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Annual Review of Fluid Mechanics top

► Internal Waves in a Nonuniformly Stratified Ocean
  22 Jan, 2026

Internal waves, generated by wind and tides, are ubiquitous in the ocean. Their dissipation and the resulting vertical mixing play an important role in setting the ocean circulation, stratification, and energetics. Ocean models usually parameterize many or all of these effects. The current generation of parameterizations often relies on assumptions of uniform or slowly varying stratification profiles. Here, we review the growing theoretical, modeling, and observational evidence that vertical nonuniformity in the stratification profile can significantly modify the assumed wave dynamics. Linear scattering, wave–wave interactions, and solitary-like internal wave generation in idealized nonuniform stratification profiles are discussed. The nonuniform features in oceanic vertical stratification profiles are characterized, followed by a discussion of the validity of the slowly varying stratification assumption for such profiles. A concerted effort is made to synthesize research in both fluid dynamics and oceanography.

► Formation and Evolution of Planetary Stagnant Lids and Crusts
  22 Jan, 2026

Earth is the only known planet with plate tectonics, which involves a mobile upper thermal boundary layer. Other terrestrial planets show a one-plate immobile lithosphere, or stagnant lid, that insulates and isolates their interior. Here, we first review the different types of lids that can develop on rocky and icy bodies. As they formed by accretion, involving high-energy impacts, terrestrial planets likely started hot and molten. We examine the process of lid initiation from a magma ocean stage and develop the equations for lid growth. We survey how lateral perturbations in lid and crust thickness can be amplified during their growth and finally discuss the possible processes at the origin of lid rupture and plate generation.

► Pattern Formation and Instabilities in Particulate Suspensions
  22 Jan, 2026

Particulate suspensions, consisting of solid particles dispersed in a fluid, exhibit complex flow behaviors influenced by multiple factors, including particle interactions, concentration gradients, and external forces. Suspensions play an important role in diverse processes, from sediment transport to food processing, and display instabilities triggered by shear-driven effects, frictional interactions, and viscous forces. These instabilities can often be understood by identifying the key mechanical quantities that govern the dynamics. Following hydrodynamic tradition, such mechanics can be characterized by dimensionless numbers, which encapsulate the interplay between geometric, kinematic, and mechanical factors. Many of these numbers represent competitions between opposing pairs of mechanical quantities, which we discuss in detail while also considering a few phenomena that require more complex combinations. By emphasizing the underlying mechanical principles, this review provides a perspective for understanding pattern formation and flow instabilities in confined particulate suspensions across different flow geometries.

► Electromagnetically Forced Flows in Shallow Electrolyte Layers
  22 Jan, 2026

Electromagnetically forced flows in shallow electrolyte layers offer a versatile and nonintrusive method for exploring quasi-two-dimensional fluid dynamics. This review focuses on the experimental and theoretical aspects of such flows driven by Lorentz forces generated by the interaction of injected electric currents and the applied magnetic fields. The method is applicable to both liquid metals and electrolytes, with the latter more commonly used due to their wide availability and ease of handling. Experimental aspects of the method and key components of mathematical flow analysis are discussed. Initially developed for geophysical flow modeling, the method has been instrumental in exploring various other physical phenomena including vortex and wake dynamics, spatiotemporal chaos, and mixing processes. The review also addresses the challenges of achieving true two-dimensionality in laboratory settings and discusses the influence of various parameters, such as layer thickness and forcing intensity, on the flow behavior. Future research directions in the field are highlighted.

► Fluid Mechanics for Green Buildings
  22 Jan, 2026

Decarbonization of buildings is one of the main challenges for the energy transition. In particular, the provision of heating, cooling, and ventilation to maintain a comfortable and healthy interior environment can be very energy intensive. Three approaches to help with the decarbonization of buildings are () upgrading the building envelope, especially the insulation, to reduce heat flow to or from the exterior; () improving the efficiency of the heating or cooling system, including the design and operation of ventilation flows; and () decarbonization of the heating and cooling systems, typically through electrification using heat pumps, and possibly the development of heat networks and interseasonal heat storage. This review touches on different elements of these challenges, mainly those related to ventilation, exploring some of the complexities of the fluid mechanics involved.

► The Dynamics of Sand Dunes
  22 Jan, 2026

Sand dunes cover 5% of Earth's land surface, and they abundantly populate river bottoms and seabeds. The subtle dynamical interplay between the granular matter and the overlaying fluid leads to rich phenomenology at different scales, from colliding grains through migrating sand dunes to slowly evolving dune fields. In this review, we survey recent developments in the literature on the dynamics of sand dunes and focus in particular on the physics and mathematics. Our discussion is organized around four central paradigms of the field: flat bed instability, single dune migration, dune–dune interactions, and dune field statistics. Besides discussing the key scientific advances, we also highlight the methodological advances in observations, experiments, and simulations that facilitated them. We conclude our review by discussing the social implications of dune dynamics, such as the interaction between dune and infrastructure, and we offer speculation on what research topics related to sand dunes might become important in the next decade.

► Fluid Mechanics of Blood Cells and Vesicles Squeezing Through Narrow Constrictions
  22 Jan, 2026

The squeezing of blood cells and vesicles through narrow constrictions, such as splenic slits, pulmonary capillaries, vascular endothelial gaps, and microfluidic channels, is crucial in physiology and biotechnology, with fluid mechanics playing a central role. The diverse geometries of these constrictions, the associated flow conditions, and the unique mechanical properties of cells and vesicles create a rich subject in fluid mechanics emerging from nonlinear dynamics of fluid–structure interactions involving both lubrication and Marangoni flows. Advances in microfluidics, video microscopy, and computational modeling have enabled investigations into these complex processes. This review surveys the key features and approaches, recent prominent studies, and unresolved challenges related to these processes, offering insights for researchers across biomechanics, biomedical engineering, biological physics, hematology, physiology, and applied mathematics.

