Adaptive Mesh Research Articles

Enhancing data representation in forging processes: Investigating discretization and R-adaptivity strategies with Proper Orthogonal Decomposition reduction

Effective data reduction techniques are crucial for enhancing computational efficiency in complex industrial processes such as forging. In this study, we investigate various discretization and mesh adaptivity strategies using Proper Orthogonal Decomposition (POD) to optimize data reduction fidelity in forging simulations. We focus particularly on r-adaptivity techniques, which ensure a consistent number of elements throughout the field representation, filling a gap in existing research that predominantly concentrates on h-adaptivity. Our investigation compares isotropic mesh approaches with anisotropic mesh adaptations, including gradient-based, isolines-based, and spring-energy-based methods. Through numerical simulations and analysis, we demonstrate that these anisotropic techniques provide superior fidelity in representing deformation fields compared to isotropic meshes. These improvements are achieved while maintaining a similar level of model reduction efficiency. This enhancement in representation leads to improved data reduction quality, forming the foundation for data-driven models. This research contributes to advancing the understanding of mesh adaptivity approaches and their potential applications in data-driven modeling across various industrial domains.

How does turbulence intensity affect the fatigue life of composite airfoils based on existing CFD and experimental data?

This research investigates the effect of airflow turbulence intensity on the fatigue life of composite airfoil structures in aerospace engineering. Using advanced Computational Fluid Dynamics (CFD) simulations, this study provides a comprehensive analysis of how varying levels of turbulence intensity—ranging from mild (5%) to severe (30%)—impact the mechanical degradation and fatigue performance of carbon-fiber-reinforced polymers (CFRPs) used in airfoil designs. The research quantifies the relationship between turbulence levels and changes in stress distribution, highlighting critical points of fatigue crack initiation and subsequent propagation. The study includes detailed comparisons of CFD results to experimental data to validate the predictive models and discusses how localized stress fluctuations under high-intensity turbulence accelerate the onset of fatigue failure. We present significant findings that demonstrate a non-linear relationship between turbulence intensity and the reduction in fatigue life, suggesting optimal design modifications for enhanced durability. Furthermore, this paper explores current challenges in merging CFD data with real-world fatigue testing and proposes advanced techniques such as adaptive mesh refinement and hybrid simulation models to improve predictive accuracy and computational efficiency in future research.

Numerical and experimental investigations on the effect of skeleton shapes and heat transfer directions on water freezing in porous media

Incorporating porous skeletons into PCMs is an effective strategy for enhancing their thermal properties. However, this approach increases the complexity of the heat transfer process and poses a challenge to accurate modeling. This study investigates the water freezing process in porous skeletons with various shapes and heat transfer directions through experiments and numerical simulations. The model employs the hybrid finite element method with mesh adaptation to optimize numerical solutions. The experimental and simulation results are in good agreement, which validates the accuracy of this model. The study aims to reveal the evolution mechanisms of the phase interface, temperature field, and freezing rate of water in various porous skeletons, enhancing the theoretical foundation and offering insights for practical applications. Results show that the square steel skeleton exhibits the highest freezing rate among the tested skeleton shapes, while the rhombus resin skeleton demonstrates the slowest. Furthermore, the square skeleton shows the smallest interface deflection before and after the pores, while the rhombus skeleton presents the largest. Additionally, vertical heat transfer from bottom to top increases the freezing rate by 38.97% compared to horizontal heat transfer from left to right.

Topology optimization designed twisted conformal cooling channel for additive-manufactured hot-stamping tool

