Journal articles on the topic 'Multi-coupled solver'
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Mulliken, J., and D. C. Rizos. "A coupled computational method for multi-solver, multi-domain transient problems in elastodynamics." Soil Dynamics and Earthquake Engineering 34, no. 1 (March 2012): 78–88. http://dx.doi.org/10.1016/j.soildyn.2011.10.004.
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Papadionysiou, Marianna, Kim Seongchan, Mathieu Hursin, Alexander Vasiliev, Hakim Ferroukhi, Andreas Pautz, and Joo Han Gyu. "COUPLING OF nTRACER TO COBRA-TF FOR HIGH-FIDELITY ANALYSIS OF VVERs." EPJ Web of Conferences 247 (2021): 02008. http://dx.doi.org/10.1051/epjconf/202124702008.
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Paul Scherrer Institut is developing a high-resolution multi-physics core solver for VVER analysis. This work presents the preliminary stages of the development, specifically the coupling of the 3D pin-by-pin neutronic solver nTRACER to the sub-channel thermal-hydraulic code COBRA-TF for single assembly multi-physics steady state calculations. The coupling scheme and the modifications performed in the codes are described in details. The results of the coupled nTRACER/COBRA-TF calculations are compared to the ones of a standalone nTRACER calculation where the feedbacks are provided by a simplified 1D thermal-hydraulic solver. The agreement is very good with fuel temperature differences around 10 K which can be attributed to the different correlations used in the various solvers. The cross-comparison of the two multi-physics computational routes serves as a preliminary verification of the coupling scheme developed between nTRACER and COBRA-TF.
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Sashi Kumar, G. N., A. K. Mahendra, and G. Gouthaman. "Multi-objective shape optimization using ant colony coupled computational fluid dynamics solver." Computers & Fluids 46, no. 1 (July 2011): 298–305. http://dx.doi.org/10.1016/j.compfluid.2011.01.016.
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WANG, W. Q., L. X. ZHANG, X. Q. HE, and Y. GUO. "LARGE EDDY SIMULATION OF HYDROELASTIC VIBRATION USING THE FINITE ELEMENT METHOD." International Journal of Modern Physics B 24, no. 24 (September 30, 2010): 4683–706. http://dx.doi.org/10.1142/s0217979210055871.
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This work is concerned with modeling the interaction of fluid flow with flexible solid structures. An improving spring smooth analogy and an improved constant volume transfer (ICVT) are used to provide fluid mesh control and transfer the information on the interfaces between fluid and structure, respectively. The time integrating algorithm is based on the predictor multi-corrector algorithm (PMA). An important aspect of this work is that we present a directly coupled approach, in which a large eddy simulation (LES) fluid solver and a structure solver have been coupled together to solve a hydroelasticity problem using the finite element method. To demonstrate the performance of the proposed approach, two working examples were used. One is the vibration of a beam immersed in incompressible fluid, another is the hydroelastic behavior of an ideal guide vane in a hydro turbine passage. The numerical results show the validity of the proposed approach.
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Falagkaris, E. J., D. M. Ingram, I. M. Viola, and K. Markakis. "PROTEUS: A coupled iterative force-correction immersed-boundary multi-domain cascaded lattice Boltzmann solver." Computers & Mathematics with Applications 74, no. 10 (November 2017): 2348–68. http://dx.doi.org/10.1016/j.camwa.2017.07.016.
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Zhang, Wei, Jin Song Bai, and De Jun Sun. "A Multi-State HLL Approximate Riemann Solver for Solid/Vacuum Riemann Problem." Applied Mechanics and Materials 872 (October 2017): 393–98. http://dx.doi.org/10.4028/www.scientific.net/amm.872.393.
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A new multi-state HLLD (‘‘D’’ stands for Discontinuities.) approximate Riemann solver for Riemann problem of nonlinear elastic solid is developed based on the assumption that a wave configuration for the solution that consists of five waves (two slow waves, two fast waves and a contact discontinuity) separating six constant states. Since the intermediate states satisfied with the Rankine-Hugoniot relations in this approximate Riemann system are analytically obtained, the HLLD Riemann solver can be constructed straightforwardly. The Piecewise Parabolic Method (PPM) is used directly to construct high-order finite-volume schemes. Numerical tests demonstrate that the scheme PPM coupled with HLLD is robust and efficient. It indicates that the scheme PPM+ HLLD can be useful in practical applications for the non-linear elasticity.
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Ridley, Jeff K., Edward W. Blockley, Ann B. Keen, Jamie G. L. Rae, Alex E. West, and David Schroeder. "The sea ice model component of HadGEM3-GC3.1." Geoscientific Model Development 11, no. 2 (February 27, 2018): 713–23. http://dx.doi.org/10.5194/gmd-11-713-2018.
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Abstract. A new sea ice configuration, GSI8.1, is implemented in the Met Office global coupled configuration HadGEM3-GC3.1 which will be used for all CMIP6 (Coupled Model Intercomparison Project Phase 6) simulations. The inclusion of multi-layer thermodynamics has required a semi-implicit coupling scheme between atmosphere and sea ice to ensure the stability of the solver. Here we describe the sea ice model component and show that the Arctic thickness and extent compare well with observationally based data.
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Gomes, Pedro, and Rafael Palacios. "Aerodynamic-driven topology optimization of compliant airfoils." Structural and Multidisciplinary Optimization 62, no. 4 (May 14, 2020): 2117–30. http://dx.doi.org/10.1007/s00158-020-02600-9.
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Abstract A strategy for density-based topology optimization of fluid-structure interaction problems is proposed that deals with some shortcomings associated to non stiffness-based design. The goal is to improve the passive aerodynamic shape adaptation of highly compliant airfoils at multiple operating points. A two-step solution process is proposed that decouples global aeroelastic performance goals from the search of a solid-void topology on the structure. In the first step, a reference fully coupled fluid-structure problem is solved without explicitly penalizing non-discreteness in the resulting topology. A regularization step is then performed that solves an inverse design problem, akin to those in compliant mechanism design, which produces a discrete-topology structure with the same response to the fluid loads. Simulations are carried out with the multi-physics suite SU2, which includes Reynolds-averaged Navier-Stokes modeling of the fluid and hyper-elastic material behavior of the geometrically nonlinear structure. Gradient-based optimization is used with the exterior penalty method and a large-scale quasi-Newton unconstrained optimizer. Coupled aerostructural sensitivities are obtained via an algorithmic differentiation based coupled discrete adjoint solver. Numerical examples on a compliant aerofoil with performance objectives at two Mach numbers are presented.
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Hu, Jianxin, Qing Xiao, and Ruoxin Li. "Numerical Simulation of a Multi-Body System Mimicking Coupled Active and Passive Movements of Fish Swimming." Journal of Marine Science and Engineering 9, no. 3 (March 17, 2021): 334. http://dx.doi.org/10.3390/jmse9030334.
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A multi-body system model is proposed for the mimicking of swimming fish with coupled active and passive movements. The relevant algorithms of the kinematics and dynamics of the multi-body system and coupled fluid solver are developed and fully validated. A simplified three-body model is applied for the investigation of the hydrodynamic performance of both an active pitch motion and passive movement. In general, there is an optimal stiffness, under which the model swims with the fastest velocity. The effect of the damper can be drawn only when the stiffness is small. Comparing with the rigid tail, the flexible tail leads to a faster speed when the stiffness and damping coefficients are in a suitable range.
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Savino, Alberto, Alessandro Cocco, Alex Zanotti, Matteo Tugnoli, Pierangelo Masarati, and Vincenzo Muscarello. "Coupling Mid-Fidelity Aerodynamics and Multibody Dynamics for the Aeroelastic Analysis of Rotary-Wing Vehicles." Energies 14, no. 21 (October 25, 2021): 6979. http://dx.doi.org/10.3390/en14216979.
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A mid-fidelity aerodynamic solver based on the vortex particle method for wake modeling, DUST, is coupled through the partitioned multi-physics coupling library preCICE to a multibody dynamics code, MBDyn, to improve the accuracy of aeroelastic numerical analysis performed on rotary-wing vehicles. In this paper, the coupled tool is firstly validated by solving simple fixed-wing and rotary-wing problems from the open literature. The transient roll maneuver of a complete tiltrotor aircraft is then simulated, to show the capability of the coupled solver to analyze the aeroelasticity of complex rotorcraft configurations. Simulation results show the importance of the accurate representation of rotary wing aerodynamics provided by the vortex particle method for loads evaluation, aeroelastic stability assessment, and analysis of transient maneuvers of aircraft configurations characterized by complex interactional aerodynamics. The limited computational effort required by the mid-fidelity aerodynamic approach represents an effective trade-off in obtaining fast and accurate solutions that can be used for the preliminary design of novel rotary-wing vehicle configurations.
