Multidimensional Modeling and Validation of Dual-Fuel Combustion in a Large Bore Medium Speed Diesel Engine

High fidelity, three-dimensional CFD was used to model the flow, fuel injection, combustion, and emissions in a large bore medium speed diesel engine with different levels of natural gas substitution. Detailed chemical kinetics was used to model the complex combustion behavior of the premixed natural gas, ignited via a diesel spray. The numerical predictions were compared against measured multiple cycle pressure data, to understand the possible factors affecting cyclic variation in experimental data. Under conditions with high natural gas substitution rates, diesel was injected much earlier than firing-TDC. This additional mixing time allowed the active radicals from diesel dissociation to initiate combustion from the cylinder wall and propagate inwards. 0%, 60%, and 93% natural gas substitution rates (by energy) were tested in this study to develop computational capabilities needed to accurately model and understand the underlying physics. Several innovative computational methods such as adaptive mesh refinement (which automatically refines and coarsens the mesh based on the existing solution parameters), and multi-zoning (which groups chemically similar cells together to reduce combustion calculation time) were utilized to obtain accurate predictions at a lower computational cost. Important engine emissions such as NOx, CO, unburnt HC, and soot were predicted numerically and compared against measured engine data.

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AMReX: Block-structured adaptive mesh refinement for multiphysics applications

The International Journal of High Performance Computing Applications ◽

10.1177/10943420211022811 ◽

2021 ◽

pp. 109434202110228

Author(s):

Weiqun Zhang ◽

Andrew Myers ◽

Kevin Gott ◽

Ann Almgren ◽

John Bell

Keyword(s):

Adaptive Mesh Refinement ◽

Mesh Refinement ◽

Computational Cost ◽

Adaptive Mesh ◽

Uniform Mesh ◽

Physical Processes ◽

Structured Adaptive Mesh Refinement ◽

Core Elements ◽

Accelerator Design ◽

Block Structured

Block-structured adaptive mesh refinement (AMR) provides the basis for the temporal and spatial discretization strategy for a number of Exascale Computing Project applications in the areas of accelerator design, additive manufacturing, astrophysics, combustion, cosmology, multiphase flow, and wind plant modeling. AMReX is a software framework that provides a unified infrastructure with the functionality needed for these and other AMR applications to be able to effectively and efficiently utilize machines from laptops to exascale architectures. AMR reduces the computational cost and memory footprint compared to a uniform mesh while preserving accurate descriptions of different physical processes in complex multiphysics algorithms. AMReX supports algorithms that solve systems of partial differential equations in simple or complex geometries and those that use particles and/or particle–mesh operations to represent component physical processes. In this article, we will discuss the core elements of the AMReX framework such as data containers and iterators as well as several specialized operations to meet the needs of the application projects. In addition, we will highlight the strategy that the AMReX team is pursuing to achieve highly performant code across a range of accelerator-based architectures for a variety of different applications.

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MOLECULAR STATICS SIMULATION OF NANOINDENTATION USING ADAPTIVE QUASICONTINUUM METHOD

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2018.15.0057 ◽

2018 ◽

Vol 15 ◽

pp. 57-62

Author(s):

Karel Mikeš ◽

Ondřej Rokoš ◽

Ron H. J. Peerlings

Keyword(s):

Adaptive Mesh Refinement ◽

Deformation Gradient ◽

Hexagonal Lattice ◽

Computational Cost ◽

Adaptive Mesh ◽

Nanoindentation Test ◽

Atomistic Model ◽

Molecular Statics ◽

Quasicontinuum Method ◽

Local Lattice

In this work, molecular statics is used to model a nanoindentation test on a two-dimensional hexagonal lattice. To this end, the QuasiContinuum (QC) method with adaptive propagation of the fully resolved domain is used to reduce the computational cost required by the full atomistic model. Three different adaptive mesh refinement criteria are introduced and tested, based on: (i) the Zienkiewicz–Zhu criterion (used for the deformation gradient), (ii) local atoms’ site energy, and (iii) local lattice disregistry. Accuracy and efficiency of individual refinement schemes are compared against the full atomistic model and obtained results are discussed.

