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steady-state multiscale CFD simulation of a circulating fluidized bed riser

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Particuology 2024年第10期93卷 54-64页

作者： Zhaojie Ke Yujie Tian Fei Li Bona Lu Wei Wang state Key Laboratory of Mesoscience and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing100049China

Compared to transient simulation,steady-state simulation of circulating fluidized bed risers is more efficient,but is also harder to perform due to the complex scale-dependency of dense gas-solid *** this work,steady-state computational fluid dynamics(CFD)simulation of a riser is performed using the steady energy-minimization multi-scale(EMMS)*** is found that the steady state corresponds to an extremely large scale of length and time,thus the grid size required in steady-state simulation is larger than that in transient *** time-averaged two-fluid model(TFM)coupled with the steady-state EMMS/1M drag model enables a good prediction of the S-shaped,axial solids distribution and the choking transition,whereas the two-phase turbulence and solids stress models are important in predicting the radially core-annular distribution of *** far as we know,this is the first time that one can predict the choking transition in a steady-state CFD *** improvement may need an EMMS modeling of the time-averaged solid stresses.

关键词： Fluidization Drag force steady state Simulation Mesoscale

steady state response of an infinite beam on a viscoelastic foundation with moving distributed mass and load

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Science China(Physics,Mechanics & Astronomy) 2020年第8期63卷 71-85页

作者： Yin Zhang state Key Laboratory of Nonlinear Mechanics(LNM) Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Compared with the moving concentrated load model,it is more realistic and proper to use the moving distributed mass and load model to simulate the dynamics of a train moving along a railway *** the problem of a moving concentrated load,there is only one critical velocity,which divides the load moving velocity into two categories:subcritical and *** locus of a concentrated load demarcates the space into two parts:the waves in these two domains are called the front and rear waves,*** comparison,in the problem of moving distributed mass and load,there are two critical velocities,which results in three categories of the distributed mass moving *** to the presence of the distributed mass and load,the space is divided into three domains,in which three different waves *** richer and different variation patterns of wave shapes arise in the problem of the moving distributed mass and *** mechanisms responsible for these variation patterns are systematically studied.A semi-analytical solution to the steady-state is also obtained,which recovers that of the classical problem of a moving concentrated load when the length of the distributed mass and load approaches zero.

关键词： steady state beam viscoelastic foundation moving distributed mass

steady state investigation on neutronics of a molten salt reactor considering the flow effect of fuel salt

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Chinese Physics C 2008年第8期32卷 624-628页

作者：张大林秋穗正刘长亮苏光辉 state Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University School of Nuclear Science and Technology Xi'an Jiaotong University

The Molten Salt Reactor （MSR）, one of the ‘Generation Ⅳ＇ concepts, is a liquid-fuel reactor, which is different from the conventional reactors using solid fissile materials due to the flow effect of fuel salt. The study on its neutronics considering the fuel salt flow, which is the base of the thermal-hydraulic calculation and safety analysis, must be done. In this paper, the theoretical model on neutronics under steady condition for a single-liquid-fueled MSR is conducted and calculated by numerical method. The neutronics model consists of two group neutron diffusion equations for fast and thermal neutron fluxes, and balance equations for six-group delayed neutron precursors considering the flow effect of fuel salt. The spatial discretization of the above models is based on the finite volume method, and the discretization equations are computed by the source iteration method. The distributions of neutron fluxes and the distributions of the delayed neutron precursors in the core are obtained. The numerical calculated results show that, the fuel salt flow has little effect on the distribution of fast and thermal neutron fluxes and the effective multiplication factor; however, it affects the distribution of the delayed neutron precursors significantly, especially the long-lived one. In addition, it could be found that the delayed neutron precursors influence the neutronics slightly under the steady condition.

关键词： MSR steady state neutronics flow effect delayed neutron precursors

Dependence of α-phase size on flow stress during dynamic recrystallization steady state in Ti60 alloy

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Rare Metals 2017年第11期36卷 851-857页

作者： hui li zhang-long zhao hong-zhen guo yong-quan ning ze-kun yao kai li vSchool of Materials Science and Engineering NorthwesternPolytechnical University Xi'an 710072 China

The dependence of α-phase size on flow stress was characterized by a proposed kinetic model during dynamic recrystallization （DRX） steady state in Ti60 alloy. Accord- ing to the isothermal compression tests, the influence of deformation parameters on the steady-state flow stress was analyzed and the constitutive equation was established to predict the steady-state flow stress under different defor- mation temperatures and strain rates. A power-law rela- tionship between the DRX average grain size and steady- state flow stress with an exponent of -2 is obtained from the dynamic balance during DRX steady state. The effect of deformation parameters on at-phase size was observed through the microstructure after deformation, and the applicability of the model for Ti60 alloy was verified by the comparison between predicted and experimental data.

关键词： Dynamic recrystallization steady state Grainsize Ti60 alloy Hot deformation

Rheological behavior of semi-solid 7075 aluminum alloy at steady state

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China Foundry 2014年第2期11卷 79-84页

作者： Li Yageng Mao Weimin Zhu Wenzhi Yang Bin University of Science&Technology Beijing

The further application of semi-solid processing lies in the in-depth fundamental study like rheological behavior. In this research, the apparent viscosity of the semi-solid slurry of 7075 alloy was measured using a Couette type viscometer. The effects of solid fraction and shearing rate on the apparent viscosity of this alloy were investigated under different processing conditions. It can be seen that the apparent viscosity increases with an increase in the solid fraction from 10% to 50% （temperature 620 ℃ to 630 ℃） at steady state. When the solid fraction was fixed, the apparent viscosity can be decreased by altering the shearing rate from 61.235 s-1 to 489.88 s-1 at steady state. An empirical equation that shows the effects of solid fraction and shearing rate on the apparent viscosity is fitted： ηα = [0.871 - 0.00849. γ0.74924]. exp（3.7311, fs） . The microstructure of quenched samples was examined to understand the alloy＇s rheological behavior.

