A UTD SOLUTION FOR THE RADIATED FIELD FROM MONOPOLE ON A CONDUCTING CYLINDER SURFACE WITH A DIELECTRIC COATING

A can0nical problem is investigated for high frequency electromagnetic radiation from amonopo1e on a conducting cylinder with c0ating-At first, the exact solution of this problem is given interms of Dyadic Green's function method. Then, using Watson transformation and high frequency asymptotic approximate technique to the exact soluton, a UTD soultion is obtained. The radiation field excitedby a monopole is expressed in terms of the compound Fock' S functions (CFF), which reduce to the geomertrical optics result in the deep lit region and the creeping waves in the shadow region.

Scattering characteristics of conducting cylinder coated with nonuniform magnetized ferrite

An analytical technique, referred to as the scattering matrix method （SMM）, is developed to analyse the scattering of a planar wave from a conductolution for the nonuniform fering cylinder coated with nonuniform magnetized ferrite. The SMM srite coating can be reduced to the expressions for the scattering and penetrated coefficients in four particular cases： nonuniform magnetized ferrite cylinder, uniform magnetized ferrite-coated conducting cylinder, uniform ferrite cylinder as well as homogeneous dielectric-coated conducting cylinder. The resonant condition for the nonuniform ferrite coating is obtained. The distinctive differences in scattering between the nonuniform ferrite coating and the nonuniform dielectric coating are demonstrated. The effects of applied magnetic fields and wave frequencies on the scattering characteristics for two types of the linear profiles are revealed.

A STUDY OF ELECTROMAGNETIC SCATTERING FROM A DIELECTRIC-COATED CONDUCTING CYLINDER

In order to solve the problem of electromagnetic scattering by a dielectric-coated conducting circular cylinder, the total field excited by an electric and amagnetic dipoles exterior to the cylinder is derived in terms of dyadic Green's function (DGF) technique. Then, the scattering problem can be solved on basis of the relation between the total and the scattered. field. The solution of the scattered field can be obtained directly from the general formula of the scattered field as the cylinder is illuminated by a spherical wave. For a plane wave of arbitrary polarization incident to the cylinder from the direction (theta-0, phi-0), the scattered field can be given by the solution of the scattered field with a spherical wave incident as the center of the spherical wave moves to infinity. For an astigmatic wave incident to the cylinder, the scattered field can be derived by superposing or integrating of the scattered field with the special spherical wave incident.

Simulation of the Scattered EM Field of a Rotating Conducting Cylinder Using Static Data

The effect of the rotation of a very good conducting cylinder on the backscattered field will be investigated where the incident wave is considered as a plane wave in both polarizations （E-wave and H-wave）. Previous work has explained that rotation or vibration of the object may induce phase changes of the scattered signal. Modulation during rotation or vibration is referred to as micro-Doppler effect. Also, the effect of the rotation of a conducting cylinder was investigated by many researchers in the past using the Galilean transformation. These analyses conclude that the effect of rotation does not exist in the case of a perfectly conducting cylinder in both polarizations. In this work, the Franklin transformation is used instead of the Galilean transformation to analyze scattering of both types of electromagnetic waves （H-wave and E-wave） by rotating a very good circular conducting cylinder. This work shows that the scattered field is affected by the rotation of a very good conducting cylinder, especially in the case of H-wave （TE-mode）. Finally, the model that will be presented is used to simulate rotation using static backscattered field data of an arbitrary object.

Flow of variable thermal conductivity fluid due to inclined stretching cylinder with viscous dissipation and thermal radiation

The aim of the present study is to investigate the flow of the Casson fluid by an inclined stretching cylinder. A heat transfer analysis is carried out in the presence of thermal radiation and viscous dissipation effects. The temperature dependent thermal conductivity of the Casson fluid is considered. The relevant equations are first simplified under usual boundary layer assumptions, and then transformed into ordinary differential equations by suitable transformations. The transformed ordinary differential equations are computed for the series solutions of velocity and temperature. A convergence analysis is shown explicitly. Velocity and temperature fields are discussed for different physical parameters by graphs and numerical values. It is found that the velocity decreases with the increase in the angle of inclination while increases with the increase in the mixed convection parameter. The enhancement in the thermal conductivity and radiation effects corresponds to a higher fluid temperature. It is also found that heat transfer is more pronounced in a cylinder when it is compared with a flat plate. The thermal boundary layer thickness increases with the increase in the Eckert number. The radiation and variable thermal conductivity decreases the heat transfer rate at the surface.

Quantitative models for microstructure and thermal conductivity of vermicular graphite cast iron cylinder block based on cooling rate

The relationships of cooling rate with microstructure and thermal conductivity of vermicular graphite cast iron(VGI) cylinder block were studied, which are important for design and optimization of the casting process of VGI cylinder blocks. Cooling rates at different positions in the cylinder block were calculated based on the cooling curves recorded with a solidification simulation software. The metallographic structure and thermal conductivity were observed and measured using optical microscopy(OM), scanning electrical microscopy(SEM) and laser flash diffusivity apparatus, respectively. The effects of the cooling rate on the vermicularity, total and average areas of all graphite particles, and the pearlite fraction in the VGI cylinder block were investigated. It is found that the vermicularity changes in parabola trend with the increase of cooling rate. The total area of graphite particles and the cooling rate at eutectoid stage can be used to predict pearlite fraction well. Moreover, it is found that the thermal conductivity at room temperature is determined by the average area of graphite particles and pearlite fraction when the range of vermicularity is from 80% to 93%. Finally, the quantitative models are established to calculate the vermicularity, pearlite fraction, and thermal conductivity of the VGI cylinder block.