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Pujol, Léo, Pierre-André Garambois, and Jérôme Monnier. "Multi-dimensional hydrological–hydraulic model with variational data assimilation for river networks and floodplains." Geoscientific Model Development 15, no. 15 (August 3, 2022): 6085–113. http://dx.doi.org/10.5194/gmd-15-6085-2022.
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Abstract. This contribution presents a novel multi-dimensional (multi-D) hydraulic–hydrological numerical model with variational data assimilation capabilities. It allows multi-scale modeling over large domains, combining in situ observations with high-resolution hydrometeorology and satellite data. The multi-D hydraulic model relies on the 2D shallow-water equations solved with a 1D–2D adapted single finite-volume solver. One-dimensional-like reaches are built through meshing methods that cause the 2D solver to degenerate into 1D. They are connected to 2D portions that act as local zooms, for modeling complex flow zones such as floodplains and confluences, via 1D-like–2D interfaces. An existing parsimonious hydrological model, GR4H, is implemented and coupled to the hydraulic model. The forward-inverse multi-D computational model is successfully validated on virtual and real cases of increasing complexity, including using the second-order scheme version. Assimilating multiple observations of flow signatures leads to accurate inferences of multi-variate and spatially distributed parameters among bathymetry friction, upstream and lateral hydrographs and hydrological model parameters. This notably demonstrates the possibility for information feedback towards upstream hydrological catchments, that is, backward hydrology. A 1D-like model of part of the Garonne River is built and accurately reproduces flow lines and propagations of a 2D reference model. A multi-D model of the complex Adour basin network, with inflow from the semi-distributed hydrological model, is built. High-resolution flow simulations are obtained on a large domain, including fine zooms on floodplains, with a relatively low computational cost since the network contains mostly 1D-like reaches. The current work constitutes an upgrade of the DassFlow computational platform. The adjoint of the whole tool chain is obtained by automatic code differentiation.
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Čiegis, Raimondas, Gerda Jankevičiūtė, and Natalija Tumanov. "ON EFFICIENT NUMERICAL ALGORITHMS FOR SIMULATION OF HIGH POWER ELECTRICAL CABLES." Mathematical Modelling and Analysis 20, no. 6 (November 23, 2015): 701–14. http://dx.doi.org/10.3846/13926292.2015.1108250.
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The new virtual modelling tool is constructed, which is used for optimal design of power transmission lines and cables. The construction of such lines should meet the latest power transmission network technical and economical requirements. The solver is is based on classical and modified mathematical models describing main heat conduction processes: diffusion, convection and radiation in various materials and environments. In basic heat conduction equation, we take into account a linear dependence of the resistance on temperature. Multi-physic and multi-scale models are required to simulate industrial cases of power transmission lines. The velocity of convective transport of the heat in air regions is simulated by solving a coupled thermo-convection problem including the heat conduction problem and the standard Navier-Stokes model of the heat flow in air. Another multi-physic model is used to describe changes of material heat conduction coefficients in soil due to influence of heating. This process is described by by solving a simplified mass balance equation for flows in porous media. The multi-scale and homogenization analysis is required to to formulate simple and accurate mathematical describing heat conduction process is metal region which consists of a bundle of tightly coupled metal wires. The FVM is used to solve the obtained systems of differential equations. Discretization of the domain is done by applying “aCute” mesh generator, which is a modification of the well-known Triangle mesh generator. The discrete schemes are implemented by using the OpenFOAM tool.
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Matrisciano, Andrea, Tim Franken, Laura Catalina Gonzales Mestre, Anders Borg, and Fabian Mauss. "Development of a Computationally Efficient Tabulated Chemistry Solver for Internal Combustion Engine Optimization Using Stochastic Reactor Models." Applied Sciences 10, no. 24 (December 16, 2020): 8979. http://dx.doi.org/10.3390/app10248979.
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The use of chemical kinetic mechanisms in computer aided engineering tools for internal combustion engine simulations is of high importance for studying and predicting pollutant formation of conventional and alternative fuels. However, usage of complex reaction schemes is accompanied by high computational cost in 0-D, 1-D and 3-D computational fluid dynamics frameworks. The present work aims to address this challenge and allow broader deployment of detailed chemistry-based simulations, such as in multi-objective engine optimization campaigns. A fast-running tabulated chemistry solver coupled to a 0-D probability density function-based approach for the modelling of compression and spark ignition engine combustion is proposed. A stochastic reactor engine model has been extended with a progress variable-based framework, allowing the use of pre-calculated auto-ignition tables instead of solving the chemical reactions on-the-fly. As a first validation step, the tabulated chemistry-based solver is assessed against the online chemistry solver under constant pressure reactor conditions. Secondly, performance and accuracy targets of the progress variable-based solver are verified using stochastic reactor models under compression and spark ignition engine conditions. Detailed multicomponent mechanisms comprising up to 475 species are employed in both the tabulated and online chemistry simulation campaigns. The proposed progress variable-based solver proved to be in good agreement with the detailed online chemistry one in terms of combustion performance as well as engine-out emission predictions (CO, CO2, NO and unburned hydrocarbons). Concerning computational performances, the newly proposed solver delivers remarkable speed-ups (up to four orders of magnitude) when compared to the online chemistry simulations. In turn, the new solver allows the stochastic reactor model to be computationally competitive with much lower order modeling approaches (i.e., Vibe-based models). It also makes the stochastic reactor model a feasible computer aided engineering framework of choice for multi-objective engine optimization campaigns.
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Knight, Earl E., Esteban Rougier, Zhou Lei, Bryan Euser, Viet Chau, Samuel H. Boyce, Ke Gao, Kurama Okubo, and Marouchka Froment. "HOSS: an implementation of the combined finite-discrete element method." Computational Particle Mechanics 7, no. 5 (July 31, 2020): 765–87. http://dx.doi.org/10.1007/s40571-020-00349-y.
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Abstract Nearly thirty years since its inception, the combined finite-discrete element method (FDEM) has made remarkable strides in becoming a mainstream analysis tool within the field of Computational Mechanics. FDEM was developed to effectively “bridge the gap” between two disparate Computational Mechanics approaches known as the finite and discrete element methods. At Los Alamos National Laboratory (LANL) researchers developed the Hybrid Optimization Software Suite (HOSS) as a hybrid multi-physics platform, based on FDEM, for the simulation of solid material behavior complemented with the latest technological enhancements for full fluid–solid interaction. In HOSS, several newly developed FDEM algorithms have been implemented that yield more accurate material deformation formulations, inter-particle interaction solvers, and fracture and fragmentation solutions. In addition, an explicit computational fluid dynamics solver and a novel fluid–solid interaction algorithms have been fully integrated (as opposed to coupled) into the HOSS’ solid mechanical solver, allowing for the study of an even wider range of problems. Advancements such as this are leading HOSS to become a tool of choice for multi-physics problems. HOSS has been successfully applied by a myriad of researchers for analysis in rock mechanics, oil and gas industries, engineering application (structural, mechanical and biomedical engineering), mining, blast loading, high velocity impact, as well as seismic and acoustic analysis. This paper intends to summarize the latest development and application efforts for HOSS.
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Pohl, László, Gusztáv Hantos, János Hegedüs, Márton Németh, Zsolt Kohári, and András Poppe. "Mixed Detailed and Compact Multi-Domain Modeling to Describe CoB LEDs." Energies 13, no. 16 (August 5, 2020): 4051. http://dx.doi.org/10.3390/en13164051.
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Large area multi-chip LED devices, such as chip-on-board (CoB) LEDs, require the combined use of chip-level multi-domain compact LED models (Spice-like compact models) and the proper description of distributed nature of the thermal environment (the CoB substrate and phosphor) of the LED chips. In this paper, we describe such a new numerical solver that was specifically developed for this purpose. For chip-level, the multi-domain compact modeling approach of the Delphi4LED project is used. This chip-level model is coupled to a finite difference scheme based numerical solver that is used to simulate the thermal phenomena in the substrate and in the phosphor (heat transfer and heat generation). Besides solving the 3D heat-conduction problem, this new numerical simulator also tracks the propagation and absorption of the blue light emitted by the LED chips, as well as the propagation and absorption of the longer wavelength light that is converted by the phosphor from blue. Heat generation in the phosphor, due to conversion loss (Stokes shift), is also modeled. To validate our proposed multi-domain model of the phosphor, dedicated phosphor and LED package samples with known resin—phosphor powder ratios and known geometry were created. These samples were partly used to identify the nature of the temperature dependence of phosphor-conversion efficiency and were also used as simple test cases to “calibrate” and test the new numerical solver. With the models developed, combined simulation of the LED chip and the CoB substrate + phosphor for a known CoB LED device is shown, and the simulation results are compared to measurement results.
