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Numerical investigation of packed granular beds subjected to thermal cycling with application to thermal energy storage systems: a continuous approach

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GRANULAR MATTER 2024年第4期26卷 86页

作者： Iliev, Pavel Bulgarian Acad Sci Inst Mech Acad G Bontchev Sofia 1113 Bulgaria

Thermal energy storage (TES) systems have been proven in their capacity as a crucial component of energy grids relying on renewable sources. An established sensible heat storage technology is a packed-bed TES, employing a granular filling material as a heat storage medium, which is subjected to repeated heating-cooling cycles. As a result of the recurring particle expansion and contraction, excessive stresses and strains can develop and cause material damage. This leads to the increasing need for reliable numerical tools in order to improve the TES design and increase their durability. For this purpose, we propose a continuous thermo-mechanical approach, within the framework of the theory of hypoplasticity, that can accurately predict the single as well as cyclic loading behavior of the filling material. This work focuses on the stress-strain relations and compaction mechanisms of the granular bed in contact with a storage wall with variable inclination and friction coefficient. Furthermore, the important aspect of the wall expansion under the temperature change is also taken into account as well as the specific case when the wall expands more than the granular material. By conducting comprehensive simulations, we demonstrate that our novel numerical model adheres to existing experimental investigations and mitigates shortcomings in the predictive capabilities of previous continuous approaches.

关键词： Thermal energy storage continuous modeling Hypoplasticity Thermal loading

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Coupling Geomechanical and Gravity Flow Models to Obtain More Representative Flow Simulations and Air-Gap Risk Identification in Caving Mining

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INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS 2025年第1期49卷 376-390页

作者： Castro, Raul Oyarzo, Diego Gomez, Rene Suzuki, Kimie Cifuentes, Miguel Univ Chile Dept Min Engn Santiago Chile Adv Min Technol Ctr Santiago Chile Univ Concepcion Fac Engn Concepcion Chile

The extraction and propagation of caving are complex phenomena involving the breaking of the rock mass, the formation of a column of broken material, and the extraction from the column base. Geomechanical modeling in cave mining commonly uses approaches to model the rock mass as a continuous material, while discontinuous modeling is frequently used for the column of broken material. However, it remains complex to include all mechanisms in a single model. Therefore, to achieve a better representation of ore breakage and extraction in caving mining, this work couples FLAC3D, a continuous finite volume tool, with FlowSim, a discrete tool based on cellular automata, to determine the air gap volume. The methodology first defines the height of caving propagation and the cave back with a tool that models solid rock mass in a continuous manner, which are used to constrain the cellular automata tool that simulates the flow of broken material. The results show that unidirectional FLAC3D-FlowSim coupling reproduces the generation of cave backs and air gaps in the propagation of caving, rendering the methodology valuable for preliminary estimation of air volumes over fragmented material and the generation of supportive data to control the caving process.

关键词： air-blast caving cellular automata continuous modeling discrete modeling gravity flow

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Vibration analysis of FGM anisogrid lattice plates with one width fold based on the continuous model using the GDQE method

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THIN-WALLED STRUCTURES 2024年 195卷

作者： Luo, Jijun Peng, Shengguang Hou, Suxia Kiani, Yaser Xijing Univ Shaanxi Engn Res Ctr Controllable Neutron Source Sch Elect Informat Xian 710123 Shaanxi Peoples R China Pingxiang Univ Sch Engn & Management Pingxiang 337055 Jiangxi Peoples R China Shahrekord Univ Fac Engn Shahrekord Iran

This research tests the idea of folding on the free vibration response of anisogrid lattice plates. It is assumed that the oblique and straight ribs with functionally graded materials (FGMs) construct the lattice plate. The stiffness and mass of the whole plate are computed by employing the global continuous model based on the shear deformable orthotropic plates. Then a width fold is created in the plate to check its effect on improving the system's natural frequencies. An element-based 2D generalized differential quadrature method recently developed solves this problem. This method divides the physical domain into simple domains (patching) and distributes a series of nodes on each patch (quadrature scheme). The motion equations of each patch are derived using Hamilton's principle. Next, the displacement and stress resultant continuity conditions are satisfied between common nodes. After that, the obtained global equations are solved, and the natural frequencies of such structures are calculated. After validating the response with the available literature, the influence of composite characteristics and geometry on the folded FGM lattice plate is distinguished.

