Fluids

46 pages, 18159 KiB

Open AccessReview

Recent Developments in the Immersed Boundary Method for Complex Fluid–Structure Interactions: A Review

by Omkar Powar, Pedapudi Anantha Hari Arun, Anwak Manoj Kumar, Mithun Kanchan, B. M. Karthik, Poornesh Mangalore and Mohith Santhya

Fluids 2025, 10(5), 134; https://doi.org/10.3390/fluids10050134 (registering DOI) - 16 May 2025

Abstract

The “immersed boundary method (IBM)” is considered to be the most efficacious and versatile technique to solve flow problems associated with intricate geometries. The first part of this review examines recent advancements in IBM, essential for the simulation of “fluid–structure interactions (FSIs)” in [...] Read more.

The “immersed boundary method (IBM)” is considered to be the most efficacious and versatile technique to solve flow problems associated with intricate geometries. The first part of this review examines recent advancements in IBM, essential for the simulation of “fluid–structure interactions (FSIs)” in sophisticated systems. This review highlights significant developments in turbulence modeling, adaptive mesh refinement, and complex geometric simulations, demonstrating IB methods’ capacity to seamlessly integrate arbitrary geometries into structured computational grids while preserving computational efficiency. Various IB techniques are analyzed for enforcing boundary conditions on dynamic immersed boundaries, with notable breakthroughs in managing velocity discontinuities, spurious oscillations, and large-scale deformations. Recent findings illustrate the versatility of IB methods, with applications encompassing biological fluid dynamics, turbulent multiphase flows, and cavitating flows. These innovations not only enhance computational performance but also address evolving challenges across engineering and scientific fields, establishing IB methods as a robust tool for resolving complex, multidisciplinary problems with high accuracy and efficiency. Full article

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40 pages, 3557 KiB

Open AccessArticle

Modified Semi-Lagrangian Godunov-Type Method Without Numerical Viscosity for Shocks

by Valeriy Nikonov

Fluids 2025, 10(5), 133; https://doi.org/10.3390/fluids10050133 - 16 May 2025

Abstract

Most high-order Euler-type methods have been proposed to solve one-dimensional scalar hyperbolic conservational law. These methods resolve smooth variations in flow parameters accurately and simultaneously identify the discontinuities. A disadvantage of Euler-type methods is the parameter change stretching in the shock over a [...] Read more.

Most high-order Euler-type methods have been proposed to solve one-dimensional scalar hyperbolic conservational law. These methods resolve smooth variations in flow parameters accurately and simultaneously identify the discontinuities. A disadvantage of Euler-type methods is the parameter change stretching in the shock over a few mesh cells. In reality, in the shock, the flow properties change abruptly at once for the computational mesh. In our considerations, the mean free path of a flow particle is much smaller than the mesh cell size. This paper describes a modification of the semi-Lagrangian Godunov-type method, which was proposed by the author in the previously published paper. The modified method also does not have numerical viscosity for shocks. In the previous article, a linear law for the distribution of flow parameters was employed for a rarefaction wave when modeling the Shu-Osher problem with the aim of reducing parasitic oscillations. Additionally, the nonlinear law derived from the Riemann invariants was used for the remaining test problems. This article proposes an advanced method, namely, a unified formula for the density distribution of rarefaction waves and modification of the scheme for modeling moderately strong shock waves. The obtained results of numerical analysis, including the standard problem of Sod, the Riemann problem of Lax, the Shu–Osher shock-tube problem and a few author’s test cases are compared with the exact solution, the data of the previous method and the Total Variation Deminishing (TVD) scheme results. This article delineates the further advancement of the numerical scheme of the proposed method, specifically presenting a unified mathematical formulation for an expanded set of test problems. Full article

38 pages, 22598 KiB

Open AccessArticle

Assessing the Effect of Air Ventilation on the Dispersion of Exhaled Aerosol Particles in a Lecture Hall: Simulation Strategy and Streamlined Workflow

by Arnav Ajmani, Lars Kirchhof, Alireza Rouhi and Carsten Mehring

Fluids 2025, 10(5), 132; https://doi.org/10.3390/fluids10050132 - 15 May 2025

Viewed by 43

Abstract

An efficient solution strategy based on fluid network modeling, computational fluid dynamics (CFD) and discrete particle modeling (DPM) is presented in order to predict and improve air quality, specifically regarding breathing aerosol concentration, in a person-occupied mechanically ventilated room. The efficiency of the [...] Read more.

An efficient solution strategy based on fluid network modeling, computational fluid dynamics (CFD) and discrete particle modeling (DPM) is presented in order to predict and improve air quality, specifically regarding breathing aerosol concentration, in a person-occupied mechanically ventilated room. The efficiency of the proposed workflow is evaluated for the specific case of a lecture hall. It is found that the actual vent system is imbalanced and inefficient in managing the aerosol concentration within the room. Despite a high volumetric exchange rate, aerosol residence times and local aerosol concentrations remain high over an extended period of time, without additional efforts to alter air flow circulation throughout the room. The proposed strategy illustrates how such changes can be efficiently implemented in the basic 1D/3D co-simulation workflow. Analysis of the lecture hall and vent system shows that the execution time for the overall process workflow can be optimized by the following: (1) CAD geometry generation of the room via 3D laser scanning, (2) mesh generation based on the anticipated air discharge behavior from the vent system and (3) by employing HPC resources. Additional simplifications such as the decoupling of vent air flow and room aerodynamics, as observed for the investigated test case, one-way coupling between air flow and aerosol dispersion at low aerosol concentrations and the successive solution of flow field equations can further reduce the problem’s complexity and processing times. Full article

(This article belongs to the Special Issue Industrial CFD and Fluid Modelling in Engineering, 2nd Edition)

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22 pages, 11898 KiB

Open AccessArticle

Impact of Viscous Droplets on Dry and Wet Substrates for Spray Painting Processes

by Qiaoyan Ye, Oliver Tiedje, Bo Shen and Joachim Domnick

Fluids 2025, 10(5), 131; https://doi.org/10.3390/fluids10050131 - 15 May 2025

Viewed by 126

Abstract

This paper presents numerical studies of the viscous droplet impact on dry and wetted solid walls for spray painting applications, focusing on air entrapment, film structure, and flake (flat pigment) orientation. The results were compared with experimental observations using various high-speed camera arrangements. [...] Read more.