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Accelerating numerical wave propagation using wavefield adapted meshes. Part I: forward and adjoint modelling

Geophysical Journal International ◽

10.1093/gji/ggaa058 ◽

2020 ◽

Vol 221 (3) ◽

pp. 1580-1590 ◽

Cited By ~ 3

Author(s):

M van Driel ◽

C Boehm ◽

L Krischer ◽

M Afanasiev

Keyword(s):

Wave Propagation ◽

Adaptive Mesh Refinement ◽

Waveform Inversion ◽

Computational Cost ◽

Model Space ◽

Adaptive Mesh ◽

Order Of Magnitude ◽

Speed Up ◽

Adjoint Modelling ◽

The Waves

SUMMARY An order of magnitude speed-up in finite-element modelling of wave propagation can be achieved by adapting the mesh to the anticipated space-dependent complexity and smoothness of the waves. This can be achieved by designing the mesh not only to respect the local wavelengths, but also the propagation direction of the waves depending on the source location, hence by anisotropic adaptive mesh refinement. Discrete gradients with respect to material properties as needed in full waveform inversion can still be computed exactly, but at greatly reduced computational cost. In order to do this, we explicitly distinguish the discretization of the model space from the discretization of the wavefield and derive the necessary expressions to map the discrete gradient into the model space. While the idea is applicable to any wave propagation problem that retains predictable smoothness in the solution, we highlight the idea of this approach with instructive 2-D examples of forward as well as inverse elastic wave propagation. Furthermore, we apply the method to 3-D global seismic wave simulations and demonstrate how meshes can be constructed that take advantage of high-order mappings from the reference coordinates of the finite elements to physical coordinates. Error level and speed-ups are estimated based on convergence tests with 1-D and 3-D models.

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Implementation and performance of adaptive mesh refinement in the Ice Sheet System Model (ISSM v4.14)

Geoscientific Model Development ◽

10.5194/gmd-12-215-2019 ◽

2019 ◽

Vol 12 (1) ◽

pp. 215-232 ◽

Cited By ~ 1

Author(s):

Thiago Dias dos Santos ◽

Mathieu Morlighem ◽

Hélène Seroussi ◽

Philippe Remy Bernard Devloo ◽

Jefferson Cardia Simões

Keyword(s):

Adaptive Mesh Refinement ◽

Mesh Refinement ◽

Computational Cost ◽

Ice Sheet ◽

Adaptive Mesh ◽

System Model ◽

Computational Time ◽

Error Estimator ◽

Fine Mesh ◽

Grounding Line

Abstract. Accurate projections of the evolution of ice sheets in a changing climate require a fine mesh/grid resolution in ice sheet models to correctly capture fundamental physical processes, such as the evolution of the grounding line, the region where grounded ice starts to float. The evolution of the grounding line indeed plays a major role in ice sheet dynamics, as it is a fundamental control on marine ice sheet stability. Numerical modeling of a grounding line requires significant computational resources since the accuracy of its position depends on grid or mesh resolution. A technique that improves accuracy with reduced computational cost is the adaptive mesh refinement (AMR) approach. We present here the implementation of the AMR technique in the finite element Ice Sheet System Model (ISSM) to simulate grounding line dynamics under two different benchmarks: MISMIP3d and MISMIP+. We test different refinement criteria: (a) distance around the grounding line, (b) a posteriori error estimator, the Zienkiewicz–Zhu (ZZ) error estimator, and (c) different combinations of (a) and (b). In both benchmarks, the ZZ error estimator presents high values around the grounding line. In the MISMIP+ setup, this estimator also presents high values in the grounded part of the ice sheet, following the complex shape of the bedrock geometry. The ZZ estimator helps guide the refinement procedure such that AMR performance is improved. Our results show that computational time with AMR depends on the required accuracy, but in all cases, it is significantly shorter than for uniformly refined meshes. We conclude that AMR without an associated error estimator should be avoided, especially for real glaciers that have a complex bed geometry.

