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A depth-averaged two-phase model for debris flows over fixed beds

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International Journal of Sediment Research 2018年第4期33卷 462-477页

作者： Ji Li Zhixian Cao Kaiheng Hu Gareth Pender Qingquan Liu State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Institute of Mountain Hazards and Environment Chinese Academy of Sciences Institute for Infrastructure and Environment.Heriot-Watt University Edinburgh Campus Department of Mechanics Beijing Institute of Technology

A depth-averaged two-phase model is proposed for debris flows over fixed beds, explicitly incorporating interphase and particle-particle interactions, fluid and solid fluctuations and multi grain sizes. A firstorder model based on the kinetic theory of granular flows is employed to determine the stresses due to solid fluctuations, while the turbulent kinetic energy-dissipation rate model is used to determine the stresses from fluid fluctuations. A well-balanced numerical algorithm is applied to solve the governing equations. The present model is benchmarked against USGS experimental debris flows over fixed *** the stresses due to fluid and solid fluctuations and properly estimating the bed shear stresses are shown to be crucial for reproducing the debris flows. Longitudinal particle segregation is resolved, demonstrating coarser sediments around the fronts and finer grains trailing the head. Based on extended modeling exercises, debris flow efficiency is shown to increase with initial volume, which is underpinned by observed datasets.

关键词： Debris flow two-phase model Depth-averaged model Fluctuation kinetic energy Multi grain sizes

A two-phase model for fluidized beds

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Progress in Natural Science:Materials International 1995年第5期 69-75页

作者：洪若瑜李洪钟朱庆山程懋圩张济宇 Beijing 100080 China Chinese Academy of Sciences Institute of Chemical Metallurgy Institute of Coal Chemistry State Key Laboratory of Coal Conversion Taiyuan 030001

The gas-solid flow in two-dimensional jet fluidiaed beds is simulated by running the general-purpose computer program CASIC, stemmed from the two-phase model which is derived from the Navier-Stokes equation of the gas phase and the Newtonian equation of a single particle using the rigorous method of control volume averaging in a control element, and discretized by the modified 1PSA method. The formation, movement, combination and burst of the bubbles in the bed also reapeares by computer modeling. The computed jet penetration heights under various jet velocities are well compared with reported or our experimental data.

关键词： fluidized bed two-phase model computer simulation flow pattern jet penetration height.

Fast Numerical Simulation of two-phase Transport model in the Cathode of a Polymer Electrolyte Fuel Cell

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Communications in Computational Physics 2009年第6期6卷 49-71页

作者： Pengtao Sun Guangri Xue Chaoyang Wang Jinchao Xu Department of Mathematical Sciences University of NevadaLas Vegas4505 Maryland ParkwayLas VegasNV 89154USA Department of Mathematics The Pennsylvania State UniversityUniversity ParkPA 16802USA Departments of Mechanical Engineering and Materials Science and Engineering Electrochemical Engine Center(ECEC)The Pennsylvania State UniversityUniversity ParkPA 16802USA Laboratory of Mathematics and Applied Mathematics School of Mathematical SciencesPeking UniversityBeijing 100871China

In this paper,we apply streamline-diffusion and Galerkin-least-squares fi-nite element methods for 2D steady-state two-phase model in the cathode of polymer electrolyte fuel cell(PEFC)that contains a gas channel and a gas diffusion layer(GDL).This two-phase PEFC model is typically modeled by a modified Navier-Stokes equation for the mass and momentum,with Darcy’s drag as an additional source term in momentum for flows through GDL,and a discontinuous and degenerate convectiondiffusion equation for water *** on the mixed finite element method for the modified Navier-Stokes equation and standard finite element method for water equation,we design streamline-diffusion and Galerkin-least-squares to overcome the dominant convection arising from the gas ***,we employ Kirchhoff transformation to deal with the discontinuous and degenerate diffusivity in water *** experiments demonstrate that our finite element methods,together with these numerical techniques,are able to get accurate physical solutions with fast convergence.

