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Active learning graph neural networks for partial charge prediction of metal-organic frameworks via dropout Monte Carlo

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npj Computational Materials 2024年第1期10卷 2360-2369页

作者： Stephan Thaler Felix Mayr Siby Thomas Alessio Gagliardi Julija Zavadlav Professorship of Multiscale Modeling of Fluid Materials Department of Engineering Physics and ComputationTUM School of Engineering and DesignTechnical University of MunichMunichGermany Valence Labs MontrealQCCanada Professorship of Simulation of Nanosystems for Energy Conversion Department of Electrical EngineeringTUM School of ComputationInformation and TechnologyTechnical University of MunichMunichGermany Munich Data Science Institute Technical University of MunichMunichGermany

Metal-organic frameworks(MOF)are an attractive class of porous materials due to their immense design space,allowing for application-tailored *** of interest,such as gas sorption,can be predicted in silico with molecular mechanics ***,the accuracy is limited by the available empirical force field and partial charge estimation *** this work,we train a graph neural network for partial charge prediction via active learning based on Dropout Monte *** show that active learning significantly reduces the required amount of labeled MOFs to reach a target *** obtained model generalizes well to different distributions of MOFs and *** addition,the uncertainty predictions of Dropout Monte Carlo enable reliable estimation of the mean absolute error for unseen *** work paves the way towards accurate molecular modeling of MOFs via next-generation potentials with machine learning predicted partial charges,supporting insilico material design.

关键词： properties charge estimation

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To bend or not to bend: Impact on heat pipe performance

To bend or not to bend: Impact on heat pipe performance

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International Workshop on Thermal Investigation of ICs and Systems (THERMINIC)

作者： Wessel W. Wits Rick Groot Davoud Jafari Multiscale Modeling and Simulation University of Twente Enschede The Netherlands Faculty of Engineering Technology University of Twente Enschede The Netherlands

Thermal management of electronics continues to be a dominant factor that needs attention already early in the design phase. Within complex systems, typically a battle for space is imminent due to the multidisciplinary nature. In this respect, the use of low-form-factor phase-transitional devices is standard industry practice nowadays. In particular, heat pipes have demonstrated high heat transfer rates, due to the utilization of a working fluid’s latent heat in combination with reliable, small and lightweight designs. Heat pipes are employed in electronics cooling in which they are often bent and operated under different perating conditions. This study aims to investigate how heat pipes function when bent at various angles and inclinations. The impact of various bending angles (no bend, 30° bend, 2x30° bend, 45° bend, 2x45° bend and 90° bend) and inclination angles (horizontal, ±45° and ±90°) is examined. Bending losses and an associated theoretical model are validated for sintered-wick heat pipes. Heat pipe bending has minimal effect on the thermal performance as long as the bending angle does not exceed 45°. It is however important to consider gravity when operating bent heat pipes outside the horizontal plane.

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Continuous data assimilation closure for modeling statistically steady turbulence in large-eddy simulation

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Physical Review Fluids 2025年第1期10卷 013801-013801页

作者： Sagy R. Ephrati Arnout Franken Erwin Luesink Paolo Cifani Bernard J. Geurts Department of Mathematical Sciences Chalmers University of Technology and University of Gothenburg 412 96 Gothenburg Sweden Mathematics of Multiscale Modeling and Simulation Faculty EEMCS University of Twente 7500 AE Enschede The Netherlands Multiscale Energy Physics CCER Faculty Applied Physics Eindhoven University of Technology 5600 MB Eindhoven The Netherlands

A closure model is presented for large-eddy simulation (LES) based on the three-dimensional variational data assimilation algorithm. The approach aims at reconstructing high-fidelity kinetic energy spectra in coarse numerical simulations by including feedback control to represent unresolved dynamics interactions in the flow as stochastic processes. The forcing uses statistics obtained from offline high-fidelity data and requires only a few parameters compared to the number of degrees of freedom of LES. This modeling strategy is applied to geostrophic turbulence on the sphere and enables simulating indefinitely at reduced cost. The method accurately recovers the energy spectra and the zonal velocity profiles in the coarse model for three generic situations.

关键词： Large eddy simulation

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Data-driven spectral turbulence modeling for Rayleigh-Bénard convection

arXiv

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arXiv 2023年

作者： Ephrati, Sagy R. Cifani, Paolo Geurts, Bernard J. Mathematics of Multiscale Modeling and Simulation Faculty EEMCS University of Twente Enschede7500 AE Netherlands Multiscale Energy Physics CCER Faculty Applied Physics Eindhoven University of Technology Eindhoven5600 MB Netherlands

A data-driven turbulence model for coarse-grained numerical simulations of two-dimensional Rayleigh-Bénard convection is proposed. The model starts from high-fidelity data and is based on adjusting the Fourier coefficients of the numerical solution, with the aim of accurately reproducing the kinetic energy spectra as seen in the high-fidelity reference findings. No assumptions about the underlying PDE or numerical discretization are used in the formulation of the model. We also develop a constraint on the heat flux to guarantee accurate Nusselt number estimates on coarse computational grids and high Rayleigh numbers. Model performance is assessed in coarse numerical simulations at Ra = 1010. We focus on key features including kinetic energy spectra, wall-normal flow statistics, and global flow statistics. The method of data-driven modeling of flow dynamics is found to reproduce the reference kinetic energy spectra well across all scales and yields good results for flow statistics and average heat transfer, leading to computationally cheap surrogate models. Large-scale forcing extracted from the high-fidelity simulation leads to accurate Nusselt number predictions across two decades of Rayleigh numbers, centered around the targeted reference at Ra = 1010MSC Codes 37M05, 37N10, 76F35, 76F55, 76F65 Copyright © 2023, The Authors. All rights reserved.

