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1.
张家麟 《中国科学院研究生院学报》1988,(2)
本文使用张量分析方法系统推导并给出了用于描述叶轮机械内跨声速位流的使用非正交曲线坐标非正交速度分量的散度形式的二维及三维势函数方程。这一整套势函数方程可应用于叶轮机械内任意形状的S_1、S_2流面上跨声速流动及准三元、全三元跨声速流动的分析及设计问题的求解计算。文中还给出了这些方程的求解步序。 相似文献
2.
同其他电解生产领域相比较,铝电解过程电流强度要大若干倍,强大的电流产生强磁场,铝电解曹钟的熔体均为带电导体,强磁场和大电流的相瓦作用产生电磁力,在力的作用下槽内熔体产生运动,对电解槽的生产操作和电流效率有重要影响,这使得电磁场的计算,磁场的合理设计是大型率电解槽设计的关键之一.但是现有的电解槽磁场的计算方法还不够完善,还存在一些不足,尤其表现在计算铁磁材料对磁场的影响方面,还难以满足电解槽母线设计的要求.因此,人们一直在不断努力完善电解槽磁场的计算方法,以便在设计率电解槽的时候尽町能精确计算出铝电解槽的磁场分布,并通过优化母线配置,使电流效率能够达到最高. 相似文献
3.
强迫耗散非线性发展方程显式差分格式的计算稳定性 总被引：1，自引：1，他引：1
基于计算准稳定的概念来分析强迫耗散非线性发展方程显式差分格式的计算稳定性,给出强迫耗散非线性大气方程组显式差分格式计算准稳定的判据,为设计强迫耗散非线性大气方程组计算稳定的显式差分格式提供了新的思路和理论依据 相似文献
4.
以波传播的观点 ,将流动工况视为连续波与动力波相互作用在特定流动条件下的非线性解 ,尝试提出了两相流分析的一种新思路 .从一维气液两相流守恒方程出发 ,应用气液两相流漂移流模型 ,推导了空泡率双曲型守恒方程 ,用特征线法数值求解气液两相流空泡率分布的传播过程 ,对传播稳定性和流型转变进行讨论 .数值分析表明 ,低空泡率时发生流型转变的位置相对于两相流平均速度将向下游蔓延 ;而高空泡率时则相对地向上游蔓延 ;空泡率很高时空泡率分布传播过程中将不会出现流型转变 .计算表明 :流型转变起始点的空泡率为 0 2 7,空泡率达到 0 5 8时流型转变终止 ;这与文献报告的气液两相流实验结果符合较好 相似文献
5.
采用电磁场理论中的多重镜像法,并结合数学中的级数与差分方程理论,分析了球型接地模型的接地电阻。同时指出教材中推导接地电阻公式时的一个疏漏,并予以一定的修正,对已有的一个多重镜像法算例加以推广。这是镜像法在实际应用中的一个实例。 相似文献
6.
非线性计算不稳定问题的进一步研究 总被引：1，自引：3，他引：1
讨论了有关非线性计算不稳定的若干问题,其主要内容有(1)考察了有代表性的三类发展方程,指出其对应的差分格式是否出现非线性计算不稳定,与原微分方程解的性质密切相关;(2)进一步讨论了带周期边条件的守恒型差分格式的非线性计算稳定性问题,总结了克服非线性不稳定的有效措施;(3)以非线性平流方程为例,着重分析了带非周期边条件的非守恒差分格式的非线性计算稳定性问题,给出了判别其计算稳定性的"综合分析判别法". 相似文献
7.
带电粒子在电磁场中的应用分析对物理学以及其他领域的研究有着重要的意义。再者新课标的改革,考察粒子在两种场力作用下的运动情况越来越多。因此,需要加大对此种情况的研究。本文通过对带电粒子在不同电磁场中的运动情况进行分析,得出了其相应的运动方程和轨迹,并对带电粒子在电磁场中的应用进行了详细阐述。 相似文献
8.
