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Analysis of the Influence of Viscosity and Thermal Conductivity on Heat transfer by Al2O3-Water Nanofluid

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fluid dynamics & Materials Processing 2020年第2期16卷 181-198页

作者： Houda Jalali Hassan Abbassi unit of computational fluid dynamics and transfer phenomena National Engineering School of Sfax(ENIS)University of SfaxSfaxTunisia

关键词： Heat transfer nanofluid viscosity thermal conductivity

Gas-kinetic numerical method for solving mesoscopic velocity distribution function equation

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Acta Mechanica Sinica 2007年第2期23卷 121-132页

作者： Zhihui Li Hanxin Zhang National Laboratory for computational fluid dynamics Beijing 100083 China Hypervelocity Aerodynamics Institute.Mianyang 621000 China

A gas-kinetic numerical method for directly solving the mesoscopic velocity distribution function equation is presented and applied to the study of three-dimensional complex flows and micro-channel flows covering various flow regimes. The unified velocity distribution function equation describing gas transport phenomena from rarefied transition to continuum flow regimes can be presented on the basis of the kinetic Boltzmann-Shakhov model equation. The gas-kinetic finite-difference schemes for the velocity distribution function are constructed by developing a discrete velocity ordinate method of gas kinetic theory and an unsteady time-splitting technique from computational fluid dynamics. Gas-kinetic boundary conditions and numerical modeling can be established by directly manipulating on the mesoscopic velocity distribution function. A new Gauss-type discrete velocity numerical integra- tion method can be developed and adopted to attack complex flows with different Mach numbers. HPF paral- lel strategy suitable for the gas-kinetic numerical method is investigated and adopted to solve three-dimensional complex problems. High Mach number flows around three-dimensional bodies are computed preliminarilywith massive scale parallel. It is noteworthy and of practical importance that the HPF parallel algorithm for solving three-dimensional complex problems can be effectively developed to cover various flow regimes. On the other hand, the gas-kinetic numerical method is extended and used to study micro-channel gas flows including the classical Couette flow, the Poiseuillechannel flow and pressure-driven gas flows in twodimensional short micro-channels. The numerical experience shows that the gas-kinetic algorithm may be a powerful tool in the numerical simulation of microscale gas flows occuring in the Micro-Electro-Mechanical System （MEMS）.

关键词： Gas kinetic theory . Velocity distributionfunction . Boltzmann model equation .Spacecraft flows . Micro-scale gas flows

Gas-kinetic numerical schemes for one- and two-dimensional inner flows

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Applied Mathematics and Mechanics(English Edition) 2009年第7期30卷 889-904页

作者：李志辉毕林唐志共 Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center National Laboratory for computational fluid dynamics

Several kinds of explicit and implicit finite-difference schemes directly solving the discretized velocity distribution functions are designed with precision of different orders by analyzing the inner characteristics of the gas-kinetic numerical algorithm for Boltzmann model equation. The peculiar flow phenomena and mechanism from various flow regimes are revealed in the numerical simulations of the unsteady Sod shock-tube problems and the two-dimensional channel flows with different Knudsen numbers. The numerical remainder-effects of the difference schemes are investigated aad analyzed based on the computed results. The ways of improving the computational efficiency of the gaskinetic numerical method and the computing principles of difference discretization are discussed.

关键词： Boltzmann model equation gas-kinetic numerical schemes discrete velocityordinate method shock-tube problems channel flows

Numerical investigation of variable viscosities and thermal stratification effects on MHD mixed convective heat and mass transfer past a porous wedge in the presence of a chemical reaction

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Applied Mathematics and Mechanics(English Edition) 2009年第11期30卷 1353-1364页

作者： I. Muhaimin R. Kandasamy Azme B. Khamis computational fluid dynamics FSSWUniversiti Tun Hussein Onn MalaysiaParit Raja 86400Batu PahatJohorMalaysia

An analysis is presented to investigate the effects of variable viscosities and thermal stratification on the MHD mixed convective heat and mass transfer of a viscous, incompressible, and electrically conducting fluid past a porous wedge in the presence of a chemical reaction. The wall of the wedge is embedded in a uniform nonDarcian porous medium in order to allow for possible fluid wall suction or injection. The governing boundary layer equations are written into a dimensionless form by similarity transformations. The transformed coupled nonlinear ordinary differential equations are solved numerically with finite difference methods. Numerical calculations up to the thirdorder level of truncation are carried out for different values of dimensionless parameters. The results are presented graphically, and show that the flow field and other quantities of physical interest are significantly influenced by these parameters. The results are compared with those available in literature, and show excellent agreement.