关键词： Heat flux

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A conservative cell-based unsplit Volume of Fluid advection scheme for three-dimensional atomization simulations 15

A conservative cell-based unsplit Volume of Fluid advection ...

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15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Fröde, Fabian Grenga, Temistocle Le Chenadec, Vincent Bode, Mathis Pitsch, Heinz Institute for Combustion Technology RWTH Aachen University Aachen Germany Multiscale Modeling and Simulation Laboratory Gustave Eiffel University Champs-sur-Marne France

The Volume of Fluid (VoF) method is widely used for capturing the interface motion in multiphase flow simulations. In particular, unsplit geometrical advection schemes have proved well-suited for flows with complex topologies. In the cell-based approach, the computational cell is followed along its Lagrangian trajectories and provides a conceptually simple framework for advancing the interface. Thus, this is a semi-Lagrangian method, and enforcing conservation is difficult. This paper presents a cell-based three-dimensional (3D) unsplit advection scheme that is conservative. The method relies on the Hybrid Lagrangian Eulerian Method (HyLEM) of Le Chenadec and Pitsch [3] but additionally ensures discrete conservation by introducing a correction of the projected cell, which is inspired by the 3D flux-based method of Owkes and Desjardins [14] and the two-dimensional cell-based method of Comminal et al. [4]. While the projected cell vertices are evaluated as in HyLEM, additional vertices are introduced to modify the projected cell faces. The positions of those are obtained from conservative flux volumes. The proposed method provides the same accuracy as the method of Owkes and Desjardins [14], but is more efficient. The proposed method is tested in various benchmark cases and applied in an atomization case. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Advection

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Analysis and Experimental Validation of a Pumped Two-Phase Loop for Multi-Component Cooling

SSRN

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SSRN 2023年

作者： Middelhuis, Myron Rojo, Miguel Muñoz Wits, Wessel Thermal and Fluid Engineering University of Twente Enschede7500 AE Netherlands Madrid Spain Mathematics of Multiscale Modeling and Simulation University of Twente Enschede7500 AE Netherlands

Miniaturization and enhanced performance of microchips have resulted in powerful electronic devices with high heat flux components. For these advanced electronic devices, the current heat transfer method of single-phase forced convection is reaching its thermal limit and more effective cooling solutions are needed. A pumped two-phase loop, in which a pump circulates a working fluid that evaporates to absorb heat, may offer a solution. In this paper, the cooling performance of a pumped two-phase loop is discussed and validated. A numerical tool has been developed to aid in designing a fit-for-purpose pumped two-phase loop and to predict its behaviour to changing system parameters and heat inputs. Results from the numerical model are compared with temperature, pressure and flow velocity measurements obtained from a prototype setup. Model predictions correspond well to the measured performances and findings regarding two-phase boiling behaviour are presented. The effects of applying varying heat loads on both a single evaporator and on multiple evaporators simultaneously either in series or in parallel have been investigated. The model is particularly useful for the rapid assessment of the layout of a pumped two-phase loop for high heat flux electronics cooling. © 2023, The Authors. All rights reserved.

关键词： Electronic cooling

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Data-driven stochastic spectral modeling for coarsening of the two-dimensional Euler equations on the sphere

arXiv

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arXiv 2023年

作者： Ephrati, Sagy R. Cifani, Paolo Viviani, Milo Geurts, Bernard J. Mathematics of Multiscale Modeling and Simulation Faculty EEMCS University of Twente Enschede7500 AE Netherlands Scuola Normale Superiore di Pisa Pisa Italy Multiscale Energy Physics CCER Faculty Applied Physics Eindhoven University of Technology Eindhoven5600 MB Netherlands

A resolution-independent data-driven stochastic parametrization method for subgrid-scale processes in coarsened fluid descriptions is proposed. The method enables the inclusion of high-fidelity data into the coarsened flow model, thereby enabling accurate simulations also with the coarser representation. The small-scale parametrization is introduced at the level of the Fourier coefficients of the coarsened numerical solution. It is designed to reproduce the kinetic energy spectra observed in high-fidelity data of the same system. The approach is based on a control feedback term reminiscent of continuous data assimilation. The method relies solely on the availability of high-fidelity data from a statistically steady state. No assumptions are made regarding the adopted discretization method or the selected coarser resolution. The performance of the method is assessed for the two-dimensional Euler equations on the sphere. Applying the method at two significantly coarser resolutions yields good results for the mean and variance of the Fourier coefficients. Stable and accurate large-scale dynamics can be simulated over long integration *** Codes 86-08, 76B99, 37M05 Copyright © 2023, The Authors. All rights reserved.