► Secondary Atomization of Droplets at Extreme Conditions
  22 Jan, 2026

Droplets, which are ubiquitous in nature, are formed through intriguing processes, and one such route is air-assisted atomization or aerobreakup. This review focuses on secondary atomization, particularly the breakup of an individual droplet subjected to high-speed flows. This process involves complex interfacial dynamics with multiscale deformations, ranging from global flattening to local unstable waves. The deformations occur at progressively smaller scales while interacting with the surrounding gas phase, forming a nonlinear cascade. Each local undulation serves as a precursor to a self-similar evolution or subsecondary breakup process that ends with a ligament-mediated mechanism. In practical scenarios, droplets often encounter nonuniform, unsteady, impulsive, or compressible flows, like shock waves, which pose extreme conditions. The spatiotemporal scales of the nonuniformity or unsteadiness of the external flow must be comparable with the drop deformation scales at either global or local levels to influence aerobreakup that cascades across hierarchical deformation scales. The compressible effects at high Mach numbers are interestingly shown to suppress the tendency toward breakup.

► Fluid Deformation and Mixing in Porous Media as Drivers for Chemical and Biological Processes
  22 Jan, 2026

Porous media flows are generally viewed as inefficient mixers, where solutes may be dispersed yet poorly mixed, making mixing a critical limiting factor for a wide range of processes. The complexity and opacity of porous structures have long made these dynamics difficult to observe. With emerging experimental techniques, concepts and models of mixing in porous media are rapidly evolving. Recent advances link mixing dynamics to fluid deformation arising in flow through porous materials. Unlike diffusion and dispersion, which only dissipate chemical gradients, fluid shear and stretching amplify and sustain them. This review explores the role of fluid deformation in governing mixing, chemical reactions, and biological processes in porous media. We begin by highlighting key experimental observations that have improved our understanding of mixing in these systems. We then examine the fundamental concepts, models, and open questions surrounding fluid deformation and mixing in porous media, emphasizing their dependence on material structure, heterogeneity, dimensionality, and transient flow phenomena, as well as their interaction with chemical and biological processes.

► Capillary Drainage in Horizontal Soap Films: Theoretical Review and Experimental Illustrations
  22 Jan, 2026

Soap films and bubbles are inherently unstable systems that evolve over time. Their thickness is primarily governed by the competition between capillary and viscous forces. The presence of surfactants introduces Marangoni stresses, which limit interfacial extension and significantly increase film lifetime. While the bulk flow is typically well-described by a simple Poiseuille profile between the two interfaces, the interfacial dynamics can induce complex behaviors, even in the simple case of horizontal film drainage, which is used as a paradigmatic example in this review. The interfacial velocity is dictated by the thickness gradients and by the interfacial rheology, which, in many practical cases, reduces to the condition of an incompressible interface. This simplified framework allows for analytical predictions and scaling laws in axisymmetric flows. It is also consistent with the spontaneous symmetry breaking that may be observed in horizontal films—a phenomenon associated with the marginal regeneration process, which remains only partially understood. This review presents the most elementary theoretical frameworks capable of capturing the essential features of these flows and provides quantitative comparisons with available experimental data.

Computers & Fluids top

► Effect of wall-collision models on the transport of rigid, elongated non-spherical particles in a turbulent channel flow using an Euler/Lagrange approach
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Manuel A. Taborda, Martin Sommerfeld

► Central-differencing quasi-Newton method for solving the Eikonal equation with application to wall distance computation
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Yair Mor-Yossef

► Leading-edge vortex monitoring in dynamically stalled flows via persistent homology
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Quentin Martinez, Chetan Jagadeesh, Marinos Manolesos, Mohammad Omidyeganeh

► Data-driven regression of thermodynamic models in entropic form using physics-informed machine learning
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Evert Bunschoten, Alessandro Cappiello, Matteo Pini

► An improved immersed boundary method for investigating flows over multiple irregular geometries with fractal interpolation
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Dongheng Lai, Xingyu Zhu

► Artificial viscosity based on the velocity gradient components in a 3D Lagrangian Lax-Wendroff scheme
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Matěj Klíma, Milan Kuchařík, Richard Liska

► High-order gas-kinetic scheme with two-derivative-based time discretization for compressible flows
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Qiushuo Qin, Jie Wu, Lan Jiang

► RANS-CNN: A physics-informed convolutional neural network for solving reynolds-averaged Navier-Stokes equations in duct flows
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Gaurav Bokil, Sebastian Merbold, Stefanie De Graaf

► Stabilization of a hypersonic boundary layer via the oxidized surface of carbon/silicon carbide composite
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Liangzhong Fan, Qingyong Zhu, Zhihui Li, Dongheng Lai

► Development of ISPH-FVM coupling method by embedded MHD model to simulate bubble rising in conductive liquids under magnetic field
    

Publication date: 15 February 2026

Source: Computers & Fluids, Volume 306

Author(s): Yixiang Xu, Gang Yang, Yulin Xing, Dean Hu

International Journal of Computational Fluid Dynamics top

► Tip-Leakage Flow Analysis on a Stationary Hydrofoil Using Detached Eddy Simulation
    7 Jan, 2026
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► Erosion Prediction Using CFD and Regression Analysis for a Pipe with Two 90° Elbows Connected in Series
  19 Dec, 2025
Volume 39, Issue 2, February 2025, Page 102-131
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► Shape Optimization of Cleaning Robot for Ships Based on Bezier Curve and Improved Optimization Algorithm
  19 Dec, 2025
Volume 39, Issue 2, February 2025, Page 83-101
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► A Grad-Div Incremental Picard-Yosida Iteration for the Steady-State Navier–Stokes Equations
    4 Dec, 2025
Volume 39, Issue 2, February 2025, Page 69-82
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► Erratum
  18 Aug, 2014
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International Journal for Numerical Methods in Fluids top

