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A comparative study on design standards of screw conveyors in China,Germany,and the USA–Part II:Discrete element method

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Particuology 2024年第9期92卷 113-125页

作者： Yuan Tan Michael Rackl Weijie Yang Johannes Fottner Wenjun Meng Stephan Kessler Technical University of Munich Chair for Materials HandlingMaterial FlowLogisticsGarchingGermany Ibracon–Ingenieurbüro Dr.-Ing.Rackl ZornedingGermany School of Mechanical Engineering Taiyuan University of Science and TechnologyTaiyuanChina

This part of the study aims to evaluate the advantages and disadvantages of technical standards of screw conveyors in China,Germany,and the USA for industrial *** source or determination method of empirical coefficients as well as the theoretical foundation of dimensioning-relevant diagrams in these standards is not explicitly documented in the ***,instead of less efficient on-site tests,the numerical simulation by discrete element method is *** on the geometrical and operational designs determined in three standards for horizontal,slightly inclined,and vertical conveyance of three representative bulk solids(barley,lignite,and sand),the potential influencing factors are *** constant particle and contact parameters,the potential deviations caused by particle models are ***,the accuracy of power consumption calculation of each standard and the divergence between accessible and required mass flows is comprehensively assessed based on the analysis of simulated *** main conclusions are drawn:(1)Particle fall back is barely considered by all three standards and leads to overestimated mass throughput;(2)The decrease in mass throughput caused by an increasing degree of filling can be compensated by slowing down the rotational speed.

关键词： Discrete element method Design standard Screw conveyor Screw auger Bulk solid

Fourier Collocation and Reduced Basis Methods for Fast Modeling of Compressible Flows

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Communications in Computational Physics 2022年第8期32卷 595-637页

作者： Jian Yu Deep Ray Jan S.Hesthaven School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China Laboratory of Aero-thermal Protection Technology for Aerospace Vehicles China Aerospace Science and Technology CorporationBeijing 100048China School of Aerospace and Mechanical Engineering University of Southern CaliforniaLos AngelesCA 90089USA chair of computationalmathematics and simulation schience Ecole Polytechnique Federale de LausanneLausanne CH-1015Switzerland

A projection-based reduced order model(ROM)based on the Fourier collocation method is proposed for compressible *** incorporation of localized artificial viscosity model and filtering is pursued to enhance the robustness and accuracy of the ROM for shock-dominated ***,for Euler systems,ROMs built on the conservative and the skew-symmetric forms of the governing equation are *** ensure efficiency,the discrete empirical interpolation method(DEIM)is *** alternative reduction approach,exploring the sparsity of viscosity is also investigated for the viscous terms.A number of one-and two-dimensional benchmark cases are considered to test the performance of the proposed *** show that stable computations for shock-dominated cases can be achieved with ROMs built on both the conservative and the skew-symmetric forms without additional stabilization components other than the viscosity model and *** the same parameters,the skew-symmetric form shows better robustness and accuracy than its conservative counterpart,while the conservative form is superior in terms of efficiency.

关键词： Projection-based reduced order modeling Fourier collocation artificial viscosity compressible flow

Flexible high-rise apartments with sparse wall-frame structure:A data-driven computational approach

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Frontiers of Architectural Research 2024年第3期13卷 639-649页

作者： Hao Hua Ludger Hovestadt Qian Wang School of Architecture Southeast UniversityNanjing 210096China chair of Digital Architectonics ETH ZürichZürich 8093Switzerland Shanghai Huihuajia Software Technology Co. Ltd.Shanghai 200082China

Flexible housing resolves the fundamental conflicts between the long-standing structure and the evolving *** propose a computational method of optimizing the structural layout of high-rise residential *** high-rise apartment buildings have widely employed shear wall-frame structure in which one big room or multiple small rooms could occupy the same *** multiple floor plans into a fixed sparse scheme of shear walls and columns is *** developed a computational framework to seek flexible structural schemes.A building scheme consists of a circulation core,shear walls,columns,and *** computer program automatically adapts floor plans to any drawn or generated *** on a large dataset of apartment layouts,the number of apartments that fit into a building scheme statistically reflects the flexibility of the *** many hypothetical plans can fit into a wallframe structure in computer simulation,this structure could probably support several generations of unknown *** a data-driven computational method provides the possibility of creating a one-to-many mapping between permanent structure and evolving apartment plans.

