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A review is conducted of the state of progress in physical modeling and computational simulations of turbulent flames as pertaining to Type Ia supernovae. The fundamental governing equations are provided, along with various assumptions made for their simplifications; and the numerical means of their discretizations. A case is made for a more systematic inclusion of turbulence, including turbulence-reaction interactions, for future investigations. [ABSTRACT FROM AUTHOR]

Highlights • A large-scale of 15,488 EnergyPlus simulations for commercial buildings in the U.S. • Nationwide energy savings for a single and combinations of multiple ECMs. • Nationwide energy savings for the ECM of fault detection and diagnostics. Abstract Buildings consumed 40% of the energy in the United States, which is more than any other sectors of the U.S. economy, including transportation and industry. The majority of this energy was used for lighting, space heating, cooling, ventilation, and water heating in the buildings. It is well known that the carbon emission is proportional to the energy consumption. Enhancing building efficiency becomes one of the easiest, most immediate and most cost-effective ways to reduce carbon emissions. This paper focuses on the simulation-based nationwide energy savings analysis of different energy conservation measures (ECMs) to enhance building energy performance. The study includes 44 different ECMs, which were simulated in 16 different climate zones for 11 different commercial building types in the U.S. Simulations were conducted using a whole building simulation program, EnergyPlus. Commercial prototype building models from the U.S. Department of Energy [1] were used as the baselines. Model input files were automatically modified to incorporate with 44 different ECMs using scripts. The baselines were based on American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) [2] Standard 90.1 and International Energy Conservation Code (IECC). A total of 15,488 simulations were conducted to study the nationwide energy savings potentials. The details of these 44 proposed ECMs and their corresponding nationwide saving potentials are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

The Korteweg–de Vries (KdV) equation is often adopted to simulate phase-resolved random waves on large scale in shallow water. It shows that the KdV equation is computationally efficient and can give sufficiently accurate results, but it is not always suitable and the error by using it cannot be predicted. This paper attempts to give the quantitative formulas for estimating the error of the statistics when simulating random waves in shallow water by using it. The formulas are obtained by fitting the errors of the KdV equation in comparison with the fully nonlinear model using the same initial condition based on the Wallops spectrum with a wide range of parameters. This paper also demonstrates how the formulas would be used, e.g., to estimate the error of the results by using the KdV model, or to justify its suitability for modelling random waves on large scale in shallow water. [ABSTRACT FROM AUTHOR]

Since there are a lot of problems of the traditional multi-resolution model and simulation technique such as the chained disaggregation problem, difficult consistence maintenance problem, high complexity and poor practicability, this paper propose a cycle drive dynamic aggregation and disaggregation (AD) multi-resolution (CADMR) simulation model. The AD operation is not controlled by the entities' complex interaction process but is by the fixed cycle, besides, cross resolution communications are allowed and the model aims to achieve the macro consistence instead of the micro consistence. Introduces the simulation and schedule mechanism, builds the formalized equation, and then the effect of this model to the characters of the system of systems is analyzed. Besides, the controllable character (error and computation complexity) of this model is proved theoretically and the existence of the macro consistence solution is also proved, at the same time, the unity-gain factor is existent and is only one, for which the solving process is simplified. Lastly, taking the weapon SoS as example and based on its multi resolution framework, the feasibility and validation of the model is verified with experimental confirmation. The model has an important promotion meaning for the popular application of the multi-resolution model and simulation technology. [ABSTRACT FROM AUTHOR]

Phase field (PF) models are one of the most popular methods for simulating solidification microstructures due to their fundamental connections to the physics of phase transformations. However, these methods are numerically very stiff due to the multiple length scales in a solidifying material, from the nanoscopic solid-liquid interface, to dendritic structures on the order of hundreds of microns. While this problem can be greatly alleviated by thin-interface analytical treatments of the PF equations, additional numerical methods are required to explore experimentally relevant sample sizes and times scales. It was shown about 18 years ago that the use of dynamic adaptive mesh refinement (AMR) can alleviate this problem by exploiting the simple fact that the majority of the solidification kinetics occur at the solid-liquid interface, which scales with a lower dimensionality than the embedding system itself. AMR methods, together with asymptotic analysis, nowadays provide one of the most efficient numerical strategies for self-consistent quantitative PF modelling of solidification microstructure processes. This paper highlights the latest developments in the AMR technique for 3D modelling of solidification using classical phase field equations. This includes a move away from finite element techniques to faster finite differencing through the use of dynamic mini-meshes which are each associated with each node of a 3D Octree data structure, and distributed MPI parallelism that uses a new communication algorithm to decompose a 3D domain into multiple adaptive meshes that are spawned on separate cores. The numerical technique is discussed, followed by demonstrations of the new AMR algorithm on select benchmark solidification problems, as well as some illustrations of multi-phase modelling using a recently developed multi-order parameter phase field model. [ABSTRACT FROM AUTHOR]