► An Improved Curvature Estimation Method Based on Height Function and Volume Preserving Mean Curvature Motion
  21 Jan, 2026
An Improved Curvature Estimation Method Based on Height Function and Volume Preserving Mean Curvature Motion

An improved height function method aimed at obtaining smooth curvature in three dimensions is proposed. The method is motivated by the volume-preserved mean curvature (VPMC) motion. The accuracy and efficiency of the improved height function technique applied to 3D problems are confirmed through the simulation of a liquid droplet impact onto a deep liquid pool.


ABSTRACT

We present an improved height function technique aimed at obtaining smooth curvature in three dimensions. The new approach is designed for estimating curvature from the volume of fluid (VOF) field. Motivated by the volume-preserved mean curvature (VPMC) motion, an iterative procedure is implemented to eliminate oscillations from the curvature field while simultaneously ensuring consistency with the VOF field. To validate the new method, the curvature of 2D and 3D drops is considered. Numerical tests demonstrate the efficient elimination of high-frequency errors in the local curvature, and the total volume enclosed by the interface is preserved. Considering the equilibrium of the static droplet problem, the spurious current is also effectively suppressed. The proposed method is further extended to an adaptive mesh and validated through the free oscillation of a 2D droplet. Finally, the accuracy and efficiency of the improved height function technique applied to 3D problems are confirmed through the simulation of a liquid droplet impact onto a deep liquid pool.

► Data Assimilation of Compressible Flows With Discontinuities: Evaluating Algorithms on Sod's Shock Tube
  19 Jan, 2026
Data Assimilation of Compressible Flows With Discontinuities: Evaluating Algorithms on Sod's Shock Tube

Data assimilation in compressible flows with shocks has not been widely explored, especially when using sparse and incomplete measurements. Here sequential and variational data assimilation methods are applied to 1D, nonreacting, shock-laden flows using sparse and incomplete measurements. The methods are assessed, successes and challenges are identified, paving the way for application to more complex flows.


ABSTRACT

Data assimilation (DA) combines noisy observations with uncertain model predictions to obtain optimal state estimation. It has been used extensively in numerical weather prediction and is increasingly used in computational fluid dynamics. However, the application of DA to compressible flows with discontinuities such as shocks or detonation fronts is far less explored. In this paper, we examine three different DA algorithms applied to 1D, non-reacting, compressible flows: The particle filter (PF), the ensemble Kalman filter (EnKF), and 4D-Var. The Sod's shock tube problem is employed as a canonical test case. While the sequential DA methods (PF and EnKF) are able to successfully assimilate sparse pressure measurements, this comes at the risk of smearing sharp gradients due to reconstructing the state as an ensemble average. On the other hand, the 4D-Var method, applied in the context of a small parameter inverse problem, preserves sharp gradients within the resolution of the forward solver, but may require many iterations to converge to the truth. This study therefore provides assessments of sequential and variational DA methods in 1D shock tube problems and contributes towards applying DA to more complex shock-laden flows (e.g., in higher dimensions, or reacting flows).

► Polymer Stress‐Tensor Calculation for a Laminar Submerged Viscoelastic Jet Flow Using Different Constitutive Models
  18 Jan, 2026
Polymer Stress-Tensor Calculation for a Laminar Submerged Viscoelastic Jet Flow Using Different Constitutive Models

This study presents an efficient method to compute polymer stress-tensor components in viscoelastic laminar jet flows using models such as Oldroyd-B, Giesekus, PTT, and FENE. By assuming a stationary and parallel flow, the methodology significantly reduces computational cost. Numerical results show excellent agreement with the analytical solution available for the UCM and Oldroyd-B models and reveal how non-Newtonian parameters influence stress distributions across different models.


ABSTRACT

Viscoelastic fluids, exhibiting both elastic and viscous properties, play a fundamental role in various industrial and biological applications. Accurate modeling of their rheological behavior requires constitutive equations that capture the complex interplay between these properties. The present study focuses on the analysis of incompressible, isothermal, two-dimensional, planar, laminar, submerged jet flow of viscoelastic fluids. A computational methodology is adopted to determine the polymer stress-tensor distribution for different viscoelastic models, including Oldroyd-B, UCM, Giesekus, Phan-Thien-Tanner (PTT), and finitely extensible nonlinear elastic (FENE). These models are chosen to represent a diverse range of viscoelastic behaviors. The Navier–Stokes equations, coupled with the appropriate constitutive model, are solved numerically. The proposed method allows one to access the distribution of the polymer stress-tensor components with very low computational cost. Results demonstrate the accuracy of the computational method for various models and their parameter values. The findings provide valuable insights into the fundamental behavior of viscoelastic jets and can serve as a foundation for subsequent linear and nonlinear stability investigations.

► Numerical Analysis of Fluid–Structure Interaction in Open and Closed Saddle‐Shaped Membrane Structures: A New Framework Based on Vortex Dynamics
  13 Jan, 2026
Numerical Analysis of Fluid–Structure Interaction in Open and Closed Saddle-Shaped Membrane Structures: A New Framework Based on Vortex Dynamics

A new framework based on vortex dynamics has been developed for bidirectional FSI simulations to analyze open and closed saddle-shaped membrane structures. Leveraging the framework's vortex tracking capability, wind pressure and flow velocity characteristics of both structures were compared. Wind tunnel tests validated simulation accuracy, and combined with wind-induced response analysis, the risk differences between the two structural types were clarified.