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Improved Mappings for Streamline-Based Simulation

SPE Journal ◽

10.2118/89352-pa ◽

2006 ◽

Vol 11 (03) ◽

pp. 294-302 ◽

Cited By ~ 6

Author(s):

Bradley T. Mallison ◽

Margot G. Gerritsen ◽

Sebastien F. Matringe

Keyword(s):

Mass Balance ◽

Adaptive Mesh Refinement ◽

Piecewise Linear ◽

Gas Injection ◽

Computational Cost ◽

Adaptive Mesh ◽

Linear Representation ◽

Compositional Simulation ◽

Background Grid ◽

Streamline Method

Summary Our interest lies in extending the streamline method to compositional simulation. In this paper, we develop improved mappings to and from streamlines that are necessary to obtain reliable predictions of gas injection processes. Our improved mapping to streamlines uses a piecewise linear representation of saturations on the background grid in order to minimize numerical smearing. Our strategy for mapping saturations from streamlines to the background grid is based on kriging. We test our improvements to the streamline method by use of a simple model for miscible flooding based on incompressible Darcy flow. Results indicate that our mappings offer improved resolution and reduce mass-balance errors relative to the commonly used mappings. Our mappings also require fewer streamlines to achieve a desired level of accuracy. In compositional cases where the computational cost of a streamline solve is high, we anticipate that this will lead to an improvement in the efficiency of streamline-based simulation. Introduction The overall goal of our research is to improve the accuracy and efficiency of the streamline method in simulating compositional problems such as those that occur in miscible or near-miscible gas injection processes. This is our second paper suggesting improvements to this end. In Mallison et al. (2005) we investigated a 1D compositional finite-difference solver based on a high-order upwind scheme and adaptive mesh refinement that is appropriate for use in a compositional streamline simulator. Here, we propose new mappings to and from streamlines that improve the accuracy of the streamline method for problems in which the flow pattern does not remain fixed for large time intervals. Such problems require that streamlines be periodically updated in order to account for changing flow directions and for the treatment of gravity terms (Thiele et al. 1996; Bratvedt et al. 1996). For each set of streamlines, fluids must be mapped from an underlying background grid, on which the pressure is solved (or, say, the flow), to the streamlines, moved forward in time, and then mapped from the streamlines back to the background grid. The mappings introduce numerical smearing and generally also mass-balance errors. When streamlines are updated frequently, the mapping errors limit the overall accuracy of the streamline method. Our improved mapping algorithms are aimed at minimizing this type of error.

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Implementation and Performance of Adaptive Mesh Refinement in the Ice Sheet System Model (ISSM v4.14)

10.5194/gmd-2018-194 ◽

2018 ◽

Cited By ~ 1

Author(s):

Thiago Dias dos Santos ◽

Mathieu Morlighem ◽

Hélène Seroussi ◽

Philippe Remy Bernard Devloo ◽

Jefferson Cardia Simões

Keyword(s):