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Delelegn, S. W., A. Pathirana, B. Gersonius, A. G. Adeogun, and K. Vairavamoorthy. "Multi-objective optimisation of cost–benefit of urban flood management using a 1D2D coupled model." Water Science and Technology 63, no. 5 (March 1, 2011): 1053–59. http://dx.doi.org/10.2166/wst.2011.290.
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This paper presents a multi-objective optimisation (MOO) tool for urban drainage management that is based on a 1D2D coupled model of SWMM5 (1D sub-surface flow model) and BreZo (2D surface flow model). This coupled model is linked with NSGA-II, which is an Evolutionary Algorithm-based optimiser. Previously the combination of a surface/sub-surface flow model and evolutionary optimisation has been considered to be infeasible due to the computational demands. The 1D2D coupled model used here shows a computational efficiency that is acceptable for optimisation. This technological advance is the result of the application of a triangular irregular discretisation process and an explicit finite volume solver in the 2D surface flow model. Besides that, OpenMP based parallelisation was employed at optimiser level to further improve the computational speed of the MOO tool. The MOO tool has been applied to an existing sewer network in West Garforth, UK. This application demonstrates the advantages of using multi-objective optimisation by providing an easy-to-comprehend Pareto-optimal front (relating investment cost to expected flood damage) that could be used for decision making processes, without repeatedly going through the modelling–optimisation stage.
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Daugherty, Robin, and Dragica Vasileska. "Multi-Scale Modeling of Self Heating Effects on Power Consumption in Silicon CMOS Devices." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2017, DPC (January 1, 2017): 1–22. http://dx.doi.org/10.4071/2017dpc-tp3_presentation4.
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This work pursues a multi-scale modeling approach to combine interconnect and device level simulation in order to study the effects of carrier self-heating and thermal transport on device performance. More specifically, this work will focus on power consumption and heat dissipation in silicon CMOS technology. As device dimensions decrease to the nanometer scale, current density in the device active regions and the circuit interconnects increases [4]. This increase in current density leads to substantial increases in operating temperatures in critical regions of nano-scale electronic devices. We have already shown these effects in n-channel MOSFETs [2], and will continue to explore how this phenomenon affects p-channel MOSFETs and CMOS circuits. This paper presents the methodology used for the study, multi-scale results from the n-channel MOSFET simulations, and preliminary results from the device level p-channel MOSFET simulation. The modeling approach combines an electro-thermal device simulation with a thermal transport solver at the circuit level. The electrical simulation solves Poisson's equations self-consistently coupled with an ensemble Monte Carlo to determine internal electric fields and model electron and hole transport in the device [3]. The thermal simulation solves the energy balance equations for acoustic and optical phonons and uses the phonon energy to determine the lattice temperature [5]. The electro-thermal solver couples these two processes by introducing temperature dependent scattering to the carrier transport solver. Thermal transport can be modeled in a variety of ways: phonon Monte Carlo simulations are necessary for modeling extreme nano-scale and hot-carrier devices, energy balance modeling is used in this study to model thermal transport at the device level, and the Joule heating method commonly used in commercial device simulators is used in this study to model thermal transport at the interconnect level. The thermal modeling in the device and the interconnects is coupled using the device structure itself as an interface: the electro-thermal simulator provides Joule heating terms throughout the device to be used in the Joule heating simulator which in turn gives the temperature profile in the interconnects to be used as a boundary condition in the electro-thermal solver. These simulations are repeated in a self-consistent loop until convergence is achieved [2]. This modeling approach has been successfully applied to n-channel MOSFET devices and the results have been confirmed using a novel experimental approach. Two identical MOSEFTs in either common source or common drain configuration can be biased such that one device is in saturation and one device is in cut-off or sub-threshold region. The device in saturation heats up and the device in sub-threshold is used as a sensor; the temperature in the sensor can be determined using the subthreshold slope [2]. Confirming the simulation results with experimental results for the temperature in the subthreshold device substantiates the accuracy of the methodology for determining the temperature throughout the device [2]. This methodology, now verified by comparison with experimental results for n-channel MOSFETS, will be applied to the study of CMOS circuits.
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Wigger, S. J., S. M. Goodnick, and M. Saraniti. "Hybrid Particle-based Full-band Analysis of Ultra-small MOS." VLSI Design 13, no. 1-4 (January 1, 2001): 125–29. http://dx.doi.org/10.1155/2001/94360.
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We report on the 2D and 3D modeling of ultra-small MOS structures using a newly developed full-band device simulator. The simulation tool is based on a novel approach, featuring a hybrid Ensemble Monte Carlo (EMC)-Cellular Automata (CA) simulation engine. In this hybrid approach charge transport is simulated using the CA in regions of momentum space where most scattering events occur and the EMC elsewhere, thus optimizing the trade-off between the fast, but memory consuming CA method and the slower EMC method. To account for the spatial distribution of the electric field and charge concentration, the hybrid EMC/CA simulator is self-consistently coupled with a 2D and 3D multi-grid Poisson solver. The solver is then used to simulate the performance of a 40 nm gate length n-MOSFET structure.
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Hoffman, Matthew J., Mauro Perego, Stephen F. Price, William H. Lipscomb, Tong Zhang, Douglas Jacobsen, Irina Tezaur, Andrew G. Salinger, Raymond Tuminaro, and Luca Bertagna. "MPAS-Albany Land Ice (MALI): a variable-resolution ice sheet model for Earth system modeling using Voronoi grids." Geoscientific Model Development 11, no. 9 (September 18, 2018): 3747–80. http://dx.doi.org/10.5194/gmd-11-3747-2018.
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Abstract. We introduce MPAS-Albany Land Ice (MALI) v6.0, a new variable-resolution land ice model that uses unstructured Voronoi grids on a plane or sphere. MALI is built using the Model for Prediction Across Scales (MPAS) framework for developing variable-resolution Earth system model components and the Albany multi-physics code base for the solution of coupled systems of partial differential equations, which itself makes use of Trilinos solver libraries. MALI includes a three-dimensional first-order momentum balance solver (Blatter–Pattyn) by linking to the Albany-LI ice sheet velocity solver and an explicit shallow ice velocity solver. The evolution of ice geometry and tracers is handled through an explicit first-order horizontal advection scheme with vertical remapping. The evolution of ice temperature is treated using operator splitting of vertical diffusion and horizontal advection and can be configured to use either a temperature or enthalpy formulation. MALI includes a mass-conserving subglacial hydrology model that supports distributed and/or channelized drainage and can optionally be coupled to ice dynamics. Options for calving include “eigencalving”, which assumes that the calving rate is proportional to extensional strain rates. MALI is evaluated against commonly used exact solutions and community benchmark experiments and shows the expected accuracy. Results for the MISMIP3d benchmark experiments with MALI's Blatter–Pattyn solver fall between published results from Stokes and L1L2 models as expected. We use the model to simulate a semi-realistic Antarctic ice sheet problem following the initMIP protocol and using 2 km resolution in marine ice sheet regions. MALI is the glacier component of the Energy Exascale Earth System Model (E3SM) version 1, and we describe current and planned coupling to other E3SM components.
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Dehghan, Mahnaz, Ali Reza Davari, and Mojtaba Dehghan Manshadi. "Numerical investigation on the weight, speed, and installation location effects on fuel tank separation trajectory." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 13 (August 12, 2016): 2331–44. http://dx.doi.org/10.1177/0954410016662799.
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A numerical survey coupled with six degree-of-freedom flight simulation have been undertaken to study the fuel tank separation trajectory, released from a trainer airplane. Two different spanwise release points for the tank, near and farther from the fuselage under the starboard wing with full and empty fuel were considered. The studies were performed at two free stream Mach numbers of 0.23 and 0.42 at zero angle of attack. Dynamic unstructured tetrahedral mesh approach combined with spring-based smoothing and local remeshing was applied with an implicit, second-order upwind accurate Euler solver. A six degree-of-freedom routine using a fourth-order multi-point time integration scheme was coupled with the flow solver to update the payload trajectory information at each time step. According to the results, the payload installed farther from the fuselage falls down with a higher forward velocity than that located closer, once released from the wing. The spanwise installation point was also found to have a strong impact on the pitch attitude of the released payload. The payload weight has been shown to play a vital role in longitudinal-lateral coupling behavior and the associated moments on the released payload.
