This work extends the Nodal Integral-Immersed Boundary Method (NIM-IBM) to the solution of steady incompressible Navier-Stokes equations in complex geometries. The NIM provides a coarse-mesh, semi-analytical discretization that maintains second-order spatial accuracy, while the sharp-interface IBM enforces boundary conditions on non-body-fitted Cartesian grids. To address the challenges of pressure-velocity coupling and mass conservation near immersed boundaries, the formulation integrates a hybrid MAC-SOLA (Marker and Cell-Solution Algorithm) pressure-correction scheme, preserving the analytical structure of NIM and avoiding complex matrix couplings at cut cells. The proposed framework is validated against multiple benchmark problems involving internal and external flows. Results show that the method accurately captures key flow features and benchmark quantities, even on coarse meshes, with good agreement to experimental and high-resolution numerical data. The approach offers a computationally efficient and geometrically flexible alternative for incompressible flow simulations, with potential for extension to unsteady and high-Reynolds-number regimes.

Fouling on heating surfaces significantly reduces the thermal efficiency of heat exchangers and increases energy losses. This study investigates a microtube heat exchanger designed for lithium-ion battery water cooling systems. A numerical investigation is conducted using the Eulerian-Lagrangian approach to evaluate the degradation of thermal performance and energy loss caused by the deposition of submicron particles on heating surfaces. The study considers laminar flow in a pipe with a constant surface heat flux. The discrete element method is employed to model particle deposition dynamics, and the coupled simulations of fluid flow and heat transfer are performed using OpenFOAM. The results indicate that the Nusselt number (Nu) decreases by up to 55 As the deposited particle volume ratio increases, Nu reduces significantly to a value of 2.5, beyond which the reduction follows an asymptotic trend. Additionally, an empirical correlation between Nu and the friction factor has been developed, providing a reliable predictive tool for evaluating the heat exchanger performance under scaling conditions. These findings offer valuable insights into mitigating fouling effects and minimizing performance losses due to fouling.

Efficient post-combustion carbon capture remains a significant challenge in the global transition toward low-carbon energy systems. Among the available separation technologies, amine-based absorption is widely adopted in industrial CO2 scrubbing due to its high selectivity and technological maturity, with methyldiethanolamine (MDEA) serving as a benchmark solvent for large-scale applications. In this study, a comparative machine learning framework is developed to predict CO2 absorption capacity in MDEA-based nanofluid systems, integrating data-driven intelligence with environmental process modeling. A comprehensive database of experimental data was curated, covering graphene oxide (GO), Fe3O4, and carbon nanotube (CNT) nanofluids over a wide range of operating conditions. Six supervised algorithms-K-Nearest Neighbors (KNN), Random Forest (RF), Gradient Boosting (GB), XGBoost, LightGBM, and a stacking ensemble with LightGBM as the meta-learner-were trained and optimized using tenfold cross-validation. All models exhibited strong predictive performance (R-2 > 0.96), while the stacking ensemble achieved the highest accuracy with MAE = 0.021 mol kg(-1), RMSE = 0.036 mol kg(-1), AARD = 2.21%, and R-2 = 0.992. Feature importance and SHAP analyses identified temperature and CO2 pressure as the dominant variables governing absorption behavior, followed by MDEA and nanoparticle concentrations. The proposed framework enables rapid solvent screening, optimization of operating windows, and digital twin integration for industrial CO2 capture systems, providing a scalable pathway toward energy-efficient and cleaner production-oriented carbon capture technologies.

In this paper, the formulation and method of implementation of boundary conditions for heterogeneous reactions in porous media are elaborated. These are implemented into a previously validated lattice Boltzmann model for the simulation of heterogeneous reactions in porous media, extending it on multiple fronts. The formulation of the boundary conditions is validated thoroughly. The conversion of solid carbon to CO and CO2 is chosen as a specific case of application. An extensive parametric study is conducted with a specific geometry consisting of spherical substrate particles, coated with a reactive soot layer, to highlight the capability of the code. The code was able to capture the expected evolution of a combustion front and the influence of process parameters onto its propagation velocity. The propagation speed linearly increased with an increase in the reactant mass fraction and exponentially increased with P & eacute;clet number. Also, the CO/CO2 ratio obtained from experimental data could be reproduced with good accuracy. Furthermore, an algorithm for the correct evaluation of the specific surface is presented, which is necessary for evolving solid domains based on realistic geometries containing enclosed cavities. The method of implementation, computational overhead and acceleration technique are discussed. Finally, the model and all boundary conditions are extended to 3D and validated.