This paper presents numerical studies of the viscous droplet impact on dry and wetted solid walls for spray painting applications, focusing on air entrapment, film structure, and flake (flat pigment) orientation. The results were compared with experimental observations using various high-speed camera arrangements. For paint droplet impact on dry substrates, a dynamic contact angle model was developed and used in numerical simulations. This contact angle model was verified with experimental observations. For the droplet impact on wet surfaces, characteristic crater sizes (diameter and depth) were defined considering also the effect of the film thickness. A strong correlation with the droplet impact Reynolds number was observed. In addition, a user-defined 6DOF (6-degrees-of-freedom) solver was implemented in a CFD program to perform calculations of rigid body motions within the impacting droplet, technically relevant for the resulting effect of flakes in metallic effect paints. The developed models were applied in parameter studies to further clarify the existing dependencies on application and fluid parameters more quantitatively. The simulation results are helpful to understand and to improve painting processes with respect to the final quality parameters. Full article

(This article belongs to the Special Issue Contact Line Dynamics and Droplet Spreading)

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16 pages, 2119 KiB

Open AccessArticle

Steady Particulate Taylor-Couette Flow with Particle Migration

by C. Q. Ru

Fluids 2025, 10(5), 130; https://doi.org/10.3390/fluids10050130 - 14 May 2025

Viewed by 192

Abstract

Steady Taylor-Couette flow of a particle-fluid suspension with non-neutrally buoyant particles between two coaxial rotating cylinders is studied with a novel two-fluid model. It is shown that steady particle distribution in particulate Taylor-Couette flow can exist in the case when the solid walls [...] Read more.

Steady Taylor-Couette flow of a particle-fluid suspension with non-neutrally buoyant particles between two coaxial rotating cylinders is studied with a novel two-fluid model. It is shown that steady particle distribution in particulate Taylor-Couette flow can exist in the case when the solid walls are permeable where the particles and the fluid can be sucked or injected with equal but opposite normal fluxes. With this assumption, an explicit formula is derived for the axisymmetric steady radial distribution of particles with particle migration in the dilute limit. Detailed results for several cases of major interest show that the local rate of particle migration depends largely on the local azimuthal speed, and the steady volume fraction of particles typically attains its maximum (or minimum) at the location of minimum (or maximum) local azimuthal speed. In particular, with a wider gap between two cylinders and a Stokes number of particles around the order of unity, the non-monotonic radial distribution of particle volume fraction with interior local maximum and/or minimum can occur when the inner cylinder rotates with the outer cylinder fixed or when the two cylinders counter-rotate with equal but opposite angular velocities. Full article

(This article belongs to the Section Flow of Multi-Phase Fluids and Granular Materials)

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41 pages, 15728 KiB

Open AccessReview

A Review of Mesh Adaptation Technology Applied to Computational Fluid Dynamics

by Guglielmo Vivarelli, Ning Qin and Shahrokh Shahpar

Fluids 2025, 10(5), 129; https://doi.org/10.3390/fluids10050129 - 13 May 2025

Viewed by 227

Abstract

Mesh adaptation techniques can significantly impact Computational Fluid Dynamics by improving solution accuracy and reducing computational costs. In this review, we begin by defining the concept of mesh adaptation, its core components and the terminology commonly used in the community. We then categorise [...] Read more.

Mesh adaptation techniques can significantly impact Computational Fluid Dynamics by improving solution accuracy and reducing computational costs. In this review, we begin by defining the concept of mesh adaptation, its core components and the terminology commonly used in the community. We then categorise and evaluate the main adaptation strategies, focusing both on error estimation and mesh modification techniques. In particular, we analyse the two most prominent families of error estimation: feature-based techniques, which target regions of high physical gradients and goal-oriented adjoint methods, which aim to reduce the error in a specific integral quantity of interest. Feature-based methods are advantageous due to their reduced computational cost: they do not require adjoint solvers, and they have a natural ability to introduce anisotropy. A substantial portion of the literature relies on second-order derivatives of scalar flow quantities to construct sensors that can be equidistributed to minimise discretisation error. However, when used carelessly, these methods can lead to over-refinement, and they are generally outperformed by adjoint-based techniques when improving specific target quantities. Goal-oriented methods typically achieve higher accuracy in fewer adaptation steps with coarser meshes. It will be seen that various approaches have been developed to incorporate anisotropy into adjoint-based adaptation, including hybrid error sensors that combine feature-based and goal-oriented indicators, sequential strategies and adjoint weighting of fluxes. After years of limited progress, recent work has demonstrated promising results, including certifiable solutions and applications to increasingly complex cases such as transonic compressor blades and film-cooled turbines. Despite these advances, several critical challenges remain: efficient parallelisation, robust geometry integration, application to unsteady flows and deployment in high-order discretisation frameworks. Finally, examples of the potential role of artificial intelligence in guiding or accelerating mesh adaptation are also discussed. Full article

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25 pages, 1437 KiB

Open AccessReview

Review of the Color Gradient Lattice Boltzmann Method for Simulating Multi-Phase Flow in Porous Media: Viscosity, Gradient Calculation, and Fluid Acceleration

by Fizza Zahid and Jeffrey A. Cunningham

Fluids 2025, 10(5), 128; https://doi.org/10.3390/fluids10050128 - 13 May 2025

Viewed by 207

Abstract

The lattice Boltzmann method (LBM) is widely applied to model the pore-scale two-phase flow of immiscible fluids through porous media, and one common variant of the LBM is the color gradient method (CGM). However, in the literature, many competing algorithms have been proposed [...] Read more.

The lattice Boltzmann method (LBM) is widely applied to model the pore-scale two-phase flow of immiscible fluids through porous media, and one common variant of the LBM is the color gradient method (CGM). However, in the literature, many competing algorithms have been proposed for accomplishing different steps in the CGM. Therefore, this paper is the first in a series that aims to critically review and evaluate different algorithms and methodologies that have been proposed for use in the CGM. Specifically, in this paper, we (1) provide a brief introduction to the LBM and CGM that enables and facilitates consideration of more sophisticated topics subsequently; (2) compare three methods for modeling the behavior of fluids of moderately different viscosities; (3) compare two methods for calculating the color gradient; and (4) compare two methods for modeling external forces or accelerations acting upon the fluids of interest. These topics are selected for the first paper in the series because proper selection of these algorithms is necessary and sufficient to perform two common “benchmark” simulations, namely bubble tests and layered Poiseuille flow. Future papers in the series will build upon these topics, considering more challenging conditions or phenomena. By systematically reviewing key aspects, features, capabilities, and limitations of the CGM, this series of papers will extend our collective ability to apply the method to a variety of important fluid flow problems in geosciences and engineering. Full article

(This article belongs to the Special Issue Recent Advances in Fluid Mechanics: Feature Papers, 2024)

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10 pages, 3383 KiB

Open AccessArticle

Droplets at Liquid-Fluid Interfaces: Stages Leading to Coalescence

by Jose Davalos-Monteiro, Qi Liu and J. Carlos Santamarina

Fluids 2025, 10(5), 127; https://doi.org/10.3390/fluids10050127 - 12 May 2025

Viewed by 116

Abstract

Droplet coalescence at interfaces affects industrial and natural processes. Previous studies focused on droplet stability and thin film drainage. We use meticulous experiments to infer the evolution of coalescence for both ascending and descending droplets under different conditions. Images show the anticipatory deformation [...] Read more.

