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1.
以无时间分裂误差的区域分解Stokes谱元算法为基础构建整体稳定性分析方法.用Jacobian-free的Inexact-Newton-Krylov算法求解不可压缩Navier-Stokes方程的定常解,将Stokes算法的时间推进步作为Newton迭代的预处理,在此基础上采用Arnoldi方法计算大规模特征值问题,对复杂流动进行稳定性分析,该方法能统一处理定常和非定常计算,没有时间分裂误差,无需显式构造Jacobian矩阵,可以减少内存使用,降低计算量,并加速迭代收敛.对有分析解的Kovasznay流动的计算表明,高阶谱元法具有指数收敛的谱精度.对亚临界方腔对称驱动流的各种定常解的计算及其稳定性分析验证了方法的可行性.  相似文献   

2.
用DES数值模拟分离绕流中的旋涡运动   总被引:1,自引:0,他引:1  
脱体涡模拟(Detached-Eddy Simulation,DES)是近年来出现的一种结合雷诺平均方法和大涡数值模拟两者优点的湍流模拟方法.采用基于Spalan-Allmaras方程模型的DES方法,数值求解Navier-Stokes方程,模拟绕流发生分离后的旋涡运动.其中空间区域离散采用有限体积法,方程空间项和时间项的数值离散分别采用Jameson中心格式和双时间步长推进方法.通过模拟圆柱绕流以及翼型失速绕流,观察到了与物理现象一致的旋涡结构,得到与实验数据相吻合的计算结果.  相似文献   

3.
水平刻槽管壁面升膜流动是一种低雷诺数流,低雷诺数流动的特点是惯性力与粘性力相比可以忽略不计,因此在求解Navier-Stokes方程时,常忽略对流项进行计算.本文通过采用一种级数解法,对含有对流项的Navier-Stokes方程进行逐级求解,分析不同雷诺数下含对流项的Navier-Stokes方程对速度解的影响.  相似文献   

4.
成娟  黄明恪 《计算物理》2003,20(3):273-278
研究如何在非结构网格上进行Navier-Stokes(N—S)方程湍流计算.采用格心有限体积方法离散N—S方程.为了适应非结构网格,计算所用的湍流模型特别选用Baldwin-Barth(B—B)单方程模型.此模型由一个单一的具有源项的对流扩散方程组成.为了能在非结构网格上求解B—B单方程模型,提出一显式有限体积格式,并直接对带源项的格式进行稳定性分析,得到了相应的时间步长限制条件.最后以平板、RAE—2822翼型、多段翼型绕流等数值算例验证了计算方法的有效性。  相似文献   

5.
三维不可压N-S方程的多重网格求解   总被引:2,自引:0,他引:2  
袁礼 《计算物理》2002,19(1):23-29
应用全近似存储(Full Approximation Storage,FAS)多重网格法和人工压缩性方法求解了三维不可压Navier-Stokes方程.在解粗网格差分方程时,对Neumann边界条件采用增量形式进行更新,离散方程用对角化形式的近似隐式因子分解格式求解,其中空间无粘项分别用MUSCL格式和对称TVD格式进行离散.对90.弯曲的方截面管道流动和41椭球体层流绕流的数值模拟表明,多重网格的计算时间比单重网格节省一半以上,且无限制函数的MUSCL格式比TVD格式对流动结构有更好的分辨能力.  相似文献   

6.
基于Hermite多项式的C1型单元构造复杂,限制了最小二乘有限元法的应用.引入高阶光滑的非均匀有理B样条作为基函数简化C1型单元构造,提出求解黏性不可压流动Navier-Stokes方程的最小二乘等几何方法.用Newton法或Picard法对Navier-Stokes方程线性化,用线性化偏微分方程的余量定义最小二乘泛函,导出最小二乘变分方程,用NURBS构造高阶光滑的有限维空间来近似速度场和压力场.计算表明:本文方法计算的二维顶盖驱动流数值解能准确描述流动状况,计算的二维通道内圆柱绕流全局质量损失由最小二乘有限元法的6%降为0.018%,该方法可用于Navier-Stokes方程的求解,并且具有较好的质量守恒性.  相似文献   