A new three-dimensional (3D) multiphase computational fluid dynamics (CFD) model for adsorption physics in packed beds of spherical beads is developed and validated. The model is constituted at a macroscopic scale that integrates new volumetric source terms in the multi-species gas transport and energy conservation equations. These new terms, for the first time, take into account the impact of pores adsorption occupation rate or gas loading. Transient 3D simulations are performed at an atmospheric pressure of about 1.02 bar for different CO2-He gas mixture feed-in compositions (100%, 50%, and 15% CO2). The 3D model validation is conducted through quantitative comparisons with experimental data from the literature for CO2 adsorption on porous Zeolite-13X beads in a cylindrical fixed-bed. Results demonstrate the new model's ability to accurately predict the breakthrough curves and the thermal front propagation inside the bed. Finally, the new CFD model is applied to investigate CO2 capture in a new 3D design of fixed-bed adsorbers of equivalent adsorbent material volume. The new design outperformed the reference cylindrical design, thanks to its new geometry with higher surface area. This allows to shorten the adsorption periods in pressure and temperature swing adsorption processes and, thus, increase the overall gas separation process productivity.

In this study, we present a lattice Boltzmann (LB) framework for electrohydrodynamic Rayleigh-Taylor instability (RTI-EHD) in Newtonian two-fluid systems treated as leaky or perfect dielectrics. The solver, implemented in the open-source parallel CooLBM code, couples a Cahn-Hilliard phase-field interface (He-Chen-Zhang model) with an incompressible LB flow solver, including consistent body forces, electric potential computation, and Maxwell stresses. The framework is validated against canonical problems, including singlephase charge relaxation, two-layer planar systems under uniform fields, droplet deformation in electric fields, and RTI without electric forcing. We then investigate RTI-EHD under horizontal and vertical electric fields for singleand multi-mode perturbations, examining the roles of field orientation, initial perturbation characteristics, and fluid electrical properties. In leaky-dielectric systems, the electric field can either suppress or enhance instability depending on contrasts in electrical properties. A key contribution is the fully LB-based RTI-EHD formulation. We also recover the analytical result that the leaky dielectric model reduces to the perfect dielectric limit when conductivity and permittivity ratios are equal, enabling both regimes to be simulated within a unified framework. In the perfect dielectric case, horizontal fields stabilize the interface more strongly for small perturbations, while vertical fields promote instability. The code is openly available at: https://gitlab.coria-cfd.fr/lbm/coolbm-rti-ehd.

In this study, we present a comprehensive analysis of Rayleigh–Taylor instability (RTI) in systems involving perfect and leaky dielectric Newtonian fluids under the influence of an oblique electric field. Using linear stability analysis and mathematical theorems, we determine the number and nature of the solutions with respect to the dispersion relation. Our findings demonstrate that the RTI can be effectively controlled by applying a uniform electric field that is not necessarily aligned with the principal axes of the interface that separates the two fluids. In the leaky dielectric model, the orientation of the electric field can be adjusted to either suppress or enhance the instability, depending on the system parameters such as the permittivity and conductivity ratios of the two fluids. In particular, when the permittivity and conductivity ratios coincide, the leaky dielectric model seamlessly reduces to the perfect dielectric model. Moreover, for the perfect dielectric model, we confirmed that an oblique electric field can stabilize the interface.

Heat exchangers–adsorbers (HEX-As) are emerging as innovative technologies in many applications (CO2 capture, gas purification and separation, thermal energy storage, etc). This review addresses the theoretical challenges within computational fluid dynamics (CFD) in modeling and simulating coupled heat and mass transfer within gas separation by using adsorbing porous media in fixed beds. Conservation equations of mass, momentum, and energy from different studies (1D, 2D-CFD, and 3D-CFD models) are presented and discussed with an emphasis on their ability to predict the complex multi-physics multi-scale heat and mass transfer phenomena involved, such as the adsorption kinematics, the thermal front propagation, and the multi-component fluid flow dynamics inside the beds. For the fist time, we show that mathematical theoretical modeling in CFD has been differently developed and applied by many authors in the literature in order to model the same physical phenomena. This sheds light on the present challenges and bottlenecks in theoretical and computational fluid dynamics when it comes to complex coupled heat and mass transfer in multi-component gas dynamics in porous media. This review make it easier for readers to understand the different models that exist in the literature for modeling and simulating HEX-As. It also opens questions on how accurately one can model multi-functional heat exchangers–adsorbers using CFD, e.g., physics multi-scale extrapolation from nano- to meso- and then to macro-scale behavior.

