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Three-dimensional biomagnetic Maxwell fluid flow over a stretching surface in presence of heat source/sink

International Journal of Biomathematics 2019年第3期12卷 207-226页

作者： M.G.Murtaza M.Ferdows J.C.Misra E.E.Tzirtzilakis Research Group of fluid Flow Modeling and Simulation Department of Applied Mathematics University of Dhaka Dhaka-1000 Bangladesh Centre for Theoretical Studies Indian Institute of Technology Kharagpur Kharagpur 721302 India fluid dynamics & Turbomachinery Laboratory Department of Mechanical Engineering Technological Educational Institute of Western Greece 1 M. Aleksandrou Str Koukouli 26334 Patras Greece

The present paper deals with the study of three-dimensional boundary layer flow of biomagnetic Maxwell fluid over a plane horizontal surface stretched linearly along two mutually perpendicular directions. Basic principles of magnetohydrodynamics (MHD) and ferro-hydrodynamics (FHD) have been employed. The effect of heat generation/absorption has been taken into consideration. The study is theoretical and is conducted by using a combination of approximate and numerical techniques. By using the method of similarity transformation, the governing nonlinear partial differential equations are converted into a set of coupled ordinary differential equations. In the sequel, a suitable numerical method has been developed to solve the coupled differential equations. The accuracy of the numerical method has been checked by comparing the numerical results with those of an earlier study reported in available literatures. Effects of various parameters involved in the study, viz. the magnetohydrodynamic and ferromagnetic parameters, Deborah number, stretching ratio and heat generation on the fluid flow profiles are investigated and the results have been presented graphically. Variations of the skin friction, heat transfer rate and relative wall pressure with change in hydrodynamic and ferromagnetic parameters have also been illustrated. It is found that due to the influence of the Kelvin force, the velocity component in xx-direction is greater than the corresponding one in the hydrodynamic case, but the opposite is true for the velocity component in the yy-direction. We also found that the temperature of the fluid for hydrodynamic flow is greater than that for MHD or FHD flow. It is even greater for BFD flows. The numerical results of the study reveal that the characteristics of blood flow are significantly affected by the presence of a magnetic field.

关键词： Biomagnetic fluid magnetic dipole magnetization heat transfer stretching surface

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DISCONTINUOUS PERIODIC SOLUTION OF THE NONLINEAR INERTIAL GRAVITY WAVE

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Chinese Science Bulletin 1988年第15期33卷 1312-1313页

作者：张铭黄思训 Laboratory for Numerical Modeling of Atmospheric Sciences and Geophysical fluid dynamics Academia Sinica

The squall line is an important mesos?ale synoptic system and is on intimate terms with the inertial gravity wave. The jump phenomena of the velocity and the pressure, which is regarded as discontinuity in mathematics... 详细信息

关键词： mathematics intimate gravity inertial WAVE discontinuity autonomous Coriolis roughly satisfied

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Spacecraft aerodynamics and trajectory simulation during aerobraking

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Applied Mathematics and Mechanics(English Edition) 2010年第9期31卷 1063-1072页

作者：张文普韩波张成义 Institute of fluid Engineering School of Aeronautics and AstronauticsZhejiang University

This paper uses a direct simulation Monte Carlo （DSMC） approach to simulate rarefied aerodynamic characteristics during the aerobraking process of the NASA Mars Global Surveyor （MGS） spacecraft. The research focuses on the flowfield and aerodynamic characteristics distribution under various free stream densities. The vari- ation regularity of aerodynamic coefficients is analyzed. The paper also develops an aerodynamics-aeroheating-trajectory integrative simulation model to preliminarily calculate the aerobraking orbit transfer by combining the DSMC technique and the classical kinematics theory. The results show that the effect of the planetary atmospheric density, the spacecraft yaw, and the pitch attitudes on the spacecraft aerodynamics is significant. The numerical results are in good agreement with the existing results reported in the literature. The aerodynamics-aeroheating-trajectory integrative simulation model can simulate the orbit transfer in the complete aerobraking mission. The current results of the spacecraft trajectory show that the aerobraking maneuvers have good performance of attitude control.

关键词： aerobraking rarefied gas dynamics direct simulation Monte Carlo (DSMC),Mars spacecraft aerodynamic characteristic trajectory simulation

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Spatially resolved investigation of flame particle interaction in a two dimensional model packed bed

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Particuology 2024年第2期85卷 167-185页

作者： Mohammadhassan Khodsiani Reza Namdar Fathollah Varnik Frank Beyrau Benoit Fond Institute of fluid dynamics and Thermodynamics Universitaetsplatz 2Magdeburg39106Saxony-AnhaltGermany Interdisciplinary Centre for Advanced Materials Simulation(ICAMS) Ruhr-University BochumBochum44801Germany ONERA The French Aerospace Lab Department of AerodynamicsAeroelasticity and Acoustics(DAAA)Paris-Saclay UniversityMeudon92190France