Hot stamping is a manufacturing process that can be used to produce complex-shaped parts with high mechanical properties. In this process, the part quality and the production rate are strongly influenced by the efficiency of the cooling system within the tool. Improving the efficiency of the cooling system is therefore a key factor in reducing production time and costs. Traditional cooling systems for hot stamping tools often rely on simple drilled channels, limiting their potential for optimization. But recent improvements in additive manufacturing of steel have made it possible to design and produce cooling channels of more complex shapes and therefore allow the use of innovative design approaches such as topology optimization. This paper proposes a new rational method for optimum design of cooling system for additively manufactured hot stamping tools. The proposed new methodology is based on fluid-thermal topology optimization (TO). A low-fidelity model using the Stokes-Darcy equations is used to simulate fluid flow in the cooling channels. The objective function and constraints are designed to minimize the maximum temperature of the tool surface (cooling efficiency) with limited pressure drop of the cooling system. Advanced computations techniques including parallel computation, stabilization techniques, adaptive mesh and iterative solvers are used to ensure the computation performance. The procedure developed is first tested on a simple example to check the consistency of the results obtained. Then, to demonstrate the contribution of our work to the field under study, the procedure developed is used to optimize the design of the cooling system for an industrial hot stamping punch to be additively manufactured. The obtained optimum design is compared with standard drilled channels design and the deign with shell and core technology (with insert). These comparisons clearly shows that the optimal design combined with additive manufacturing can reduce quenching time by 37 % compared to conventional drilled straight channels, with very similar pressure drop and very similar load-bearing capacity. This research offers significant potential for improving efficiency and reducing costs in hot stamping and other manufacturing processes.

A high-order physical-constraints-preserving arbitrary Lagrangian–Eulerian discontinuous Galerkin scheme for one-dimensional compressible multi-material flows

In this paper, a high-order physical-constraints-preserving arbitrary Lagrangian–Eulerian (ALE) discontinuous Galerkin scheme is proposed for one-dimensional compressible multi-material flows. Our scheme couples a conservative equation related to the volume-fraction model with the Euler equations for describing the dynamics of fluid mixture. The mesh velocity in the ALE framework is obtained by using an adaptive mesh method that can automatically concentrate the mesh nodes near the regions with large gradient values and greatly reduce the numerical dissipation near material interfaces. Using this adaptive mesh, the resolution of solution near some special regions such as material interfaces can be improved effectively by our scheme. With the appropriate time step condition and using a bound-preserving and positivity-preserving limiter, our scheme can ensure the positivity of density and pressure and the boundness of volume-fraction, which further ensures the computational robustness and degree of confidence of simulations under large density or pressure ratios and so on. In general, our scheme can be applied to the simulations of compressible multi-material flows efficiently with the essentially non-oscillatory property and physical-constraints-preserving (bound-preserving and positivity-preserving) property, and its steps are more concise compared to some other methods such as the indirect ALE methods. Some examples are tested to demonstrate the accuracy, essentially non-oscillatory property and physical-constraints-preserving property of our scheme.

An improved goal-oriented adaptive finite-element method for 3-D direct current resistivity anisotropic forward modeling using nested tetrahedra

We developed a novel adaptive finite element method (FEM) to address the problem of 3-D direct current (DC) resistivity forward modeling with complex surface topography and arbitrary conductivity anisotropy. The tetrahedra-based FEM and secondary virtual potential algorithm are first used to handle arbitrary complex geo-models. Then, to ensure the accuracy of the simulation solution, an improved goal-oriented adaptive mesh refinement (AMR) algorithm is proposed to realize an optimized mesh density distribution. To avoid the drawback of the traditional goal-oriented AMR algorithm for the DC forward modeling problem, we incorporate a volume-based weighting factor into the posterior error estimation procedure to further optimize the density distribution of the forward modeling grid. In addition, instead of traditional open source mesh generation software, we propose using the longest-edge bisection (LEB) algorithm to perform the mesh refinement process, which can preserve the topological structure between different-level meshes. Finally, the comprehensive test using a two-layered model and two complex 3-D models demonstrate the capability of our newly developed code to obtain highly accurate solutions even on relatively coarse initial grids. By incorporating the volume factor, our novel AMR algorithm achieves a more uniform and reasonable mesh density distribution during these experiments. The LEB refinement technique can generate a series of nested tetrahedral elements and provide fewer tetrahedral elements compared to the traditional Delaunay-based AMR method. The proposed 3-D DC forward modeling method has been implemented into an open source C++ code, which will contribute to the advancement of the 3-D DC resistivity imaging field.