关键词： apparent viscosity semi-solid 7075 aluminum alloy steady state

A Fixed-Point Fast Sweeping WENO Method with Inverse Lax-Wendroff Boundary Treatment for steady state of Hyperbolic Conservation Laws

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Communications on Applied Mathematics and Computation 2023年第1期5卷 403-427页

作者： Liang Li Jun Zhu Chi-Wang Shu Yong-Tao Zhang Key Laboratory of Mathematical Modelling and High Performance Computing of Air Vehicles(NUAA) MIITNanjing University of Aeronautics and AstronauticsNanjing 210016JiangsuChina state Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory of Mathematical Modelling and High Performance Computing of Air Vehicles(NUAA) MIITNanjing University of Aeronautics and AstronauticsNanjing 210016JiangsuChina Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA Department of Applied and Computational Mathematics and Statistics University of Notre DameNotre DameIN 46556USA

Fixed-point fast sweeping WENO methods are a class of efficient high-order numerical methods to solve steady-state solutions of hyperbolic partial differential equations(PDEs).The Gauss-Seidel iterations and alternating sweeping strategy are used to cover characteristics of hyperbolic PDEs in each sweeping order to achieve fast convergence rate to steady-state solutions.A nice property of fixed-point fast sweeping WENO methods which distinguishes them from other fast sweeping methods is that they are explicit and do not require inverse operation of nonlinear local ***,they are easy to be applied to a general hyperbolic *** deal with the difficulties associated with numerical boundary treatment when high-order finite difference methods on a Cartesian mesh are used to solve hyperbolic PDEs on complex domains,inverse Lax-Wendroff(ILW)procedures were developed as a very effective approach in the *** this paper,we combine a fifthorder fixed-point fast sweeping WENO method with an ILW procedure to solve steadystate solution of hyperbolic conservation laws on complex computing *** experiments are performed to test the method in solving various problems including the cases with the physical boundary not aligned with the *** results show highorder accuracy and good performance of the ***,the method is compared with the popular third-order total variation diminishing Runge-Kutta(TVD-RK3)time-marching method for steady-state *** examples show that for most of examples,the fixed-point fast sweeping method saves more than half CPU time costs than TVD-RK3 to converge to steady-state solutions.

关键词： Fixed-point fast sweeping methods Multi-resolution WENO schemes steady state ILW procedure Convergence

A computationally efficient method for identification of steady state in time series data from ship monitoring

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Journal of Ocean Engineering and Science 2020年第4期5卷 333-345页

作者： Øyvind Øksnes Dalheim Sverre Steen Department of Marine Technology Norwegian University of Science and Technology(NTNU)Otto Nielsens vei 10Trondheim 7491Norway Rolls-Royce 1 University Technology Centre(UTC)-Ship performance and cyber-physical systems TrondheimNorway

Most applied time series are non-stationary,or exhibit some kind of non-stationarity for at least parts of the time *** time series analyses or mathematical modeling purposes,the non-stationarities can be difficult to ***,identification of stationary and non-stationary behavior is of great practical interest in time series *** this study a robust and computationally efficient method to identify steady state parts of time series data is *** method is based on the class of deterministic trend models using a sliding window,and is focused towards being easy to implement,efficient and practical in use and to preserve data *** demonstrate the performance of the steady state identifier,the method is applied on different sets of time series data from two ships equipped with systems for in-service *** method is shown to be reliable and practical for identifying steady state parts of time series data,and can serve as a practical preprocessing tool for time series data analysis.

关键词： Stationarity steady state Signal extraction Change point In-service data Ship monitoring

Experimental and Finite Element Study of steady state Micro-cutting Characteristics of Aluminum Alloy (2A12)

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Transactions of Tianjin University 2011年第5期17卷 344-350页

作者：陈光任成祖靳新民郭韬 Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University

This paper studies the micro-cutting characteristics of aluminum alloy (2A12) based on a series of orthogonal experiments and finite element method (FEM) simulations. An energy-based ductile failure law was proposed in the FEM simulation. The simulated cutting forces and chip morphology were compared with experimental results. The simulation result indicates that there is a close relationship between the cutting force and cutting heat. The micro-cutting force decreases as the heat flux vector increases. Both the cutting heat and the micro-cutting force need a finite time to achieve a steady state. It is observed that with the cutting speed of 169.95 m/min and uncut chip thickness of 6 μm, the heat flux vector in the workpiece increases to a stable value after 0.06 ms; meanwhile, the principal cutting force decreases to a steady state correspondingly, i.e., the micro-cutting process achieves the steady state. It is concluded that the steady state micro-cutting simulation can reflect the cutting process accurately.

关键词： micro-cutting aluminum alloy steady state finite element method

Existence and Stability of steady state in an Augmented Solow Model with Multiple Capital Goods

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Frontiers of Economics in China-Selected Publications from Chinese Universities 2018年第4期13卷 685-702页

作者： Jian Li Yao Lu School of Economics Nanjing UniversityNanjing 210093China

This paper relaxes two assumptions on the traditional augmented Solow model: strict concavity of production functions and dual capital goods. It generalizes traditional conclusions of the Solow model by demonstrating that neoclassical properties of a production function are sufficient for the existence and global stability of the steady state in the augmented Solow model with multiple capital goods. Moreover, we prove necessity of essentiality of inputs for a neoclassical production function and generalize the golden rule of capital accumulation.

关键词： multiple capital goods augmented Solow model essentiality of inputs steady state strict concavity