Droplet coalescence at interfaces affects industrial and natural processes. Previous studies focused on droplet stability and thin film drainage. We use meticulous experiments to infer the evolution of coalescence for both ascending and descending droplets under different conditions. Images show the anticipatory deformation of the interface and dimple formation during the approach phase. While the droplet rests at the interface, the two surfaces interact through the draining thin film, and the effective interfacial tension can be higher than twice the interfacial tension between the two fluids, suggesting not only concurrent action but also potential changes in interfacial tension in thin films. Following the film breakage, the unbalanced force propels the droplet into the continuous phase, i.e., the slingshot effect. Multiple droplets may coexist at the interface and collectively contribute to its deformation, which in turn pushes the droplets together. The various stages of droplet coalescence are influenced by the droplet and host fluid viscosities, densities, interfacial tension, size, and initial interface curvature. Full article

(This article belongs to the Section Flow of Multi-Phase Fluids and Granular Materials)

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12 pages, 5641 KiB

Open AccessArticle

A Numerical Investigation of Sinusoidal Flow in Porous Media with a Simple Cubic Beam Structure at 1 Hz and 100 Hz Under Different Porosity Conditions

by Sin-Mao Chen, Boe-Shong Hong and Shiuh-Hwa Shyu

Fluids 2025, 10(5), 126; https://doi.org/10.3390/fluids10050126 - 12 May 2025

Viewed by 198

Abstract

This study aims to clarify how porosity and frequency interact to influence permeability and flow behavior in porous media subjected to sinusoidal pressure variations. Specifically, we investigate oscillatory flow at 1 Hz and 100 Hz under varying porosity conditions using a pore-scale Computational [...] Read more.

This study aims to clarify how porosity and frequency interact to influence permeability and flow behavior in porous media subjected to sinusoidal pressure variations. Specifically, we investigate oscillatory flow at 1 Hz and 100 Hz under varying porosity conditions using a pore-scale Computational Fluid Dynamics (CFD) model. The model is validated against the Johnson–Koplik–Dashen (JKD) model to ensure accuracy in capturing dynamic permeability. At 1 Hz, where the oscillation period greatly exceeds the system’s time constant

τ

, the flow reaches a quasi-steady state with dynamic permeability approximating static permeability. Increasing porosity enhances Darcy velocity, with minimal phase difference between velocity and pressure. At 100 Hz, flow behavior depends on the ratio of the oscillation period

T

to

τ

. For high porosity (

φ = 0.840

,

T \approx τ

), the flow does not fully develop before the pressure gradient reverses, leading to significant phase lag. For low porosity (

φ = 0.370

,

T \approx 12 τ

), the phase lag is smaller but remains non-zero due to the smooth temporal variation in pressure. This work contributes to the understanding of porous flow dynamics by revealing how porosity modulates both the amplitude and phase angle of dynamic permeability in frequency-dependent porous flows, providing a framework for predicting phase lag in frequency-sensitive applications. Full article

(This article belongs to the Collection Feature Paper for Mathematical and Computational Fluid Mechanics)

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94 pages, 11117 KiB

Open AccessReview

An Overview of Viscous and Highly Viscous Fluid Flows in Straight and Elbow Pipes: I—Single-Phase Flows

by Leonardo Di G. Sigalotti and Enrique Guzmán

Fluids 2025, 10(5), 125; https://doi.org/10.3390/fluids10050125 - 11 May 2025

Viewed by 197

Abstract

The flow of viscous and highly viscous fluids in straight and bent pipes and channels is a fundamental process in a wide variety of industrial applications and is, therefore, of great interest in science and engineering. Understanding the physics behind such flows has [...] Read more.

The flow of viscous and highly viscous fluids in straight and bent pipes and channels is a fundamental process in a wide variety of industrial applications and is, therefore, of great interest in science and engineering. Understanding the physics behind such flows has a direct impact on the design of efficient, safe and reliable systems. The type of fluid, which can be viscous or even highly viscous, and the pipe geometry can affect the flow dynamics, the pressure loss and the overall efficiency of the process. In this paper, we provide an extensive review of the state-of-the-art research concerning the flow of Newtonian and non-Newtonian, single-phase fluids in straight and bent pipes. Since a big amount of work in the literature is devoted to the study of Newtonian pipe flows, the paper starts with a brief outline of the nonlinear theory of viscous Newtonian fluid flow in pipes, including a survey of early and recent analytical solutions to the Navier–Stokes equations. The central part of the paper deals with an extensive overview of existing experimental and numerical research work on viscous Newtonian pipe flows. Separate sections are devoted to non-Newtonian fluid flows, the problem of entropy generation due to irreversible processes in the flow and hydromagnetic Newtonian and non-Newtonian pipe flow. The review closes with a brief survey of machine learning and artificial intelligence modeling applied to pipe flow along with future trends and challenges in pipe flow research. Full article

(This article belongs to the Special Issue Pipe Flow: Research and Applications, 2nd Edition)

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16 pages, 6209 KiB

Open AccessArticle

Numerical Simulation of Blood Clot Extraction Process Using Aspiration-Based Mechanical Thrombectomy

by Sreenivas Venguru, Shyam Sunder Yadav, Tanmaya Mahapatra and Sanjay Kumar Kochar

Fluids 2025, 10(5), 124; https://doi.org/10.3390/fluids10050124 - 9 May 2025

Viewed by 174

Abstract

This paper simulates the blood clot extraction process inside an idealized cylindrical blood vessel model using the aspiration-based thrombectomy technique. A fully Eulerian technique is used within the finite volume method where incompressible Navier–Stokes equations are solved in the fluid region. In contrast, [...] Read more.