ABSTRACT

The strong fluid–structure interaction (FSI) between the membrane structure and the surrounding airflow directly impacts the wind pressure distribution and structural stability, which are concerned with structural safety. This paper comparatively investigates the FSI of open and closed-type saddle-shaped membrane structures under wind loads, in terms of wind pressure distribution and flow field characteristics. First, a bidirectional FSI numerical simulation, integrated into this vortex dynamics-based framework, was implemented for the spatial membrane structure in laminar flows. The accuracy of the simulation was verified based on previous wind tunnel tests, from the perspective of both structural vibration and flow field. Subsequently, leveraging the framework's ability to track vortex evolution, a comparative analysis of wind pressure distribution and velocity trajectories was conducted for both configurations. Finally, the framework enabled a deep analysis of how vortex structures–their formation, development, and dissipation–influence structural vibration. The results indicate that the peak wind pressure coefficients of the open membrane structure at the leading edge under 0° and 90° wind directions reach 0.5 and 0.7, respectively. At a 45° wind direction, the flange area becomes a risk focus due to conical vortices. For closed membrane structures, the minimum average wind pressure coefficients under 0° and 90° wind directions were −0.52 and −1.0, respectively, with significant overall wind suction force. The open-type membrane structures exhibit both positive and negative pressure zones at all wind directions. Airflow separation results in wind pressure peaks at the leading edge of the windward side. Wind direction obviously affects the type of vortex structure, and the more sufficient vortex development would lead to increased trailing edge amplitude. Then, the local dynamic response of open-type membrane structures should be paid more attention. However, closed-type membrane structures experience upward lifting at all wind directions. The enhanced stiffness of the internal gas would reduce pulsations, and therefore the risk of structural overall instability should be considered as priorities.

► A Novel Mesh‐Free Approach for Solving Incompressible Fluid Flow Problems
    9 Jan, 2026
A Novel Mesh-Free Approach for Solving Incompressible Fluid Flow Problems

We introduce a novel mesh-free method for steady incompressible flow by combining a Weighted Least Squares approximation with a High-Order Continuation Method. The approach solves the Navier–Stokes equations without mesh generation or numerical integration, using only discrete domain points. It improves accuracy and reduces computational cost compared to MLS-based formulations by avoiding weight-function derivative evaluation. Results show superior precision and efficiency relative to classical and recent mesh-free methods.


ABSTRACT

In this study, we present a novel mesh-free approach for solving incompressible fluid flow problems, which is introduced here for the first time. Our approach solves the steady-state Navier–Stokes equations without requiring traditional mesh generation. For this purpose, we adopt a discrete framework in which variables are defined at specific points within the domain, thereby eliminating the need for numerical integration. The proposed approach combines a weighted least squares (WLS) approximation with a high-order continuation method (HOCM). This approach significantly enhances the accuracy of steady-state incompressible flow simulations, offering both improved precision and reduced computation time compared to classical methods. Our results indicate that this approach holds substantial potential for expanding practical applications across various engineering fields. In contrast to the coupling of the moving least squares (MLS) method with the HOCM, our approach avoids computing derivatives of the weight function within the influence domain, which reduces the computational cost and enhances accuracy. This original combination highlights the novelty of our work compared to research conducted in recent years. A comparison is presented between the results obtained using the HOCM with MLS approximation and those reported in the literature.

► A Gridless Method for Computing Interior Ballistic Flows With Moving Discrete Points
    8 Jan, 2026
A Gridless Method for Computing Interior Ballistic Flows With Moving Discrete Points

A 2D/axisymmetric meshless ALE solver was developed for interior ballistics, with a 1-DOF shell model incorporating shot start pressure, engraving resistance, and bore friction. Validated on multiple benchmark test cases, the solver reproduced 155 mm shell acceleration, velocity, and displacement in close agreement with experiments. Spectral analysis revealed dominant frequencies (160–300 Hz) but no resonance with the 1316 Hz modal frequency. Pressure-wave amplitudes (3.52–14.24 MPa) stayed below failure.


ABSTRACT

This study presents a meshless computational framework for simulating unsteady fluid dynamics in interior ballistic applications. The proposed meshless method eliminates the need for grid generation and deformation by utilizing a cloud of dynamically moving points, based on the Arbitrary Lagrangian–Eulerian (ALE) formulation. The key novelty of this work is integrating the meshless solver with a moving points system, which makes it highly suitable for ballistics applications involving complex geometries. Furthermore, the combustion process has been simplified, streamlining the simulation by avoiding the need for fully modeling propellant combustion, as required in multiphase solvers. The framework discretizes the unsteady axisymmetric Euler equations using local weighted least-squares approximations to calculate derivatives. Numerical fluxes are computed using a modified Harten, Lax, van Leer, Contact (HLLC) scheme, which is essential for achieving high accuracy and effectively capturing complex flow features. Temporal evolution is handled using the Explicit Strong Stability Preserving (ESSP) Runge–Kutta method, ensuring stability and accuracy under unsteady flow conditions. The method is applied to interior ballistic simulations, such as the motion of an M107–155 mm shell launched through an M185 cannon, achieving excellent agreement with experimental observations, particularly in predicting muzzle velocity and peak pressure. The simplified setup of this framework enables it to handle large grid deformations and complex geometries, and makes it an efficient, high-fidelity solution for dynamic flow problems in ballistics and aerospace, serving as a reliable predictive and assessment tool for interior ballistics studies. Further, the pressure wave analysis conducted within this framework provides valuable insights for optimizing shell design and propellant combustion characteristics, while also enhancing its role as a predictive tool for assessing shell integrity and mitigating resonance-induced structural risks in interior ballistics applications.