在Euler方程组的预处理方法的研究方向上,采用一种新式的带有自适应人工粘性的显式中心差分格式,对无粘凸包流动进行了数值计算。计算结果表明,该方法可以较好地直接进行Euler方程组对于10-5的低马赫数下的不可压缩流动的计算。 相似文献
9.
10.
这篇文章通过一些典型例子讨论了在用启示性方法时从原偏微分方程推导来的稳定性条件与从差分方程展开式推导来的稳定性条件间的不同点。结果表明，对于部分有限差分方程，在用启示性方法分析其计算稳定性的过程中最好采用从差分方程推导来的展开式以期得到较合理的结果。在文章的另一部分，反证法的运用表明了从启示性方法推导来的稳定性条件并非全都是必要条件，在应用中应引起注意。 相似文献
11.
The ability to pump and manipulate fluid at the micron-scale is a basic requirement for microfluidic platforms. Many current manipulation methods, however, require expensive and bulky external supporting equipment, which are not typically compatible for portable applications. We have developed a contactless metal electro-osmotic micropump capable of pumping conductive buffers. The pump operates using two pairs of gallium metal electrodes, which are activated using an external voltage source and separated from a main flow channel by a thin micron-scale polydimethylsiloxane (PDMS) membrane. The thin contactless membrane allows for field penetration and electro-osmotic flow within the microchannel, but eliminates electrode damage and sample contamination commonly associated with traditional DC electro-osmotic pumps that utilize electrodes in direct contact with the working fluid. Our previous work has demonstrated the effectiveness of this method in pumping deionized water. However, due to the high resistivity of PDMS, this method proved difficult to apply towards manipulating conductive buffers. To overcome this limitation, we fabricated conductive carbon black (CB) powder directly into the contactless PDMS membranes. The increased electrical conductivity of the contactless PDMS membrane significantly increased micropump performance. Using a microfluidic T-channel device and an electro-osmotic flow model, we determined the influence that CB has on pump pressure for CB weight percents varying between 0 and 20. The results demonstrate that the CB increases pump pressure by two orders of magnitude and enables effective operations with conductive buffers. 相似文献
12.
随着电力系统的不断发展和进步,输电线路的电压等级也在不断的上升,对埋地金属的影响越来越明显,本文分析了输电线路对埋地金属的电化学腐蚀和电磁耦合等影响,介绍了各种影响的机理,并提出了对各种影响的防护措施。 相似文献
13.
Hameed A. Elnaggar Raymond J. Krizek Gabor M. Karadi 《Journal of The Franklin Institute》1973,296(5):323-337
The effect of non-Darcian flow on the consolidation behavior of clay soils is studied, and its role in the extrapolation of laboratory test results to field problems is evaluated. This is accomplished by postulating a reasonably general four-parameter velocity-gradient relationship which, by proper choice of parameters, is capable of characterizing much of the published experimental data; then, this relationship is combined with the standard assumptions of classical consolidation theory to develop a nonlinear parabolic partial differential equation, which is solved by use of a finite difference technique. The stability and convergence criteria for related linear and quasi-linear equations are empirically extended to the associated nonlinear equations, and a comparison is made between various explicit and implicit finite difference schemes, with the result that a sufficiently accurate and more economical numerical solution is obtained by use of an explicit scheme. Typical solutions for various specific cases confirm and offer an explanation for the well-known phenomenon wherein the time rate of consolidation is found to decrease as the load increment decreases; also, the thickness of the consolidating layer is shown to affect the dimensionless time rate of consolidation. These conditions indicate that laboratory consolidation test results can be applied to a field situation only if appropriate stress and thickness corrections are made. 相似文献
14.
The effect of an electrical double layer (EDL) on microchannel flow has been studied widely, and a constant bulk electric conductivity is often used in calculations of flow rate or pressure drop. In our experimental study of pressure-driven micropipette flows, the pipette diameter is on the same order of magnitude as the Debye length. The overlapping EDL resulted in a much higher electric conductivity, lower streaming potential, and lower electroviscous effect. To elucidate the effect of overlapping EDL, this paper developed a simple model for water flow without salts or dissolved gases (such as CO2) inside a two-dimensional microchannel. The governing equations for the flow, the Poisson, and Nernst equations for the electric potential and ion concentrations and the charge continuity equation were solved. The effects of overlapping EDL on the electric conductivity, velocity distribution, and overall pressure drop in the microchannel were quantified. The results showed that the average electric conductivity of electrolyte inside the channel increased significantly as the EDL overlaps. With the modified mean electric conductivity, the pressure drop for the pressure-driven flow was smaller than that without the influence of the EDL on conductivity. The results of this study provide a physical explanation for the observed decrease in electroviscous effect for microchannels when the EDL layers from opposing walls overlap. 相似文献
15.