This paper simulates the blood clot extraction process inside an idealized cylindrical blood vessel model using the aspiration-based thrombectomy technique. A fully Eulerian technique is used within the finite volume method where incompressible Navier–Stokes equations are solved in the fluid region. In contrast, the Cauchy stress equation is solved in the clot region. Blood is assumed to be a Newtonian fluid, while the clot is either hyperelastic or viscoelastic material. In the hyperelastic formulation, the clot deformation is calculated based on the left Cauchy–Green deformation tensor, while the stresses are based on the linear Mooney–Rivlin model. In the viscoelastic formulation, the Oldroyd B model is used within the log conformation approach to calculate the viscoelastic stresses in the clot. The interface between the blood and the clot is tracked with the help of the geometric volume-of-fluid method. We focus on the role of flow variables like the pressure, velocity, and proximity between the clot and the catheter tip to successfully capture the clot under catheter suction. We observe that, once the clot is attracted to the catheter port due to pressure forces, the viscous stresses try to drag it inside the catheter. On the other hand, if the clot is not initially attracted, it is carried downstream by the viscous stresses. If the suction velocity is low (∼0.2 m/s), the clot cannot be sucked inside the catheter, even if it is touching the catheter. At a higher suction velocity of 0.4 m/s, the suction effect is strong enough to capture the clot despite the larger initial distance from the catheter. Hence, the pressure distribution and viscous stresses play essential roles in the suction or escape of the clot during the thrombectomy process. Also, the viscoelastic model predicts the rupture of the clot inside the catheter during suction. Full article

(This article belongs to the Special Issue Advances in Hemodynamics and Related Biological Flows)

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23 pages, 6282 KiB

Open AccessArticle

Computational Modeling of Droplet-Based Printing Using Multiphase Volume of Fluid (VOF) Method: Prediction of Flow, Spread Behavior, and Printability

by Rauf Shah and Ram V. Mohan

Fluids 2025, 10(5), 123; https://doi.org/10.3390/fluids10050123 - 8 May 2025

Viewed by 214

Abstract

The evolution of droplets during the printing process is modeled using the volume of fluid (VOF) method, which involves solving the Navier–Stokes and continuity equations for incompressible flow with multiple immiscible phases on a finite volume grid. An indicator function tracks the interfaces [...] Read more.

The evolution of droplets during the printing process is modeled using the volume of fluid (VOF) method, which involves solving the Navier–Stokes and continuity equations for incompressible flow with multiple immiscible phases on a finite volume grid. An indicator function tracks the interfaces and calculates surface tension forces. A grid independence study confirmed the convergence and efficacy of the solutions. The computational model agreed well with experimental data, accurately capturing the impact, spreading, and recoiling of droplets on a solid surface. Additionally, the model validated the interaction of droplets with hydrophilic and hydrophobic surfaces for both constant and dynamic contact angles. Key non-dimensional numbers (Re, We, Oh) were considered to study the interplay of forces during droplet impact on a solid surface. The final print quality is influenced by droplet dynamics, governed by body forces (surface tension, gravity), contact angle, dissipative forces due to motion, and material properties. Computational studies provide insights into the overall process performance and final print quality under various process conditions and material properties. Full article

(This article belongs to the Special Issue Contact Line Dynamics and Droplet Spreading)

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21 pages, 11237 KiB

Open AccessArticle

Investigation of Heat Transfer Enhancement Mechanisms in Elastic Tube Bundles Subjected to Exogenous Self-Excited Fluid Oscillation

by Jing Hu, Lei Guo and Shusheng Zhang

Fluids 2025, 10(5), 122; https://doi.org/10.3390/fluids10050122 - 8 May 2025

Viewed by 178

Abstract

Flow-induced vibration (FIV) characteristics are key factors in enhancing heat transfer. However, challenges such as insufficient heat transfer enhancement and the fatigue strength of the tube bundle persist in the context of improving the heat transfer in elastic tube bundle heat exchangers. This [...] Read more.

Flow-induced vibration (FIV) characteristics are key factors in enhancing heat transfer. However, challenges such as insufficient heat transfer enhancement and the fatigue strength of the tube bundle persist in the context of improving the heat transfer in elastic tube bundle heat exchangers. This study proposes a novel passive heat transfer enhancement paradigm for elastic tube bundles based on externally induced self-excited oscillations of fluid. By constructing a non-contact energy transfer system, the external oscillation energy is directed into the elastic tube bundle heat exchanger, achieving dynamic stress buffering and breaking through the steady-state flow heat transfer boundary layer. A three-dimensional fluid–structure interaction numerical model is established using Star CCM+2021.3 (16.06.008) to conduct a comparative analysis of the flow characteristics and heat transfer performance between the original structure without an oscillator and the improved structure equipped with a fluid oscillator. The results indicate that the improved structure, through the periodic unsteady jet induced by the fluid oscillator, significantly enhances the turbulence intensity of the shell-side fluid, with the turbulent kinetic energy increasing by over 50%. The radial flow area is notably expanded, thereby reducing the thermal resistance of the boundary layer. At cooling fluid velocities of 6 to 9 m/s, the heat transfer capability of the improved structure is enhanced by more than 50%. Compared with the original structure, the new structure, due to the loading of an external oscillation structure, causes the cold air to present a periodic up and down jet phenomenon. This jet phenomenon, on the one hand, increases the heat exchange area between the cold air and the outer surface of the tube bundle, thereby enhancing the heat exchange capacity. On the other hand, the large-area impact of the fluid reduces the thickness of the boundary layer, lowers the thermal resistance and thereby enhances the heat exchange capacity. Furthermore, this improved structure buffers the mechanical vibrations through self-excited oscillations of the fluid medium, ensuring that the stress levels in the tube bundle remain below the fatigue threshold, effectively mitigating the failure risks associated with traditional active vibration strategies. Full article

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26 pages, 10313 KiB

Open AccessArticle

Design of a Portable Integrated Fluid–Structure Interaction-Based Piezoelectric Flag Energy-Harvesting System

by Haochen Wang, Xingrong Huang, Zhe Li and Le Fang

Fluids 2025, 10(5), 121; https://doi.org/10.3390/fluids10050121 - 8 May 2025

Viewed by 167

Abstract

Fluid–structure interaction-based energy-harvesting technology has gained significant attention due to its potential for energy conversion. However, most existing studies primarily focus on energy capture, resulting in incomplete systems with limited portability and a lack of integrated circuitry. To address these limitations, this study [...] Read more.