An open-source, adaptive solver for particle-resolved simulations with both subcycling and non-subcycling methods

We present the IAMReX (incompressible flow with adaptive mesh refinement for the eXascale), an adaptive and parallel solver for particle-resolved simulations on the multi-level grid. The fluid equations are solved using a finite-volume scheme on the block-structured semi-staggered grids with both subcycling and non-subcycling methods. The particle-fluid interaction is resolved using the multidirect forcing immersed boundary method. The associated Lagrangian markers used to resolve fluid-particle interface only exist on the finest-level grid, which greatly reduces memory usage. The volume integrals are numerically calculated to capture the free motion of particles accurately, and the repulsive potential model is also included to account for the particle–particle collision. We demonstrate the versatility, accuracy, and efficiency of the present multi-level framework by simulating fluid-particle interaction problems with various types of kinematic constraints. The cluster of monodisperse particles case is presented at the end to show the capability of the current solver in handling multiple particles. It is demonstrated that the three-level AMR (Adaptive Mesh Refinement) simulation leads to a 72.46% grid reduction compared with the single-level simulation. The source code and testing cases used in this work can be accessed at https://github.com/ruohai0925/IAMR/tree/development. Input scripts and raw postprocessing data are also available for reproducing all results.

Shear-induced oil separation from a sand particle moving in water

Removing oil attached to fine solid particles in water purification presents challenging technical, economic, and ecological issues. The present work numerically investigates the shear effect on oil that contains a 100-μm-diameter sand particle in a water medium. In this research, we employ the coupled level set and volume of fluid method to track interface evolution accurately. An adaptive mesh refinement technique allows us to resolve an interface down to 60 nm. Computations at various particle Reynolds numbers (Rep=2−200) and oil film thicknesses (5%, 10%, 20%, and 40% of the diameter) reveal four coating behaviour scenarios: deformation, tail formation, partial separation, and full separation. The oil film negligibly deforms at Rep≤5 at most film thicknesses. The separation occurs in full or partial regimes at higher Rep and thicker films. A thinner film forms a tail that periodically fluctuates. The analysis shows that these fluctuations uniquely reshape the oil tail at each time period.

An improved efficient adaptive method for large-scale multi-explosives explosion simulations

Shock wave caused by a sudden release of high-energy, such as explosion and blast, usually affects a significant range of areas. The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise results is inefficient in terms of computational resource. This is particularly evident when large-scale fluid field simulations are conducted with significant differences in computational domain size. In this work, a variable-domain-size adaptive mesh enlargement (vAME) method is developed based on the proposed adaptive mesh enlargement (AME) method for modeling multi-explosives explosion problems. The vAME method reduces the division of numerous empty areas or unnecessary computational domains by adaptively suspending enlargement operation in one or two directions, rather than in all directions as in AME method. A series of numerical tests via AME and vAME with varying nonintegral enlargement ratios and different mesh numbers are simulated to verify the efficiency and order of accuracy. An estimate of speedup ratio is analyzed for further efficiency comparison. Several large-scale near-ground explosion experiments with single/multiple explosives are performed to analyze the shock wave superposition formed by the incident wave, reflected wave, and Mach wave. Additionally, the vAME method is employed to validate the accuracy, as well as to investigate the performance of the fluid field and shock wave propagation, considering explosive quantities ranging from 1 to 5 while maintaining a constant total mass. The results show a satisfactory correlation between the overpressure versus time curves for experiments and numerical simulations. The vAME method yields a competitive efficiency, increasing the computational speed to 3.0 and approximately 120,000 times in comparison to AME and the fully fine mesh method, respectively. It indicates that the vAME method reduces the computational cost with minimal impact on the results for such large-scale high-energy release problems with significant differences in computational domain size.

