chains. At high surfactant concentrations, recharging and disentanglement of polymer chains probably take place. Full article
(This article belongs to the Section Non-Newtonian and Complex Fluids)
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15 pages, 2750 KB  
Article
Study on the Spreading Dynamics of Droplet Pairs near Walls
by Jing Li, Junhu Yang, Xiaobin Liu and Lei Tian
Fluids 2025, 10(10), 252; https://doi.org/10.3390/fluids10100252 - 26 Sep 2025
Viewed by 307
Abstract
This study develops an incompressible two-phase flow solver based on the open-source OpenFOAM platform, employing the volume-of-fluid (VOF) method to track the gas–liquid interface and utilizing the MULES algorithm to suppress numerical diffusion. This study provides a comprehensive investigation of the spreading dynamics [...] Read more.
This study develops an incompressible two-phase flow solver based on the open-source OpenFOAM platform, employing the volume-of-fluid (VOF) method to track the gas–liquid interface and utilizing the MULES algorithm to suppress numerical diffusion. This study provides a comprehensive investigation of the spreading dynamics of droplet pairs near walls, along with the presentation of a corresponding mathematical model. The numerical model is validated through a two-dimensional axisymmetric computational domain, demonstrating grid independence and confirming its reliability by comparing simulation results with experimental data in predicting drConfirmedoplet collision, spreading, and deformation dynamics. The study particularly investigates the influence of surface wettability on droplet impact dynamics, revealing that increased contact angle enhances droplet retraction height, leading to complete rebound on superhydrophobic surfaces. Finally, a mathematical model is presented to describe the relationship between spreading length, contact angle, and Weber number, and the study proves its accuracy. Analysis under logarithmic coordinates reveals that the contact angle exerts a significant influence on spreading length, while a constant contact angle condition yields a slight monotonic increase in spreading length with the Weber number. These findings provide an effective numerical and mathematical tool for analyzing the spreading dynamics of droplet pairs. Full article
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24 pages, 17188 KB  
Article
Assessment of the Combined Effects of Valve Phenotype and Aneurysm Progression on Ascending Thoracic Aortic Hemodynamics
by Federica Galbiati, Katia Capellini, Emanuele Vignali, Claudia Angeletti, Francesca Romana Parente, Margherita Cioffi, Stephane Avril, Emiliano Costa and Simona Celi
Fluids 2025, 10(10), 251; https://doi.org/10.3390/fluids10100251 - 26 Sep 2025
Viewed by 433
Abstract
In the context of ascending aorta hemodynamics, it is well established that both valve morphology and vessel geometry play a key role. However, the possibility of conducting systematic comparisons is limited by the challenges associated with acquiring patient-specific follow-up data. In this paper, [...] Read more.
In the context of ascending aorta hemodynamics, it is well established that both valve morphology and vessel geometry play a key role. However, the possibility of conducting systematic comparisons is limited by the challenges associated with acquiring patient-specific follow-up data. In this paper, we combined a novel definition for a parametric time-varying inlet velocity profile with a virtual aneurysm growth model to investigate the combined effects of valve morphology and aneurysm progression on aortic hemodynamics. We successfully modeled the reduced orifice area and eccentric inflow characteristic of bicuspid aortic valves and their consequent effects on hemodynamics. Controlled comparisons revealed that flow patterns and related biomarkers are primarily influenced by the presence of an eccentric inflow that induces disrupted hemodynamics, elevated wall shear stresses, and increased oscillatory indexes. While aneurysm growth exerts minimal influence on hemodynamic parameters for small diameter increases, its impact becomes more relevant with substantial aortic bulge enlargement, and it remains dependent on the specific valve phenotype. The current study underlines the pivotal role of aortic valve boundary conditions and the influence of eccentric inlet velocity on ascending aortic flow patterns in both healthy and aneurysmal conditions. Knowledge of valve morphology and the definition of corresponding inflow conditions are essential for patient-specific analyses when in vivo patient-specific boundary conditions are unavailable. Full article
(This article belongs to the Special Issue Advances in Hemodynamics and Related Biological Flows)
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17 pages, 3884 KB  
Article
Experimental and CFD Study of Parameters Affecting Glue Spray Atomization
by Zixian Jiang, Shutao Wei and Fuzeng Wang
Fluids 2025, 10(10), 250; https://doi.org/10.3390/fluids10100250 - 25 Sep 2025
Viewed by 335
Abstract
This study investigates the effects of air pressure, glue pressure, and viscosity on atomization characteristics through experimental and simulation methods, aiming to reveal gas–liquid interaction mechanisms and optimize process parameters. The rheological parameters of aqueous polyurethane adhesives with varying viscosities were characterized. Spray [...] Read more.