Fluid–structure interaction-based energy-harvesting technology has gained significant attention due to its potential for energy conversion. However, most existing studies primarily focus on energy capture, resulting in incomplete systems with limited portability and a lack of integrated circuitry. To address these limitations, this study presents a portable, integrated piezoelectric flag energy-harvesting system that achieves a complete closed-loop conversion from fluid kinetic energy, through structural strain energy, to electrical energy. The system utilizes an upstream bluff body to generate vortex-induced vibrations, a downstream support structure that maintains operational stability, and an internally integrated wiring channel that enables overall energy conversion. Charge–discharge experiments on the energy storage unit enable a comprehensive evaluation of system performance, marking the first efficiency measurement of a fully integrated energy-harvesting system. Experimental results demonstrate the first quantified map of losses across all conversion stages in a portable piezo-flag platform, highlighting the system’s potential for powering small-scale, low-power self-sustaining devices. This work establishes a reference framework and provides a novel technological pathway for advancing practical applications of fluid-induced energy harvesting, contributing to the development of autonomous power sources in various engineering fields. Full article

(This article belongs to the Section Mathematical and Computational Fluid Mechanics)

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21 pages, 7419 KiB

Open AccessArticle

On Numerical Simulations of Turbulent Flows over a Bluff Body with Aerodynamic Flow Control Based on Trapped Vortex Cells: Viscous Effects

by Dmitry A. Lysenko

Fluids 2025, 10(5), 120; https://doi.org/10.3390/fluids10050120 - 8 May 2025

Viewed by 164

Abstract

Turbulent flows over a semi-circular cylinder (a limiting case of a thick airfoil with a chord equal to the diameter base) are investigated using high-fidelity large-eddy simulations at a diameter-based Reynolds number, Re = 130,000, Mach number, M = 0.05, and a zero [...] Read more.

Turbulent flows over a semi-circular cylinder (a limiting case of a thick airfoil with a chord equal to the diameter base) are investigated using high-fidelity large-eddy simulations at a diameter-based Reynolds number, Re = 130,000, Mach number, M = 0.05, and a zero angle of attack. The aerodynamic flow control system, designed with two trapped vortex cells, achieves a complete non-separated flow over the bluff body, except for low-scale turbulence effects, reaching approximately 80% of the theoretical lift coefficient limit (

2 π

for the half-circular airfoil). Viscous effects are analyzed using the conventional Reynolds-averaged Navier–Stokes approach for a broad range of Reynolds numbers, 75,000 ≤ Re ≤ 1,000,000. Numerical results demonstrate that the aerodynamic properties of the implemented concept are independent of the Reynolds number within this interval, highlighting its significant potential for further development. Full article

(This article belongs to the Collection Feature Paper for Mathematical and Computational Fluid Mechanics)

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21 pages, 8781 KiB

Open AccessArticle

Optimizing the Mobile Pump and Its Equipment to Reduce the Risk of Pluvial Flooding

by Horas Yosua, Muhammad Syahril Badri Kusuma, Joko Nugroho, Eka Oktariyanto Nugroho and Deni Septiadi

Fluids 2025, 10(5), 119; https://doi.org/10.3390/fluids10050119 - 7 May 2025

Viewed by 102

Abstract

Pluvial flooding in South Jakarta poses significant economic disruptions, requiring efficient mitigation strategies. This study focuses on optimizing mobile pump deployment as a non-structural flood control measure. Despite the use of mobile pumps in flood response, there is limited research on their systematic [...] Read more.

Pluvial flooding in South Jakarta poses significant economic disruptions, requiring efficient mitigation strategies. This study focuses on optimizing mobile pump deployment as a non-structural flood control measure. Despite the use of mobile pumps in flood response, there is limited research on their systematic optimization for pluvial flood mitigation. This study presents a transferable framework for deploying mobile pumps to mitigate pluvial flood risks in urban areas, demonstrated through a case study in South Jakarta, Indonesia. The findings indicate that flood depths of 75 cm have a 20–50% probability of occurrence, and rainfall in South Jakarta follows a distinct hourly distribution, with 56.6% of the rainfall occurring in the first hour and 43.4% in the second. Radar imagery from the BMKG is used here as the main tool for real-time rainfall detection. The optimization framework considers channel capacity, flood frequency, impact severity, accessibility, and operational protocols. Among 29 flood-prone locations analyzed, 8 of them require mobile pump intervention. Seven locations benefit from integration with weather prediction tools and SCADA systems, while three require dedicated operational procedures (SOPs). Simulation results indicate that placing mobile pumps near the upstream section of the flooded area yields the most effective flood reduction. A minimum pump capacity of 0.5 m³/s is recommended for optimal performance. This study demonstrates that strategic mobile pump deployment, coupled with predictive tools, significantly reduces pluvial flood risks in South Jakarta and offers a transferable framework for other urban areas. Full article

(This article belongs to the Special Issue Environmental Hydraulics, Turbulence and Sediment Transport, 3rd Edition)

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29 pages, 13402 KiB

Open AccessArticle

Modeling Microplastic Dispersion in the Salado Estuary Using Computational Fluid Dynamics

by Luis Velazquez-Araque, José Flor, Alfredo Méndez and Maritza Cárdenas-Calle

Fluids 2025, 10(5), 118; https://doi.org/10.3390/fluids10050118 - 6 May 2025

Viewed by 229

Abstract

Microplastics (MPs) have emerged as a major pollutant in aquatic ecosystems, primarily originating from industrial activities and plastic waste degradation. Understanding their transport dynamics is crucial for assessing environmental risks and developing mitigation strategies. This study employs Computational Fluid Dynamics (CFD) simulations to [...] Read more.

Microplastics (MPs) have emerged as a major pollutant in aquatic ecosystems, primarily originating from industrial activities and plastic waste degradation. Understanding their transport dynamics is crucial for assessing environmental risks and developing mitigation strategies. This study employs Computational Fluid Dynamics (CFD) simulations to model the trajectory of MPs in section B of the Salado Estuary in the city of Guayaquil, Ecuador, using ANSYS FLUENT 2024 R2. The transient behavior of Polyethylene Terephthalate (PET) particles was analyzed using the Volume of Fluid (VOF) multiphase model, k-omega SST turbulence model, and Discrete Phase Model (DPM) under a continuous flow regime. Spherical PET particles (5 mm diameter, 1340 kg/m³ density) were used to establish a simplified baseline scenario. Two water velocities, 0.5 m/s and 1.25 m/s, were selected based on typical flow rates reported in similar estuarine systems. Density contour analysis facilitated the modeling of the air-water interface, while particle trajectory analysis revealed that at 0.5 m/s, particles traveled 18–22.5 m before sedimentation, whereas at 1.25 m/s, they traveled 50–60 m before reaching the bottom. These findings demonstrate that higher flow velocities enhance MP transport distances before deposition, emphasizing the role of hydrodynamics in microplastic dispersion. While limited to one particle type and idealized conditions, this study underscores the potential of CFD as a predictive tool for assessing MP behavior in aquatic environments, contributing to improved pollution control and remediation efforts. Full article

(This article belongs to the Section Flow of Multi-Phase Fluids and Granular Materials)

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37 pages, 1062 KiB

Open AccessReview

The Universal Presence of the Reynolds Number

by Aldo Tamburrino and Yarko Niño

Fluids 2025, 10(5), 117; https://doi.org/10.3390/fluids10050117 - 1 May 2025

Viewed by 235

Abstract

The Reynolds number is a fundamental parameter in fluid dynamics, initially introduced by O. Reynolds in 1883 to characterize the transition between laminar and turbulent flow in fluids and necessary in the scaling of viscous resistance. Over time, its application has expanded significantly, [...] Read more.