A method for the large-scale simulation with the lattice Boltzmann method (LBM) is proposed for liquid water movement in a gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells. The LBM is able to analyze two-phase flows in complex structures, however the simulation domain is limited due to heavy computational loads. This study investigates a variety means to reduce computational loads and increase the simulation areas. One is applying an LBM treating two-phases as having the same density, together with keeping numerical stability with large time steps. The applicability of this approach is confirmed by comparing the results with rigorous simulations using actual density. The second is establishing the maximum limit of the Capillary number that maintains flow patterns similar to the precise simulation; this is attempted as the computational load is inversely proportional to the Capillary number. The results show that the Capillary number can be increased to 3.0 × 10 −3 , where the actual operation corresponds to Ca = 10 −5 ∼10 −8 . The limit is also investigated experimentally using an enlarged scale model satisfying similarity conditions for the flow. Finally, a demonstration is made of the effects of pore uniformity in GDL as an example of a large-scale simulation covering a channel. [ABSTRACT FROM AUTHOR]

Conventional interatomic potential methods for Li-ion battery cathode materials normally use fixed-charge models, which are not accurate enough to model the dynamical oxidation state change of transition metals during electrochemical reactions. In order to enable more accurate large-scale simulations for battery cathode materials, here we report a semiempirical interatomic potential of the Li-Ni-O ternary system based on an advanced dynamic charge method: Charge-Transfer Modified Embedded-Atom Method (CT-MEAM). The potential is parameterized by fitting the atomic Bader charges and energy-strain curves of the LiNiO 2 cathode material under uniaxial, biaxial and hydrostatic strains to results obtained with ab initio density-functional theory (DFT) calculations. A variety of structural, electrochemical and dynamical properties derived from the fitted CT-MEAM potential are observed to be in excellent agreement with previous DFT and experimental data. The transferability of the potential is validated by comparing relative phase stabilities and charge distribution states within the ternary Li-Ni-O systems. Our results support the capability of the present CT-MEAM to model complex ternary transition metal oxides. This method will facilitate not only the optimal design of Lithium-ion battery cathode materials, but also other transition metal oxide-based applications involving electrochemical reactions. [ABSTRACT FROM AUTHOR]

A slender body's impact and water entry generate a violent flow with the free surface, time-dependent hydrodynamic loads, and motion or structural responses. The strong three-dimensional effects of the two-phase flow amplify the computational cost of predicting the hydrodynamic flows accurately with the free surface. This paper proposed a high-efficiency Smoothed Particle Hydrodynamics (SPH) model to simulate the oblique water entry of a cylinder. The number of particles is almost 50 million. The numerical model is validated by comparison with the experimental data and the convergence study of particle resolution. The results show that the cavity may shift transversely due to the unbalanced pressure gradients. The transverse shift is stronger with a smaller entry angle. The results are compared with Logvinovich's model, which shows that Logvinovich's model can accurately predict the shape of the cavity away from the splash, whereas the SPH model can accurately predict violent deformation, sealing, and breaking of the free surface in all stages of cavity evolution. The splash dynamics are quantified, benefiting from the sharp interface computed by the SPH method of high resolution. The splash can obtain more kinetic energy when the entry angle is small. Besides, The pinch-off pattern is more complicated than the vertical water entry due to the transverse shift of the cavity. Two columnar bubbles are separated from the cavity due to the transverse shift of the cavity when the entry angle is small. [Display omitted] • The oblique water entry is computed by multi-resolution two-phase SPH method. • The pressure gradient generated transveral shift of the cavity is found. • The changes of the potential and kinetic energy of splashes are presented. [ABSTRACT FROM AUTHOR]