7.
王兵  卢梦 《气体物理》2016,1(6):5-21
在不同参数条件下, 计算分析了H2O和N2等混合物界面上激波诱导Richtmyer-Meshkov(R-M)不稳定性过程.采用有限差分方法数值求解了二维可压缩Navier-Stokes方程, 对流项以5阶特征紧致-WENO混合格式离散, 输运项以6阶对称紧致格式离散, 时间方向以3阶显式Runge-Kutta方法推进.研究表明, 界面振幅和激波强度增大, 均可增强界面附近涡量场, 强化混合.   相似文献   

8.
任意马赫数非定常流动数值模拟的统一算法   总被引:2,自引:0,他引:2  
欧平  马汉东  汪翼云 《计算物理》2007,24(2):166-170
发展适用于从低速到高速任意马赫数非定常流动数值模拟的统一算法.通过引入一个伪时间导数项和一个新的预处理矩阵,得到双时间非定常预处理可压缩Navier-Stokes方程.方程的对流项采用三阶Roe通量近似差分格式离散,粘性项采用二阶中心差分格式离散.基于数值通量的线性化技术,实现伪时间步的隐式ADILU格式迭代,进而获得物理时间步的二阶推进精度.重点以低马赫数流动为例,求解了圆柱绕流和NACA0015翼型等速上仰动态失速问题.计算结果表明该统一算法能够较好地模拟低马赫数乃至任意马赫数非定常流动.  相似文献   

9.
梁强  杨永年  樊则文 《计算物理》2004,21(2):179-184
以多台微机组成分布式计算系统,利用无限插值方法(TFI)生成三维多块贴体运动网格,以Navier-Stokes方程为控制方程,求解三维机翼的跨音速非定常气动力,并与颤振方程耦合迭代计算,求解机翼广义位移响应的时间历程,根据广义位移的时间历程的衰减、等幅和发散振荡等情况确定机翼跨音速颤振临界条件.通过算例验证,计算结果与实验结果和理论分析相吻合.  相似文献   

10.
本文采用预处理的时间推进方法,求解可压形式的Euler/Navier-Stokes方程,数值模拟低马赫数范围内的无粘、粘性流动.为了进一步加速收敛,并使用了多重网格技术.计算表明预处理能够保持可压缩求解方法在高速时的收敛特征,对于低速流动计算可以加速收敛并提高精度.  相似文献   

11.
MODAL ANALYSIS OF ROTATING COMPOSITE CANTILEVER PLATES   总被引:1,自引:0,他引:1  
A modelling method for the modal analysis of a rotating composite cantilever plate is presented in this paper. A set of linear ordinary differential equations of motion for the plate is derived by using the assumed mode method. Two in-plane stretch variables are employed and approximated to derive the equations of motion. The equations of motion include the coupling terms between the in-plane and the lateral motions as well as the motion-induced stiffness variation terms. Dimensionless parameters are identified and the explicit mass and the stiffness matrices for the modal analysis are obtained with the dimensionless parameters. The effects of the dimensionless angular velocity and the fiber orientation angles of rotating composite cantilever plates on their modal characteristics are investigated. Natural frequency loci veering and crossing along with associated mode shape variations are observed.  相似文献   

12.
The problem of calculating the rate of mutual information between two coarse-grained variables that together specify a continuous time Markov process is addressed. As a main obstacle, the coarse-grained variables are in general non-Markovian, therefore, an expression for their Shannon entropy rates in terms of the stationary probability distribution is not known. A numerical method to estimate the Shannon entropy rate of continuous time hidden-Markov processes from a single time series is developed. With this method the rate of mutual information can be determined numerically. Moreover, an analytical upper bound on the rate of mutual information is calculated for a class of Markov processes for which the transition rates have a bipartite character. Our general results are illustrated with explicit calculations for four-state networks.  相似文献   

