定常Navier-Stokes方程的一种高效稳定有限元方法

提出了二维定常Navier-Stokes(N-S)方程的一种两层稳定有限元方法.该方法基于局部高斯积分技术,通过不满足inf-sup条件的低次等阶有限元对N-S方程进行有限元求解.该方法在粗网格上解定常N-S方程,在细网格上只需解一个Stokes方程.误差分析和数值试验都表明:两层稳定有限元方法与直接在细网格上采用的传统有限元方法得到的解具有同阶的收敛性,但两层稳定有限元方法节省了大量的工作时间.     

解Stokes方程的一种无散稳定二次有限体积法格式

在三角形网格上构造了一种求解Stokes方程的Lagrange二次有限体积法格式.取连续的二次有限元空间与间断的线性有限元空间分别作为Stokes方程的速度项与压力项的试探空间,从而保证了离散方程的速度解在宏元三角形单元上满足局部质量守恒性,且有限元空间对自然满足所谓的inf-sup条件.采用特殊的有限体积法映射与对偶剖分,求解Stokes方程的Lagrange二次有限体积法格式等价于相对应的有限元法格式,因此确保了有限体积法格式的无条件(无需约束三角形网格的几何形状)稳定性和关于速度项的最优阶H1范数的误差估计.最后,数值实验展示了理论结果的正确性以及有限体积法的数值模拟在计算流体力学中的有效性.     

粘性不可压缩对流占优Oseen方程的非协调子格稳定化有限元法分析

<正>1引言本文考虑粘性不可压缩对流占优Oseen方程,(?)(1)其中:Ω(?)R~d(d=2)为具有Lipschitz连续边界的有界开集,β∈W~(1,∞)(Ω)且▽·β=0,μ、σ为常数,f∈L~2(Ω).当采用通常的混合有限元方法(MFEM)求解时,一般会遇到以下两个困难:·为保证速度和压力数值解稳定,要求有限元空间满足inf-sup(or Babuska-Brezzi)条件.·当对流占优,即0μ《||β||_(L~∞(Ω))时,数值解会产生伪振荡.     

非定常Stokes方程的降阶稳定化CN有限体积元外推模型

利用稳定化的Crank-Nicolson(CN)有限体积元方法和特征投影分解方法,建立非定常Stokes方程的一种自由度很少、精度足够高的降阶稳定化CN有限体积元外推模型,并给出这种降阶稳定化CN有限体积元外推模型解的误差估计和算法的实现.最后用数值例子说明数值结果与理论结果相吻合,并阐明这种降阶稳定化CN有限体积元外推模型的优越性.     

定常Navier-Stokes方程基于完全重叠型区域分解的并行稳定化有限元方法

基于完全重叠型区域分解技巧,针对低阶P_1-P_1有限元,本文提出求解二维定常不可压缩Navier-Stokes方程的并行稳定化有限元方法,其稳定项是基于两局部Gauss积分的压力投影.该方法的基本思想是,使用一局部加密的多尺度网格计算给定子区域上的局部稳定化有限元解.理论分析上借助有限元解的局部先验误差估计,推导出并行稳定化方法所得速度和压力解的误差界.选取适当的算法参数比例,该方法能取得与标准稳定化有限元方法相同的收敛阶,同时减少大量的计算时间.最后给出两类数值算例验证并行稳定化方法的高效性.     

可压缩流动的Fourier谱-有限元解法

本文考虑n维(n=2,3)可压缩流动的带有单向周期边值条件问题的数值解.我们在周期方向采用Fourier谱方法,在非周期方向采用有限元方法,从而构造了一类谱-有限元格式.文中严格分析了计算误差,得到了收敛阶的估计.     

三维非牛顿流体动力学方程衰减性的一个注记

利用Stokes算子的谱分解方法和线性Lp-Lq估计研究一类三维不可压缩非牛顿流体弱解的最优代数衰减速率,证明了当初速度满足u0∈L2(R3)和∫R3(1+|x|)|u0(x)|dx∞,其弱解在L2范数下的衰减率为t-5/4.     

一种抽象的稳定化方法及在非线性不可压缩弹性问题上的应用

针对非线性不可压缩弹性力学问题,本文提出了一种抽象的稳定化方法并将其应用于非线性不可压缩弹性问题上.在该框架中,我们证明了只要连续的混合问题是稳定的,则可以修正任何满足离散inf-sup条件的混合有限元方法使其是稳定的且最优收敛的.我们将这种抽象的稳定化理论框架应用于非线性不可压缩弹性力学问题,给出了稳定性和收敛性理论结论,并通过数值实验验证了该结论.     

新的投影混合稳定化方法在抛物问题中的应用

针对抛物问题提出一种新的投影混合稳定化方法.该方法基于等阶的混合有限元,相比通常的局部投影稳定化方法,增加了新的投影稳定项及压力跳跃项,有效地克服了等阶有限元不满足inf-sup条件而导致的解的不稳定性,也保证了该方法不仅对连续的压力空间适用,且对不连续的压力空间亦适用.本文证明了该方法的稳定性,并给出了误差估计.最后,数值算例验证了该方法的理论分析及有效性.     

