共查询到20条相似文献,搜索用时 328 毫秒
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本文在[1]和[5]的基础上,研究最大网络流问题.与已有的研究不同的是,本文对最大流问题进行了分解,即把最大流网络分解成几个相互独立的子网络. 相似文献
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最大利润流问题及算法 总被引:3,自引:0,他引:3
最大利润流是以运输利润最大为目标的网络优化问题 .一个利润可行流可分解为若干个路流和圈流 ,相应地该可行流的利润也等于这些路流和圈流的利润之和 .本文证明了一个可行流为最大利润流的充要条件是不存在利润增广路 ,并据此提出了求解算法 .文章最后给出了一个计算实例 . 相似文献
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该文首先提出了流面和流层的概念,然后推导出了半测地坐标系下流层内的三维NS (Navier-Stokes)方程,以及流面上的二维NS方程.通过引入流面上的流函数,得到了流函数方程的非线性初边值问题,并讨论了方程解的存在性和唯一性.基于以上讨论,提出了求解三维NS方程的维数分裂方法, 并给出了算例. 相似文献
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对于一些特殊的流动,尤其是平面上的位势流动,速度图方法有其显著的优点.对于理想流体来说,流面总是存在的,在流面上,流动的速度向量总是在其切空间里.通过引入流函数和势函数,采用张量分析作为工具,给出了二维曲流面上位势流动的速度图方法,得到了流函数满足的速度图方程,为一些特殊的流动问题提供了一类分析方法.并且,对于得到的二维速度图方程,得到了相应的特征方程和特征根,从而可以对方程的类型进行分类.最后,给出了一些特殊流动的实例. 相似文献
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本文研究了半无限长圆管内Stokes流的入口流问题.我们导出了一种新的级数解,它与文献[1,2]的解有一个明显的区别就是该解中不包含无穷积分,因此有利于计算.本文利用配点法进行了计算,得到了满意的结果. 相似文献
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本文依据文献[1]的密相两相流动的数学模型,对垂直圆管中密相两相流动进行了解析求解,分别得到了连续相和分散相的速度解析表达式.在相间阻力与相间速度差成比例时,除了在离管壁面很近的薄区之外,管道流动规律与达西渗流定律完全一致.本文验证了文献[1]的密相两相流动数学模型的假定在本文情形下是合理的. 相似文献
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本文详细阐述了旋风分离器内流动在球坐标系中的数学表述和结果,应用质量守恒定律和定常流动的运动定律,在轴对称的考虑下,用流函数方法详尽推导了流动的三个速度分量.此讨论是从三维的整体观点来全面分析流动状况的.此外,对文[1]中的一些结果作了必要的修正. 相似文献
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T型分叉血管的定常/脉动流动和大分子传质 总被引:1,自引:1,他引:0
采用计算流体动力学方法,数值求解了T型分叉流动的定常/脉动流场和低密度脂蛋白(LDL)以及血清白蛋白(Albumin)的浓度分布。计算了雷诺数、主管和支管的流量比等参数对流场和大分子传质的影响,计算结果表明,流体动力学因素影响大分子的分布和跨壁渗透,在动脉硬化的发生和发展过程中起着重要的作用。在流动发生分离处,即支管入口外侧壁面剪应力变化最剧烈,这儿LDL和Albumin的壁面浓度变化也是最剧烈,是动脉硬化危险区。 相似文献
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《Journal of the Egyptian Mathematical Society》2014,22(1):123-133
A numerical model is presented to study the effects of temperature-dependent viscosity and variable thermal conductivity on mixed convection problem. Two important types of wall heating conditions namely, prescribed surface temperature and prescribed wall heat flux which arise in polymer industries are considered. The problem is solved numerically by using the fifth-order Runge–Kutta Fehlberg method with shooting technique. It is found that the Prandtl number is to decrease the skin friction coefficient, local Nusselt number and local Sherwood number. The effects of non-uniform heat source/sink and porous parameter are analyzed on velocity, temperature, skin friction co-efficient, Nusselt and Sherwood numbers. 相似文献
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针对当前多介质流体计算中出现的速度和压强在介质界面处产生伪振荡的问题,我们设计了一种基于非平衡态的Lax-Friedrichs格式.我们构造的算法保证了多个守恒性质:总质量和分质量守恒,总动量和总能量守恒,它还可以保证分质量非负.更重要的是它消除了速度和压强在介质界面处的伪振荡.数值例子表明这一算法是有效的. 相似文献
14.