This paper demonstrates a new process that has been specifically designed for the support of the U.S. Department of Transportation's (DOT's) Corporate Average Fuel Economy (CAFE) standards. In developing the standards, DOT's National Highway Traffic Safety Administration made use of the CAFE Compliance and Effects Modeling System (the 'Volpe model' or the 'CAFE model'), which was developed by DOT's Volpe National Transportation Systems Center for the 2005-2007 CAFE rulemaking and has been continuously updated since. The model is the primary tool used by the agency to evaluate potential CAFE stringency levels by applying technologies incrementally to each manufacturer's fleet until the requirements under consideration are met. The Volpe model relies on numerous technology-related and economic inputs, such as market forecasts, technology costs, and effectiveness estimates; these inputs are categorized by vehicle classification, technology synergies, phase-in rates, cost learning curve adjustments, and technology 'decision trees'. Part of the model's function is to estimate CAFE improvements that a given manufacturer could achieve by applying additional technology to specific vehicles in its product line. A significant number of inputs to the Volpe decision-tree model are related to the effectiveness (fuel consumption reduction) of each fuel-saving technology. Argonne National Laboratory has developed a fullvehicle simulation tool named Autonomie, which has become one of the industry's standard tools for analyzing vehicle energy consumption and technology effectiveness. Full-vehicle simulation tools use physics-based mathematical equations, engineering characteristics (e.g., engine maps, transmission shift points, and hybrid vehicle control strategies), and explicit drive cycles to predict the effectiveness of individual and combined fuel-saving technologies. The Large-Scale Simulation Process accelerates and facilitates the assessment of individual technological impacts on vehicle fuel economy. This paper will show how Argonne efficiently simulates hundreds of thousands of vehicles to model anticipated future vehicle technologies. [ABSTRACT FROM AUTHOR]

ReaxFF MD (Reactive Force Field Molecular Dynamics) is a promising method for investigating complex chemical reactions in relatively larger scale molecular systems. The existing analysis tools for ReaxFF MD lack the capability of capturing chemical reactions directly by analyzing the simulation trajectory, which is critical in exploring reaction mechanisms. This paper presents the algorithms, implementation strategies, features, and applications of VARxMD, a tool for Visualization and Analysis of Reactive Molecular Dynamics. VARxMD is dedicated to detailed chemical reaction analysis and visualization from the trajectories obtained in ReaxFF MD simulations. The interrelationships among the atoms, bonds, fragments, species and reactions are analyzed directly from the three-dimensional (3D) coordinates and bond orders of the atoms in a trajectory, which are accomplished by determination of atomic connectivity for recognizing connected molecular fragments, perception of bond types in the connected fragments for molecules or radicals, indexing of all these molecules or radicals (chemical species) based on their 3D coordinates and recognition of bond breaking or forming in the chemical species for reactions. Consequently, detailed chemical reactions taking place between two sampled frames can be generated automatically. VARxMD is the first tool specialized for reaction analysis and visualization in ReaxFF MD simulations. Applications of VARxMD in ReaxFF MD simulations of coal and HDPE (high-density polyethylene) pyrolysis show that VARxMD provides the capabilities in exploring the reaction mechanism in large systems with complex chemical reactions involved that are difficult to access manually. [ABSTRACT FROM AUTHOR]

Abstract: A novel program package has been developed which allows for the simultaneous treatment of atomistic kinetics in collision cascades caused by energetic ion impacts and thermally activated relaxation and diffusion. In this 3D program named TRIDER (TRansport of Ions in matter with DEfect Relaxation) the collision cascades treated in the framework of the Binary Collision Approximation has been combined with kinetic lattice Monte-Carlo simulations of the atomistic relaxation and diffusion. TRIDER simulations allow a more realistic description of ion-induced surface patterning because subsurface defect kinetics can be included in the simulations, which is demonstrated for low-energy Ar+ ion irradiation of silicon. A deeper understanding of ion beam mixing of bimetal interfaces can also be achieved: it is shown that the conventional Gaussian mixing profile is changed substantially for immiscible metals due to precipitation and for chemically active metals due to formation of intermetallics of different stoichiometry. [Copyright &y& Elsevier]

The fragmentation of a brittle plate subjected to dynamic biaxial loading is investigated via numerical simulations. The aim is to extend our understanding of the dynamic processes affecting fragment size distributions. A scalable computational framework based on a hybrid cohesive zone model description of fracture and a discontinuous Galerkin formulation is employed. This enables large-scale simulations and, thus, the consideration of rich distributions of defects, as well as an accurate account of the role of stress waves. We study the dependence of the fragmentation response on defect distribution, material properties, and strain rate. A scaling law describing the dependence of fragment size on the parameters is proposed. It is found that fragmentation exhibits two distinct regimes depending on the loading rate and material defect distribution: one controlled by material strength and the other one by material toughness. At low strain rates, fragmentation is controlled by defects, whereas at high strain rates energy balance arguments dominate the fragmentation response. [ABSTRACT FROM AUTHOR]

Abstract: Spatial partitioning is commonly used for parallel simulation of spatial–temporal systems, such as simulations of wildfires. Achieving effective spatial partitioning is a challenging task due to the dynamic behavior of the simulation models. This paper presents a partitioning method named profile-based spatial partitioning for parallel simulation of large scale wildfires. The profile-based partitioning exploits the dynamic behavior of a wildfire spread simulation model and uses it as a profile to guide the spatial partitioning for parallel simulations. Experimental results show that the profile-based partitioning can increase the degree of parallelism and improve the scalability of parallel simulations of large-scale wildfires. [Copyright &y& Elsevier]