The Reynolds number is a fundamental parameter in fluid dynamics, initially introduced by O. Reynolds in 1883 to characterize the transition between laminar and turbulent flow in fluids and necessary in the scaling of viscous resistance. Over time, its application has expanded significantly, becoming essential for studying a vast range of fluid phenomena—from microscopic scales such as cellular motion to macroscopic scales like turbulent flows and even intergalactic dynamics. The article highlights the universal relevance of the Reynolds number across various fields, including its adaptation to non-Newtonian fluids and granular flows. It emphasizes how the Reynolds number has evolved from a simple dimensionless group to a critical tool for understanding complex physical processes across different scales and environments. Full article

(This article belongs to the Special Issue Recent Advances in Fluid Mechanics: Feature Papers, 2024)

24 pages, 10198 KiB

Open AccessArticle

Analysis of Two Protection Strategies for Reducing Aerosol Expulsion from Wind Instruments

by Miriam Baron, Bogac Tur, Marie Köberlein, Laila Ava Hermann, Sophia Gantner, Matthias Echternach and Stefan Kniesburges

Fluids 2025, 10(5), 116; https://doi.org/10.3390/fluids10050116 - 30 Apr 2025

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Abstract

(1) Background: the aim of this study is to assess the effectiveness of two protection systems for aerosol cloud reduction while playing different wind instruments. (2) Methods: The protection systems used were a cotton molton construction combined with a bell filter attached at [...] Read more.

(1) Background: the aim of this study is to assess the effectiveness of two protection systems for aerosol cloud reduction while playing different wind instruments. (2) Methods: The protection systems used were a cotton molton construction combined with a bell filter attached at the bell of the instruments, as well as a household paper towel. For visualization of the emitted aerosol particles, e-cigarettes were used. With three full HD cameras, cloud dispersion was captured in the forward, sideways, and upwards directions. The effectiveness of aerosol spread reduction was statistically evaluated. (3) Results: Without protection, aerosol clouds dispersed, on average, up to 1.23 m in the forward direction, 0.46 m sideways, and 0.86 m upwards. The cotton molton mask reduced forward spread by 42%, while the paper towel achieved a 15% reduction, although both systems increased lateral and vertical dispersion. Specifically, the cotton molton mask yielded a 9% increase to the side and 7% in the upward direction, while the paper towel resulted in a 66% increase to the sides and a 10% increase in the upward direction. The cotton molton mask’s effectiveness was attributed to its additional coverage of the tone holes, which contribute to aerosol emission in woodwind instruments. A statistical analysis via the Friedman test confirmed significant reductions in forward dispersion with the cotton molton system. (4) Conclusions: Protective systems can partially reduce aerosol emissions. However, these alone are not sufficient, and further measures to reduce the spread of particles are necessary. Full article

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22 pages, 4445 KiB

Open AccessArticle

Research on Dual-Mode Self-Calibration Tensioning System

by Xuling Liu, Yusong Zhang, Chaofeng Peng, Le Bo, Kaiyi Zhang, Guoyong Ye, Jinggan Shao, Jinghui Peng and Songjing Li

Fluids 2025, 10(5), 115; https://doi.org/10.3390/fluids10050115 - 30 Apr 2025

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Abstract

In this paper, a double-mode self-calibration tension system is proposed, which adopts the conversion of hydraulic meter tension and the monitoring of standard force sensors. According to the material characteristics of the jack and the viscosity and temperature characteristics of the hydraulic oil, [...] Read more.

In this paper, a double-mode self-calibration tension system is proposed, which adopts the conversion of hydraulic meter tension and the monitoring of standard force sensors. According to the material characteristics of the jack and the viscosity and temperature characteristics of the hydraulic oil, the differential model of heat conduction in the hydraulic cylinder and the mathematical model of oil film friction heat generation are established, and the internal thermodynamic characteristics of the jack are theoretically analyzed, which provides theoretical support for the temperature compensation of the hydraulic oil pressure gauge of the jack. A simulation analysis was conducted on the thermodynamic characteristics of the hydraulic jack, and the distribution patterns of the temperature field, thermal stress field, and thermal strain field inside the hydraulic cylinder during normal operation were determined by measuring the temperature changes in five different parts of the jack at different times (t = 200 s, 2600 s, 5000 s, 7400 s, and 10,000 s). For the issue of heat generation due to oil film friction in the hydraulic jack, a simulation calculation model is developed by integrating Computational Fluid Dynamics (CFD) techniques with dynamic grid and slip grid methods. By simulating and analyzing frictional heating under conditions where the inlet pressures are 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.7 MPa, and 0.9 MPa, respectively, we can obtain the temperature distribution on the jack, determine the frictional resistance, and subsequently conduct a theoretical analysis of the simulation results. Using the high-precision standard force sensor after data processing and the hydraulic oil gauge after temperature compensation, the online self-calibration of the tensioning system is carried out, and the regression equation of the tensioning system under different oil temperatures is obtained. The double-mode self-calibration tensioning system with temperature compensation is used to verify the compensation accuracy of the proposed double-mode self-calibration tensioning system. Full article

(This article belongs to the Topic Applied Heat Transfer)

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22 pages, 3296 KiB

Open AccessArticle

Performance of an L-Shaped Duct OWC-WEC Integrated into Vertical and Sloped Breakwaters by Using a Free-Surface RANS-Based Numerical Model

by Eric Didier and Paulo R. F. Teixeira

Fluids 2025, 10(5), 114; https://doi.org/10.3390/fluids10050114 - 30 Apr 2025

Viewed by 224

Abstract

Waves generated by the wind in oceans and seas have a significant available quantity of clean and renewable energy. However, harvesting their energy is still a challenge. The integration of an oscillating water column (OWC) wave energy converter into a breakwater leads to [...] Read more.