Adaptive Mesh Refinement ◽

Mesh Refinement ◽

Computational Cost ◽

Ice Sheet ◽

Adaptive Mesh ◽

System Model ◽

Computational Time ◽

Error Estimator ◽

Grounding Line ◽

Refined Meshes

Abstract. Accurate projections of the evolution of ice sheets in a changing climate require a fine mesh/grid resolution to correctly capture fundamental physical processes, such as the evolution of the grounding line, the region where grounded ice starts to float. The evolution of the grounding line indeed plays a major role in ice sheet dynamics, as it is a fundamental control on marine ice sheet stability. Numerical modeling of grounding line requires significant computational resources since the accuracy of its position depends on grid or mesh resolution. A technique that improves accuracy with reduced computational cost is the adaptive mesh refinement approach, AMR. We present here the implementation of the AMR technique in the finite element Ice Sheet System Model (ISSM) to simulate grounding line dynamics under two different benchmarks, MISMIP3d and MISMIP+. We test different refinement criteria: (a) distance around grounding line, (b) a posteriori error estimator, the Zienkiewicz-Zhu (ZZ) error estimator, and (c) different combinations of (a) and (b). We find that for MISMIP3d setup, refining 5 km around the grounding line, both on grounded and floating ice, is sufficient to produce AMR results similar to the ones obtained with uniformly refined meshes. However, for the MISMIP+ setup, we note that there is a minimum distance of 30 km around the grounding line required to produce accurate results. We find this AMR mesh-dependency is linked to the complex bedrock topography of MISMIP+. In both benchmarks, the ZZ error estimator presents high values around the grounding line. Particularly for MISMIP+ setup, the estimator also presents high values in the grounded part of the ice sheet, following the complex shape of the bedrock geometry. This estimator helps guide the refinement procedure such that AMR performance is improved. Our results show that computational time with AMR depends on the required accuracy, but in all cases, it is significantly shorter than for uniformly refined meshes. We conclude that AMR without an associated error estimator should be avoided, especially for real glaciers that have a complex bed geometry.

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Efficient Simulations of Propagating Flames and Fire Suppression Optimization Using Adaptive Mesh Refinement

Fluids ◽

10.3390/fluids6090323 ◽

2021 ◽

Vol 6 (9) ◽

pp. 323

Author(s):

Caelan Lapointe ◽

Nicholas T. Wimer ◽

Sam Simons-Wellin ◽

Jeffrey F. Glusman ◽

Gregory B. Rieker ◽

...

Keyword(s):

Adaptive Mesh Refinement ◽

Optimization Problems ◽

Solid Phase ◽

Fire Suppression ◽

Spatial Scales ◽

Mesh Refinement ◽

Computational Cost ◽

Adaptive Mesh ◽

Fire Spread ◽

Wide Range

Fires are complex multi-physics problems that span wide spatial scale ranges. Capturing this complexity in computationally affordable numerical simulations for process studies and “outer-loop” techniques (e.g., optimization and uncertainty quantification) is a fundamental challenge in reacting flow research. Further complications arise for propagating fires where a priori knowledge of the fire spread rate and direction is typically not available. In such cases, static mesh refinement at all possible fire locations is a computationally inefficient approach to bridging the wide range of spatial scales relevant to fire behavior. In the present study, we address this challenge by incorporating adaptive mesh refinement (AMR) in fireFoam, an OpenFOAM solver for simulations of complex fire phenomena involving pyrolyzing solid surfaces. The AMR functionality in the extended solver, called fireDyMFoam, is load balanced, models gas, solid, and liquid phases, and allows us to dynamically track regions of interest, thus avoiding inefficient over-resolution of areas far from a propagating flame. We demonstrate the AMR capability and computational efficiency for fire spread on vertical panels, showing that the AMR solver reproduces results obtained using much larger statically refined meshes, but at a substantially reduced computational cost. We then leverage AMR in an optimization framework for fire suppression based on the open-source Dakota toolkit, which is made more computationally tractable through the use of fireDyMFoam, minimizing a cost function that balances water use and solid-phase mass loss. The extension of fireFoam developed here thus enables the use of higher fidelity simulations in optimization problems for the suppression of fire spread in both built and natural environments.