► Impact of Uncertain Parameters on Navier–Stokes Equations With Heat Transfer via Polynomial Chaos Expansion
    7 Jan, 2026
Impact of Uncertain Parameters on Navier–Stokes Equations With Heat Transfer via Polynomial Chaos Expansion

This study investigates the impact of uncertain parameters on Navier–Stokes equations coupled with heat transfer using the Intrusive Polynomial Chaos Method (IPCM). Sensitivity equations are formulated for key input parameters, such as viscosity and thermal diffusivity, and solved numerically using the Finite Element-Volume method. The Rayleigh–Bénard convection test validates the approach, demonstrating its relevance to applications in solar energy, materials processing, and energy storage.


ABSTRACT

Performing sensitivity analysis in computational fluid dynamics is essential for assessing model robustness and reliability, since it determines how parameter variations or boundary conditions affect the simulation results. Specifically, this study focuses on the Navier–Stokes equations coupled with heat transfer, relevant to scenarios where temperature affects fluid flow behavior. Our sensitivity analysis is based on the Intrusive Polynomial Chaos Method (IPCM), which uses Probability Density Functions (PDFs) to describe stochastic variables. We extend previous work on uncertain initial or boundary conditions by focusing on input parameters such as viscosity and thermal diffusivity. We show that the sensitivity equations are well-posed and solve them numerically using the Finite Element Volume (FEV) method. The Rayleigh–Bénard convection test is used to validate the approach. This test is particularly relevant to applications in solar energy, materials processing, and energy storage, making it an excellent choice for demonstrating the effectiveness of our method.

► Numerical Investigation of the Impact of Heat Distribution on Fluid Flow for the Combination of Newtonian–Newtonian and Newtonian–Non‐Newtonian Fluid
    7 Jan, 2026
Numerical Investigation of the Impact of Heat Distribution on Fluid Flow for the Combination of Newtonian–Newtonian
and Newtonian–Non-Newtonian Fluid

The change in temperature distribution has the same pattern in section B in the case of all fins structure. From section A, it is observed that the difference in temperature distribution near the inlet for the two Re is maximum for triangular fins and least for rectangular fins. The difference in temperature distribution is in between these two fin structures in the case of circular fins.


ABSTRACT

Microchannels are used for thermal exchange because of their precise volume and higher heat dissipation capacity due to its surface to volume ratio. The thermal performance of microfluidic systems is greatly influenced by the dynamics of Newtonian and non-Newtonian fluid flows inside microchannels. In the current study, the regulation of temperature fluctuations within the working fluid is evaluated by executing the thermo-fluid coupling effects in micro-channels. For a combination of Newtonian–Newtonian and Newtonian–non-Newtonian influx fluid, the impact of flowing fluid on heat distributions with regards to micro-fins heat element sources within a microchannel was investigated numerically. Three micro-fins shape, viz., rectangular, triangular, and circular fin structures were used in the study. Rectangular fins had the largest as well as lowest heat transfer to the fluid flow for the combination of Newtonian–Newtonian fluids. It is also evaluated that for rectangular fins, the maximum Nu value obtained was 18.42 and the minimum Nu value obtained was 1.04. In addition, for triangular fins, the maximum Nu value obtained was 16.16 and the minimum Nu value obtained was 1.13. Finally, for circular fins, the maximum Nu value obtained was 9.82 and the minimum Nu value obtained was 1.22.

► Issue Information
    5 Jan, 2026
International Journal for Numerical Methods in Fluids, Volume 98, Issue 2, February 2026.
► CFD Study of Indian Coal to Assess the Severity of Coal Dust Explosion and Its Classification as Per Explosibility
    5 Jan, 2026
CFD Study of Indian Coal to Assess the Severity of Coal Dust Explosion and Its Classification as Per Explosibility

The maximum rate of pressure rise for all samples ranging from 176.4 (NCPH) to 403.1 bar/second (Narsamunda) and deflagration index ranges from 47.90 (NCPH) to 109.43 bar·m/s (Narsamunda). The highest deflagration index of the Narsamunda sample is attributed to the fact that it has the highest volatile matter (VMd), volatile ratio, lowest CPT, lowest activation energies for both volatiles (Ev) and char (Ec) allowing it to burn or react more readily than other samples producing high explosion pressure. Predict Kst with given values of CPT and VMd polynomial fit equation Kst=1253.394−13.712CPT−4.552VMd−0.04(CPT)2−0.113VMd2$$ {K}_{st}=1253.394-13.712 CPT-4.552{VM}_d-0.04\ {(CPT)}^2-0.113{\left({VM}_d\right)}^2 $$ having R2 value of 0.909, adjusted R2 of 0.891 and standard error of estimate of 5.19. The hierarchal clustering proclaimed that there are three clusters for 24 coal samples with a degree of severity defined as highly susceptible, moderately susceptible, and potentially susceptible towards coal dust explosion.