13.
The Fibonacci method is considered for stationary distributions. The initial postulates of this method are opposite to the postulates of statistical mechanics. The inapplicability of the hypothesis on identical dynamic particles is demonstrated on the example of the stationary state of a macromolecule in a thermostat. A new model of the stationary state of a substance is constructed based on the equality of chaos and order measures specified in terms of variables of three classes. The limiting transition from the new model to the well-known models is given. The law of evolution is expressed in terms of the symmetry of chaos and order.  相似文献   

14.
In this work, Fractional Optimal Control Problem (FOCP) of a Distributed system is investigated in cylindrical coordinates. Axis-symmetry naturally arises in the problem formulation. The fractional time derivative is described in the Riemann-Liouville (RL) sense. The performance index of a FOCP is considered as a function of state and control variables and system dynamics are given as a Partial Fractional Differential Equation (PFDE). The method of separation of variables is used to find the solution of the problem. Eigenfunctions are used to eliminate the terms containing space parameters and to define the problem in terms of a set of generalized state and control variables. For numerical computations, Grünwald-Letnikov (GL) approach is used. A time-invariant example is considered to demonstrate the effectiveness of the formulation. The comparison of analytical and numerical solutions is given using simulation results and also it can be seen that analytical and numerical results converge each other. In addition, simulation results for different values of order of derivative, time discretizations and eigenfunctions are analyzed.  相似文献   

15.
A method is provided to compute the exponent parameter λ yielding the dynamic exponents of critical slowing down in mode coupling theory. It is independent from the dynamic approach and based on the formulation of an effective static field theory. Expressions of λ in terms of third order coefficients of the action expansion or, equivalently, in terms of six point cumulants are provided. Applications are reported to a number of mean-field models: with hard and soft variables and both fully connected and dilute interactions. Comparisons with existing results for the Potts glass model, the random orthogonal model, hard and soft-spin Sherrington-Kirkpatrick, and p-spin models are presented.  相似文献   

16.
A separation of variables method based on expansions of the electromagnetic fields in terms of spherical wave functions is expanded at nonspherical (axisymmetric) particles with a rather large number of layers. Commonly used alternative approaches to systems of linear algebraic equations relative to unknown field expansion coefficients for layered particles are considered in some detail. The SVM code developed is compared with the EBCM, GMT and DDA codes designed for multilayered scatterers and some numerical results obtained for nonspherical scatterers with up to 100 layers are presented as illustrations.  相似文献   

17.
采用非交错网格压力修正法计算不可压及可压亚、跨、超音速流动朱斌,蔡睿贤,蒋洪德(中国科学院工程热物理研究所北京100080)关键词:压力修正法,亚、跨、超音速流动一、前言源于计算不可压流动的压力修正方法,由于具有计算时间短及不受马赫数限制的优点,近年...  相似文献   

18.
A method, called beatification, is presented for rapidly extracting weakly nonlinear Hamiltonian systems that describe the dynamics near equilibria of systems possessing Hamiltonian form in terms of noncanonical Poisson brackets. The procedure applies to systems like fluids and plasmas in terms of Eulerian variables that have such noncanonical Poisson brackets, i.e., brackets with nonstandard and possibly degenerate form. A collection of examples of both finite and infinite dimensions is presented.  相似文献   

19.
A technique of expanding arbitrary functions of two variables in separable terms is applied to nuclear single-particle potentials, and a method for high-speed calculation of the eigenstates of the Hamiltonian has been developed. The applicability of the scheme, for spherical as well as highly eccentric shapes. is demonstrated for a sequence of two-centered potentials.  相似文献   

20.
A method is described for solving the inverse problem of determining the profile of an acoustic horn when time-domain reflectance (TDR) is known only at the entrance. The method involves recasting Webster's horn equation in terms of forward and backward propagating wave variables. An essential feature of this method is a requirement that the backward propagating wave be continuous at the wave-front at all locations beyond the entrance. Derivation of the inverse solution raises questions about the meaning of causality in the context of wave propagation in non-uniform tubes. Exact reflectance expressions are presented for infinite exponential, conical and parabolic horns based on exact solutions of the horn equation. Diameter functions obtained with the inverse solution are a good match to all three horn profiles.  相似文献   

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