共查询到20条相似文献,搜索用时 597 毫秒
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本文讨论用有限元求解Orr-Sommerfeld方程的方法。由于选取7阶Hermite多项式为元素的基函数和按照流体在各个区域中的不同物理特性选取元素的网格分布,保证了函数在元素节点处C3连续及计算误差的较好控制,所得的结果比以前较为准确。应用这种方法讨论Plane Poi-seuille流的稳定性问题,求得临界雷诺数Rc=5772.2218,在雷诺数从Rc到R=1010范围内较精确地计算了该流体的中性曲线。 相似文献
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本文给出了数值求解以流函数表示的Navier-Stokes方程的交替方向部分隐式和交替方向完全隐式方法;作为算例,计算了低雷诺数的二维方腔流动问题,并与已知结果进行了比较。 相似文献
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用粒子模拟方法求解描述环形等离子体中电子温度梯度静电模的回旋动力学方程.方程采用圆磁通面的轴对称环形几何系统,考虑了有限拉摩半径、电子渡越频率k∥v ∥以及环形漂移(曲率和磁场梯度)运动wD(v2⊥,v 2∥,θ)的效应.简述了粒子模拟的基本方法.采用了四阶变步长积分格式,使计算省时、简便.讨论了模的基本特征 , 并且给出了临界梯度对电子温度与离子温度之
关键词:
电子温度梯度不稳定性
粒子模拟
变步长积分格式
临界梯度 相似文献
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微通道内流动因表面积/体积比值极大, 造成许多微尺度效应, 进而使微通道内出现完全不同于宏观流动的流体密度分布特性. 本文以纳米通道内液态Poiseuille流为对象, 采用非平衡分子动力学模拟方法研究了流体原子间相互作用强度εLL, 流体原子间平衡距离σLL以及壁面原子与流体原子间平衡距离σLS对通道内流体密度分布的影响规律. 数值模拟中, 统计系综取微正则系综, 势能函数选用LJ/126模型, 壁面设为Rigid-atom壁面, 温度校正使用速度定标法, 牛顿运动方程的求解则采用Verlet算法. 模拟结果表明, 随εLL的减弱, 近壁面区密度分布的振荡幅度则逐渐增大; 而σLL 则同时影响流体原子的存在形态和密度分布, 较大的σLL 会造成流体原子在整个通道内呈现面心立方结构的类似固体排列, 较小的σLL会使得流体原子呈现不断变化的 "团簇" 结构; 随σLS的变大, 近壁面区流体密度振荡幅度增大, 且流体密度分布起点离壁面越远. 另外, 本文还从近壁面区流体原子的 "俘获-逃逸" 行为角度, 初步解释了原子间相互作用强度对密度分布的影响规律.
关键词:
纳米通道
微流动
密度分布
分子动力学 相似文献
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文章考察了相邻双侧边盖驱动方腔流动(即上壁面向右运动和左侧壁面向下运动)的三维线性整体稳定性.首先,采用Taylor-Hood有限元方法并经由Newton迭代过程计算得到双侧边盖驱动方腔流动的二维稳态基本流.其次,Taylor-Hood有限元在Chebyshev Gauss配置点上进行离散,同时Gauss配置点也可以用于线性稳定性方程的高阶有限差分格式离散.然后,离散得到的矩阵形式的广义特征值问题可以结合shift-and-invert算法采用隐式重启Arnoldi方法计算.最后,通过对线性稳定性方程特征值的计算,发现了一个最不稳定的驻定模态和两对对称行波模态.最不稳定的三维驻定模态的临界Reynolds数为Rec=261.5,远远小于二维不稳定的临界Reynolds数Rec2d=1 061.7.通过画出这3类三维不稳定模态的流向扰动速度和扰动涡量的空间等值面图像,可以发现不稳定扰动位于稳态基本流的两个主涡区域,因此可以认为主涡区域是三维扰动失稳的主要能量来源地. 相似文献
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一种三维环流模型及其应用 总被引:1,自引:0,他引:1
本文建立了一种广泛适用于大陆架浅海的三维环流模型。模型的支配方程是具有自由面的三维非线性瞬态Navier-Stokes方程。支配方程经σ坐标变换后与边界条件一起在空间交错网格系统上用差分法求解。为提高计算效率,基于问题的物理性质引入过程分裂概念没计了计算框架:将三维流动过程分成长重力波的传播(外模式)和速度的垂向剪变(内模式)两大组成部分,对每个部分分别选用最适宜各自物理特性和数值行为的数值方法求解。最后做为本模型的应用实例,计算了渤海三维潮流,获得了很好的结果。 相似文献
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Under investigation in this paper are the inhomogeneous nonlinear Schrödinger Maxwell–Bloch (INLS-MB) equations which model the propagation of optical waves in an inhomogeneous nonlinear light guide doped with two-level resonant atoms. Higher-order nonautonomous breather as well as rogue wave solutions in terms of the determinants for the INLS-MB equations are presented via the n-fold variable-coefficient modified Darboux transformation. The interactions among two nonautonomous breathers are graphically discussed, including the fundamental breather, bound breather, two-breather compression and two-breather evolution, etc. Moreover, several patterns of the higher-order rogue waves are also exhibited, such as the square rogue wave, two- and three-order periodic rogue waves, periodic fission and fusion, two-order stationary rogue waves, and recurrence of the two-order rogue waves. The character of the trajectory of the two-order periodic rogue wave is analyzed. Additionally, a novel type of interaction, namely, the collision between the breather and long-lived rogue waves, is found to be elastic. Our results could be useful for controlling the nonautonomous optical breathers and rogue waves in the inhomogeneous erbium doped fiber. 相似文献