ABSTRACT

This paper presents a comprehensive study using computational fluid dynamics (CFD) to evaluate the explosibility of Indian coals and classify their explosion severity. A Siwek 20 L explosion chamber was simulated by ASTM standard 1226-19 to analyze coal samples collected from 24 coal mines across various coalfields of India. The explosibility parameters that is, maximum explosion pressure (Pmax), maximum rate of pressure rise ((dP/dt)max), explosion delay time (Ted), time to reach Pmax (Tep), and deflagration index (Kst) were estimated for each coal sample to evaluate the deflagration index, which measures the severity of explosions. The deflagration index (Kst) of all coal samples varied significantly between 47.90 bar·ms−1 and 109.43 bar·ms−1 indicating weak explosion potentials (0 < Kst < 200) as per OSHA 2009 standards. Based on this result, a classification system can be proposed for Indian coals depending on shared characteristics, which may be helpful in identifying coal according to their deflagration index (degree of severity). Presently, no formal classification system exists for Indian coal, and current assessments rely on USA OSHA regulations. Hence, multivariate statistical techniques, including feature selection, correlation analysis, multiple regression, and hierarchical clustering, were employed to identify the factors influencing explosion severity and to categorize the coal samples. Volatile matter dry (VMd) and crossing point temperature (CPT) were the most influential factors impacting Kst. A non-linear regression model yielded a polynomial equation with a strong fit (R2 = 0.909, std. error of estimate = 5.19%) for predicting the deflagration index and validated with test results. Hierarchical clustering further classified the coal samples into three distinct groups based on their explosion susceptibility: highly susceptible, moderately susceptible, and potentially susceptible. The proposed classification and prediction model can guide industry stakeholders to implement more effective explosion mitigation strategies and safety protocols.

Journal of Computational Physics top

► BiLO: Bilevel Local Operator Learning for PDE Inverse Problems
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Ray Zirui Zhang, Christopher E. Miles, Xiaohui Xie, John S. Lowengrub

► A dual physics-informed neural network for topology optimization
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Ajendra Singh, Souvik Chakraborty, Rajib Chowdhury

► Enabling probabilistic learning on manifolds through double diffusion maps
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Dimitris G. Giovanis, Nikolaos Evangelou, Ioannis G. Kevrekidis, Roger G. Ghanem

► Differentiable neural network representation of multi-well, locally-convex potentials
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Reese E. Jones, Adrian Buganza Tepole, Jan N. Fuhg

► R-PINN: Recovery-type a-posteriori estimator enhanced adaptive PINN
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Rongxin Lu, Jiwei Jia, Young Ju Lee, Zheng Lu, Chen-Song Zhang

► An implicit shock tracking method for simulation of shock-dominated flows over complex domains using mesh-based parametrizations
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Alexander M. Pérez Reyes, Matthew J. Zahr

► Physics-graph-informed neural networks (PGINNs): From local point-wise constraint to global nodal association
    

Publication date: 15 April 2026

Source: Journal of Computational Physics, Volume 551

Author(s): Feng Chen, Yiran Meng, Kegan Li, Chaoran Yang, Jincheng Dai

► A cell-centered AMR-ALE framework for 3D multi-material hydrodynamics. Part I: Lagrangian and indirect Euler AMR algorithms
    

Publication date: Available online 22 January 2026

Source: Journal of Computational Physics

Author(s): A. Colaïtis, S. Guisset, J. Breil

► High-Order Hermite Optimization: Fast and Exact Gradient Computation in Open-Loop Quantum Optimal Control using a Discrete Adjoint Approach
    

Publication date: Available online 22 January 2026

Source: Journal of Computational Physics

Author(s): Spencer Lee, Daniel Appel

► A high-order, conservative and positivity-preserving intersection-based remapping method between meshes with isoparametric curvilinear cells
    

Publication date: Available online 15 January 2026

Source: Journal of Computational Physics

Author(s): Nuo Lei, Juan Cheng, Chi-Wang Shu

Journal of Turbulence top

► Spatially explicit deterministic forcing scheme for forced homogeneous isotropic turbulence
  13 Jan, 2026
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► Delayed detached-eddy simulations of NACA wing sections using spectral elements
    9 Jan, 2026
Volume 26, Issue 10-11, October-November 2025, Page 354-381
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► Turbulent boundary layer superstructures and their implications to surface pressure fluctuations
    8 Jan, 2026
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► CFD-GRNN framework for wind interference on tall buildings with variable heights and orientations
  22 Dec, 2025
Volume 26, Issue 10-11, October-November 2025, Page 323-353
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► Why some heat waves last longer: insights on the atmospheric boundary layer characteristics over the Central India from high-resolution modelling
    9 Dec, 2025
Volume 26, Issue 10-11, October-November 2025, Page 305-322
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► Modelling of turbulent shear stress in vertical bubbly flows at low void fractions and low flow velocities
  26 May, 2025
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Physics of Fluids top