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Totounferoush, Amin, Frédéric Simonis, Benjamin Uekermann, and Miriam Schulte. "Efficient and Scalable Initialization of Partitioned Coupled Simulations with preCICE." Algorithms 14, no. 6 (May 27, 2021): 166. http://dx.doi.org/10.3390/a14060166.
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preCICE is an open-source library, that provides comprehensive functionality to couple independent parallelized solver codes to establish a partitioned multi-physics multi-code simulation environment. For data communication between the respective executables at runtime, it implements a peer-to-peer concept, which renders the computational cost of the coupling per time step negligible compared to the typical run time of the coupled codes. To initialize the peer-to-peer coupling, the mesh partitions of the respective solvers need to be compared to determine the point-to-point communication channels between the processes of both codes. This initialization effort can become a limiting factor, if we either reach memory limits or if we have to re-initialize communication relations in every time step. In this contribution, we remove two remaining bottlenecks: (i) We base the neighborhood search between mesh entities of two solvers on a tree data structure to avoid quadratic complexity, and (ii) we replace the sequential gather-scatter comparison of both mesh partitions by a two-level approach that first compares bounding boxes around mesh partitions in a sequential manner, subsequently establishes pairwise communication between processes of the two solvers, and finally compares mesh partitions between connected processes in parallel. We show, that the two-level initialization method is fives times faster than the old one-level scheme on 24,567 CPU-cores using a mesh with 628,898 vertices. In addition, the two-level scheme is able to handle much larger computational meshes, since the central mesh communication of the one-level scheme is replaced with a fully point-to-point mesh communication scheme.
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Si, Nan, and Alan Brown. "A Framework of Runge–Kutta, Discontinuous Galerkin, Level Set and Direct Ghost Fluid Methods for the Multi-Dimensional Simulation of Underwater Explosions." Fluids 7, no. 1 (December 29, 2021): 13. http://dx.doi.org/10.3390/fluids7010013.
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This work describes the development of a hybrid framework of Runge–Kutta (RK), discontinuous Galerkin (DG), level set (LS) and direct ghost fluid (DGFM) methods for the simulation of near-field and early-time underwater explosions (UNDEX) in early-stage ship design. UNDEX problems provide a series of challenging issues to be solved. The multi-dimensional, multi-phase, compressible and inviscid fluid-governing equations must be solved numerically. The shock front in the solution field must be captured accurately while maintaining the total variation diminishing (TVD) properties. The interface between the explosive gas and water must be tracked without letting the numerical diffusion across the material interface lead to spurious pressure oscillations and thus the failure of the simulation. The non-reflecting boundary condition (NRBC) must effectively absorb the wave and prevent it from reflecting back into the fluid. Furthermore, the CFD solver must have the capability of dealing with fluid–structure interactions (FSI) where both the fluid and structural domains respond with significant deformation. These issues necessitate a hybrid model. In-house CFD solvers (UNDEXVT) are developed to test the applicability of this framework. In this development, code verification and validation are performed. Different methods of implementing non-reflecting boundary conditions (NRBCs) are compared. The simulation results of single and multi-dimensional cases that possess near-field and early-time UNDEX features—such as shock and rarefaction waves in the fluid, the explosion bubble, and the variation of its radius over time—are presented. Continuing research on two-way coupled FSI with large deformation is introduced, and together with a more complete description of the direct ghost fluid method (DGFM) in this framework will be described in subsequent papers.
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Olorunfemi, Tope Roseline, and Nnamdi I. Nwulu. "Multi-Agent Based Optimal Operation of Hybrid Energy Sources Coupled with Demand Response Programs." Sustainability 13, no. 14 (July 12, 2021): 7756. http://dx.doi.org/10.3390/su13147756.
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Electricity is an indispensable commodity on which both urban and rural regions heavily rely. Rural areas where the main grid cannot reach make use of distributed energy resources (DER), especially renewable energy sources (RES), in an islanded microgrid. Therefore, it is necessary to make sure there is a sufficient power supply to balance the demand and supply curve and meet people’s demands. The work done in this paper aims to minimize the daily operating cost of the hybrid microgrid while incorporating a demand response strategy built on an incentive-based demand response (IBDR) model. Three case studies were constructed and analyzed to derive the best, most reduced daily operational cost. This was achieved using the CPLEX solver embedded in algebraic modeling language in the Advanced Interactive Multidimensional Modeling Systems (AIMMS) software with multi-agent system (MAS); the MAS was used to make sure that the developed intelligent-based agents work independently to achieve an optimal microgrid system. The sensitivity analysis employed established that case study 2 gave the most reduced daily operation cost (USD 119), which represents an 8% reduction in the daily operational cost from case study 1 and a 9% reduction from case study 3. Then, we achieved 17% and 25% reductions, as compared to specific other approaches.
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Athani, Abdulgaphur, Nik Nazri Nik Ghazali, Irfan Anjum Badruddin, Abdullah Y. Usmani, Sarfaraz Kamangar, Ali E. Anqi, and Nandalur Ameer Ahammad. "Two-Phase Non-Newtonian Pulsatile Blood Flow Simulations in a Rigid and Flexible Patient-Specific Left Coronary Artery (LCA) Exhibiting Multi-Stenosis." Applied Sciences 11, no. 23 (December 1, 2021): 11361. http://dx.doi.org/10.3390/app112311361.
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Coronary artery disease (CAD) is stated as one of the most common causes of death all over the world. This article explores the influence of multi stenosis in a flexible and rigid left coronary artery (LCA) model using a multiphase blood flow system which has not yet been studied. Two-way fluid–solid interaction (FSI) is employed to achieve flow within the flexible artery model. A realistic three-dimensional model of multi-stenosed LCA was reconstructed based on computerized tomography (CT) images. The fluid domain was solved using a finite volume-based commercial software (FLUENT 2020). The fluid (blood) and solid (wall) domains were fully coupled by using the ANSYS Fluid-Structure Interaction solver. The maximum pressure drops, and wall shear stress was determined across the sever stenosis (90% AS). The higher region of displacement occurs at the pre-stenosis area compared to the other area of the left coronary artery model. An increase in blood flow velocity across the restricted regions (stenosis) in the LCA was observed, whereas the recirculation zone at the post-stenosis and bifurcation regions was noted. An overestimation of hemodynamic descriptors for the rigid models was found as compared to the FSI models.
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Keser, Robert, Michele Battistoni, Hong G. Im, and Hrvoje Jasak. "A Eulerian Multi-Fluid Model for High-Speed Evaporating Sprays." Processes 9, no. 6 (May 26, 2021): 941. http://dx.doi.org/10.3390/pr9060941.
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Advancements in internal combustion technology, such as efficiency improvements and the usage of new complex fuels, are often coupled with developments of suitable numerical tools for predicting the complex dynamic behavior of sprays. Therefore, this work presents a Eulerian multi-fluid model specialized for the dynamic behavior of dense evaporating liquid fuel sprays. The introduced model was implemented within the open-source OpenFOAM library, which is constantly gaining popularity in both industrial and academic settings. Therefore, it represents an ideal framework for such development. The presented model employs the classes method and advanced interfacial momentum transfer models. The droplet breakup is considered using the enhanced WAVE breakup model, where the mass taken from the parent droplets is distributed among child classes using a triangular distribution. Furthermore, the complex thermal behavior within the moving droplets is considered using a parabolic temperature profile and an effective thermal conductivity approach. This work includes an uncertainty estimation analysis (for both spatial and temporal resolutions) for the developed solver. Furthermore, the solver was validated against two ECN Spray A conditions (evaporating and non-evaporating). Overall, the presented results show the capability of the implemented model to successfully predict the complex dynamic behavior of dense liquid sprays for the selected operating conditions.
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Xiang, Jiansheng, John-Paul Latham, Axelle Vire, Elena Anastasaki, and Christopher C. Pain. "COUPLED FLUIDITY/Y3D TECHNOLOGY AND SIMULATION TOOLS FOR NUMERICAL BREAKWATER MODELLING." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 66. http://dx.doi.org/10.9753/icce.v33.structures.66.
