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41.
Ryoichi Chiba Masaaki Izumi Yoshihiro Sugano 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(1):61-74
Forced convection heat transfer in a non-Newtonian fluid flow inside a pipe whose external surface is subjected to non-axisymmetric
heat loads is investigated analytically. Fully developed laminar velocity distributions obtained by a power-law fluid rheology
model are used, and viscous dissipation is taken into account. The effect of axial heat conduction is considered negligible.
The physical properties are assumed to be constant. We consider that the smooth change in the velocity distribution inside
the pipe is piecewise constant. The theoretical analysis of the heat transfer is performed by using an integral transform
technique – Vodicka’s method. An important feature of this approach is that it permits an arbitrary distribution of the surrounding
medium temperature and an arbitrary velocity distribution of the fluid. This technique is verified by a comparison with the
existing results. The effects of the Brinkman number and rheological properties on the distribution of the local Nusselt number
are shown. 相似文献
42.
Experimental work on two-phase vertical upward flow was carried out using a 19 mm internal diameter, 7 m long pipe and studying the time series of cross-sectional average void fractions and pressure gradient which were obtained simultaneously. With the aid of a bank of published data in which the pipe diameter is the range from 0.5 to 70 mm, the effect of pipe diameter on flow characteristics of two-phase flow is investigated from various aspects. Particularly, the work focuses on the periodic structures of two-phase flow. Average film thicknesses and the gas flow rate where slug/churn and churn/annular flow transitions occur all increase as the diameter of the pipe becomes larger. On the other hand, the pressure gradients, the frequencies of the periodic structures and the velocities of disturbance waves decrease. The velocity of disturbance waves has been used to test the model of Pearce (1979). It is found that the suggested value of Pearce coefficient 0.8 is reasonable for lower liquid flow rates but becomes insufficient for higher liquid flow rates. 相似文献
43.
Inhyeop Yi 《Transactions of the American Mathematical Society》2001,353(9):3741-3767
We define canonical subshift of finite type covers for Williams' one-dimensional generalized solenoids, and use resulting invariants to distinguish some closely related solenoids.
44.
To any compact hyperbolic Riemann surface X, we associate a new type of automorphism group — called its commensurability automorphism group, ComAut(X). The members of ComAut(X) arise from closed circuits, starting and ending at X, where the edges represent holomorphic covering maps amongst compact connected Riemann surfaces (and the vertices represent
the covering surfaces). This group turns out to be the isotropy subgroup, at the point represented by X (in $ T_\infty $), for the action of the universal commensurability modular group on the universal direct limit of Teichmüller
spaces, $ T_\infty $. Now, each point of $ T_\infty $ represents a complex structure on the universal hyperbolic solenoid.
We notice that ComAut(X) acts by holomorphic automorphisms on that complex solenoid. Interestingly, this action turns out to be ergodic (with respect
to the natural measure on the solenoid) if and only if the Fuchsian group uniformizing X is arithmetic. Furthermore, the action of the commensurability modular group, and of its isotropy subgroups, on some natural vector bundles
over $ T_\infty $, are studied by us. 相似文献
45.
在空间Ωn-span{cos t,sint,tCOSt,tsin t, 1,t,t^2,…,t^n-4。}(n≥4)中构造拟Bernstein基,并用其来构造Q。中的曲线,称为拟B6zier曲线,该类曲线具有很多与B6zier曲线类似的性质,利用这些性质可以对曲线进行升阶,升阶得到的控制多边形序列收敛到曲线.拟B6zier曲线这类曲线可以精确表示圆锥螺线,圆的渐开线等超越曲线. 相似文献
46.
基于计算流体力学(CFD)理论,研究了不同曲率半径的螺旋导流片的托卡马克真空室内线圈水冷管道接头。利用湍流数值模拟方法,分析了线圈管道接头导流片曲率半径比、冷却水入口流速对线圈管道内流体平均雷诺数分布的影响。结果表明,不同导流片曲率半径比的线圈管道内的流体雷诺数分布曲线相似,平均雷诺数随入口流速的增加而增大,管道接头出口雷诺数随导流片曲率半径比的增大而减小,导流片曲率半径比小的管接头更适用于线圈水冷曲线管的二次流强化。此外,还为导流片曲率半径比为0.2的管接头拟合了管接头出口雷诺数与入口流速的关系式,为进一步研究类似于托卡马克真空室内线圈管道的曲线管接头的二次流强化提供理论基础。 相似文献
47.
48.
49.
针对压条固定方式、粘胶固定方式和全外围夹持方式进行理论建模和数值计算分析,并讨论了不同夹持方式的优缺点及其对KDP晶体面形和三倍频转换效率的影响。研究结果表明:晶体面形形变对高斯光束三倍频转换效率的影响明显小于平面波时的情况。当入射基频光光强为6 GW·cm-2时,对于平面波的情况,压条固定方式、粘胶固定方式和全外围夹持方式3种夹持方式相对于不考虑夹持作用时的三倍频转换效率分别减小7.5%,9.0%和7.2%;对于高斯光束的情况,三倍频转换效率分别减小了1.3%,1.0%和1.5%。 相似文献
50.
高压直流连续波光阴极注入器中发射度补偿 总被引:2,自引:2,他引:0
空间电荷效应是引起发射度增长的主要因素,特别是在高压直流连续波光阴极注入器中。分析了高压直流连续波光阴极注入器中线性空间电荷力的特点及其对电子束横向发射度的影响,并从理论上解析地研究了螺线管发射度补偿的原理及特点。最后利用Parmela程序对中国工程物理研究院高压直流连续波光阴极注入器的发射度补偿作了模拟计算。结果表明,束团电荷量为80 pC的电子束在350 keV高压直流电子枪出口处的横向归一化发射度为5.14 mmmrad,经过螺线管补偿后,其最小横向发射度变为1.27 mmmrad。电子束的发射度得到了很好的补偿。 相似文献