High-order discontinuous Galerkin method with immersed boundary treatment for compressible flows on parallel adaptive Cartesian grids

Adaptive mesh refinement (AMR) technology and high-order methods are important means to improve the quality of simulation results and have been hotspots in the computational fluid dynamics community. In this paper, high-order discontinuous Galerkin (DG) and direct DG (DDG) finite element methods are developed based on a parallel adaptive Cartesian grid to simulate compressible flow. On the one hand, a high-order multi-resolution weighted essentially nonoscillatory limiter is proposed for DG and DDG methods. This limiter can enhance the stability of DG/DDG methods for compressible flows dominated by shock waves. It is also compact, making it suitable for the implementation of AMR with frequent refinement/coarsening. On the other hand, a coupling method of DG and immersed boundary method is proposed to simulate flow around objects. Due to the compactness of DG, the physical quantities of image points can be directly obtained through the DG/DDG polynomial of the corresponding cells. It avoids the wide interpolation stencil of traditional IBM and makes it more suitable for the parallel adaptive Cartesian grid framework in this paper. Finally, the performance of the proposed method is verified through typical two- and three-dimensional cases. The results indicate that the method proposed in this paper has low numerical dissipation in smooth areas and can effectively handle compressible flow dominated by discontinuities. Moreover, for transonic flow over a sphere, the error of results between the proposed method and direct numerical simulation is within 1%, fully validating the accuracy of the method presented in this paper.

Investigation of cloud cavitating flow in a venturi using adaptive mesh refinement

Investigation of cloud cavitating flow in a venturi using adaptive mesh refinement

A simulation study on the influence of marginal pinching upon liquid film dynamics

In fluid dynamics, the generation and bursting of surface bubble liquid films in surfactant-laden environments involve complex phenomena, one of which is marginal pinching at the film's foot—a crucial yet inadequately understood aspect due to experimental limitations. Considering its profound impact on liquid film drainage and lifetime, we utilize high-resolution numerical simulations incorporating a weakly compressible scheme and adaptive mesh refinement to dissect the marginal pinching dynamics with unprecedented detail. Our approach elucidates the pinching dynamics and tracks the evolution of film thickness during the critical late-stage drainage process. By leveraging detailed geometric data from pinched regions, we significantly refine existing drainage models, enhancing their predictive accuracy regarding rupture thickness and film lifetime across various viscosities, surfactant concentrations, and bubble sizes. This refined model demonstrates robust alignment with our simulation results. Furthermore, we establish a quantifiable relationship between the prefactor governing reverse flow induced by the Marangoni effect and surfactant concentration. The methodologies and findings of this study provide foundational knowledge that paves the way for optimized industrial processes and an enhanced understanding of natural phenomena.

Detailed analysis on primary and secondary break up characteristics of liquid fuel jet in crossflow using homogeneous mixture model and large eddy simulation

The detailed breakup characteristics of the liquid jet fuel, Jet-A, in crossflow to various ranges of momentum flux ratios and Weber numbers have been investigated using a high-fidelity compressible multi-phase numerical technique. Multi-phase large eddy simulation with adaptive mesh refinement and Eulerian to Lagrangian transformation are applied to the homogeneous mixture model. The liquid surface instabilities and their frequencies inside the injector orifice are observed and analyzed. Interactions between liquid jet and crossflow result in phenomena such as horse-shoe vortex formation, boundary separation, liquid trailing, and counter-rotating vortex pair. Liquid column breakup characteristics and wave structures are analyzed from both temporal and spatial viewpoints. The Sauter mean diameter distribution and cumulative distributions of droplets resulting from secondary breakup are presented, along with the droplet size distribution derived from the momentum flux ratio and Weber number. Several engineering models, including the instability frequencies, the breakup length, and the penetration depth, are proposed in terms of the momentum flux ratio and Weber number, providing valuable insights for injector and combustor design.