Waves generated by the wind in oceans and seas have a significant available quantity of clean and renewable energy. However, harvesting their energy is still a challenge. The integration of an oscillating water column (OWC) wave energy converter into a breakwater leads to more viability, since it allows working as both harbor and coastal protection and harvesting wave energy. The main objective of this study is to investigate different configurations of L-shaped duct OWC devices inserted into vertical and sloped (2:3) impermeable breakwaters for different lengths of the lip by using a numerical model based on the Reynolds-Averaged Navier-Stokes equations. The ANSYS FLUENT^® software (2016) is used in 2D numerical simulations by adopting the volume of fluid method to consider the two-phase free surface flow (water and air). It was observed that both the length of the lip and the length of the L-shaped duct OWC significantly influence the resonance and the efficiency of the OWC device. In addition, the performance of the OWC device varies significantly with its geometric configuration, which needs to be adapted for the local sea state. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Applied to Transport Phenomena)

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26 pages, 9399 KiB

Open AccessArticle

Investigation of Multiphase Flow in Continuous-Casting Water Model with Measurements and Computational Modeling

by Hamed Olia, Dylan Palmer, Ehsan Jebellat and Brian G. Thomas

Fluids 2025, 10(5), 113; https://doi.org/10.3390/fluids10050113 - 28 Apr 2025

Viewed by 259

Abstract

This work introduces a 0.6-scale water model of the continuous slab-casting process and a MATLAB-based model to study the effects of non-primed and multiphase flow on pressure and flow rate. The water model uses stopper-rod flow control and features pressure and velocity measurements [...] Read more.

This work introduces a 0.6-scale water model of the continuous slab-casting process and a MATLAB-based model to study the effects of non-primed and multiphase flow on pressure and flow rate. The water model uses stopper-rod flow control and features pressure and velocity measurements at multiple locations. The new computational model, PFSR V4 (Pressure-drop Flow-rate model of Stopper Rod metal delivery systems, Version 4), improves upon a prior one-dimensional Bernoulli-based framework by incorporating a bubble accumulation zone. This zone represents a region of bubbly flow with an intermediate gas fraction between constant-pressure gas pockets below the stopper tip and the downstream bubbly flow regime. Parametric studies with the water model show that flow remains fully primed at low gas flow rates but transitions to non-primed flow as the gas flow rate exceeds 10–16 SLPM. Three different flow regions are observed inside the water model nozzle: air pocket, bubble accumulation, and bubbly flow, which are also captured by the new computational model. Above a critical gas flow rate, the flow becomes unstable and difficult to control, though higher hot gas flow rates are expected for similar transitions in a real steel caster due to gas expansion at high temperatures. Pressure changes are minimal in the air pocket region and increase significantly in the upper bubble accumulation zone, where liquid velocity is much higher than in the classic bubbly-flow region, found lower in the nozzle. The new model was successfully calibrated to match the observed flow regimes and shows good agreement with the water-model measurements. Full article

(This article belongs to the Special Issue Multiphase Flow for Industry Applications)

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19 pages, 5624 KiB

Open AccessArticle

Research on the Improvement of BEM Method for Ultra-Large Wind Turbine Blades Based on CFD and Artificial Intelligence Technologies

by Shiyu Yang, Mingming Zhang, Yu Feng, Haikun Jia, Na Zhao and Qingwei Chen

Fluids 2025, 10(5), 112; https://doi.org/10.3390/fluids10050112 - 27 Apr 2025

Viewed by 206

Abstract

With the development of the wind power industry, wind turbine blades are increasingly adopting ultra-large-scale designs. However, as the size of blades continues to increase, existing aerodynamic calculation methods struggle to achieve both relatively high computational accuracy and efficiency simultaneously. To tackle this [...] Read more.

With the development of the wind power industry, wind turbine blades are increasingly adopting ultra-large-scale designs. However, as the size of blades continues to increase, existing aerodynamic calculation methods struggle to achieve both relatively high computational accuracy and efficiency simultaneously. To tackle this challenge, this research focuses on the low accuracy issues of the traditional Blade Element Momentum theory (BEM) in predicting the aerodynamic performance of wind turbine blades. Consequently, a correction framework is proposed, to integrate the Computational Fluid Dynamics (CFD) method with the Multilayer Perceptron (MLP) neural network. In this approach, the CFD method is used to predict the airflow characteristics around the blades, and the MLP neural network is employed to model the intricate functional relationships between multiple influencing factors and key aerodynamic parameters. This process results in high-precision predictive functions for key aerodynamic parameters, which are then used to correct the traditional BEM. When this correction framework is applied to the rotor of the IEA 15 MW wind turbine, the effectiveness of MLP in predicting key aerodynamic parameters is demonstrated. The research findings suggest that this framework can enhance the accuracy of BEM aerodynamic load predictions to a level comparable to that of RANS. Full article

(This article belongs to the Special Issue Drag Reduction Through Traditional or Machine Learning-Based Flow Control)

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15 pages, 326 KiB

Open AccessArticle

Weakly Nonlinear Instability of a Convective Flow in a Plane Vertical Channel

by Natalja Budkina, Valentina Koliskina, Andrei Kolyshkin and Inta Volodko

Fluids 2025, 10(5), 111; https://doi.org/10.3390/fluids10050111 - 26 Apr 2025

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Abstract

The weakly nonlinear stability analysis of a convective flow in a planar vertical fluid layer is performed in this paper. The base flow in the vertical direction is generated by internal heat sources distributed within the fluid. The system of Navier–Stokes equations under [...] Read more.

The weakly nonlinear stability analysis of a convective flow in a planar vertical fluid layer is performed in this paper. The base flow in the vertical direction is generated by internal heat sources distributed within the fluid. The system of Navier–Stokes equations under the Boussinesq approximation and small-Prandtl-number approximation is transformed to one equation containing a stream function. Linear stability calculations with and without a small-Prandtl-number approximation lead to the range of the Prantdl numbers for which the approximation is valid. The method of multiple scales in the neighborhood of the critical point is used to construct amplitude evolution equation for the most unstable mode. It is shown that the amplitude equation is the complex Ginzburg–Landau equation. The coefficients of the equation are expressed in terms of integrals containing the linear stability characteristics and the solutions of three boundary value problems for ordinary differential equations. The results of numerical calculations are presented. The type of bifurcation (supercritical bifurcation) predicted by weakly nonlinear calculations is in agreement with experimental data. Full article

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20 pages, 3854 KiB

Open AccessArticle

EHD Instability Modes of Power-Law Fluid Jet Issuing in Gaseous Streaming via Permeable Media

by Mohamed F. El-Sayed, Mohamed F. E. Amer and Doaa M. Mostafa

Fluids 2025, 10(5), 110; https://doi.org/10.3390/fluids10050110 - 25 Apr 2025

Viewed by 245

Abstract

The instability of a non-Newtonian dielectric fluid jet of power-law (P-L) type injected when streaming dielectric gas through porous media is examined using electrohydrodynamic (EHD) linear analysis. The interfacial boundary conditions (BCs) are used to derive the dispersion relation for both shear-thinning (s-thin) [...] Read more.