关键词： two-phase model polymer electrolyte fuel cell Kirchhoff transformation convection dominated diffusion problem streamline diffusion Galerkin-least-squares

Global Existence of Solutions for Baer-Nunziato two-phase Flow model in a Bounded Domain

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Open Journal of Applied Sciences 2022年第4期12卷 631-649页

作者： Wenhui Kou College of Science University of Shanghai for Science and Technology Shanghai China

In this paper, we study the global existence and uniqueness of strong solutions for the Baer-Nunziato two-phase flow model in a bounded domain with a no-slip boundary. The global existence and uniqueness of strong solutions are obtained when the initial value is near the equilibrium state in H2 (Ω). Furthermore, the exponential convergence rates of the pressure and velocity are also proved by delicate energy methods.

关键词： two-phase model Bounded Domain Global Existence Energy Method

Coupled model of two-phase Debris Flow,Sediment Transport and Morphological Evolution

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Acta Geologica Sinica(English Edition) 2016年第6期90卷 2206-2215页

作者： HE Siming OUYANG Chaojun LIU Wei WANG Dongpo Key laboratory of Mountain Hazards and Surface Process Chinese Academy of Science Institute of Mountain Hazards and Environment (IMHE) Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology

The volume fraction of the solid and liquid phase of debris flows, which evolves simultaneously across terrains, largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper, we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth, the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress, and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition （Iverson and Ouyang, 2015） is presented. In this formula, the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe’s Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.

关键词： debris flows two-phase model sediment transport entrainment rate finite volume method

Comparative numerical study of single and two-phase models of nanofluid heat transfer in wavy channel

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Applied Mathematics and Mechanics(English Edition) 2014年第7期35卷 831-848页

作者： M.M.RASHIDI A.HOSSEINI I.POP S.KUMAR N.FREIDOONIMEHR Department of Mechanical Engineering Faculty of EngineeringBu-Ali Sina UniversityHamedan 65178-38695 Iran Department of Mathematics Babe?Bolyai UniversityCluj-Napoca 400084Romania Department of Mathematics National Institute of TechnologyJamshedpur 831014Jharkhand India Young Researchers & Elite Club Hamedan BranchIslamic Azad UniversityHamedan 65181-15743 Iran

The main purpose of this study is to survey numerically comparison of two- phase and single phase of heat transfer and flow field of copper-water nanofluid in a wavy channel. The computational fluid dynamics （CFD） prediction is used for heat transfer and flow prediction of the single phase and three different two-phase models （mixture, volume of fluid （VOF）, and Eulerian）. The heat transfer coefficient, temperature, and velocity distributions are investigated. The results show that the differences between the temperature fie].d in the single phase and two-phase models are greater than those in the hydrodynamic tleld. Also, it is found that the heat transfer coefficient predicted by the single phase model is enhanced by increasing the volume fraction of nanoparticles for all Reynolds numbers; while for the two-phase models, when the Reynolds number is low, increasing the volume fraction of nanoparticles will enhance the heat transfer coefficient in the front and the middle of the wavy channel, but gradually decrease along the wavy channel.

关键词： nanofluid two-phase model wavy channel semi implicit method for pres-sure linked equation (SIMPLE) method

Progresses on two-phase modeling of proton exchange membrane water electrolyzer

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Energy Reviews 2024年第3期3卷 30-57页

作者： Boshi Xu Tao Ouyang Yang Wang Yang Yang Jun Li Liangliang Jiang Chaozhong Qin Dingding Ye Rong Chen Xun Zhu Qiang Liao Key Laboratory of Low-grade Energy Utilization Technologies and Systems Ministry of EducationChongqing UniversityChongqing400030China Institute of Engineering Thermophysics School of Energy and Powering EngineeringChongqing UniversityChongqing400030China Department of Chemical and Petroleum Engineering The University of CalgaryCalgaryAlbertaCanada State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400044China