Smectic liquid crystals are materials formed by stacking deformable, fluid layers. Although smectics prefer to have flat, uniformly-spaced layers, boundary conditions can impose curvature on the layers. Since the layer spacing and curvature are intertwined, the problem of finding minimal configurations for the layers becomes nontrivial. We discuss various topological and geometrical aspects of these materials and present recent progress on finding some exact layer configurations. We also exhibit connections to the study of certain embedded minimal surfaces and briefly summarize some important open problems. 相似文献
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The constrained maximum flow problem is to send the maximum flow from a source to a sink in a directed capacitated network where each arc has a cost and the total cost of the flow cannot exceed a budget. This problem is similar to some variants of classical problems such as the constrained shortest path problem, constrained transportation problem, or constrained assignment problem, all of which have important applications in practice. The constrained maximum flow problem itself has important applications, such as in logistics, telecommunications and computer networks. In this research, we present an efficient specialized network simplex algorithm that significantly outperforms the two widely used LP solvers: CPLEX and lp_solve. We report CPU times of an average of 27 times faster than CPLEX (with its dual simplex algorithm), the closest competitor of our algorithm. 相似文献
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Subrata Mukhopadhyay Mani Shankar Mandal Swati Mukhopadhyay 《Mathematical Methods in the Applied Sciences》2019,42(2):488-504
The objective of the present study is to investigate the effects of variable viscosity on incompressible laminar pulsatile flow of blood through an overlapping doubly constricted tapered artery. To mimic the realistic situation, wall of the artery is taken to be flexible, and physiologically relevant pulsatile flow is introduced. The governing equations of blood flow are made dimensionless. A coordinate transformation is used to make the overlapping doubly constricted wall geometry of tube to a straight tube. Taking advantage of the Stream function–Vorticity formulation, the system of partial differential equations is then solved numerically by finite difference approximations. Effects of Reynolds number, Strouhal number, degree of contraction, tapering angle, and viscosity parameters are presented graphically and analyzed. The results show that formation of stenosis and tapering disturb the flow field significantly, and degree of stenosis is more important in influencing blood flow compared with tapering. 相似文献
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提出了可渗透近球体轴对称流动的分析方法.用修正边界条件的办法反映可渗透性.用正规摄动法求解了Stokes方程,达到ε的2阶修正.ε是描述不变形球体半径偏差的小参数.计算了阻力和流量,并从几何方面和表面渗透性方面考查了计算结果.还尝试将此理论应用于过滤供水问题.小型的生态学上重要的水生生物体的过滤器,被模型化为轴对称可渗透物体,用扁球体或近球体建立了该问题的初级模型. 相似文献
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提高企业效益的一个很重要方面是提高企业的投资效益.针对这一问题,运用动态规划的方法,提出了一个决策模型,使该模型得出的投资方案产生最大的贴现现金流(DCF). 相似文献
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In this work we studied the cluster formation of particles flowing between two parallel plates hitting a rectangular obstacle. After a short time a cluster is formed on top of the obstacle. Quantification of the cluster formation, shows that the number of clusters decrease with time, whereas the mean and maximum cluster size grow during the simulation. Our results indicate that for the development of clusters the value of the restitution coefficient for particle–particle collisions is most important parameter for this formation process. We found that changes in the value of the restitution parameters for particle–obstacle and particle–wall did not show significant changes in the cluster development. 相似文献
20.
Summary. We derive a set of asymptotically exact coupled amplitude-streaming flow ({CASF}) equations governing the evolution of weakly nonlinear nearly inviscid multimode Faraday waves and the associated
streaming flow in finite geometries. The streaming flow is found to play a particularly important role near mode interactions.
Such interactions come about either through a suitable choice of parameters or through breaking of degeneracy among modes
related by symmetry. An example of the first case is provided by the interaction of two nonaxisymmetric modes in a circular
container with different azimuthal wavenumbers. The second case arises when the shape of the container is changed from square
to slightly rectangular, or from circular to slightly noncircular but with a plane of symmetry. The generation of streaming
flow in each of these cases is discussed in detail and the properties of the resulting CASF equations are described. A preliminary
analysis suggests that these equations can resolve discrepancies between existing theory and experimental results in the first
two of the above cases. 相似文献