The instability of a non-Newtonian dielectric fluid jet of power-law (P-L) type injected when streaming dielectric gas through porous media is examined using electrohydrodynamic (EHD) linear analysis. The interfacial boundary conditions (BCs) are used to derive the dispersion relation for both shear-thinning (s-thin) and shear-thickening (s-thick) fluids. A detailed discussion is outlined on the impact of dimensionless flow parameters. The findings show that jet breakup can be categorized into two instability modes: Rayleigh (RM) and Taylor (TM), respectively. For both fluids, the system in TM is found to be more unstable than that found in RM, and, for s-thick fluids, it is more unstable. For all P-L index values, the system is more unstable if a porous material exists than when it does not. It is demonstrated that the generalized Reynolds number (

{R e}_{n}

), Reynolds number (

R e

), P-L index, dielectric constants, gas-to-liquid density, and viscosity ratios have destabilizing influences; moreover, the Weber number (

W e

), electric field (EF), porosity, and permeability of the porous medium have a stabilizing impact. Depending on whether its value is less or more than one, the velocity ratio plays two different roles in stability, and the breakup length and size of P-L fluids are connected to the maximal growth level and the instability range in both modes. Full article

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37 pages, 15268 KiB

Open AccessReview

Subchannel Reactor Studies: Applications and Advances Using Lattice Boltzmann Method—Comprehensive Review Study

by Abutiatey Eugene and Pil-Seung Chung

Fluids 2025, 10(5), 109; https://doi.org/10.3390/fluids10050109 - 25 Apr 2025

Viewed by 214

Abstract

Computational fluid dynamics (CFD) is an instrumental tool used in tackling the challenges of flow behavior and safety within nuclear reactor cores. Traditional CFD methods like finite volume, finite element, and finite difference have driven significant progress in nuclear engineering, particularly in single-phase [...] Read more.

Computational fluid dynamics (CFD) is an instrumental tool used in tackling the challenges of flow behavior and safety within nuclear reactor cores. Traditional CFD methods like finite volume, finite element, and finite difference have driven significant progress in nuclear engineering, particularly in single-phase and two-phase flow modeling, multiscale analysis, and multiphysics coupling. However, the Lattice Boltzmann Method (LBM), an advancing CFD tool for nuclear reactor subchannel study, remains underexplored in this field. LBM takes a unique mesoscopic approach by modeling particle distributions on a discrete lattice, offering a bridge between microscopic dynamics and macroscopic continuum behavior. Since the integration of LBM into the Lattice Bhatnagar–Gross–Krook (LBGK) model, it has significantly advanced, proving its efficiency in handling complex flow conditions. This review explores the potential of LBM in nuclear reactor subchannel applications. This study emphasizes LBM as a robust computational tool for subchannel study by highlighting its strengths, limitations, and future possibilities. Full article

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13 pages, 987 KiB

Open AccessArticle

Concentration Monitoring of Highly-Diluted Crude Oil-In-Water Emulsions by Ultrasonic Backscattering Sensors

by Carlos A. B. Reyna, Ediguer E. Franco, Santiago Laín, Timoteo F. de Oliveira, Marcos S. G. Tsuzuki and Flávio Buiochi

Fluids 2025, 10(5), 108; https://doi.org/10.3390/fluids10050108 - 25 Apr 2025

Viewed by 250

Abstract

This work deals with the feasibility of ultrasonic monitoring of the crude oil content in highly diluted crude oil-in-water emulsions, common mixtures obtained in the coalescence process of the petroleum industry. The measurement principle is the determination of the time of flight using [...] Read more.

This work deals with the feasibility of ultrasonic monitoring of the crude oil content in highly diluted crude oil-in-water emulsions, common mixtures obtained in the coalescence process of the petroleum industry. The measurement principle is the determination of the time of flight using the reflected pulses from a set of scatterers located in the near field of commercial transducers of 5 and 10 MHz. Dispersers consist of two rows of metal wires tensioned in front of the transducer using a specially designed mechanical part. The resulting assembly is a probe that can be introduced into a tank or pipe to perform the measurement. Experiments with crude oil-in-water emulsions with concentrations from 10 to 2000 ppm (parts per million) at a temperature of 20 °C were carried out. The results show that the small changes in the propagation velocity resulting from changes in concentration and temperature can be detected by the developed ultrasonic sensor. This opens up the possibility of determining the oil content in the emulsion by means of a calibration approach. The main motivation is the development of techniques for real-time monitoring of crude oil content in the wastewater produced in the petroleum industry. Full article

(This article belongs to the Special Issue Numerical Modeling and Experimental Studies of Two-Phase Flows, 2nd Edition)

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18 pages, 6280 KiB

Open AccessArticle

Hydrodynamic Resistance Analysis of Large Biomimetic Yellow Croaker Model: Effects of Shape, Body Length, and Material Based on CFD

by Donglei Zhao, Kexiang Lu and Weiguo Qian

Fluids 2025, 10(5), 107; https://doi.org/10.3390/fluids10050107 - 24 Apr 2025

Viewed by 220

Abstract

The marine environment is highly complex, characterized by substantial fluctuations in flow velocity. To enhance the adaptability of robotic large yellow croakers to such conditions, this study takes into account multiple factors, including shape, dimensions, and material properties, and evaluates their hydrodynamic resistance [...] Read more.

The marine environment is highly complex, characterized by substantial fluctuations in flow velocity. To enhance the adaptability of robotic large yellow croakers to such conditions, this study takes into account multiple factors, including shape, dimensions, and material properties, and evaluates their hydrodynamic resistance characteristics. A 2D model of large yellow croakers aged 1, 4, 7, 10, and 12 months was established as the bionic object. Based on computational fluid dynamics, the water resistance characteristics of this model were investigated in the same water environment. A 3D model of this species based on the 2D model and three skin materials, PE, PC, and ST, was added, and the effects of these materials on the water resistance of the 3D model were investigated. It was shown that in a water environment with a current speed of 0.1~1 m/s, the water resistance of large yellow croaker models at different ages ranged from 0.1006 to 6.8485 N; that of croakers with different body lengths ranged from 0.1067 to 28.5760 N; and that of croakers with different skin materials ranged from 0.0048 to 0.8672 N. The results showed that in the water environment with a current speed of 0.1–1 m/s, the 12-month-old large yellow croaker model had a lower water resistance range of 0.1006~3.6512 N in the watershed compared with other models of the same age; the large yellow croaker models with body lengths of 20, 30, and 40 cm had a smaller range of water resistance of 0.1125~12.5110 N in the watershed compared with other models of the same body length; and large yellow croaker models made of PE had a smaller range of resistance of 0.0048~0.7523 N in the watershed compared to those made of PC and ST materials. The results of this study are important for the design and fabrication of robotic fish capable of prolonged underwater operations. Full article

(This article belongs to the Section Mathematical and Computational Fluid Mechanics)

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Fluids, Volume 10, Issue 5 (May 2025) – 28 articles

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