Study on Periodic MHD Flow with Temperature Dependent Viscosity and Thermal Conductivity past an Isothermal Oscillating Cylinder

Temperature dependent viscosity and thermal conducting heat and mass transfer flow with chemical reaction and periodic magnetic field past an isothermal oscillating cylinder have been considered. The partial dimensionless equations governing the flow have been solved numerically by applying explicit finite difference method with the help Compaq visual 6.6a. The obtained outcome of this inquisition has been discussed for different values of well-known flow parameters with different time steps and oscillation angle. The effect of chemical reaction and periodic MHD parameters on the velocity field, temperature field and concentration field, skin-friction, Nusselt number and Sherwood number have been studied and results are presented by graphically. The novelty of the present problem is to study the streamlines by taking into account periodic magnetic field.

ANALYTICAL SOLUTION OF AXIAL SYMMETRICAL WALL TEMPERATURE DISTRIBUTION FOR HOLLOW CYLINDER

Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distribution and the wall heat flux distribution in both axial and radial direction can be calculated by the temperature distribution of the liquid medium both inside and outside the cylinder with temperature changing in axial direction.The calculation results are almost consistent with the experience results.The applicative condition of the formulae in this paper consists with most of practice.They can be applied to the engineering calculation of the steady heat conduction.The calculation is simple and accurate.

Effects of material properties on the competition mechanism of heat transfer of a granular bed in rotary cylinders

Mixing and heat transfer processes of the granular materials within rotary cylinders play a key role in industrial processes. The numerical simulation is carried out by using the discrete element method （DEM） to investigate the influences of material properties on the bed mixing and heat transfer process, including heat conductivity, heat capacity, and shear modulus. Moreover, a new Prclet number is derived to determine the dominant mechanism of the heating rate within the particle bed, which is directly related to thermal and mechanical properties. The system exhibits a faster heating rate with the increase of ratio of thermal conductivity and heat capacity, or the decrease of shear modulus when inter-particle conduction dominates the heating rate; conversely, it shows a fast-mixing bed when particle convection governs the heating rate. The simulation results show good agreement with the theoretical predictions.

基于CFD的烟叶松散润叶筒气固耦合数值模拟

针对烟叶松散润叶筒内部的“黑箱”问题,基于计算流体力学(CFD)对其进行气固双向耦合的数值模拟,通过建立可视化的流场和温度场模型,探讨润叶过程的影响因素和影响机理。结果表明:流场模拟中,颗粒的存在能有效改善气体流动形式,总体气相速率从1.0 m/s降低到0.3 m/s,增加了气固间的接触,强化了两相间的传热;温度场模拟中,温度变化呈现阶段式变化,在润叶筒前半段气固之间传热显著,气相平均温度由81.0℃下降至68.8℃,颗粒平均温度从25.0℃迅速升温到64.8℃,后半段温度维持相对稳定,气固间传热的热流密度随着轴向位置呈现先逐步下降后平稳的趋势;气相、颗粒温度的模拟值与试验实测值的相对误差分别为0.7%、-2.5%,模拟值与试验实测值整体吻合良好,说明模型合理有效;随着筒体倾角、转速增大,两相间的传热效果随之减弱,为满足润叶工艺要求,筒体倾角应小于8°,综合考虑生产速率与能耗,转速应选择15 r/min。

Dependence of Weak Localization Magnetoconductivity on Flux Line Structure

A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.

General Temperature Computational Method of Linear Heat Conduction Multilayer Cylinder

According to the axisymmetric heat conduction of monolayer cylinder, a general method was deduced to calculate the axisymmetric temperature of linear heat conduction multilayer cylinder. Four types of boundary conditions were summarized and formulas for each type were derived. Then, a general calculating program was developed. Four temperature formulas could be expressed by a uniform equation, and the intermediate interface temperatures of axisymmetrical linear conduction multilayer cylinder satisfied tridiagonal linear and nonlinear systems of equations, which could be solved with the pursuit method and the Newton＇s method, respectively. With the calculating program, the temperature at any point of linear heat conduction multilayer cylinder could be obtained.