Additive Manufacturing simulations: An approach based on space partitioning and dynamic 3D mesh adaptation

Additive Manufacturing simulations: An approach based on space partitioning and dynamic 3D mesh adaptation

Improving EEG Forward Modeling Using High-Resolution Five-Layer BEM-FMM Head Models: Effect on Source Reconstruction Accuracy

Electroencephalographic (EEG) source localization is a fundamental tool for clinical diagnoses and brain-computer interfaces. We investigate the impact of model complexity on reconstruction accuracy by comparing the widely used three-layer boundary element method (BEM) as an inverse method against a five-layer BEM accelerated by the fast multipole method (BEM-FMM) and coupled with adaptive mesh refinement (AMR) as forward solver. Modern BEM-FMM with AMR can solve high-resolution multi-tissue models efficiently and accurately. We generated noiseless 256-channel EEG data from 15 subjects in the Connectome Young Adult dataset, using four anatomically relevant dipole positions, three conductivity sets, and two head segmentations; we mapped localization errors across the entire grey matter from 4,000 dipole positions. The average location error among our four selected dipoles is ∼5mm (±2mm) with an orientation error of ∼12∘ (±7∘). The average source localization error across the entire grey matter is ∼9mm (±4mm), with a tendency for smaller errors on the occipital lobe. Our findings indicate that while three-layer models are robust under noiseless conditions, substantial localization errors (10–20mm) are common. Therefore, models of five or more layers may be needed for accurate source reconstruction in critical applications involving noisy EEG data.

Hydrodynamic simulations of white dwarf–white dwarf mergers and the origin of R Coronae Borealis stars

ABSTRACT We study the properties of double white dwarf (DWD) mergers by performing hydrodynamic simulations using the new and improved adaptive mesh refinement code octo-tiger. We follow the orbital evolution of DWD systems of mass ratio $q=0.7$ for tens of orbits until and after the merger to investigate them as a possible origin for R Coronae Borealis (RCB) type stars. We reproduce previous results, finding that during the merger, the helium WD donor star is tidally disrupted within 20–80 min since the beginning of the simulation onto the accretor carbon–oxygen WD, creating a high temperature shell around the accretor. We investigate the possible helium burning in this shell and the merged object’s general structure. Specifically, we are interested in the amount of oxygen-16 dredged-up from the accretor to the hot shell and the amount of oxygen-18 produced. This is critical as the discovery of very low oxygen-16 to oxygen-18 ratios in RCB stars pointed out the merger scenario as a favourable explanation for their origin. A small amount of hydrogen in the donor may help keep the oxygen-16 to oxygen-18 ratios within observational bounds, even if moderate dredge-up from the accretor occurs. In addition, we perform a resolution study to reconcile the difference found in the amount of oxygen-16 dredge-up between smoothed-particle hydrodynamics and grid-based simulations.

Evaluating the Accuracy of the COMSOL-Based Finite-Element Method for Simulating Plasmon-Modified Fluorescence.

Accurately modeling plasmon-modified fluorescence is important for understanding and guiding the design of experimental nanostructures that reliably enhance fluorescence. They are of particular interest due to their potential to allow localized "hot spots" of high fluorescence enhancement in a reproducible manner. Given the increasingly prevalent use of the COMSOL Multiphysics software package for simulating these phenomena, we investigate its accuracy using an analytically tractable model consisting of a gold nanosphere interacting with either a plane wave or a radiating point dipole. COMSOL simulation results were compared with a formally exact analytical theory. It was found that simulation parameters commonly used for plane-wave scattering do not necessarily produce accurate results for the nanoparticle-plasmon-coupled dipole emission case. Instead, user-input adaptive meshing parameters were found to be helpful in achieving quantitative agreements between COMSOL and analytical theory results for plasmon-modified fluorescence. Our studies suggest convergence to analytically calculated values when a minimum of two additional user-input mesh elements separate the point-dipole position and the nanoparticle surface. This practical insight is expected to aid in the application of COMSOL simulations to planning and interpreting fluorescence modification experiments.