The Proton Exchange Membrane(PEM)water electrolyzer is considered one of the promising energy storing means for harnessing variable renewable energy sources to produce *** the internal fluid dynamics,which are often challenging to directly observe experimentally,has prompted the use of numerical models to investigate two-phase flow within PEM water *** this study,we provide a comprehensive review of prior research focusing on two-phase modeling of PEM electrolyzers,encompassing both components at mesoscopic scales and the full electrolyzer at the macroscopic *** delve into the specifics of various modeling approaches for two-phase flow at different scales and summarize and discuss the current state of the art in the ***,two-phase models for the full electrolyzer predominantly employ a macroscopic homogeneous ***,mesoscopic and microscopic models capable of tracking phase interfaces are limited to *** persist in integrating various modeling scales into a comprehensive electrolyzer model,particularly in coupling two-phase flow between the channels and porous *** efforts should focus on developing multi-scale models and simulating two-phase flow under fluctuating input ***,given the structural similarities between PEM water electrolyzers and PEM fuel cells,we compare and discuss differences in two-phase modeling between the two *** work offers the insights for researchers in the field of modeling of PEM water electrolyzers and even fuel cells.

关键词： Proton exchange membrane(PEM)water electrolyzer two-phase model Multiscale modeling Water management Numerical simulation

Numerical simulation of macrosegregation during solidification of binary alloys

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Rare Metals 2016年第8期35卷 591-597页

作者： Wu-Tao Tu Hou-Fa Shen Bai-Cheng Liu Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University

Macrosegregation as a consequence of solidifi- cation of a binary Pb-48 wt% Sn alloy in two-dimensional rectangle cavity was investigated by two-phase model instead of the common used continuum model. The macroscopic transport of mass, momentum, species and energy was cou- pled with the microscopic descriptions of grain nucleation and growth. The mathematic equations of the two-phase model were discretized on staggered grids and solved by the finite volume method. The final tin concentrations along different heights over the bottom face were compared with the ex- periment measurements. Simulations with different mi- crostructure parameters （second dendrite arm spacing （SDAS）） were conducted to ascertain the influence of microstructure on the final macrosegregation. The results show that with the decrease in SDAS value, the drag force as the resistance to relative motion between solid and liquid phase increases, and the macrosegregation during solidification is alleviated.

关键词： Macrosegregation two-phase model Solidification Second dendrite arm spacing

Numerical investigation of water and temperature distributions in a proton exchange membrane electrolysis cell

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Science China(Technological Sciences) 2021年第7期64卷 1555-1566页

作者： WANG ZhiMing XU Chao WANG XueYe LIAO ZhiRong DU XiaoZe Key Laboratory of Power Station Energy Transfer Conversion and System of MOE School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

A three-dimensional, non-isothermal, two-phase model for a PEM water electrolysis cell(PEMEC) is established in this *** effective connection between two-phase transport and performance in the PEMECs is built through coupling the liquid water saturation and temperature in the charge conservation equation. The distributions of liquid water and temperature with different operating(voltage, temperature, inlet velocity) and physical(contact angle, and porosity of anode gas diffusion layer) parameters are examined and discussed in detail. The results show that the water and temperature distributions, which are affected by the operating and physical parameters, have a combined effect on the cell performance. The effects of various parameters on the PEMEC are of interaction and restricted mutually. As the voltage increases, the priority factor caused by the change of inlet water velocity changes from the liquid water saturation increase to the temperature drop in the anode catalyst layer. While the priority influence factor caused by the contact angle and porosity of anode gas diffusion layer is the liquid water saturation. Decreasing the contact angle or/and increasing the porosity can improve the PEMEC performance especially at the high voltage. The results can provide a better understanding of the effect of heat and mass transfer and the foundation for optimization design.

关键词： proton exchange membrane electrolysis cell two-phase model liquid water saturation flow rate temperature distribution