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FEMDEM modelling which combines the multi-body particle interaction and motion modelling (i.e. Discrete Element Model, DEM) with the ability to model internal deformation of arbitrary shape (Finite Element Model, FEM) has been applied to breakwater models. There are two versions of a FEMDEM solver developed; Y3D_D is for deformable materials and is required for dynamic and static stress analysis and Y3D-R is the rigid version often used to numerically construct the armour unit packs. This paper also reports the placement protocols: POSITIT.
FEMDEM modelling deals with solids interactions and is one modelling component that is to be coupled to other modelling technologies e.g. CFD, interface tracking, wave models, porous media etc. so that the key fluid-solid interactions can be modelled in a full scale virtual breakwater alongside work on scaled hydraulic laboratory models and prototype structures. The latest developments of two-way coupled interactions of waves with coastal structures are also described in this paper.
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De Paola, F., N. Fontana, M. Giugni, G. Marini, and F. Pugliese. "Optimal solving of the pump scheduling problem by using a Harmony Search optimization algorithm." Journal of Hydroinformatics 19, no. 6 (August 28, 2017): 879–89. http://dx.doi.org/10.2166/hydro.2017.132.
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Abstract Pumps are installed in water distribution networks (WDNs) to ensure adequate service levels in the case of poor water pressure (e.g. because of low elevation of reservoirs or high head losses within the WDN). In such cases optimal pump scheduling is often required for the opportunity of significant energy saving. Optimizing the pump operation also allows a reduction in damage and maintenance times. Among the approaches available in the literature to solve the problem, meta-heuristic algorithms ensure reduced computational times, although they are not able to guarantee the optimal solution can be found. In this paper, a modified Harmony Search Multi-Objective optimization algorithm is developed to solve the pump scheduling problem in WDNs. The hydraulic solver EPANET 2.0 is coupled with the algorithm to assess the feasibility of the achieved solutions. Hydraulic constraints are introduced and penalties are set in case of violation of the set constraints to reduce the space of feasible solutions. Results show the high performances of the proposed approach for pumping optimization, guaranteeing optimal (or near optimal) solutions with short computational times.
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Coroado, A., and P. Ricci. "A self-consistent multi-component model of plasma turbulence and kinetic neutral dynamics for the simulation of the tokamak boundary." Nuclear Fusion 62, no. 3 (March 1, 2022): 036015. http://dx.doi.org/10.1088/1741-4326/ac47b8.
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Abstract A self-consistent model is presented for the simulation of a multi-component plasma in the tokamak boundary. A deuterium plasma is considered, with the plasma species that include electrons, deuterium atomic ions and deuterium molecular ions, while the deuterium atoms and molecules constitute the neutral species. The plasma and neutral models are coupled via a number of collisional interactions, which include dissociation, ionization, charge-exchange and recombination processes. The derivation of the three-fluid drift-reduced Braginskii equations used to describe the turbulent plasma dynamics is presented, including its boundary conditions. The kinetic advection equations for the neutral species are also derived, and their numerical implementation discussed. The first results of multi-component plasma simulations carried out by using the global Braginskii solver (GBS) code are then presented and analyzed, being compared with results obtained with the single-component plasma model.
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Benakrach, Hind, Mohamed Bounouib, Mourad Taha-Janan, and Mohamed Zeriab Essadek. "A Three-dimensional Multi-species Flow Solver for the Euler Equations Combined with a Stiffened Gas Equation of State." International Journal of Mechanics 16 (May 17, 2022): 55–64. http://dx.doi.org/10.46300/9104.2022.16.7.
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Although numerical simulation in fluid mechanics is undergoing a significant development due to the dazzling evolution of computing means, complex physical phenomena, such as multidimensional viscous effects in turbomachinery and cavitation, remain mysterious and attract the curiosity of several researchers. Highresolution shock captures are often obtained by the WENO family of schemes, except that in problems that depend on discontinuities and shocks, an appearance of numerical oscillations weakens its ability to provide adequate captures. The use of the characteristic construction methods prevents this type of oscillation. The present paper contributes to the numerical resolution of multi-species flows of viscous, compressible, or incompressible fluids with shocks and discontinuities. The proposed numerical model can handle various configurations with a unique method based on a conservative and consistent threedimensional finite volume scheme with an aligned mesh. The system of equations is a set of Euler equations coupled with a two-parameters generalized state equation of state in three-dimensional Cartesian coordinates. This system is solved using a Roe type approximate Riemann solver, and second-order precision is obtained using limiters. The obtained numerical results maintain a nonoscillatory flow near the discontinuities, which makes the method satisfactory and shows its accuracy and robustness in different cases.
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GE, JIE, XUAN LIU, YI YANG, YIXU SONG, and TIANLING REN. "REACTION SIMULATION AND EXPERIMENT OF A Cl2/Ar INDUCTIVELY COUPLED PLASMA FOR ETCHING OF SILICON." Surface Review and Letters 21, no. 03 (June 2014): 1450038. http://dx.doi.org/10.1142/s0218625x14500383.
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As the key feature size keeps shrinking down, inductively coupled plasma (ICP) has been widely used for etching. In this study, a commercial ICP etcher filled with Cl 2/ Ar mixture was simulated. The simulation was based on a commercial software CFD-ACE+, which is a multi-module solver. For the simulation part, CFD-ACE module was used for reactor scale and CFD-TOPO module was used for feature scale simulation. We have reached a reasonable agreement between the simulative and experimental results. Specifically, the different causes of sidewall bowing and microtrenching were discussed. We also analyzed the causes of special profile as trench width scaling down. Moreover, the agreement validates correctness of the chemistry mechanism, so it can be used as guidance for the process designing and manufacturing equipment improvement.
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Wyser, Emmanuel, Yury Alkhimenkov, Michel Jaboyedoff, and Yury Y. Podladchikov. "An explicit GPU-based material point method solver for elastoplastic problems (ep2-3De v1.0)." Geoscientific Model Development 14, no. 12 (December 22, 2021): 7749–74. http://dx.doi.org/10.5194/gmd-14-7749-2021.
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Abstract. We propose an explicit GPU-based solver within the material point method (MPM) framework using graphics processing units (GPUs) to resolve elastoplastic problems under two- and three-dimensional configurations (i.e. granular collapses and slumping mechanics). Modern GPU architectures, including Ampere, Turing and Volta, provide a computational framework that is well suited to the locality of the material point method in view of high-performance computing. For intense and non-local computational aspects (i.e. the back-and-forth mapping between the nodes of the background mesh and the material points), we use straightforward atomic operations (the scattering paradigm). We select the generalized interpolation material point method (GIMPM) to resolve the cell-crossing error, which typically arises in the original MPM, because of the C0 continuity of the linear basis function. We validate our GPU-based in-house solver by comparing numerical results for granular collapses with the available experimental data sets. Good agreement is found between the numerical results and experimental results for the free surface and failure surface. We further evaluate the performance of our GPU-based implementation for the three-dimensional elastoplastic slumping mechanics problem. We report (i) a maximum 200-fold performance gain between a CPU- and a single-GPU-based implementation, provided that (ii) the hardware limit (i.e. the peak memory bandwidth) of the device is reached. Furthermore, our multi-GPU implementation can resolve models with nearly a billion material points. We finally showcase an application to slumping mechanics and demonstrate the importance of a three-dimensional configuration coupled with heterogeneous properties to resolve complex material behaviour.
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Wenz, F., T. Lutz, and E. Krämer. "Impact of turbulent inflow and orography on the low-frequency noise sources of a wind turbine." Journal of Physics: Conference Series 2265, no. 3 (May 1, 2022): 032060. http://dx.doi.org/10.1088/1742-6596/2265/3/032060.
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Abstract A high-fidelity process chain is used to numerically investigate the low-frequency emissions from a generic wind turbine under turbulent inflow conditions. It consists of the Computational Fluid Dynamics (CFD) solver FLOWer, which is coupled to the multi-body simulation software SIMPACK to take unsteady aeroelastic effects into account. A realistic flow field for the complex terrain of Perdigão, Portugal is obtained by including the orography and vegetation in the simulation and using a precursor simulation with E-Wind to generate a site- and situation-specific inflow. The acoustic emissions are calculated with the Fflowcs-Williams-Hawkings (FW-H) acoustic solver ACCO. The simulations show that the tower emits noise caused by the blade-tower interaction (BTI) equally strong in all directions. To the sides of the turbine, this contribution is dominant, regardless of the turbulent inflow. The blades, on the other hand, emit significantly more noise under turbulent inflow, especially in streamwise direction, where they become the dominant source. The main noise mechanism here is the low-frequency part of the inflow turbulence (IT), followed by the BTI. The flow field in Perdigão causes additional large-scale variations in IT noise over time.