Effect of hot rolling process parameters on surface wear of descaling rolls

Purpose The purpose of this study is to explain the effect of slab and roll initial temperatures on the wear characteristics of the surface of hot roll descaling rolls. Design/methodology/approach The UMESHMOTION subroutine and the Arbitrary Lagrangian-Eulerian adaptive mesh technique are used to investigate the wear profile of the descale roll surface and to evaluate the effect of the slab and roll’s initial temperature on the wear depth. Findings Wear is more pronounced at the edges of the roll-slab contact area and less severe in the roll-body’s central region. A rise in the initial slab temperature from 1,337 K to 1,429 K results in a 67% rise in maximum wear depth and 52% in frictional stress. The peak wear region progressively shifted toward the center of the roll body. A rise in the initial roll temperature from 308.15 K to 673.15 K caused a 46% reduction in maximum wear depth and 73% in frictional stress. The location of the peak wear region remained primarily unchanged. Originality/value This study used the UMESHMOTIONI subroutine and the Arbitrary Lagrangian-Eulerian adaptive mesh technique in ABAQUS® to evaluate the quantitative correlation between the wear depth of the descaling roll surfaces and the initial temperatures of the slab and rolls. This study offers valuable insights into improving the wear of descaling roll surfaces. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0231/

Numerical evaluation of wear parameters using meta-models

AbstractWear parameters identified by linear friction tester (LFT) experiments overestimate the wear mass loss when applied on a laboratory abrasion & skid tester 100 (LAT100) simulation. On the other hand, the identification of wear parameters directly from the LAT100 experiment can be challenging since variables such as the contact area and the slip velocity are not measured experimentally and need to be assumed. To improve the identification process, numerical calibration is used as a more suitable approach. This approach relies on meta-models as a target function for minimization. The meta-models are generated using a sample of wear parameters applied to an LAT100 finite element modeling (FEM) to calculate the corresponding wear mass.. In this model, a transport velocity is defined for the rolling simulation, and an arbitrary lagrangian–eulerian (ALE) adaptive meshing approach is adopted for the wear modeling. For the wear model, a combination of archard’s wear model and schallamach’s abrasion law is used. This model contains a pair of wear parameters to be identified. The ALE adaptive meshing technique moves the nodes independently of the material. Since the mesh topology remains the same, failure of the simulation occurs if the wear volume loss exceeds that of the element. Meta-models are created to extend wear modeling beyond this failure. Once the meta-models are created, they are used as a target function for the minimization algorithm. The minimization algorithm aims to find the optimal wear parameters by minimizing the difference between experimentally observed and numerically produced wear mass loss. The minimization algorithm inputs a set of wear parameters into the meta-models which in turn yield a prediction of the wear mass loss. The process is carried out until an optimum parameter set is identified. Such an approach has a lower accuracy if the parameters are identified directly from the experiment using assumptions regarding the contact shear stress and the sliding velocity. Nonetheless, the main advantage of parameters identified using the meta-model approach is the usability of these parameters in an LAT100 model.

N exus: a framework for controlled simulations of idealized galaxies

ABSTRACT Motivated by the need for realistic, dynamically self-consistent, evolving galaxy models that avoid the complexity of full, and zoom-in, cosmological simulations, we have developed Nexus, an integral framework to create and evolve synthetic galaxies made of collisionless and gaseous components. Nexus leverages the power of publicly available, tried-and-tested packages: the stellar-dynamics, action-based library Action-based Galaxy Modelling Architecture (AGAMA); and the adaptive mesh refinement, N-body/hydrodynamical code Ramses, modified to meet our needs. In addition, we make use of a proprietary module to account for galaxy formation physics, including gas cooling and heating, star formation, stellar feedback, and chemical enrichment. Nexus’ basic functionality consists in the generation of bespoke initial conditions (ICs) for a diversity of galaxy models, which are advanced in time to simulate the galaxy’s evolution. The fully self-consistent ICs are generated with a distribution-function-based approach, as implemented in the galaxy modelling module of AGAMA – up to now restricted to collisionless components, extended in this work to treat two types of gaseous configurations: hot haloes and gas discs. Nexus allows constructing equilibrium models with disc gas fractions $0~\le ~f_{\rm {\rm gas}}~\le ~1$, appropriate to model both low- and high-redshift galaxies. Similarly, the framework is ideally suited to the study of galactic ecology, i.e. the dynamical interplay between stars and gas over billions of years. As a validation and illustration of our framework, we reproduce several isolated galaxy model setups reported in earlier studies, and present a new, ‘nested bar’ galaxy simulation. Future upgrades of Nexus will include magnetohydrodynamics and highly energetic particle (‘cosmic ray’) heating.