This study aims to present an innovative fully Lagrangian particle-based approach, called the Ellipsoidal Kernel Particle (EKP) method, for simulating free-surface flows, multi-fluid flows and convective heat transfer. To achieve this, a novel elliptical kernel function is initially developed. Building on this foundation, a new gradient operator is formulated for calculating velocity divergence, as well as pressure and temperature gradients. Furthermore, a new MLS operator, derived from the elliptical kernel, is introduced to interpolate field variables, while a high-order Laplacian operator is designed to solve the Pressure Poisson Equation (PPE) for incompressible fluid flow. To handle temporal discretization, the study utilizes the two-step projection method for solving transient terms in the Navier-Stokes and energy equations. The proposed EKP model undergoes rigorous validation through a series of challenging benchmark tests, including dam-break scenarios with and without a stationary obstacle, dam-break flow over a wet bed, two- and three-fluid Rayleigh-Taylor instabilities (RTI), a rotating square patch of fluid, natural convection heat transfer, and the oscillating concentric circular drop problem. The results show that EKP method maintains numerical stability, achieves convergence, and effectively handles free-surface and multi-fluid flows, while avoiding unphysical pressure fluctuations. Lastly, the validated model is applied to analyze natural convection heat transfer in a square cavity containing two hot obstacles. The results indicate that the average Nusselt number increases with increasing Rayleigh number.

Multiport minichannel thermosyphons with hydraulic diameters below 1.2 mm often encounter severe flow instabilities and oscillations in vapor and condensate movement, which hinder effective phase change processes. These instabilities can cause partial and localized dry-out, resulting in higher operating temperatures and reduced thermal performance. To overcome these limitations, a novel multiport minichannel thermosyphon loop (MPMCTSL) is proposed. This design integrates a compensation chamber (CC) to ensure uniform fluid distribution across all channels and suppress instabilities near the evaporator. Additionally, the loop features separate flow paths for vapor and liquid to mitigate entrainment issues. The study experimentally investigates the thermal performance of MPMCTSL using acetone as the working fluid, considering fill ratios of 40 %, 50 %, and 60 %, inclination angles of 0 degrees, 30 degrees, 60 degrees, and 90 degrees, and varying heat loads from 10 to 80 W. Results demonstrate that 5 mm CC length delivers optimal performance by stabilizing condensate flow and ensuring continuous fluid replenishment to the evaporator. This results in minimum thermal resistance of 0.34 K/W and a peak vapor velocity of 4.36 m/s at 80 W heat load. Furthermore, the observed flow regime transition from churn to annular with increasing heat input confirms the improved stability and effectiveness of the MPMCTSL design.

Our current study proposes a lattice Boltzmann (LB) model which is to be used for simulating the combustion process within the porous structure of soot filters. A multi-distribution function (MDF) approach is utilized for the simulation of fluid flow in porous media, for the temperature fields in the fluid and solid domain as well as for the transport of reactive components in the fluid phase. Furthermore, the developed model accounts for the conjugate heat transfer between the solid and fluid phases and incorporates a first order heterogeneous reaction, occurring at the interface between the fluid and solid coke phase. To enhance model stability over a broader range of Reynolds numbers, a multi-relaxation time (MRT) approach is employed. The proposed model is validated by systematically examining its ability to address the mass and momentum conservation of the model, its ability to accurately describe the continuity of the conjugate heat transport at the interface between solid and gas phases and finally all aspects of the proposed model collectively by comparing the results of a combustion test case with existing literature data. A parametric study is conducted to explore different combustion regimes by variation of both the P & eacute;clet and Damk & ouml;hler numbers.

This study explores the efficiency of employing a particle-spray cloud to mitigate shock wave propagation, which is essential in various industrial applications, especially in preventing potential hydrogen explosions within nuclear reactor containment buildings. Numerical simulations, primarily in one- and two-dimensional configurations, are utilized to examine the interaction between shock waves and a cloud of polydisperse particles, considering both air and hydrogen-air mixtures as carrier gases. A novel reduced-order theoretical model is developed to analyze the dispersion pattern of polydisperse particles, with validation conducted through direct numerical simulations. Results demonstrate that the polydispersion of cloud particles significantly reduces shock wave propagation compared to monodisperse particles. Notably, particles with smaller diameters and higher standard deviations (sigma) show increased attenuation effects. Additionally, scenarios with higher particle volume fractions (tau(v,0)) contribute to enhanced shock wave attenuation. A critical incident Mach number is identified, indicating a significant change in shock wave transmission from supersonic to subsonic when M-s < 2.8.