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Munk, David J., Gareth A. Vio, and Dries Verstraete. "A Hypersonic Aircraft Optimization Tool with Strong Aerothermoelastic Coupling." Applied Mechanics and Materials 846 (July 2016): 494–99. http://dx.doi.org/10.4028/www.scientific.net/amm.846.494.
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The design and optimization of hypersonic aircraft is severely impacted by the high temperatures encountered during flight as they can lead to high thermal stresses and a significant reduction in material strength and stiffness. This reduction in rigidity of the structure requires innovative structural concepts and a stronger focus on aerothermoelastic deformations in the early design and optimization phase of the design cycle. This imposes the need for a closer coupling of the aerodynamic, thermal and structural design tools than is currently in practice. The paper presents a multi-disciplinary, closely coupled optimization suite that is suitable for preliminary design in the hypersonic regime. The time varying temperature distribution is applied through an equilibrium analysis, and is coupled to the aerodynamics through the Tranair® solver. An analysis of the effect that the aerothermodynamic coupling has on the sizing of the aircraft is given, along with the effect of skin buckling. It is shown that the coupling of the aerothermodynamics drives the sizing of the structure and therefore must be considered for hypersonic applications.
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GOODNICK, STEPHEN M., and MARCO SARANITI. "CELLULAR MONTE CARLO SIMULATION OF HIGH FIELD TRANSPORT IN SEMICONDUCTOR DEVICES." International Journal of High Speed Electronics and Systems 17, no. 03 (September 2007): 465–73. http://dx.doi.org/10.1142/s0129156407004655.
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Here we discuss the use of the Cellular Monte Carlo (CMC) method for full band simulation of semiconductor transport and device modeling. The electronic band structure and phonon spectra are used as direct inputs to the program for both cubic, hexagonal, and strained crystal structures using both empirical and ab initio methods. As a particular example, this method is applied to study high field transport in GaN and GaN/AlGaN heterostructures, where good agreement is obtained between the simulated results, and experimental pulse I-V measurements of transport. For device simulation, the CMC algorithm is coupled to an efficient 2D/3D multi-grid Poisson solver. We discuss the application of this algorithm to several technological problems of interest, including ultra-short channel Si/Ge MOSFETs, III-V compound HEMTs, and AlGaN/GaN HEMTs.
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Chinappi, M., and E. De Angelis. "Confined dynamics of a single DNA molecule." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1944 (June 13, 2011): 2329–36. http://dx.doi.org/10.1098/rsta.2011.0096.
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The effect of a slit-like confinement on the relaxation dynamics of DNA is studied via a mesoscale model in which a bead and spring model for the polymer is coupled to a particle-based Navier–Stokes solver (multi-particle collision dynamics). The confinement is found to affect the equilibrium stretch of the chain when the bulk gyration radius is comparable to or smaller than the channel height and our data are in agreement with the ( R g,bulk / h ) 1/4 scaling of the polymer extension in the wall tangential direction. Relaxation simulation at different confinements indicates that, while the overall behaviour of the relaxation dynamics is similar for low and strong confinements, a small, but significant, slowing of the far-equilibrium relaxation is found as the confinement increases.
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Morrell, Benjamin J., David J. Munk, Gareth A. Vio, and Dries Verstraete. "Development of a Hypersonic Aircraft Design Optimization Tool." Applied Mechanics and Materials 553 (May 2014): 847–52. http://dx.doi.org/10.4028/www.scientific.net/amm.553.847.
Full textAbstract:
The design and optimization of hypersonic aircraft is severely impacted by the high temperatures encountered during flight as they can lead to high thermal stresses and a significant reduction in material strength and stiffness. This reduction in rigidity of the structure requires innovative structural concepts and a stronger focus on aeroelastic deformations in the early design and optimisation of the aircraft structure. This imposes the need for a closer coupling of the aerodynamic and structural design tools than is current practice. The paper presents the development of a multi-disciplinary, closely coupled optimisation suite for hypersonic aircraft. An overview of the setup and structure of the optimization suite is given and the integration between the Tranair solver, used to determine the aerodynamic loads and temperatures, and MSC/NASTRAN, used for the structural sizing and design, will be given.
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Matos, Nuno M. B., and Andre C. Marta. "Concurrent Trajectory Optimization and Aircraft Design for the Air Cargo Challenge Competition." Aerospace 9, no. 7 (July 13, 2022): 378. http://dx.doi.org/10.3390/aerospace9070378.
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A coupled aerostructural aircraft design and trajectory optimization framework is developed for the Air Cargo Challenge competition to maximize the expected score based on cargo carried, altitude achieved and distance traveled. Its modular architecture makes it easily adaptable to any problem where the performance depends not only on the design of the aircraft but also on its flight trajectory. It is based on OpenAeroStruct, an aerostructural solver that uses analytic derivatives for efficient gradient-based optimization. A trajectory optimization module using a collocation method is coupled with the option of using b-splines to increase computational efficiency together with an experimentally-based power decay model that accurately determines the aircraft propulsive response to control input depending on the battery discharge level. The optimization problem totaled 206 variables and 283 constraints and was solved in less than 7 h on a standard computer with 12% reduction when using b-splines for trajectory control variables. The results revealed the need to consider the multi-objective total score to account for the different score components and highlighted the importance of the payload level and chosen trajectory. The wing area should be increased within allowable limits to maximize payload capacity, climb to maximum target height should be the focus of the first 60 s of flight and full throttle should be avoided in cruise to reduce losses and extend flight distance. The framework proved to be a valuable tool for students to easily obtain guidelines for both the model aircraft design and control to maximize the competition score.
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Sanchez-Espinoza, V. H., L. Mercatali, J. Leppänen, E. Hoogenboom, R. Vocka, and J. Dufek. "THE McSAFE PROJECT - HIGH-PERFORMANCE MONTE CARLO BASED METHODS FOR SAFETY DEMONSTRATION: FROM PROOF OF CONCEPT TO INDUSTRY APPLICATIONS." EPJ Web of Conferences 247 (2021): 06004. http://dx.doi.org/10.1051/epjconf/202124706004.
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The increasing use of Monte Carlo methods for core analysis is fostered by the huge and cheap computer power available nowadays e.g. in large HPC. Apart from the classical criticality calculations, the application of Monte Carlo methods for depletion analysis and cross section generation for diffusion and transport core simulators is also expanding. In addition, the development of multi-physics codes by coupling Monte Carlo solvers with thermal hydraulic codes (CFD, subchannel and system thermal hydraulics) to perform full core static core analysis at fuel assembly or pin level has progressed in the last decades. Finally, the extensions of the Monte Carlo codes to describe the behavior of prompt and delay neutrons, control rod movements, etc. has been started some years ago. Recent coupling of dynamic versions of Monte Carlo codes with subchannel codes make possible the analysis of transient e.g. rod ejection accidents and it paves the way for the simulation of any kind of design basis accidents as an alternative option to the use of diffusion and transport based deterministic solvers. The H2020 McSAFE Project is focused on the improvement of methods for depletion considering thermal hydraulic feedbacks, extension of the coupled neutronic/thermal hydraulic codes by the incorporation of a fuel performance solver, the development of dynamic Monte Carlo codes and the development of methods to handle large depletion problems and to reduce the statistical uncertainty. The validation of the multi-physics tools developed within McSAFE will be performed using plant data and unique tests e.g. the SPERT III E REA test. This paper will describe the main developments, solution approaches, and selected results.
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Funari, Marco Francesco, Anjali Mehrotra, and Paulo B. Lourenço. "A Tool for the Rapid Seismic Assessment of Historic Masonry Structures Based on Limit Analysis Optimisation and Rocking Dynamics." Applied Sciences 11, no. 3 (January 21, 2021): 942. http://dx.doi.org/10.3390/app11030942.