关键词： variable viscosity chemical reaction non-Darcy flow mixed convection,thermal stratification magnetic effect

Numerical study on the gas-kinetic high-order schemes for solving Boltzmann model equation

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Science China(Physics,Mechanics & Astronomy) 2011年第9期54卷 1687-1701页

作者： LI ZhiHui PENG AoPing ZHANG HanXin DENG XiaoGang National Laboratory for computational fluid dynamics Beifing 100191 China China Aerodynamics Research and Development Center Mianyang 621000 China

The high-order compact finite difference technique is introduced to solve the Boltzmann model equation, and the gas-kinetic high-order schemes are developed to simulate the different kinetic model equations such as the BGK model, the Shakhov model and the Ellipsoidal Statistical (ES) model in this paper. The methods are tested for the one-dimensional unsteady shock-tube problems with various Knudsen numbers, the inner flows of normal shock wave for different Mach numbers, and the two-dimensional flows past a circular cylinder and a NACA 002 airfoil to verify the reliability of the present high-order algorithm and simulate gas transport phenomena covering various flow regimes. The computed results are found in good agreement both with the theoretical prediction from continuum to rarefied gas dynamics, the related DSMC solutions, and with the experimental results. The numerical effect of the schemes with the different precision and the different types of Boltzmann collision models on the computational efficiency and computed results is investigated and analyzed. The numerical experience indicates that an approach developing and applying the gas-kinetic high-order algorithm is feasible for directly solving the Boltzmann model equation.

关键词： Boltzmann model equation velocity distribution function high-order compact scheme discrete velocity ordinate method gas-kinetic high order accurate algorithm

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Applied Mathematics and Mechanics(English Edition) 2010年第12期31卷 1517-1526页

作者： P.LOGANATHAN P.PUVI-ARASU R.KANDASAMY Department of Mathematics Anna University Erode Sengunthar Engineering College computational fluid dynamics FSSWUniversiti Tun Hussein Onn Malaysia

Combined heat and mass transfer on free, forced, and mixed convection flow along a porous wedge with magnetic effect in the presence of chemical reaction is investigated. The flow field characteristics are analyzed by the Runge-Kutta-Gill scheme with the shooting method as well as the local non-similarity method up to the third level of truncation, which are used to reduce the governing partial differential equations into nine ordinary differential equations. The governing boundary layer equations are converted to a dimensionless form by Falkner-Skan transformations. Because of the effect of suction/injection on the wall of the wedge with buoyancy force and variable wall temperature, the flow field is locally non-similar. Numerical calculations up to the third order level of truncation are carried out as a special case for different values of dimensionless parameters. Effects of the magnetic field strength in the presence of chemical reaction with variable wall temperature and concentration on the dimensionless velocity, temperature and concentration profiles are shown graphically.

关键词： local non-similarity suction/injection buoyancy force magnetic field wallof wedge

Study on the unified algorithm for three-dimensional complex problems covering various flow regimes using Boltzmann model equation

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Science China(Physics,Mechanics & Astronomy) 2009年第1期52卷 124-138页

作者： LI ZhiHui1,2 & ZHANG HanXin1 1 National Laboratory for computational fluid dynamics, Beijing 100083, China 2 China Aerodynamics Research and Development Center, Hypervelocity Aerodynamics Institute, Mianyang 621000, China National Laboratory for computational fluid dynamics Beijing China China Aerodynamics Research and Development Center Hypervelocity Aerodynamics Institute Mianyang China