关键词： FGM lattice Folded plate GDQE method continuous modeling Global equivalent stiffness

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continuous Riemannian Geometric Learning for Sleep Staging Classification 10

Continuous Riemannian Geometric Learning for Sleep Staging C...

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10th International Winter Conference on Brain-Computer Interface (BCI)

作者： Jeong, Seungwoo Ko, Wonjun Mulyadi, AhmadWisnu Suk, Heung-Il Korea Univ Dept Artificial Intelligence Seoul 02841 South Korea Korea Univ Dept Brain & Cognit Engn Seoul 02841 South Korea

ISBN: (纸本)9781665413374

Sleep staging classification has recently received a lot of attention because of its importance and has shown remarkable achievements through deep neural models, but lacks consideration of geometrical structure or continuous time. In this paper, we propose to exploit a diffeomorphism mapping between Riemannian manifolds and a Cholesky space. Further, in order for continuous modeling, we devise a continuous manifold learning method by integrating a manifold ordinary differential equation and a gated recurrent neural network. We demonstrate the validity of our proposed method through experiments using a publicly available SleepEDF-20 dataset.

关键词： Sleep staging classification Deep neural network Manifold learning continuous modeling

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Multi-site hydrometeorological simulation of streamflow for upper Jhelum basin in northwest Himalayas using HEC-HMS soil moisture accounting algorithm

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modeling EARTH SYSTEMS AND ENVIRONMENT 2023年第1期9卷 431-455页

作者： Naqash, Taroob Bashir Ahanger, Manzoor Ahmad Maity, Rajib Natl Inst Technol Srinagar Dept Civil Engn Srinagar 190006 Jammu & Kashmir India Indian Inst Technol Kharagpur Dept Civil Engn Kharagpur 721302 W Bengal India

Hydrometeorological influence on run-off is a process-driven mechanism in basin hydrology that needs to be captured for a reliable assessment of the basin-scale hydrological responses in the context of climate change. In this study, one of such process-based model, the Hydrologic Engineering Center-Hydrologic modeling System model is used to simulate multi-site streamflow in the upper Jhelum basin, northwest Himalayas, India. The soil moisture accounting algorithm was used to calibrate and validate the model for continuous simulation on a monthly timescale at three gauging stations Ram Munshi Bhag, Sangam, and Rambiara. The model was calibrated for a period of 12 years (2003-2014) and validated for 5 years (2015-2019). Observed and simulated streamflow values during the calibration period were found to be in good agreement with R-2 ranging from 0.783 to 0.808, NSE from 0.753 to 0.793, and P.B from 2.7 to 5.1%. Similar performance was obtained during the validation period also with R-2 ranging from 0.80 to 0.83, NSE from 0.70 to 0.80, and PB from 2 to 6.8%. The sensitivity analysis of the model was performed using one-at-a-time analysis method. This helps to rank the parameter according to their sensitivities towards the model performance in simulating run-off volume. Soil storage, soil tension storage, and soil percolation were found to be the most sensitive parameters while groundwater-2 coefficient storage, and percolation were the least sensitive parameters in the basin. The overall model performance was reasonably good, and can be further used for rainfall-run-off simulation in the upper Jhelum basin for the climate change impact related studies in future.