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This paper presents a user-friendly, CAD-interfaced methodology for the rapid seismic assessment of historic masonry structures. The proposed multi-level procedure consists of a two-step analysis that combines upper bound limit analysis with non-linear dynamic (rocking) analysis to solve for seismic collapse in a computationally-efficient manner. In the first step, the failure mechanisms are defined by means of parameterization of the failure surfaces. Hence, the upper bound limit theorem of the limit analysis, coupled with a heuristic solver, is subsequently adopted to search for the load multiplier’s minimum value and the macro-block geometry. In the second step, the kinematic constants defining the rocking equation of motion are automatically computed for the refined macro-block model, which can be solved for representative time-histories. The proposed methodology has been entirely integrated in the user-friendly visual programming environment offered by Rhinoceros3D + Grasshopper, allowing it to be used by students, researchers and practicing structural engineers. Unlike time-consuming advanced methods of analysis, the proposed method allows users to perform a seismic assessment of masonry buildings in a rapid and computationally-efficient manner. Such an approach is particularly useful for territorial scale vulnerability analysis (e.g., for risk assessment and mitigation historic city centres) or as post-seismic event response (when the safety and stability of a large number of buildings need to be assessed with limited resources). The capabilities of the tool are demonstrated by comparing its predictions with those arising from the literature as well as from code-based assessment methods for three case studies.
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Huang, Langwen, and David Topping. "JlBox v1.1: a Julia-based multi-phase atmospheric chemistry box model." Geoscientific Model Development 14, no. 4 (April 27, 2021): 2187–203. http://dx.doi.org/10.5194/gmd-14-2187-2021.
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Abstract. As our knowledge and understanding of atmospheric aerosol particle evolution and impact grows, designing community mechanistic models requires an ability to capture increasing chemical, physical and therefore numerical complexity. As the landscape of computing software and hardware evolves, it is important to profile the usefulness of emerging platforms in tackling this complexity. Julia is a relatively new programming language that promises computational performance close to that of Fortran, for example, without sacrificing the flexibility offered by languages such as Python. With this in mind, in this paper we present and demonstrate the initial development of a high-performance community mixed-phase atmospheric 0D box model, JlBox, written in Julia. In JlBox v1.1 we provide the option to simulate the chemical kinetics of a gas phase whilst also providing a fully coupled gas-particle model with dynamic partitioning to a fully moving sectional size distribution, in the first instance. JlBox is built around chemical mechanism files, using existing informatics software to parse chemical structures and relationships from these files and then provide parameters required for mixed-phase simulations. In this study we use mechanisms from a subset and the complete Master Chemical Mechanism (MCM). Exploiting the ability to perform automatic differentiation of Jacobian matrices within Julia, we profile the use of sparse linear solvers and pre-conditioners, whilst also using a range of stiff solvers included within the expanding ODE solver suite the Julia environment provides, including the development of an adjoint model. Case studies range from a single volatile organic compound (VOC) with 305 equations to a “full” complexity MCM mixed-phase simulation with 47 544 variables. Comparison with an existing mixed-phase model shows significant improvements in performance for multi-phase and mixed VOC simulations and potential for developments in a number of areas.
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Chen, Xiao-Peng, and Ming Liu. "Simulation of Acoustic Behavior of Bubbly Liquids with Hybrid Lattice Boltzmann and Homogeneous Equilibrium Models." Communications in Computational Physics 17, no. 4 (April 2015): 925–36. http://dx.doi.org/10.4208/cicp.2014.m283.
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AbstractHomogeneous equilibrium model (HEM) has been widely used in cavitating flow simulations. The major feature of this model is that a single equation of state (EOS) is proposed to describe the thermal behavior of bubbly liquid, where both kinematic and thermal equilibrium is assumed between two phases. In this paper, the HEM was coupled with multi-relaxation-time lattice Boltzmann model (MRT-LBM) and the acoustic behavior was simulated. Two approaches were applied alternatively: adjusting speed of sound (Buick, J. Phys. A, 2006, 39:13807-13815) and setting real gas EOS. Both approaches result in high accuracy in acoustic speed predictions for different void (gas) volume of fractions. It is demonstrated that LBM could be successfully applied as a Navier-Stokes equation solver for industrial applications. However, further dissipation and dispersion analysis shows that Shan-Chen type approaches of LBM are deficient, especially in large wave-number region.
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Tai, Chang-Hsien, Jr-Ming Miao, and Chun-Chi Li. "Numerical study of Transient Flow in a Full-Size Reflected Shock Tunnel." Journal of Mechanics 17, no. 3 (September 2001): 109–19. http://dx.doi.org/10.1017/s1727719100004470.
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ABSTRACTThe aim of this paper is to develop a CFD solver that used to simulate the transient flow phenomena in a reflected shock tunnel. The transient flow phenomena in a shock tunnel include the reflected shock/boundary layer interaction and the starting process of nozzle flow that can affect the duration of test flow in actual conditions. To numerically simulate these transient flow features, a full-size, axisymmetric reflected shock tunnel model is used. The governing equations are a full Navier-Stokes equation, a species equation and a simplified polynomial correlation to simulate the real gas effects. The numerical code is developed based on the finite volume method coupled with the upwind Roe's scheme and the total variation diminishing (TVD) method. To increase the calculation efficiency, a multi-block and multi-mesh grid generation technique is employed in a huge computational domain. The present computational results have not only confirmed the theoretical characteristics of a shock tube, but have also qualitatively presented the phenomena of reflected shock/boundary layer interaction and the starting process of nozzle flow. This numerical code is a useful tool to demonstrate the actual flow phenomena and to assist the design of experiments.
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Nakamura, Tomoaki, Norimi Mizutani, and Koji Fujima. "THREE-DIMENSIONAL NUMERICAL ANALYSIS ON DEFORMATION OF RUN-UP TSUNAMI AND TSUNAMI FORCE ACTING ON SQUARE STRUCTURES." Coastal Engineering Proceedings 1, no. 32 (January 30, 2011): 14. http://dx.doi.org/10.9753/icce.v32.currents.14.
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A three-dimensional two-way coupled fluid-sediment interaction model (FSM) is applied to investigate run-up tsunami deformation and tsunami force acting on square structures on land. The FSM consists of a generalized Navier-Stokes solver (GNS) for multi-phase flow including porous flow, a volume of fluid module (VFM) for air-water interface tracking, and a sediment transport module (STM) for fluid-sediment interface tracking. In the FSM, a two-way coupling procedure is implemented at each time step to connect the GNS with the VFM and the STM. The predictive capability of the FSM is demonstrated through comparison between numerical results and experimental data in terms of water surface elevation, inundation depth, and tsunami force. The process of tsunami run-up in the presence of square structures is investigated in terms of vortex structures. The result shows that the FSM is a useful tool providing detailed information in discussing run-up tsunami deformation and tsunami force.
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Tonini, S., M. Gavaises, C. Arcoumanis, A. Theodorakakos, and S. Kometani. "Multi-component fuel vaporization modelling and its effect on spray development in gasoline direct injection engines." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, no. 10 (October 1, 2007): 1321–42. http://dx.doi.org/10.1243/09544070jauto545.
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A multi-component fuel vaporization model has been developed and implemented into an in-house multi-phase computational fluid dynamics flow solver simulating the flow, spray, and air-fuel mixing processes taking place in gasoline direct injection (GDI) engines. Multi-component fuel properties are modelled assuming a specified composition of pure hydrocarbons. High-pressure and -temperature effects, as well as gas solubility and compressibility, are considered. Remote droplet vaporization is initially investigated in order to quantify and validate the most appropriate vaporization model for conditions relevant to those realized with GDI engines. Phenomena related to the fuel injection system and pressure-swirl atomizer flow as well as the subsequent spray development are considered using an one-dimensional fuel injection equipment model predicting the wave dynamics inside the injection system, a Eulerian volume of fluid-based two-phase flow model simulating the liquid film formation process inside the injection hole of the swirl atomizer and a Lagrangian spray model simulating the subsequent spray development, respectively. The computational results are validated against experimental data obtained in an optical engine and include laser Doppler velocimetry measurements of the charge air motion in the absence of spray injection and charge coupled device images of the fuel spray injected during the induction stroke. The results confirm that fuel composition affects the overall fuel spray vaporization rate, but not significantly relative to other flow and heat transfer processes taking place during the engine operation.
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Deshmukh, Abhishek Y., Carsten Giefer, Dominik Goeb, Maziar Khosravi, David van Bebber, and Heinz Pitsch. "A quasi-one-dimensional model for an outwardly opening poppet-type direct gas injector for internal combustion engines." International Journal of Engine Research 21, no. 8 (November 28, 2019): 1493–519. http://dx.doi.org/10.1177/1468087419871117.