The Boltzmann simplified velocity distribution function equation describing the gas transfer phenomena from various flow regimes will be explored and solved numerically in this study. The discrete velocity ordinate method of the gas kinetic theory is studied and applied to simulate the complex multi-scale flows. Based on the uncoupling technique on molecular movement and colliding in the DSMC method, the gas-kinetic finite difference scheme is constructed to directly solve the discrete velocity distribution functions by extending and applying the unsteady time-splitting method from computational fluid dynamics. The Gauss-type discrete velocity numerical quadrature technique for different Mach number flows is developed to evaluate the macroscopic flow parameters in the physical space. As a result, the gas-kinetic numerical algorithm is established to study the three-dimensional complex flows from rarefied transition to continuum regimes. The parallel strategy adapted to the gas-kinetic numerical algorithm is investigated by analyzing the inner parallel degree of the algorithm, and then the HPF parallel processing program is developed. To test the reliability of the present gas-kinetic numerical method, the three-dimensional complex flows around sphere and spacecraft shape with various Knudsen numbers are simulated by HPF parallel computing. The computational results are found in high resolution of the flow fields and good agreement with the theoretical and experimental data. The computing practice has confirmed that the present gas-kinetic algorithm probably provides a promising approach to resolve the hypersonic aerothermodynamic problems with the complete spectrum of flow regimes from the gas-kinetic point of view of solving the Boltzmann model equation.

关键词： Boltzmann model equation kinetic theory velocity distribution function discrete velocity ordinate technique hypersonic flow parallel computing numerical methods

Three-dimensional heat transfer in a particulate bed in a rotary drum studied via the discrete element method

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Particuology 2020年第4期18卷 155-162页

作者： Esmaeil Yazdani Seyed Hassan Hashemabadi computational fluid dynamics(CFD)Research Laboratory School of ChemicalPetroleum and Gas EngineeringIran University of Science and Technology(IUST)16846-13114 TehranIran

We simulated three-dimensional heat transfer inside a horizontal rotating drum using the discrete element method and a thermal conduction *** aim was to determine the effect of end-wall heating on thermal behavior of a granular *** simulation showed that the end-wall heating significantly affects the axial temperature profile of the bed,particularly when the length-to-diameter ratio is *** near the wall heated faster and became more thermally uniform than those in the center of the *** region affected by the end heating gradually increased over *** the rotation speed enhanced the heat conduction rate,and increasing the fill level reduced the mean temperature and thermal uniformity of the granular *** transfer was also simulated for drums with different length-to-diameter ratios.

关键词： Discrete element method Three-dimensional heat transfer Rotary drum Numerical simulation Axial temperature Particulate bed

Impact of Clocking on the Aero-Thermodynamics of a Second Stator tested in a One and a Half Stage HP Turbine

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Journal of Thermal Science 2008年第2期17卷 97-110页

作者： N.Billiard G.Paniagua R.Dénos Turbomachinery and Propulsion Department von Karman Institute for fluid dynamics

This paper focuses on the experimental investigation of the time-averaged and time-accurate aero- thermodynamics of a second stator tested in a 1.5 stage high-pressure turbine. The effect of clocking on aerodynamic and heat transfer are investigated. Tests are performed under engine representative conditions in the VKI compression tube CT3. The test program includes four different clocking positions, i.e. relative pitch-wise positions between the fh-st and the second stator. Probes located upstream and downstream of the second stator provide the thermodynamic conditions of the flow field. On the second stator airfoil, measurements are taken around the blade profile at 15, 50 and 85% span with pressure sensors and thin-film gauges. Both time-averaged and time-resolved aspects of the flow field are addressed. Regarding the time-averaged results, clocking effects are mainly observed within the leading edge region of the second stator, the largest effects being observed at 15% span. The surface static pressure distribution is changed locally, hence affecting the overall airfoil performance. For one clocking position, the thermal load of the airfoil is noticeably reduced. Pressure fluctuations are attributed to the passage of the up- stream transonic rotor and its associated pressure gradients. The pattern of these fluctuations changes noticeably as a function of docking. The time-resolved variations of heat flux and static pressure are analyzed together showing that the major effect is due to a potential interaction. The time-resolved pressure distribution integrated along the second stator surface yields the unsteady forces on the vane. The magnitude of the unsteady force is very dependent on the clocking position.

关键词： transonic flow turbines stator clocking forces heat transfer.