► A sharp interface immersed edge-based smoothed finite element method with extended fictitious domain scheme
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
This paper proposes a versatile and robust immersed edge-based smoothed finite element method with the mass conservation algorithm (IESFEM/Mass) to solve partitioned fluid–structure interaction (FSI). A gradient smoothing technique was used to solve the system governing equations, which can improve the calculated capability of the linear triangular elements in two phases. Based on the quadratic sharp interface representation of immersed boundary, an extended fictitious domain constructed by a least squares method approximately corrected the residual flux error. The compatibility for boundary conditions on moving interfaces was satisfied, thus eliminating spurious oscillations. The results from all numerical examples were consistent with those from the existing experiments and published numerical solutions. Furthermore, the present divergence-free vector field had a faster-converged rate in the flow velocity, pressure, and FSI force. Even if in distorted meshes, the proposed algorithm maintained a stable accuracy improvement. The aerodynamics of one- and two-winged flapping motions in insect flight has been investigated through the IESFEM/Mass. It can be seen that the wing–wake interaction mechanism is a vital factor affecting the lift. The applicability of the present method in the biological FSI scenario was also well-demonstrated.
► Enhanced and reduced solute transport and flow strength in salt finger convection in porous media
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
We report a pore-scale numerical study of salt finger convection in porous media, with a focus on the influence of the porosity in the non-Darcy regime, which has received little attention in previous research. The numerical model is based on the lattice Boltzmann method with a multiple-relaxation-time scheme and employs an immersed boundary method to describe the fluid–solid interaction. The simulations are conducted in a two-dimensional, horizontally periodic domain with an aspect ratio of 4, and the porosity [math] is varied from 0.7 to 1, while the solute Rayleigh number [math] ranges from [math] to [math]. Our results show that, for all explored [math], solute transport first enhances unexpectedly with decreasing [math] and then decreases when [math] is smaller than a [math]-dependent value. On the other hand, while the flow strength decreases significantly as [math] decreases at low [math], it varies weakly with decreasing [math] at high [math] and even increases counterintuitively for some porosities at moderate [math]. Detailed analysis of the salinity and velocity fields reveals that the fingered structures are blocked by the porous structure and can even be destroyed when their widths are larger than the pore scale, but become more ordered and coherent with the presence of porous media. This combination of opposing effects explains the complex porosity dependencies of solute transport and flow strength. The influence of porous structure arrangement is also examined, with stronger effects observed for smaller [math] and higher [math]. These findings have important implications for passive control of mass/solute transport in engineering applications.
► On the instability of the magnetohydrodynamic pipe flow subject to a transverse magnetic field
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
The linear stability of a fully developed liquid–metal magnetohydrodynamic pipe flow subject to a transverse magnetic field is studied numerically. Because of the lack of axial symmetry in the mean velocity profile, we need to perform a BiGlobal stability analysis. For that purpose, we develop a two-dimensional complex eigenvalue solver relying on a Chebyshev–Fourier collocation method in physical space. By performing an extensive parametric study, we show that in contrast to the Hagen–Poiseuille flow known to be linearly stable for all Reynolds numbers, the magnetohydrodynamic pipe flow with transverse magnetic field is unstable to three-dimensional disturbances at sufficiently high values of the Hartmann number and wall conductance ratio. The instability observed in this regime is attributed to the presence of velocity overspeed in the so-called Roberts layers and the corresponding inflection points in the mean velocity profile. The nature and characteristics of the most unstable modes are investigated, and we show that they vary significantly depending on the wall conductance ratio. A major result of this paper is that the global critical Reynolds number for the magnetohydrodynamic pipe flow with transverse magnetic field is Re = 45 230, and it occurs for a perfectly conducting pipe wall and the Hartmann number Ha = 19.7.
► The turbulence development at its initial stage: A scenario based on the idea of vortices decay
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
In this paper, a model of the development of a quantum turbulence in its initial stage is proposed. The origin of the turbulence in the suggested model is the decay of vortex loops with an internal structure. We consider the initial stage of this process, before an equilibrium state is established. As result of our study, the density matrix of developing turbulent flow is calculated. The quantization scheme of the classical vortex rings system is based on the approach proposed by the author earlier.
► Interstage difference and deterministic decomposition of internal unsteady flow in a five-stage centrifugal pump as turbine
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
A five-stage centrifugal pump is utilized to investigate the interstage flow characteristics of the multistage centrifugal pump as turbine (PAT). The simulation results of performance are verified by comparing with the experimental results. Owing to the distinct structural attributes, significant differences in flow occur between the first stage and the other stages of the multistage PAT. To enhance the understanding of these disparities and explore their repercussions, this study focuses on analyzing the flow within the impellers in the first and second stages by a deterministic analysis. The main conclusions are as follows: The discrepancies in the inflow conditions are the major reason for the dissimilarities in the flow of impellers between stages. The impact loss generated by the misalignment between the positive guide vane outlet angle and the impeller inlet angle leads to flow deviation between impeller passages and affects the internal flow pattern. The unsteadiness under low flow rates is mostly produced by the spatial gradient of the blade-to-blade nonuniformities, which is relevant to the relative position between blades and the positive guide vanes. At high flow rates, especially in the second-stage impeller, the pure unsteady term is the primary cause of flow unsteadiness as a result of the flow separation induced by interactions between the blades and the positive guide vanes. This study can provide some references for the practical operation and performance optimization of the multistage PATs in the future.
► Effect of gravity on phase transition for liquid–gas simulations
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
Direct simulations of phase-change and phase-ordering phenomena are becoming more common. Recently, qualitative simulations of boiling phenomena have been undertaken by a large number of research groups. One seldom discussed limitation is that large values of gravitational forcing are required to simulate the detachment and rise of bubbles formed at the bottom surface. The forces are typically so large that neglecting the effects of varying pressure in the system becomes questionable. In this paper, we examine the effect of large pressure variations induced by gravity using pseudopotential lattice Boltzmann simulations. These pressure variations lead to height dependent conditions for phase coexistence and nucleation of either gas or liquid domains. Because these effects have not previously been studied in the context of these simulation methods, we focus here on the phase stability in a one-dimensional system, rather than the additional complexity of bubble or droplet dynamics. Even in this simple case, we find that the different forms of gravitational forces employed in the literature lead to qualitatively different phenomena, leading to the conclusion that the effects of gravity induced pressure variations on phase-change phenomena should be very carefully considered when trying to advance boiling and cavitation as well as liquefaction simulations to become quantitative tools.