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Direct injection of compressed natural gas in internal combustion engines is a promising technology to achieve high indicated thermal efficiency and, at the same time, reduce harmful exhaust gas emissions using relatively low-cost fuel. However, the design and analysis of direct injection–compressed natural gas systems are challenging due to small injector geometries and high-speed gas flows including shocks and discontinuities. The injector design typically involves either a multi-hole configuration with inwardly opening needle or an outwardly opening poppet-type valve with small geometries, which make accessing the near-nozzle-flow field difficult in experiments. Therefore, predictive simulations can be helpful in the design and development processes. Simulations of the gas injection process are, however, computationally very expensive, as gas passages of the order of micrometers combined with a high Mach number compressible gas flow result in very small simulation time steps of the order of nanoseconds, increasing the overall computational wall time. With substantial differences between in-nozzle and in-cylinder length and velocity scales, simultaneous simulation of both regions becomes computationally expensive. Therefore, in this work, a quasi-one-dimensional nozzle-flow model for an outwardly opening poppet-type injector is developed. The model is validated by comparison with high-fidelity large-eddy simulation results for different nozzle pressure ratios. The quasi-one-dimensional nozzle-flow model is dynamically coupled to a three-dimensional flow solver through source terms in the governing equations, named as dynamically coupled source model. The dynamically coupled source model is then applied to a temporal gas jet evolution case and a cold flow engine case. The results show that the dynamically coupled source model can reasonably predict the gas jet behavior in both cases. All simulations using the new model led to reductions of computational wall time by a factor of 5 or higher.
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Lin, Yu-Hsien, and Xian-Chen Li. "The Investigation of a Sliding Mesh Model for Hydrodynamic Analysis of a SUBOFF Model in Turbulent Flow Fields." Journal of Marine Science and Engineering 8, no. 10 (September 25, 2020): 744. http://dx.doi.org/10.3390/jmse8100744.
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A computational fluid dynamics (CFD)-based simulation using a finite volume code for a full-appendage DARPA (Defense Advanced Research Projects Agency) SUBOFF model was investigated with a sliding mesh model in a multi-zone fluid domain. Unsteady Reynolds Averaged Navier–Stokes (URANS) equations were coupled with a Menter’s shear stress transport (SST) k-ω turbulence closure based on the Boussinesq approximation. In order to simulate unsteady motions and capture unsteady interactions, the sliding mesh model was employed to simulate flows in the fluid domain that contains multiple moving zones. The pressure-based solver, semi-implicit method for the pressure linked equations-consistent (SIMPLEC) algorithm was employed for incompressible flows based on the predictor-corrector approach in a segregated manner. After the grid independence test, the numerical simulation was validated by comparison with the published experimental data and other numerical results. In this study, the capability of the CFD simulation with the sliding mesh model was well demonstrated to conduct the straight-line towing tests by analyzing hydrodynamic characteristics, viz. resistance, vorticity, frictional coefficients, and pressure coefficients.
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Barakos, G. N., and A. Jimenez Garcia. "CFD analysis of hover performance of rotors at full- and model-scale conditions." Aeronautical Journal 120, no. 1231 (June 13, 2016): 1386–424. http://dx.doi.org/10.1017/aer.2016.58.
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ABSTRACTAnalysis of the performance of a 1/4.71 model-scale and full-scale Sikorsky S-76 main rotor in hover is presented using the multi-block computational fluid dynamics (CFD) solver of Glasgow University. For the model-scale blade, three different tip shapes were compared for a range of collective pitch and tip Mach numbers. It was found that the anhedral tip provided the highest Figure of Merit. Rigid and elastic full-scale S-76 rotor blades were investigated using a loosely coupled CFD/Computational Structural Dynamics (CSD) method. Results showed that aeroelastic effects were more significant for high thrust cases. Finally, an acoustic study was performed in the tip-path-plane of both rotors, showing good agreement in the thickness and loading noise with the theory. For the anhedral tip of the model-scale blade, a reduction of 5% of the noise level was predicted. The overall good agreement with the theory and experimental data demonstrated the capability of the present CFD method to predict rotor flows accurately.
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Nagalakshmi, P. S. S., and N. Vijaya. "Three Dimensional Boger Nanofluid Flow Explored with Carbon Nanotubes Over a Riga Plate." Journal of Nanofluids 9, no. 2 (June 1, 2020): 114–20. http://dx.doi.org/10.1166/jon.2020.1736.
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An extensive diversity of industrial processes captivate the transfer of heat energy. An extensive task for industrial necessity throughout every industrial efficiency, heat and mass transfer taking place from one process stream to another. These processes provide a source for energy recovery and process fluid heating/cooling. In the present investigation we study the Boger nanofluid flow with carbon nanotubes over a riga plate. Borger nanofluid model is used to characterize the behavior of the fluids having activation energy (E), Solvent fraction parameter (β1), and ratio of relaxation time parameter (λ1) over a riga plate. The modeled boundary layer conservation equations are renovated to non-linear coupled ordinary differential equations by a suitable transformation. Python programming language with bvp solver was adopted to obtain numerical solutions of the resulting equations by using the Runge–Kutta method along with shooting technique. This analysis reveals many significant physical aspects of flow and heat transfer. Estimations are achieved over thermo-physical parameter with single walled carbon nanotubes (SWCNT) and multi walled carbon nanotubes (MWCNT).
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Tang, Jie, Chungang Chen, Xueshun Shen, Feng Xiao, and Xingliang Li. "A Positivity-preserving Conservative Semi-Lagrangian Multi-moment Global Transport Model on the Cubed Sphere." Advances in Atmospheric Sciences 38, no. 9 (July 22, 2021): 1460–73. http://dx.doi.org/10.1007/s00376-021-0393-7.
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AbstractA positivity-preserving conservative semi-Lagrangian transport model by multi-moment finite volume method has been developed on the cubed-sphere grid. Two kinds of moments (i.e., point values (PV moment) at cell interfaces and volume integrated average (VIA moment) value) are defined within a single cell. The PV moment is updated by a conventional semi-Lagrangian method, while the VIA moment is cast by the flux form formulation to assure the exact numerical conservation. Different from the spatial approximation used in the CSL2 (conservative semi-Lagrangian scheme with second order polynomial function) scheme, a monotonic rational function which can effectively remove non-physical oscillations is reconstructed within a single cell by the PV moments and VIA moment. To achieve exactly positive-definite preserving, two kinds of corrections are made on the original conservative semi-Lagrangian with rational function (CSLR) scheme. The resulting scheme is inherently conservative, non-negative, and allows a Courant number larger than one. Moreover, the spatial reconstruction can be performed within a single cell, which is very efficient and economical for practical implementation. In addition, a dimension-splitting approach coupled with multi-moment finite volume scheme is adopted on cubed-sphere geometry, which benefitsthe implementation of the 1D CSLR solver with large Courant number. The proposed model is evaluated by several widely used benchmark tests on cubed-sphere geometry. Numerical results show that the proposed transport model can effectively remove nonphysical oscillations and preserve the numerical non-negativity, and it has the potential to transport the tracers accurately in a real atmospheric model.
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Wick, Markus, Matthias Jüttner, and Wolfgang M. Rucker. "Harmonic balanced Jiles-Atherton hysteresis implementation for finite element simulation." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 36, no. 5 (September 4, 2017): 1386–95. http://dx.doi.org/10.1108/compel-02-2017-0098.
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Purpose The high calculation effort for accurate material loss simulation prevents its observation in most magnetic devices. This paper aims at reducing this effort for time periodic applications and so for the steady state of such devices. Design/methodology/approach The vectorized Jiles-Atherton hysteresis model is chosen for the accurate material losses calculation. It is transformed in the frequency domain and coupled with a harmonic balanced finite element solver. The beneficial Jacobian matrix of the material model in the frequency domain is assembled based on Fourier transforms of the Jacobian matrix in the time domain. A three-phase transformer is simulated to verify this method and to examine the multi-harmonic coupling. Findings A fast method to calculate the linearization of non-trivial material models in the frequency domain is shown. The inter-harmonic coupling is moderate, and so, a separated harmonic balanced solver is favored. The additional calculation effort compared to a saturation material model without losses is low. The overall calculation time is much lower than a time-dependent simulation. Research limitations/implications A moderate working point is chosen, so highly saturated materials may lead to a worse coupling. A single material model is evaluated. Researchers are encouraged to evaluate the suggested method on different material models. Frequency domain approaches should be in favor for all kinds of periodic steady-state applications. Practical implications Because of the reduced calculation effort, the simulation of accurate material losses becomes reasonable. This leads to a more accurate development of magnetic devices. Originality/value This paper proposes a new efficient method to calculate complex material models like the Jiles-Atherton hysteresis and their Jacobian matrices in the frequency domain.