关键词： Stochastic systems

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A continuous data assimilation closure for modeling statistically steady turbulence in large-eddy simulation

arXiv

引用

arXiv 2023年

作者： Ephrati, Sagy R. Franken, Arnout Luesink, Erwin Cifani, Paolo Geurts, Bernard J. Department of Mathematical Sciences Chalmers University of Technology University of Gothenburg Gothenburg412 96 Sweden Mathematics of Multiscale Modeling and Simulation Faculty EEMCS University of Twente Enschede7500 AE Netherlands Multiscale Energy Physics CCER Faculty Applied Physics Eindhoven University of Technology Eindhoven5600 MB Netherlands

A closure model is presented for large-eddy simulation (LES) based on the three-dimensional variational data assimilation algorithm. The approach aims at reconstructing high-fidelity kinetic energy spectra in coarse numerical simulations by including feedback control to represent unresolved dynamics interactions in the flow as stochastic processes. The forcing uses statistics obtained from offline high-fidelity data and requires only few parameters compared to the number of degrees of freedom of LES. This modeling strategy is applied to geostrophic turbulence on the sphere and enables simulating indefinitely at reduced costs. It proves to accurately recover the energy spectra and the zonal velocity profiles in the coarse model, for three generic *** Codes 76F65, 76U60, 65P99 Copyright © 2023, The Authors. All rights reserved.

关键词： Large eddy simulation

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Approximate Deconvolution Discretisation

SSRN

引用

SSRN 2023年

作者： Boguslawski, Andrzej Tyliszczak, Artur Geurts, B.J. Czestochowa University of Technology Poland Mathematics of Multiscale Modeling and Simulation Faculty EEMCS University of Twente PO Box 217 Enschede7500 AE Netherlands Multiscale Physics of Energy Systems Center for Computational Energy Research Faculty of Applied Physics Eindhoven University of Technology PO Box 513 Eindhoven5600 MB Netherlands

A new strategy is presented for the construction of high-order spatial discretisations extracted from a lower-order basic discretisation. The key consideration is that any discretisation of a derivative can be associated with exact differentiation of a `filtered' solution. By approximately inverting the numerically implied filter of the basic discretisation an augmented high-order method can be obtained. This construction is illustrated for finite difference (FD) discretisation schemes, solving partial differential equations in fluid mechanics. Knowing the implied filter of the basic discretisation, one can arrive at a corresponding much higher order method by (approximately) eliminating the implied spatial filter. We use deconvolution to compensate for the implied filter. This corresponds to a `sharpening' of numerical solution features before the application of the basic FD method. The combination will be referred to as Approximate Deconvolution Discretisation (ADD). The accuracy of the deconvolved FD scheme depends on the order of approximation of the inverse filter. We present the `sharpening' of several well-known FD operators for first- and second-order derivatives and quantify the achieved accuracy in terms of the modified wavenumber spectrum. Examples include high-order extensions up to new schemes with spectral accuracy. The practicality of the deconvolved FD schemes is illustrated by showing that ADD yields spectral accuracy for the Burgers equation and for double-jet flow of an incompressible fluid. © 2023, The Authors. All rights reserved.

关键词： Computational fluid dynamics

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Deconvolution of induced spatial discretization filters subgrid modeling in LES: application to two-dimensional turbulence 10

Deconvolution of induced spatial discretization filters subg...

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10th International Conference on Mathematical modeling in Physical Sciences, IC-MSQUARE 2021

作者： Boguslawski, A. Wawrzak, K. Paluszewska, A. Geurts, B.J. Czestochowa University of Technology al. Armii Krajowej 21 Czestochowa42-201 Poland Multiscale Modeling and Simulation Applied Mathematics University of Twente P.O. Box 217 Enschede7500 AE Netherlands

The paper presents a new approximate deconvolution subgrid model for Large Eddy simulation in which corrections to implicit filtering due to spatial discretization are integrated explicitly. The top-hat filter implied by second-order central finite differencing is a key example, which is discretised using the discrete Fourier transform involving all the mesh points in the computational domain. This discrete filter kernel is inverted by inverse Wiener filtering. The inverse filter obtained in this way is used to deconvolve the resolved scales of the implicitly filtered velocity field on the computational grid. Subgrid stresses are subsequently calculated directly from the deconvolved velocity field. The model was applied to study decaying two-dimensional turbulence. Results were compared with predictions based on the Smagorinsky model and the dynamic Germano model. A posteriori testing in which Large Eddy simulation is compared with filtered Direct Numerical simulation obtained with a Fourier spectral method is included. The new model presented strictly speaking applies to periodic problems. The idea of recovering a high-order inversion of the numerically induced filter kernel can be extended to more general non-periodic problems, also in three spatial dimensions. © 2021 Institute of Physics Publishing. All rights reserved.

关键词： Large eddy simulation

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