This study investigates the interaction between a premixed methane-air flame and particles inside a model packed *** opacity of the spherical packed beds to visible light poses a major barrier to the implementation of highly resolved optical diagnostics,so that no detailed experimental data were so far available for the validation of numerical ***,a two-dimensional cylindrical packed bed design is set up,which enables direct line-of-sight optical measurements without loss of spatial reso-lution over the fluid region between the *** this study,the case of cold metallic cylindrical particles(T=377 K)relevant to start-up of a reactor is investigated using internal particle cooling,which also allows cylinder specific heat transfer rate measurements by differential temperature measurements on the coolant *** two dimensional assumption is first verified by measuring the inflow ve-locity and cylinder temperature profile along the *** imaging is then per-formed using a telecentric lens to observe the position and geometry of the two-dimensional flame front with respect to the surrounding cylinders without loss of ***,the cylinder-specific flame to cylinder heat transfer rates and cylinder surface temperature are *** the flame is closely surrounded by the three cooled cylinders,intense heat transfer is observed in this region corresponding to 25±2.5%of the flame thermal *** were stabilised at different positions depending on inflow velocity and equivalence ratio,and a direct correlation between flame to cylinder stand-off distance and the heat transfer rate normalised to the flame thermal power was found for both top and side ***,sidewall quenching distances to the curved cylinder surfaces were evaluated,and seem to be influenced by the presence of a warm recirculation zone behind the *** investigation provides fully resolved flame front position and heat tra

关键词： Packed beds Flame-particle interaction Optical diagnostics Sidewall quenching

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Numerical simulation of leading edge cavitation within the whole flow passage of a centrifugal pump

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Science China(Technological Sciences) 2013年第9期56卷 2156-2162页

作者： LI XiaoJun YUAN ShouQi PAN ZhongYong YUAN JianPing FU YanXia Research Center of fluid Machinery Engineering and Technology Jiangsu University

In this paper, the periodically unsteady pressure field and head-drop phenomenon caused by leading edge cavitation have been investigated numerically by computational fluid dynamics （CFD） in a single stage centrifugal pump. A CFD model for cavita- tion steady and unsteady simulation has been calculated using the κ-ω SST turbulence model combining with a multiphase ap- proach, based on a homogeneous model assumption. A truncated form of Rayleigh-Plesset equation is used as a source term for the inter-phase mass transfer. The CFD computational region includes the suction cone, impeller, side chambers and volute, as well as suction and pressure pipes. The results were compared with experimental data under non-cavitation and cavitation conditions and a good agreement was obtained for the global performance, the experimental data of the head and the efficiency are 34.04 m and 74.42% at BEP, respectively, the predicted head is 34.31 m and the predicted efficiency is 73.75%. The analy- sis of inner flow pattern shows that the vortex flow generation in the rear of cavity region is the main reason of the head-drop. Obvious increasing can be observed for the amplitude of the pressure fluctuation at the blade passing frequency with different cavitation situations, and subpeak can be found. Besides, the effects of unsteady flow in the side chambers cannot be neglected for accurately predicting the inner flow of the pump. These results imply that this numerical method is suitable for the cavitat- ing flow in the pump.

关键词： centrifugal pump whole flow field leading edge cavitation turbulence kinetic energy pressure fluctuation

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Fourier mode decomposition of PIV data.

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Science China(Technological Sciences) 2015年第11期58卷 1935-1948页

作者： MA LiQun FENG LiHao PAN Chong GAO Qi WANG JinJun fluid Mechanics Key Laboratory of Education Ministry Beijing University of Aeronautics and Astronautics

The modal decomposition technique is one of the most effective methods for studying the flow dynamics in a complex flow. By rejuvenating the discrete Fourier transform(DFT), this paper proposes a Fourier mode decomposition(FMD) method for the time series of particle image velocimetry(PIV) data from the fluid field. An experimental case concerning the control of the flow around a circular cylinder by a synthetic jet positioned at the rear stagnation point is used to demonstrate the use of the FMD method. In the three different regimes where the natural shedding frequency and actuation frequency dominate respectively or simultaneously, it is found that the FMD method is capable of extracting the dynamic mode along with its amplitude and phase according to the selected characteristic frequency based on the global power spectrum. For the quasiperiodic flow phenomena presented in this particular case, the FMD method can reconstruct the original flow field using the zero-th mode and the selected mode corresponding to the characteristic frequency. Similarities and differences between the FMD method and the dynamical mode decomposition(DMD) and proper orthogonal decomposition(POD) methods are also discussed.