关键词： Flexible housing High-rise apartment Data driven Computational design Wall-frame structure

Uplifting the complexity of analysis for probabilistic security of electricity supply assessments using artificial neural networks

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Energy and AI 2024年第3期17卷 313-326页

作者： Justin Münch Jan Priesmann Marius Reich Marius Tillmanns Aaron Praktiknjo Mario Adam University of Applied Sciences Duesseldorf Centre of Innovative Energy SystemsMuensterstr.15640476 DuesseldorfGermany RWTH Aachen University E.ON Energy Research CenterChair for Energy System Economics(FCN-ESE)Mathieustrasse 1052074 AachenGermany

The energy sector faces rapid decarbonisation and decision-makers demand reliable assessments of the security of electricity supply. For this, detailed simulation models with a high temporal and technological resolution are required. When confronted with increasing weather-dependent renewable energy generation, probabilistic simulation models have proven. The significant computational costs of calculating a scenario, however, limit the complexity of further analysis. Advances in code optimization as well as the use of computing clusters still lead to runtimes of up to eight hours per scenario. However ongoing research highlights that tailor-made approximations are potentially the key factor in further reducing computing time. Consequently, current research aims to provide a method for the rapid prediction of widely varying scenarios. In this work artificial neural networks (ANN) are trained and compared to approximate the system behavior of the probabilistic simulation model. To do so, information needs to be sampled from the probabilistic simulation in an efficient way. Because only a limited space in the whole design space of the 16 independent variables is of interest, a classification is developed. Finally it required only around 35 min to create the regression models, including sampling the design space, simulating the training data and training the ANNs. The resulting ANNs are able to predict all scenarios within the validity range of the regression model with a coefficient of determination of over 0.9998 for independent test data (1.051.200 data points). They need only a few milliseconds to predict one scenario, enabling in-depth analysis in a brief period of time.

关键词： Security of electricity supply Probabilistic simulation Metamodeling Artificial neural networks Regression

Role of fragmentation in as-cast structure:numerical study and experimental validation

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China Foundry 2017年第5期14卷 321-326页

作者： Yong-jian Zheng Meng-huai Wu A.Kharicha A.Ludwig chair of simulation and Modelling of Metallurgical Processes Montanuniversitaet Leoben Christian Doppler Laboratory for Advanced Process simulation of Solidification and Melting Department of Metallurgy University of Leoben

A volume average solidification model is extended to incorporate fragmentation as the source of equiaxed crystals during mixed columnar-equiaxed solidification. This study is to use this model to analyze the role of fragmentation in the formation of as-cast structure. Test simulations are made for the solidification of a model alloy(Sn-10wt.%Pb) with two different geometries. The first one is a 2D rectangular domain(50 × 60 mm^2) as cooled from the top boundary. Solidification starts unidirectionally as columnar structure from the top. The solute(Pb) enriched interdendritic melt is heavier than the bulk melt, and sinks downwards, hence leads to solutal convection. Fragmentation phenomenon occurs near the columnar tip front. The fragments are transported out of the columnar region, and they continue to grow and sink, and finally settle down and pile up at the bottom. The growing columnar structure from the top and pile-up of equiaxed crystals from the bottom finally lead to a mixed columnar-equiaxed structure, in turn leading to a columnar-to-equiaxed transition(CET). The second geometry is a 3D plate, 100 × 60 ×10 mm^3, as cooled laterally from one side. It was cast experimentally and analyzed for the as-cast structure. The equiaxed fragments are produced in the solidification front and transported into the bulk melt, leading to a special pattern of as-cast structure: columnar structure in the cool wall side and equiaxed structure in the upper left corner near the hot wall side, extending downwards to the middle bottom region. Numerically calculated as-cast structures agree with the experiment results.

关键词： macrostructure interdendritic fluid flow fragmentation

Numerical microstructure prediction for an aluminium casting and its experimental validation

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China Foundry 2011年第3期8卷 331-336页

作者： Unterreiter Guenter Ludwig Andreas Wu Menghuai Materials Center Leoben Forschung GmbH Leoben Austria chair for simulation and Modelling of Metallurgical Processes Department of Metallurgy University of Leoben Leoben Austria

Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. Numerical prediction of the as-cast microstructure is an initial and critical step in the whole through- process modelling chain for engineering components. A commercial software package with the capability of calculating important microstructure features for aluminium alloys is used to simulate a G-AISi7MgCu0.5 laboratory casting. The simulated microstructure, namely grain size, secondary dendrite arm spacing and diverse phase fractions are verified experimentally. Correspondence and discrepancies are reported and discussed.