关键词： Calibration continuous modeling HEC-HMS model Sensitivity analysis SMA Validation

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An evidence for enhancing the design hydrograph estimation for small and ungauged basins in Ethiopia

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JOURNAL OF HYDROLOGY-REGIONAL STUDIES 2022年 42卷

作者： Ayalew, Dessalegn Worku Petroselli, Andrea De Luca, Davide Luciano Grimaldi, Salvatore Woldia Univ Coll Agr Dept Soil Resources & Watershed Management Amhara Ethiopia Tuscia Univ Dept Econ Engn Soc & Business Org DEIM I-01100 Viterbo Italy Univ Calabria Dept Informat Modelling Elect & Syst Engn I-87036 Arcavacata di Rende Italy Tuscia Univ Dept Innovat Biol Agrofood & Forest Syst DIBAF I-01100 Viterbo Italy

Study region: Ethiopia and Upper Blue Nile *** focus: Estimating design hydrograph characteristics (e.g. flood peak discharge, volume and duration) is a crucial topic in hydrology and this is particularly challenging in data scarce regions. In recent years, significant innovations in hydrological modeling were introduced, allowing for more advanced analyses also in ungauged areas, in doing so limiting the application of empirical approaches (e.g. the rational formula). In the present work we summarize the current practice in Ethiopia and explore the possibility to apply a simplified continuous modeling for estimating design *** hydrological insights for the region: This study supports the conclusion that COSMO4SUB (continuous Simulation Model for Small and Ungauged Basins) framework, a simplified continuous rainfall-runoff model specifically tailored for small and ungauged basins, can be applied in Ethiopia. Indeed, the minimal information available in the country are sufficient for applying such modeling approach, that can provide useful outputs for a variety of practical hydrological studies.

关键词： Small and ungauged basins continuous modeling Event-based approach Design hydrographs Design simulation

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continuous KAOS, ASM, and formal control system design across the continuous/discrete modeling interface: a simple train stopping application

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FORMAL ASPECTS OF COMPUTING 2014年第2期26卷 319-366页

作者： Banach, Richard Zhu, Huibiao Su, Wen Huang, Runlei Univ Manchester Sch Comp Sci Manchester M13 9PL Lancs England E China Normal Univ Inst Software Engn Shanghai 200062 Peoples R China Alcatel Lucent Shanghai Bell Shanghai 201206 Peoples R China

A very simple model for train stopping is used as a vehicle for investigating how the development of a control system, initially designed in the continuous domain and subsequently discretized, can be captured within a formal development process compatible with standard model based refinement methodologies. Starting with a formalized requirements analysis using KAOS, an abstract model of the continuous system is created in the ASM formalism. This requires extensions of the KAOS and ASM formalisms, capable of dealing with quantities evolving continuously over real time, which are developed. After considering how the continuous system, described as a continuous control system in the state space framework, can be discretized, a discrete control system is created in the state space framework. This is re-expressed in the ASM formalism. The rigorous results on the relationship between continuous and discrete control system models that are needed to establish provable properties of the discretization, then become the ingredients of a retrenchment between continuous and discrete ASM models, and are thus fully integrated into the formal development. The discrete ASM model can then be further refined towards implementation.

关键词： continuous KAOS continuous ASM Control systems Rigorous design Refinement Retrenchment continuous modeling Discrete modeling Train control

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modeling and nonlinear dynamics of thermomechanically coupled composite plates

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2020年 187卷 106106-106106页

作者： Rega, Giuseppe Saetta, Eduardo Settimi, Valeria Sapienza Univ Rome Dept Struct & Geotech Engn Rome Italy

An overview of extended research recently pursued on unified continuous/reduced-order modeling and nonlinear dynamics of thermomechanical composite plates of interest in aerospace, mechanical and civil engineering is presented. Reduced models exhibit the fundamental features of geometrical nonlinearity and thermomechanical coupling of the underlying continua. The role of multiphysics coupling and the main features of nonlinear response obtained with variably refined minimal models is highlighted. Besides transverse mechanical excitation and mechanically or thermally-induced buckling, a variety of active thermal excitations, of body or boundary nature, are considered. Features of thermal response obtained with variably refined thermal assumptions are compared, in view of detecting cheap, yet reliable, models to be used for systematic numerical investigations. The effects of two-way thermomechanical coupling on local and global nonlinear dynamics are addressed through bifurcation diagrams, phase portraits and planar cross sections of 4D basins of attraction, highlighting the important role played by the slow transient thermal dynamics solely detectable with coupled models in the steady outcome of the swifter mechanical response. Conditions allowing to utilize partially coupled models or even the uncoupled mechanical one with prescribed steady temperature are discussed.