Abstract: We have developed a GPU-based molecular dynamics simulation for the study of flows of fluids with anisotropic molecules such as liquid crystals. An application of the simulation to the study of macroscopic flow (backflow) generation by molecular reorientation in a nematic liquid crystal under the application of an electric field is presented. The computations of intermolecular force and torque are parallelized on the GPU using the cell-list method, and an efficient algorithm to update the cell lists was proposed. Some important issues in the implementation of computations that involve a large number of arithmetic operations and data on the GPU that has limited high-speed memory resources are addressed extensively. Despite the relatively low GPU occupancy in the calculation of intermolecular force and torque, the computation on a recent GPU is about 50 times faster than that on a single core of a recent CPU, thus simulations involving a large number of molecules using a personal computer are possible. The GPU-based simulation should allow an extensive investigation of the molecular-level mechanisms underlying various macroscopic flow phenomena in fluids with anisotropic molecules. [Copyright &y& Elsevier]

[Display omitted] In this work, the Quasi-particle Approach (QA) is applied to qualitatively reproduce the underlying mechanisms of the displacive fcc (γ) → bcc (α) transformation. At the microstructural scale, we demonstrate that the QA is able to predict the growth of a bcc nucleus in a fcc matrix, and the eventual formation of an internally twinned structure consisting in two variants with Kurdjumov-Sachs orientation relationship. At the atomic level, the defect structure of twinning boundaries and fcc/bcc interfaces is identified, and the main mechanism for the propagation of the fcc/bcc interface is analyzed. In detail, it is confirmed that twin boundaries are propagated by the glide of pairs of partial twin dislocations, while the propagation of fcc screw dislocations along coherent terrace edges is the pivotal vector of the fcc/bcc transformation. The simulation results are compared qualitatively with our TEM and HRTEM observations of Fe-rich bcc twinned particle embedded in the fcc Cu-rich matrix in the Cu-Fe-Co system. [ABSTRACT FROM AUTHOR]

Abstract: Dislocation dynamics (DD), a discrete dynamic simulation method in which dislocations are the fundamental entities, is a powerful tool for investigation of plasticity, deformation and fracture of materials at the micron length scale. However, severe computational difficulties arising from complex, long-range interactions between these curvilinear line defects limit the application of DD in the study of large-scale plastic deformation. We present here the development of a parallel algorithm for accelerated computer simulations of DD. By representing dislocations as a 3D set of dislocation particles, we show here that the problem of an interacting ensemble of dislocations can be converted to a problem of a particle ensemble, interacting with a long-range force field. A grid using binary space partitioning is constructed to keep track of node connectivity across domains. We demonstrate the computational efficiency of the parallel micro-plasticity code and discuss how O(N) methods map naturally onto the parallel data structure. Finally, we present results from applications of the parallel code to deformation in single crystal fcc metals. [Copyright &y& Elsevier]

• SIMREG is a stochastic tree-level distance-independent forest model. • Model the impact of silviculture and management on forest development. • Calibrated with widely available national forest inventory data. • Generic growth, thinning and recruitment models for 17 species groups. • Current management of Walloon spruce forests is unsustainable. SIMREG is a non-deterministic tree-level distance independent forest model that can simulate forest growth, yield and management on a regional scale while representing the wide diversity of composition, structure and management found in forest stands. It is composed of several sub-models to represent the main forest dynamics (growth, recruitment, removal, clearcut and reforestation) and to account for species composition, stand density, tree size and social status, forest ownership type and some sites characteristics. We used the data collected by the permanent forest inventory of Wallonia (IPRFW) between 1994 and 2015 to calibrate SIMREG and forecast the development of Wallonia's 479 500 ha of productive forest (465 million simulated trees) until 2050. According to our simulation, the harvesting rate of Norway spruce (the main production species) is currently unsustainable and it is gradually being replaced by other species such as Douglas-fir, larch and various hardwoods. It appears that in terms of total softwood volume production, the higher production level of Douglas-fir and larch should eventually compensate for the decline in spruce. In contrast, the harvest rate in hardwood stands is around 75% of the annual yield, resulting in a steady increase in the total hardwood stock of about 600 000 m³ per year. Our methodology is easily replicable and the data required for sub-model calibration are consistent with those measured by most permanent NFIs, so our forest simulation model could be adapted to other regions and countries. [ABSTRACT FROM AUTHOR]