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根据简化的二维流动方程,编写了正问题的计算机程序.对亚声速轴流式压气机级进行了计算,把计算结果与试验结果进行了比较.对这种计算方法作了评价并提出了特性计算中需要解决的问题。 相似文献
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针对目前有限时间Lyapunov指数(FTLE)计算方法准确度不高和无法获得边界值的问题,基于对偶数理论提出了一种新的高精度计算方法.首先描述了基于有限空间差分方法计算FTLE的缺点和问题:其次介绍了基于对偶数理论的高精度导数计算方法及其显著优点,并将动力系统的柯西一格林形变张量计算问题转化为对偶数空间中非线性微分方程数值求解问题;最后对单摆和非线性Duffing振子两个典型物理动力系统进行了数值实验.结果表明:基于对偶数理论的新方法能有效、方便和高精度地计算出有限时间Lyapunov指数场,并成功识别出所包含的拉格朗日相关结构. 相似文献
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三维频域自由面格林函数及其偏导数的数值计算是海洋结构物水动力分析的难点.本文对有限水深格林函数及其偏导数的数值算法作出两点改进:①对原函数的级数表达式进行变形,提出适用于数值计算的形式,解决高频率情况下级数解的计算失真问题;②对Gauss-Laguerre积分法作出改进,解决高频率大水深情况下积分解的数值溢出问题.计算... 相似文献
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发展了一种基于MOF(Moment of Fluid)界面重构的二维中心型MMALE(Multi-Material Arbitrary Lagrangian-Eulerian)方法.其中,流体力学方程组采用中心型拉氏方法进行离散求解.混合网格的热力学封闭采用Tipton压力松弛模型.混合网格内的界面重构采用MOF方法,并对MOF方法作了简化和改进.重映步采用一种基于多边形剪裁算法的精确积分守恒重映方法.计算了若干数值例子,包括二维漩涡发展问题、Sedov问题、激波与氦气泡相互作用问题、水中强激波与空气泡相互作用问题、二维RT不稳定性问题等.数值算例表明,该方法具有二阶精度,能够计算界面两侧密度比和压力比很大的问题,并且其健壮性优于交错型MMALE方法,适合计算多介质复杂流体动力学问题. 相似文献
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提出一种在自由重映移动网格下的广义黎曼问题方法模拟反应流.该方法基于显式的自由重映移动网格广义黎曼问题的解.为保证在时间和空间上的高精度,应用广义黎曼问题方法构造数值通量.为保证反应区的高分辨率,采用变分法生成自适应移动网格.该方法不仅能够保证网格质量,而且能有效地避免任意拉格朗日—欧拉方法中由于显式重映过程而带来的数值误差.包括CJ爆轰及不稳定爆轰的数值实验说明该格式的精确性和鲁棒性,证明这种移动网格下的二阶广义黎曼问题方法可以较好地捕捉反应流的间断与光滑结构. 相似文献
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A new characteristic approach that guarantees conservative property is proposed and is applied to the shallow water equations. CIP–CSL (Constrained Interpolation Profile/Conservative Semi-Lagrangian) interpolation is applied to the CIP method of characteristics in order to enhance the mass conservation of the numerical result. Although the characteristic formulation is originally derived from non-conservative form, present scheme achieves complete mass conservation by solving mass conservation simultaneously and reflecting conserving mass in interpolation profile. Present method has less height error compared to the CIP method of characteristics by several orders of magnitude. By the enhanced conservation property, present scheme is applicable to nonlinear problem such as shock. Furthermore, application to two dimensions including the Coriolis term is straightforward with directional splitting technique. 相似文献
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Binary Level Set Methods for Dynamic Reservoir Characterization by Operator Splitting Scheme
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Changhui Yao 《advances in applied mathematics and mechanics.》2012,4(6):780-798
In this paper, operator splitting scheme for dynamic reservoir
characterization by binary level set method is employed.
For this problem, the absolute permeability of the two-phase
porous medium flow can be simulated by the constrained augmented
Lagrangian optimization method with well data and seismic
time-lapse data. By transforming the constrained optimization
problem in an unconstrained one, the
saddle point problem can be solved by Uzawas algorithms
with operator splitting scheme, which is based on the essence
of binary level set method. Both the simple and complicated
numerical examples demonstrate that the given algorithms are
stable and efficient and the absolute permeability can be
satisfactorily recovered. 相似文献
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This article addresses the resolution of the inverse problem for the parameter
identification in orthotropic materials with a number of measurements merely on
the boundaries. The inverse problem is formulated as an optimization problem of
a residual functional which evaluates the differences between the experimental and
predicted displacements. The singular boundary method, an integration-free, mathematically
simple and boundary-only meshless method, is employed to numerically
determine the predicted displacements. The residual functional is minimized by the
Levenberg-Marquardt method. Three numerical examples are carried out to illustrate
the robustness, efficiency, and accuracy of the proposed scheme. In addition, different
levels of noise are added into the boundary conditions to verify the stability of the
present methodology. 相似文献
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Transient flow over erodible bed is solved in this work assuming that the dynamics of the bed load problem is described by two mathematical models: the hydrodynamic model, assumed to be well formulated by means of the depth averaged shallow water equations, and the Exner equation. The Exner equation is written assuming that bed load transport is governed by a power law of the flow velocity and by a flow/sediment interaction parameter variable in time and space. The complete system is formed by four coupled partial differential equations and a genuinely Roe-type first order scheme has been used to solve it on triangular unstructured meshes. Exact solutions have been derived for the particular case of initial value Riemann problems with variable bed level and depending on particular forms of the solid discharge formula. The model, supplied with the corresponding solid transport formulae, is tested by comparing with the exact solutions. The model is validated against laboratory experimental data of different unsteady problems over erodible bed. 相似文献
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在二维柱坐标系下Lagrange流体力学的计算中,积分梯度法是动量方程的一种有效离散方法.积分梯度法中,IGT(Integral Gradient Total)格式不能保持柱几何下一维球对称性;IGA(Integral Gradient Average)格式可以保持一维球对称性,但当相邻网格质量相差比较大时,会得到远远脱离真实物理现象的加速度.深入研究IGA和IGT格式发现,当相邻网格边界压力取为质量加权时,即使相邻网格质量相差较大,对于一维平面和一维柱问题,IGT与IGA等价;在二维情形下,可以缩小IGT和IGA之间的差异.理论证明,IGA格式不能保持系统的动量守恒,IGT格式能保持系统的动量守恒性.数值模拟结果进一步显示了这两个格式的优缺点. 相似文献
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基于两重网格离散和区域分解技巧,提出三种求解非定常Navier-Stokes方程的有限元并行算法.算法的基本思想是在每一时间迭代步,在粗网格上采用Oseen迭代法求解非线性问题,在细网格上分别并行求解Oseen、Newton、Stokes线性问题以校正粗网格解.对于空间变量采用有限元离散,时间变量采用向后Euler格式离散.数值实验验证了算法的有效性. 相似文献