关键词： Unified thermomechanical formulation Composite plates continuous modeling Reduced order models Local and global nonlinear dynamics Thermomechanical response Two-/one-way coupling

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Pipedream: An interactive digital twin model for natural and urban drainage systems

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ENVIRONMENTAL MODELLING & SOFTWARE 2021年 144卷 105120-105120页

作者： Bartos, Matthew Kerkez, Branko Univ Texas Austin Dept Civil Architectural & Environm Engn Austin TX 78712 USA Univ Michigan Dept Civil & Environm Engn Ann Arbor MI 48109 USA

Faced with persistent flooding and water quality challenges, water managers are now seeking to build digital twins of surface water systems that combine sensor data with online models to better understand and control system dynamics. Towards this goal, this study presents pipedream-an end-to-end simulation engine for realtime modeling and state estimation in natural/urban drainage networks. The engine combines (i) a new hydraulic solver based on the one-dimensional Saint-Venant equations and (ii) a Kalman filtering scheme that efficiently updates hydraulic states based on observed data. Using sensor data from a real-world watershed, we find that the simulation engine is effective at both interpolating hydraulic states and forecasting future states based on current measurements. By providing a complete, real-time view of system hydraulics, our software will enable rapid detection of flooding, improved characterization of maintenance and remediation needs, and robust real-time control for both small-scale (stormwater) and large-scale (river/reservoir) networks.

关键词： Hydraulic modeling Data assimilation Storm water Kalman filtering continuous modeling Real-time sensing and control

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Understanding the Role of Interfaces for Water Management in Platinum Group Metal-Free Electrodes in Polymer Electrolyte Fuel Cells

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ACS APPLIED ENERGY MATERIALS 2019年第5期2卷 3542-3553页

作者： Liu, Jiangjin Talarposhti, Morteza Rezaei Asset, Tristan Sabarirajan, Dinesh C. Parkinson, Dilworth Y. Atanassov, Plamen Zenyuk, Iryna V. Tufts Univ Dept Mech Engn Medford MA 02155 USA Univ Calif Irvine Natl Fuel Cell Res Ctr Irvine CA 92697 USA Univ Calif Irvine Dept Chem & Biomol Engn Irvine CA 92697 USA Lawrence Berkeley Natl Lab Adv Light Source Berkeley CA 94720 USA

A systematic analysis, both experimental and model-assisted, has been performed over three main configurations of platinum group metal-free (PGM-free) electrodes in polymer electrolyte fuel cells (PEFCs): catalyst-coated membrane CCM technology is being compared to the gas-diffusion electrode (GDE) method of electrode fabrication and juxtaposed to a hybrid/combined GDE-CCM method of membrane-electrode assembly (MEA) fabrication. The corresponding electrodes were evaluated for their electrochemical performance, modeled, and studied with in situ and operando X-ray computed tomography (X-ray CT). The study establishes that through-thickness inhomogeneities play the most important role in water withdrawal/water management and affect most significantly PGM-free PEFC performance. The catalyst integration technique results in formation of interfacial regions with increased porosity and surface roughness. These regions form critical interfaces de facto responsible for flooding type behavior of the PEFC as shown for a first time by operando X-ray CT. The computational model shows that the PEFC performance critically depends on liquid water formation and transport at cold and wet conditions.

关键词： platinum group metal-free catalyst layers gas-diffusion electrodes catalysts-coated membranes hybrid membrane-electrode assembly in situ and operando X-ray CT water management continuous modeling

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