In this paper, we introduce a computational technique for modeling heterogeneous thermoresponsive hydrogels. The model resolves local fluid-solid interactions in hydrogel pores during the deswelling process. The model is a Lagrangian particle-based technique, which benefits from computational grids that represent polymer beads inside hydrogel scaffolds. The results show that the mechanical properties of hydrogels during deswelling, e.g., shrinkage ratio and elastic modulus, have a direct effect on the development of the front of expelled fluid. It is also observed that in certain parameter regimes the hydrogel may generate inertial fluid jets at the early stages of deswelling. Finally, simple heterogeneous designs are developed using Menger sponge-inspired shapes to investigate the effect of design heterogeneity on promoting directional release.

In this research, we utilized the Lattice Boltzmann Method (LBM) to model surface chemical reactions and the heat transfer occurring between gas and solid materials within porous media. Our comprehensive approach involved a detailed analysis of fluid flow dynamics, heat transfer mechanisms, and the complex behavior of reactive species. To ensure precise modeling, we employed the thermal counter-slip method to represent heat transfer and carefully chose the wet node scheme to manage surface chemical reactions and species transfer. We placed significant emphasis on methodically explaining our selected models and providing practical guidelines for their implementation, as well as establishing initial and boundary conditions. An essential part of our study was investigating the influence of specific physical parameters governing these processes, including the Péclet, Damköhler, and Prandtl numbers. Consequently, we successfully identified various combustion regimes and elucidated the roles played by chemical reaction rates, diffusion, and convection processes within each of these regimes.

The widely used leaky dielectric model often overlooks the rate of change in electric charges, leaving the impact of the charge conservation mechanism on two-phase electro-hydrodynamics (EHD) flows inadequately explored. In this study, we address this gap by introducing a charge-conservative model (CCM) for simulating such EHD systems within the framework of the smoothed particle hydrodynamics (SPH) method. Our methodology employs a fully explicit incompressible SPH (EISPH) approach to discretize the pressure Poisson, the electric potential Poisson, and the Nernst-Planck (N-P) equations. This work presents two notable contributions: (i) the introduction of the charge-conservative model into the incompressible SPH framework and (ii) the achievement of its discretization through a fully explicit methodology. To validate the proposed CCM, we conduct a comprehensive comparison with analytical solutions, as well as existing numerical and experimental results. The results affirm that the CCM consistently produces accurate outcomes across various test cases.

This work presents a Lagrangian meshless method for modeling transient heat transfer and thermo-capillary effects at the interface of two-phase incompressible fluids. To simulate the thermo-capillary effect, we add the Marangoni force to the continuum surface force (CSF) model, by considering the forces caused by the surface tension gradient which acts tangentially to the interface position. In the current study, we extend our previously proposed model which uses a fully explicit incompressible smoothed particle hydrodynamics (EISPH) approach along with corrected SPH and VKF kernel function, to obtain stable and accurate results in non-isothermal single and multi-phase problems. The model is validated for several test cases, including transient heat conduction, natural convection heat transfer, and thermo-capillary droplet migration, against conventional numerical methods. The validated model is used to study the effects of several dimensionless parameters on thermo-capillary droplet migration. The results show that the proposed EISPH method can model accurately complex heat transfer problems such as thermo-capillary induced motion.

We present for the first time an experimental investigation of electrohydrodynamic (EHD) flows within a neutrally buoyant drop with initial radius of 2.25 mm. Utilizing particle image velocimetry (PIV) and high-speed shadowgraphy, we measure the internal circulation and reported velocity profiles in the bulk and at the interface of the drop. Two leaky dielectric liquids, Silicone and Castor oils, are employed as the drop and external phase, allowing for the analysis of two shape configurations: oblate and prolate. The strength of the applied uniform electric field, $E_o$, spans from 0.125 to 1.75 kV/cm, enabling the analysis covering the small-deformation limit, where the leaky dielectric model (LDM) is applicable. Drops with larger deformations, for which no analytical velocity field is available, are also investigated. Our measurements show a good agreement with the LDM theory for the small-deformation cases. The flows begin at the interface as a result of jump in the electric stresses, leading then to four counter-rotating vortices inside the drop. At permanent regime, the analytical solutions adequately predicts the radial and tangential velocity components both in the bulk and at the interface of the drop. However, a nuanced behavior is noticed for larger deformations, where the LDM theory underpredicts the internal circulation. Moreover, due to the increased deformation, a non-uniform azimuthal profile is observed for the velocity at the interface. Transient measurements of this velocity component enlighten the dynamic response of the EHD flows of the drop. Following the currently available analytical solutions, the dynamic response is governed by the time-scale of its deformation. We propose a critical value of electric capillary number of roughly 0.1 below which the LDM adequately describes the velocity field in both quasi steady-state and transitory regimes.