超疏水管束流动传热数值分析

为了研究超疏水表面的滑移特征对散热器管束的流动减阻及传热强化的影响,针对层流状态下滑移边界条件对二维圆柱表面的流动及传热特性影响进行了数值分析。基于ANSYS FLUENT18.0软件,利用有限元方法计算了雷诺数Re=120时,不同滑移长度下横掠二维圆柱的流场及温度场。圆柱表面采用了Navier模型来表征超疏水滑移现象。计算结果表明:圆柱表面综合传热性能是随着滑移长度增加而呈线性增加的趋势,而圆柱表面综合摩擦阻力是随着滑移长度增加而呈线性减小的趋势;圆柱表面附近速度边界层厚度是随着滑移长度增加而逐渐变薄,明显变薄的发生区域是在圆柱前驻点附近;圆柱表面局部摩擦性能是随着滑移长度的增加而在前驻点区域减小明显,在后驻点区域变化不明显,这也导致了相似的圆柱表面局部传热性能的变化。上述流动传热特性结果将为高效-紧凑型散热器的研究提供参考。

MHD Stagnation Point Flow of Williamson Fluid over a Stretching Cylinder with Variable Thermal Conductivity and Homogeneous/Heterogeneous Reaction

The present study reveals the effect of homogeneous/hetereogeneous reaction on stagnation point flow of Williamson fluid in the presence of magnetohydrodynamics and heat generation/absorption coefficient over a stretching cylinder. Further the effects of variable thermal conductivity and thermal stratification are also considered. The governing partial differential equations are converted to ordinary differential equations with the help of similarity transformation.The system of coupled non-linear ordinary differential equations is then solved by shooting technique. MATLAB shooting code is validated by comparison with the previously published work in limiting case. Results are further strengthened when the present results are compared with MATLAB built-in function bvp4c. Effects of prominent parameters are deliberated graphically for the velocity, temperature and concentration profiles. Skin-friction coefficient and Nusselt number for the different parameters are investigated with the help of tables.

同心圆筒法测定磷铵料浆的导热系数

用同心圆筒法测定了酸性磷铵料浆溶液的导热系数。采用含P2O5 23.682%的试剂稀磷酸与气氨中和得到中和度分别为0.1841、0.4074、0.5947、0.8297、0.9456的酸性磷铵料浆，并加热浓缩到20.337%-70.208%的含水量。测定了60℃、75℃、90℃下不同浓度的料浆溶液的导热系数。结果表明，料浆溶液的导热系数随温度的升高、含水量的增大和中和度的增大而增大。

±800kV特高压直流GIL关键技术研究

为了提高特高压直流输电线路走廊选择的灵活性,研究可以替代部分架空输电线路的直流气体绝缘金属封闭输电线路(gas insulated metal enclosed transmission line,GIL)具有重要意义。提出了在进行直流GIL绝缘子相关试验时,以带绝缘子的圆柱平板电极替代带绝缘子的同轴圆柱电极的试验方法。结合国外小尺寸电极试验结果,采用麦夸特法拟合得到了考虑表面粗糙度的同轴圆柱电极SF6气体间隙下临界击穿场强估算公式。设计了包含微粒陷阱、微粒驱赶电极和屏蔽环的直流GIL电极结构,并对此进行了电场分布的仿真,结果表明此结构具有抑制金属导电微粒运动的作用。

激光辐照下旋转柱壳温度场的数值模拟

采用有限元方法数值模拟在连续激光辐照下旋转柱壳温度场的变化和分布情况,并分析了热性能参数对温度场造成的影响,同时还比较分析了不同旋转频率对柱壳温度场分布的影响。结果表明,激光作用下旋转柱壳的温升大大低于静止柱壳的温升,外表面温度呈现出与旋转频率相符的周期性上升过程,而内表面温升由于热传导的原因在较小频率下才表现出这种周期性,当频率增大到一定值时,内表面温升不出现周期性的台阶而是曲线上升。

渐近波形估计技术在涂敷导体柱宽角度RCS快速计算中的应用

采用渐近波形估计技术 (AWE)和矩量法相结合的方法 ,计算了TM波入射下表面涂敷有耗介质的导体柱的宽角度单站RCS ,本方法首先采用矩量法求解由电磁场等效原理得到的介质层表面等效电磁流耦合方程 ,得到柱体在某一给定方向入射波照射下的电流和磁流密度 ,然后采用渐近波形估计技术将任意角度入射波照射下的电流和磁流密度在给定的角度附近按Taylor级数展开 ,通过Pad埁逼近将Ｔａｙｌｏｒ级数转化为有理函数 ,由此可以得到涂敷导体柱在任意角度TM波入射下的电流和磁流密度 ,进而可以得到柱体的宽角度RCS。此方法得到的结果与由MOM计算的结果完全吻合 ,而AWE的计算效率却提高了一个数量级。

稳态圆筒壁法自动测量颗粒导热系数的改进

依据稳态圆筒壁法测量导热系数的原理 ,推导出颗粒导热系数测量公式 ,通过试验确定颗粒粒径、材料密度、材料温度与导热系数的关系。采用将细热电偶丝的两极拉成直线 ,直接固定在圆筒上下端面的测温方法 ,保持了物料中温度场的真实性。采用单片机简化了检测电路 ,减少了过多元件的器件噪音 ,系统的可靠性和稳定性高。

多层组合圆筒体的轴对称温度和热应力的通用计算方法

根据圆筒体轴对称导热的分析原理,推导了多层组合圆筒轴对称导热温度分布和热应力的通用计算式方法,多层组合圆筒体的内部界面温度和径向压力的三对角型方程组形式,给出了计算流程,编写了相应的计算程序,给出了算例.