Ioannis M. Besieris 《Journal of The Franklin Institute》1974,297(4):243-258
The electromagnetic radiation arising from a longitudinally and a transversely oriented magnetic dipole in a dissipative uniaxially anisotropic medium is determined by writing separate equations for the electromagnetic field intensities, and utilizing a spectral representation in the space-time Fourier domain. It is established that explicit, time- dependent, analytical solutions are possible in the case where the permitivity, permeability and conductivity tensors are simultaneously diagonalizable by means of a collineatory transformation, and the permittivity and conductivity tensors are directly proportional to each other. 相似文献
16.
A numerical modeling of natural convection under the influence of either axial (Bz) or radial (Br) magnetic field in a cylindrical configuration filled with a low-Prandtl number electrically conducting fluid, is studied. The finite volume method is used to discretize the equations of continuity, Navier Stokes and energy. A computer program based on the SIMPLER algorithm is developed. The flow and temperature fields are presented by stream function and isotherms, respectively. Stability diagrams are established according to the numerical results of this investigation. These diagrams put in evidence the dependence of the critical Grashof number, Grcr with the increase of the Hartmann number, Ha. The strongest stabilization of the convective flows occurs when the magnetic field is applied in the radial direction. This study confirms the possibility of stabilization of a liquid metal flow in natural convection by application of a radial magnetic field. 相似文献
17.
量化长江经济带水资源消耗时空差异的驱动效应,对双控行动的贯彻实施具有重要意义。本文采用LMDI方法,将用水量的时空差异分解为经济规模效应、产业结构效应和技术进步效应,用水强度的时空差异分解为产业结构效应和技术进步效应。结果显示：技术进步、产业结构调整是抑制用水量上升和促进用水强度下降的主次因素,而经济增长始终推动用水量上升;三次产业用水效率普遍提高和第一产业比重下降,有力促进了用水量和用水强度下降;与重庆相比,其他省份产业用水强度始终较大,尤其是第一、二产业,不利于用水量空间差异的缩小,长江三角洲省份产业结构更加高级缩小了用水量空间差异;与上海相比,其他省份第三产业用水强度始终较大和产业结构低级扩大了用水强度空间差异;水资源消耗时空差异之间存在相互转换的关系。因此,用水量控制应该围绕提高用水效率和优化产业结构,还需要辅助于经济、制度等手段,同时,根据三次产业特征差异而有所侧重;各省份选定参照对象后,依据空间差异驱动效应情况,提出适用的节水对策。 相似文献
18.
P. Hammond 《Journal of The Franklin Institute》1978,306(2):133-157
Electromagnetic fields can be treated as systems in which the field equations are the equations of equilibrium. This formulation draws the subject into the unified approach of mechanics. Close analogies to potential and kinetic energy exist and these can be used to provide double bounds to the electromagnetic energy. 相似文献
19.
D. Schieber 《Journal of The Franklin Institute》1973,296(1):15-31
The present paper deals with the transient electromechanical interaction in a thin layer of liquid metal on sudden disruption of an imposed magnetic field. The problem is of fundamental importance for understanding the transient performance of various magnetohydrodynamic devices, such as electromagnetic agitators, pumps, liquid metal machines, etc. 相似文献
20.
The properties of the hysteresis machine are analyzed on the basis of a cylindrical model. The electromagnetic field in the various regions of the motor is derived by field-theoretical methods (such as Maxwell's equations and Poynting's theorem), and the resulting parameters are applied in turn in determining torques and other relevant quantities. Three limiting particular cases of special interest are examined. 相似文献