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提出一种新的线性化微分求积法(LDQM),将这种目的应用到流函数和涡量形式的Navier-Stokes方程.通过LDQM,非线性方程很容易被解出来,并且容易处理压力的边界条件.为检验本目的,计算了两个数值算例. 相似文献
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谱元方法求解正方形封闭空腔内的自然对流换热 总被引:6,自引:0,他引:6
提出谱元方法计算正方形截面封闭空腔内的自然对流问题,具体求解了原始变量速度和压力的不可压Navier-Stokes方程和温度方程,所有的求为量均采用Chebyshev谱逼近,Navier-Stokes方程和温度方程的时间离散采用时间分裂法,非线性项用4阶Runge-Kutta法,扩散项用Crank-Nicolson半隐方法,获得了与文献发表的基准解较一致的计算结果。 相似文献
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Starting from the Navier-Stokes equations we treat the onset of the wavy vortex flow of the Taylor problem in a fully nonlinear manner. To this end we first transform the original partial differential equations into a set of ordinary differential equations by means of a Galerkin method. By a specific choice of the basic functions the Galerkin coefficients acquire a very concise form. Since these functions fulfil the boundary conditions individually, there are no additional constraints on these coefficients, which usually stem from the boundary conditions. We then first calculate the Taylor vortex flow and perform a linear stability analysis of it. Finally we calculate the coefficients of the generalized Ginzburg-Landau equations in the vicinity of the second threshold and solve these equations. 相似文献
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A. M. Balonishnikov 《Technical Physics》2005,50(10):1251-1254
A model of parallel noninteracting cascades in the spectral space is suggested in terms of which the turbulent flow of an
incompressible fluid subject to arbitrary large-scale velocity gradients is described. The linear parts of model equations
for two polarization components of the velocity are derived from the Navier-Stokes equations, and their nonlinear parts correspond
to the 1D Burgers model. Using the model suggested, explicit expressions for subgrid Reynolds stresses without empiric parameters
are obtained. 相似文献
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A Discontinuous Galerkin Method Based on a BGK Scheme for the Navier-Stokes Equations on Arbitrary Grids
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A discontinuous Galerkin Method based on a Bhatnagar-Gross-Krook
(BGK) formulation is presented for the solution of the compressible
Navier-Stokes equations on arbitrary grids. The idea behind this
approach is to combine the robustness of the BGK scheme with the
accuracy of the DG methods in an effort to develop a more accurate,
efficient, and robust method for numerical simulations of viscous
flows in a wide range of flow regimes. Unlike the traditional
discontinuous Galerkin methods, where a Local Discontinuous Galerkin
(LDG) formulation is usually used to discretize the viscous fluxes
in the Navier-Stokes equations, this DG method uses a BGK scheme to
compute the fluxes which not only couples the convective and
dissipative terms together, but also includes both discontinuous and
continuous representation in the flux evaluation at a cell interface
through a simple hybrid gas distribution function. The developed
method is used to compute a variety of viscous flow problems on
arbitrary grids. The numerical results obtained by this BGKDG method
are extremely promising and encouraging in terms of both accuracy
and robustness, indicating its ability and potential to become not
just a competitive but simply a superior approach than the current
available numerical methods. 相似文献