This study investigates the effects of air pressure, glue pressure, and viscosity on atomization characteristics through experimental and simulation methods, aiming to reveal gas–liquid interaction mechanisms and optimize process parameters. The rheological parameters of aqueous polyurethane adhesives with varying viscosities were characterized. Spray characteristics, including spray angle, cured film diameter, and thickness, were quantitatively measured under different operating conditions. The internal flow field and droplet dynamics were numerically analyzed. The results indicate the following: Increasing the air pressure (from 0.3 to 0.7 MPa) enlarges the spray angle and film diameter while reducing the film thickness. In contrast, increasing the glue pressure enlarges all three parameters: spray angle, film diameter, and film thickness. Furthermore, increasing the viscosity within the test range reduces the spray angle, film diameter, and film thickness. These effects stem from enhanced gas kinetic energy and shear intensity (promoting liquid film fragmentation), an increased fluid flow rate with glue pressure, and strengthened droplet resistance to breakup with suppressed spreading at higher viscosities. This research provides useful criteria for nozzle design and the optimization of industrial atomization processes involving non-Newtonian adhesives. Full article
(This article belongs to the Section Non-Newtonian and Complex Fluids)
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24 pages, 4890 KB  
Article
Turbulent Hybrid Nanofluid Flow in Corrugated Channels with Vortex Generators: A Numerical Study
by Aimen Tanougast, Issa Omle and Krisztián Hriczó
Fluids 2025, 10(10), 249; https://doi.org/10.3390/fluids10100249 - 24 Sep 2025
Viewed by 345
Abstract
Nanofluids are an important technology for enhancing heat transfer in industrial applications by incorporating high thermal conductivity nanoparticles into base fluids. However, they often require higher pumping power and energy consumption. This study employs a two-dimensional (2D) approximation of vortex generators (VGs) in [...] Read more.
Nanofluids are an important technology for enhancing heat transfer in industrial applications by incorporating high thermal conductivity nanoparticles into base fluids. However, they often require higher pumping power and energy consumption. This study employs a two-dimensional (2D) approximation of vortex generators (VGs) in a turbulent trapezoidal channel with nanoparticle concentrations of Al2O3, SiO2, and TiO2. Simulations are performed using ANSYS Fluent 2021 with the Finite Volume Method (FVM) and the k–ε turbulence model to capture turbulence characteristics, eddy viscosity, and turbulent kinetic energy production. The introduction of vortex generators improves fluid mixing and reduces the thermal boundary layer, resulting in enhanced heat transfer, with a performance evaluation criterion (PEC) of 1.08 for water (baseline case without nanofluids). The single nanofluids further optimize heat transfer, increasing the Nusselt number and pressure drop while balancing thermal performance, reaching a PEC of 1.6 for SiO2 at 3% concentration, representing a 48% improvement over the baseline. A hybrid mixture of 1% Al2O3 and 2% SiO2 achieves the same PEC of 1.6 as single SiO2 nanoparticles, but with higher heat transfer and lower pressure drop, demonstrating improved thermal performance. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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