关键词： flow control vortex dynamics Fourier mode decomposition (FMD)

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Three-dimensional human thermoregulation model based on pulsatile blood flow and heating mechanism

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Chinese Physics B 2018年第11期27卷 278-288页

作者： Si-Na Dang Hong-Jun Xue Xiao-Yan Zhang Jue Qu Cheng-Wen Zhong Si-Yu Chen Department of fluid Mechanics School of Aeronautics Northwestern Polytechnical University Xi＇ an 710072 China

A three-dimensional thermoregulation mathematical model of temperature fluctuations for the human body is developed based on predecessors＇ thermal models. The following improvements are necessary in real situations： ellipsoids and elliptical cylinders are used to adequately approximate body geometry, divided into 18 segments and five layers; the core layer consists of the organs; the pulsation of the heart cycle, the pulsatile laminar flow, the peripheral resistance, and the thermal effect of food are considered. The model is calculated by adopting computational fluid dynamics（CFD） technology, and the results of the model match with the experimental data. This paper can give a reasonable explanation for the temperature fluctuations.

关键词： thermoregulation pulsating laminar flow heat transfer computational fluid dynamics (CFD)

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The SLA （Second Law Analysis） in Convective Heat transfer Processes

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Journal of Energy and Power Engineering 2016年第5期10卷 283-286页

作者： Heinz Herwig Institute of Thermo-fluid dynamics Hamburg University of Technology Hamburg D-21073 Germany

In all convective heat transfer situations, losses occur in the flow field （by dissipation） as well as in the temperature field （by conduction）. Typically these losses are more or less quantified by the friction factorfwith respect to losses in the flow field, and the Nusselt number Nu for the heat transfer quality. Assessing the process of convective heat transfer as a whole, then becomes problematic because two different non-dimensional quantities, f and Nu, have to be combined somehow. From a thermodynamics point of view, there is a reasonable alternative： Since all losses become manifest in corresponding entropy generation rates, these rates are determined in the velocity as well as in the temperature field. Based on the integration of the entropy generation fields, an energy devaluation number is introduced. It basically determines how much oftbe so-called entropic potential of the energy involved in a convective heat transfer process is used within it. This approach is called SLA （second law analysis）.

关键词： Second law analysis energy devaluation number entropic potential.

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The Effects of Line-Wing Cutoff in LBL Integration on Radiation Calculations

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Acta meteorologica Sinica 2008年第2期22卷 248-255页

作者：张华石广玉刘毅 Laboratory for Climate Studies of China Meteorological Administration National Climate Center State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical fluid dynamics (LASG) Institute of Atmospheric Physics Laboratory for Middle Atmosphere and Global Environment Observation (LAGEO) Institute of Atmospheric Physics

There are three basic methods in radiative transfer calculations, i.e., line-by-line （LBL） integration, correlated k-distribution method, and band model. The LBL integration is the most accurate of all, in which, there are two quadrature algorithms named in this paper as integration by lines and by sampling points when calculating atmospheric transmittance in the considered wavenumher region. Because the LBL integration is the most expensive of all, it is necessary and important to save calculation time hut increase calculation speed when it is put into use in the daily operation in atmospheric remote sensing and atmospheric sounding. A simplified LBL method is given in this paper on the basis of integration by lines, which increases computational speed greatly with keeping the same accuracy. Then, we discuss the effects of different cutoff schemes on atmospheric absorption coefficient, transmittance, and cooling rate under both of accurate and simplified LBL methods in detail. There are four cutoff schemes described in this paper, i.e., CUTOFFs 1, 2, 3, and 4. It is shown by this numerical study that the way to cut off spectral line-wing has a great effect on the accuracy and speed of radiative calculations. The relative errors of the calculated absorption coefficients for CUTOFF 2 are the largest under different pressures, while for CUTOFF 1, they are less than 2% at most of sampling points and for CUTOFFs 3 or 4, they are almost less than 5% in the calculated spectral region, however, the calculation time is reduced greatly. We find in this study that the transmittance in the lower atmosphere is not sensitive to different LBL methods and different cutoff schemes. Whereas for the higher atmosphere, the differences of transmittance results between CUTOFF 2 and each of other three cutoff schemes are the biggest of all no matter for the accurate LBL or for the simplified LBL integrations. By comparison, the best and optimized cutoff scheme is given in this paper fina

关键词： LBL (line-by-line) integration line-wing cutoff absorption coefficient transmittance cooling rate

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Liquid Metal Modelling of Continuous Steel Casting

Liquid Metal Modelling of Continuous Steel Casting

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第十届中国钢铁年会暨第六届宝钢学术年会

作者： Gerbeth Gunter Wondrak Thomas Stefani Frank Shevchenko Natalia Eckert Sven Timmel Klaus Helmholtz-Zentrum Dresden-Rossendorf Institute of Fluid Dynamics MHD Department

Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. We present recent results from the three LIMMCAST facilities working either with room-temperature alloy Ga In Sn or with the alloy Sn Bi at temperatures of 20050°C. The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution, which is essential for code validation. Experimental results are presented covering the following phenomena: contactless electromagnetic tomography of the flow in the mold, flow monitoring by ultrasonic sensors, mold flow under the influence of an electromagnetic brake, injection of argon bubbles through the stopper rod, X-ray visualization of gas bubble two-phase flow in the nozzle and in the mold.

关键词： continuous casting physical modeling flow measurements magnetic field flow control electromagnetic brake

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