关键词： numerical microstructure prediction aluminium casting through-process modelling

F）remature melt solidification during mold filling and its nfluence on the as-cast structure

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Frontiers of Mechanical Engineering 2018年第1期13卷 53-65页

作者： M. WU M. AHMADEIN A. LUDWIG chair for simulation and Modeling of Metallurgical Processes University of Leoben Leoben A-8700 Austria Christian-Doppler Laboratory for Advanced Process simulation ofSolidification and Melting Department of Metallurgy University ofLeoben Leoben A-8700 Austria Production Engineering and Mechanical Design Department Faculty ofEngineering Tanta University Tanta 31111 Egypt

Premature melt solidification is the solidifica- tion of a melt during mold filling. In this study, a numerical model is used to analyze the influence of the pouring process on the premature solidification. The numerical model considers three phases, namely, air, melt, and equiaxed crystals. The crystals are assumed to have originated from the heterogeneous nucleation in the undercooled melt resulting from the first contact of the melt with the cold mold during pouring. The transport of the crystals by the melt flow, in accordance with the so- called ＂big bang＂ theory, is considered. The crystals are assumed globular in morphology and capable of growing according to the local constitutional undercooling. These crystals can also be remelted by mixing with the super- heated melt. As the modeling results, the evolutionary trends of the number density of the crystals and the volume fraction of the solid crystals in the melt during pouring are presented. The calculated number density of the crystals and the volume fraction of the solid crystals in the melt at the end of pouring are used as the initial conditions for the subsequent solidification simulation of the evolution of the as-cast structure. A five-phase volume-average model for mixed columnar-equiaxed solidification is used for the solidification simulation. An improved agreement between the simulation and experimental results is achieved by considering the effect of premature melt solidification during mold filling. Finally, the influences of pouring parameters, namely, pouring temperature, initial mold temperature, and pouring rate, on the premature melt solidification are discussed.

关键词： premature solidification mold filling as-caststructure modeling

Enhance liquid nitrogen fracturing performance on hot dry rock by cyclic injection

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Petroleum Science 2023年第2期20卷 951-972页

作者： Chun-Yang Hong Rui-Yue Yang Zhong-Wei Huang Xiao-Ying Zhuang Hai-Tao Wen Xiao-Li Hu State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China chair of Computational Science and simulation Technology Faculty of Mathematics and PhysicsLeibniz Universität HannoverHannover30167Germany

Producing complex fracture networks in a safe way plays a critical role in the hot dry rock (HDR) geothermal energy exploitation. However, conventional hydraulic fracturing (HF) generally produces high breakdown pressure and results only in single main fracture morphology. Furthermore, HF has also other problems such as the increased risk of seismic events and consuption of large amount of water. In this work, a new stimulation method based on cyclic soft stimulation (CSS) and liquid nitrogen (LN2) fracturing, known as cyclic LN2 fracturing is explored, which we believe has the potential to solve the above issues related to HF. The fracturing performances including breakdown pressure and fracture morphology on granites under true-triaxial stresses are investigated and compared with cyclic water fracturing. Cryo-scanning electron microscopy (Cryo-SEM) tests and X-ray computed tomography (CT) scanning tests were used for quantitative characterization of fracture parameters and to evaluate the cyclic LN2 fracturing performances. The results demonstrate that the cyclic LN2 fracturing results in reduced breakdown pressure, with between 21% and 67% lower pressure compared with using cyclic water fracturing. Cyclic LN2 fracturing tends to produce more complex and branched fractures, whereas cyclic water fracturing usually produces a single main fracture under a low number of cycles and pressure levels. Thermally-induced fractures mostly occur around the interfaces of different particles. This study shows the potential benefits of cyclic LN2 fracturing on HDR. It is expected to provide theoretical guidance for the cyclic LN2 fracturing application in HDR reservoirs.

关键词： Hot dry rock Liquid nitrogen fracturing Cyclic injection Thermal stress Fatigue damage

Multi-Energy simulation of a Smart Grid with Optimal Local Demand and Supply Management

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Smart Grid and Renewable Energy 2015年第11期6卷 303-315页

作者： Christian Kuschel Harald Kostler Ulrich Rüde Friedrich-Alexander Universitat Erlangen-Nurnberg chair for System simulation ErlangenGermany

A simulation approach of a smart grid by cooperative bargaining is presented in this paper. Each participant of the smart grid determines its optimal schedule to meet its power and heating demand at minimal costs employing solar panels, fuel cells and batteries. This is done by solving a quadratic optimisation problem which takes the energy prices and the available devices into account. The energy prices are related to the demand and supply in the smart grid, so that a lower demand yields lower prices. The cooperative bargaining game is used to tune the participants’ optimal solution to obtain a Nash equilibrium. The computed solutions of the participants are validated against the capacities and structure of the smart grid by solving a multi-commodity flow problem. The presented model features multiple types of energy, so that they may be substituted to meet the participants’ demand. Furthermore, the participants may also act as supplier and not only as consumer, which allows decentralised generation of energy. The approach is validated in several experiments where effects like negative energy prices if generated energy exceeds the smart grid’s total demand and peak-shaving with even small-capacity batteries are exhibited.

关键词： Cooperative Bargaining Pricing Model Multi-Agent System Multi-Commodity Flow Smart Grid