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Parallel-GPU-accelerated adaptive mesh refinement for three-dimensional phase-field simulation of dendritic growth during solidification of binary alloy

Materials Theory ◽

10.1186/s41313-021-00033-5 ◽

2022 ◽

Vol 6 (1) ◽

Author(s):

Shinji Sakane ◽

Tomohiro Takaki ◽

Takayuki Aoki

Keyword(s):

Parallel Computing ◽

Phase Field ◽

Adaptive Mesh Refinement ◽

Computational Cost ◽

Three Dimensional ◽

Adaptive Mesh ◽

Dendrite Growth ◽

Dynamic Load Balancing ◽

Phase Field Simulation ◽

Field Simulation

AbstractIn the phase-field simulation of dendrite growth during the solidification of an alloy, the computational cost becomes extremely high when the diffusion length is significantly larger than the curvature radius of a dendrite tip. In such cases, the adaptive mesh refinement (AMR) method is effective for improving the computational performance. In this study, we perform a three-dimensional dendrite growth phase-field simulation in which AMR is implemented via parallel computing using multiple graphics processing units (GPUs), which provide high parallel computation performance. In the parallel GPU computation, we apply dynamic load balancing to parallel computing to equalize the computational cost per GPU. The accuracy of an AMR refinement condition is confirmed through the single-GPU computations of columnar dendrite growth during the directional solidification of a binary alloy. Next, we evaluate the efficiency of dynamic load balancing by performing multiple-GPU parallel computations for three different directional solidification simulations using a moving frame algorithm. Finally, weak scaling tests are performed to confirm the parallel efficiency of the developed code.

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An Embedded Ghost-Fluid Method for Compressible Flow in Complex Geometry

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.366.31 ◽

2016 ◽

Vol 366 ◽

pp. 31-39

Author(s):

M. Al-Marouf ◽

R. Samtaney

Keyword(s):

Adaptive Mesh Refinement ◽

Numerical Solutions ◽

Complex Geometry ◽

Computational Cost ◽

Adaptive Mesh ◽

Navier Stokes ◽

Ghost Fluid Method ◽

Structured Adaptive Mesh Refinement ◽

Number Flow ◽

High Mach

We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. The PDE multidimensional extrapolation approach of Aslam [1] is used to reconstruct the solution in the ghost-fluid regions and impose boundary conditions at the fluid-solid interface. The CNS equations are numerically solved by the second order multidimensional upwind method of Colella [2] and Saltzman [3]. Block-structured adaptive mesh refinement implemented under the Chombo framework is utilized to reduce the computational cost while keeping high-resolution mesh around the embedded boundary and regions of high gradient solutions. Numerical examples with different Reynolds numbers for low and high Mach number flow will be presented. We compare our simulation results with other reported experimental and computational results. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well.

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Accuracy Verification of a 2D Adaptive Mesh Refinement Method Using Backward-Facing Step Flow of Low Reynolds Numbers

International Journal of Computational Methods ◽

10.1142/s0219876220410121 ◽

2020 ◽

pp. 2041012

Author(s):

Zhenquan Li ◽

Miao Li

Keyword(s):

Adaptive Mesh Refinement ◽

Numerical Solutions ◽

Stokes Equations ◽

Mesh Refinement ◽

Computational Cost ◽

Adaptive Mesh ◽

Navier Stokes ◽

Vortex Center ◽

Backward Facing Step ◽

Step Flow

Identifying centers of vortices of fluid flow accurately is one of the accuracy measures for computational methods. After verifying the accuracy of the 2D adaptive mesh refinement (AMR) method in the benchmarks of 2D lid-driven cavity flow, this paper shows the accuracy verification by the benchmarks of 2D backward-facing step flow. The AMR method refines a mesh using the numerical solution of the Navier–Stokes equations computed on the mesh by an open source software Navier2D which implemented a vertex centered finite volume method (FVM) using the median dual mesh to form control volumes about each vertex. The accuracy is shown by the comparison between vortex center locations calculated from the linearly interpolated numerical solutions and those obtained in the benchmark. The AMR method is proposed based on the qualitative theory of differential equations, and it can be applied to refine a mesh as many times as required and used to seek accurate numerical solutions of the mathematical models including the continuity equation for incompressible fluid or steady-state compressible flow with low computational cost.

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