► Entrapment and mobilization dynamics during the flow of viscoelastic fluids in natural porous media: A micro-scale experimental investigation
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
Capillary desaturation process was investigated as a function of wetting phase rheological signatures during the injection of Newtonian and non-Newtonian fluids. Two sets of two-phase imbibition flow experiments were conducted on a water-wet sandstone core sample using brine and viscoelastic polymer solutions. During the experiments, a high-resolution micro-computed tomography scanner was employed to directly map pore-level fluid occupancies within the pore space. The results of the experiments revealed that at a given capillary number, the viscoelastic polymer was more efficient than the brine in recovering the non-wetting oil phase. At low capillary numbers, this is attributed to the improved accessibility of the viscoelastic polymer solution to the entrance of pore elements, which suppressed snap-off events and allowed more piston-like and cooperative pore-body filling events to contribute to oil displacement. For intermediate capillary numbers, the onset of elastic turbulence caused substantial desaturation, while at high capillary numbers, the superimposed effects of higher viscous and elastic forces further improved the mobilization of the trapped oil ganglia by the viscoelastic polymer. In the waterflood, however, the mobilization of oil globules was the governing recovery mechanism, and the desaturation process commenced only when the capillary number reached a threshold value. These observations were corroborated with the pore-level fluid occupancy maps produced for the brine and viscoelastic polymer solutions during the experiments. Furthermore, at the intermediate and high capillary numbers, the force balance and pore-fluid occupancies suggested different flow regimes for the non-Newtonian viscoelastic polymer. These regions are categorized in this study as elastic-capillary- and viscoelastic-dominated flow regimes, different from viscous-capillary flow conditions that are dominant during the flow of Newtonian fluids. Moreover, we have identified novel previously unreported pore-scale displacement events that take place during the flow of viscoelastic fluids in a natural heterogeneous porous medium. These events, including coalescence, fragmentation, and re-entrapment of oil ganglia, occurred before the threshold of oil mobilization was reached under the elastic-capillary-dominated flow regime. In addition, we present evidence for lubrication effects at the pore level due to the elastic properties of the polymer solution. Furthermore, a comparison of capillary desaturation curves generated for the Newtonian brine and non-Newtonian viscoelastic polymer revealed that the desaturation process was more significant for the viscoelastic polymer than for the brine. Finally, the analysis of trapped oil clusters showed that the ganglion size distribution depends on both the capillary number and the rheological properties of fluids.
► Impact of wettability on interface deformation and droplet breakup in microcapillaries
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
The objective of this research paper is to relate the influence of dynamic wetting in a liquid/liquid/solid system to the breakup of emulsion droplets in capillaries. Therefore, modeling and simulation of liquid/liquid flow through a capillary constriction have been performed with varying dynamic contact angles from highly hydrophilic to highly hydrophobic. Advanced advection schemes with geometric interface reconstruction (isoAdvector) are incorporated for high interface advection accuracy. A sharp surface tension force model is used to reduce spurious currents originating from the numerical treatment and geometric reconstruction of the surface curvature at the interface. Stress singularities from the boundary condition at the three-phase contact line are removed by applying a Navier-slip boundary condition. The simulation results illustrate the strong dependency of the wettability and the contact line and interface deformation.
► Drag increase and turbulence augmentation in two-way coupled particle-laden wall-bounded flows
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
The exact regularized point particle method is used to characterize the turbulence modulation in two-way momentum-coupled direct numerical simulations of a turbulent pipe flow. The turbulence modification is parametrized by the particle Stokes number, the mass loading, and the particle-to-fluid density ratio. The data show that in the wide region of the parameter space addressed in the present paper, the overall friction drag is either increased or unaltered by the particles with respect to the uncoupled case. In the cases where the wall friction is enhanced, the fluid velocity fluctuations show a substantial modification in the viscous sub-layer and in the buffer layer. These effects are associated with a modified turbulent momentum flux toward the wall. The particles suppress the turbulent fluctuations in the buffer region and concurrently provide extra stress in the viscous sub-layer. The sum of the turbulent stress and the extra stress is larger than the Newtonian turbulent stress, thus explaining the drag increase. The non-trivial turbulence/particles interaction turns out in a clear alteration of the near-wall flow structures. The streamwise velocity streaks lose their spatial coherence when two-way coupling effects are predominant. This is associated with a shift of the streamwise vortices toward the center of the pipe and with the concurrent presence of small-scale and relatively more intense vortical structures near the wall.
► Partial and complete wetting of thin films with dynamic contact angle
  17 Apr, 2023
Physics of Fluids, Volume 35, Issue 4, April 2023.
The wetting of thin films depends critically on the sign of the spreading coefficient [math]. We discuss the cases S < 0, S = 0, and S > 0 for transient models with contact line dissipation and find that the use of a dynamic contact angle solves problems for S > 0 that models might otherwise have. For initial data with a non-zero slope and S > 0, we show that there exists a finite time [math] at which the contact angle of the thin film goes to zero. Then, a molecular precursor emerges from the thin film and moves outward at a constant velocity.

Theoretical and Computational Fluid Dynamics top

► Natural and mixed convection in a vertical rectangular duct under solar radiation
  16 Jan, 2026
► The coherent structures of EVP fluid flow past a circular cylinder
  16 Jan, 2026
► Study on the swimming velocity of an inertial ellipsoidal microswimmer in a square tube
  14 Jan, 2026
► Exploring the instabilities of a three-dimensional viscoplastic Rayleigh-Bénard convection
    7 Jan, 2026
► Modelling rectangular-jet screech via dimensional reduction
  19 Dec, 2025
► Mathematical and computer models of the process of liquid filling a capillary in the system “experimental closed tank + capillary”
  15 Dec, 2025
► Modal decomposition of flow behind a harmonically oscillating circular cylinder
    8 Dec, 2025
► Design and Dimensional Transfer of Reinforcement Learning-Based Closed-Loop Airfoil Flow Control
    3 Dec, 2025
► Variable density stratification of Kelvin–Helmholtz instability in a force field
  20 Nov, 2025
► Effect of density ratio on the stability of a Couette flow past viscoelastic compliant solid
    4 Nov, 2025
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