双曲型积分-微分方程的有限体积元方法

本文研究了双曲型积分—微分方程的有限体积元方法，利用基于有限体积元的Ritz—Volterra投影的逼近性质，得到了半离散有限体积元解的最优阶L2，H^1，L∞和W^1,∞模误差估计．     

Numerical analysis of a Picard multilevel stabilization of mixed finite volume method for the 2D/3D incompressible flow with large data

In this article, we develop a branch of nonsingular solutions of a Picard multilevel stabilization of mixed finite volume method for the 2D/3D stationary Navier‐Stokes equations without relying on the unique solution condition. The method presented consists of capturing almost all information of initial problem (the nonlinear problems) on the coarsest mesh and then performs one Picard defect correction (the linear problems) on each subsequent mesh based on previous information thus only solving one large linear systems. What is more, the method presented can results in a better coefficient matrix in the model presented with small viscosity. Theoretical results show that the method presented is derived with the convergence rate of the same order as the corresponding finite volume method/finite element method solving the stationary Navier‐Stokes equations on a fine mesh. Therefore, the method presented is definitely more efficient than the standard finite volume method/finite element method. Finally, numerical experiments clearly show the efficiency of the method presented for solving the stationary Navier‐Stokes equations.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 34: 30–50, 2018     

Finite volume method based on stabilized finite elements for the nonstationary Navier–Stokes problem

A finite volume method based on stabilized finite element for the two‐dimensional nonstationary Navier–Stokes equations is investigated in this work. As in stabilized finite element method, macroelement condition is introduced for constructing the local stabilized formulation of the nonstationary Navier–Stokes equations. Moreover, for P₁ ? P₀ element, the H¹ error estimate of optimal order for finite volume solution (u_h,p_h) is analyzed. And, a uniform H¹ error estimate of optimal order for finite volume solution (u_h, p_h) is also obtained if the uniqueness condition is satisfied. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007     

解Stokes特征值问题的一种两水平稳定化有限元方法

基于局部Gauss积分,研究了解Stokes特征值问题的一种两水平稳定化有限元方法．该方法涉及在网格步长为H的粗网格上解一个Stokes特征值问题,在网格步长为h=O(H2)的细网格上解一个Stokes问题．这样使其能够仍旧保持最优的逼近精度,求得的解和一般的稳定化有限元解具有相同的收敛阶,即直接在网格步长为h的细网格上解一个Stokes特征值问题．因此,该方法能够节省大量的计算时间．数值试验验证了理论结果．     

On the semi-discrete stabilized finite volume method for the transient Navier–Stokes equations

A stabilized finite volume method for solving the transient Navier–Stokes equations is developed and studied in this paper. This method maintains conservation property associated with the Navier–Stokes equations. An error analysis based on the variational formulation of the corresponding finite volume method is first introduced to obtain optimal error estimates for velocity and pressure. This error analysis shows that the present stabilized finite volume method provides an approximate solution with the same convergence rate as that provided by the stabilized linear finite element method for the Navier–Stokes equations under the same regularity assumption on the exact solution and a slightly additional regularity on the source term. The stability and convergence results of the proposed method are also demonstrated by the numerical experiments presented.     

Analysis of newton multilevel stabilized finite volume method for the three‐dimensional stationary Navier‐Stokes equations

This article proposes and analyzes a multilevel stabilized finite volume method(FVM) for the three‐dimensional stationary Navier–Stokes equations approximated by the lowest equal‐order finite element pairs. The method combines the new stabilized FVM with the multilevel discretization under the assumption of the uniqueness condition. The multilevel stabilized FVM consists of solving the nonlinear problem on the coarsest mesh and then performs one Newton correction step on each subsequent mesh thus only solving one large linear systems. The error analysis shows that the multilevel‐stabilized FVM provides an approximate solution with the convergence rate of the same order as the usual stabilized finite element solution solving the stationary Navier–Stokes equations on a fine mesh for an appropriate choice of mesh widths: h_j ～ h_j‐1², j = 1,…,J. Therefore, the multilevel stabilized FVM is more efficient than the standard one‐level‐stabilized FVM. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2013     

Adaptive stabilized mixed finite volume methods for the incompressible flow

In this article, we study adaptive stabilized mixed finite volume methods for the incompressible flows approximated using the lower order elements. A residual type of a posteriori error estimator is designed and studied with the derivation of upper and lower bounds between the exact solution and the finite volume solution. A discrete local lower bound between two successive finite volume solutions is also obtained. Also, convergence of the adaptive stabilized mixed finite volume methods is established. The presented methods have three prominent features. First, it is of practical convenience in real applications with the same partitions for velocity and pressure. Second, less computational time is required by easily applying both the lower order elements and the local grid refinement necessary for the elements of interest. Third, compared with the standard finite element method, its analysis of H¹‐norm and L²‐norm for the velocity and pressure are usually derived without any high order regularity conditions on the exact solution. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1424–1443, 2015     

A Two‐Parameter Stabilized Finite Element Method for Incompressible Flows

Based on two‐grid discretizations, a two‐parameter stabilized finite element method for the steady incompressible Navier–Stokes equations at high Reynolds numbers is presented and studied. In this method, a stabilized Navier–Stokes problem is first solved on a coarse grid, and then a correction is calculated on a fine grid by solving a stabilized linear problem. The stabilization term for the nonlinear Navier–Stokes equations on the coarse grid is based on an elliptic projection, which projects higher‐order finite element interpolants of the velocity into a lower‐order finite element interpolation space. For the linear problem on the fine grid, either the same stabilization approach (with a different stabilization parameter) as that for the coarse grid problem or a completely different stabilization approach could be employed. Error bounds for the discrete solutions are estimated. Algorithmic parameter scalings of the method are also derived. The theoretical results show that, with suitable scalings of the algorithmic parameters, this method can yield an optimal convergence rate. Numerical results are provided to verify the theoretical predictions and demonstrate the effectiveness of the proposed method. © 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 425–444, 2017     

Analysis of a finite volume element method for the Stokes problem

In this paper we propose a stabilized conforming finite volume element method for the Stokes equations. On stating the convergence of the method, optimal a priori error estimates in different norms are obtained by establishing the adequate connection between the finite volume and stabilized finite element formulations. A superconvergence result is also derived by using a postprocessing projection method. In particular, the stabilization of the continuous lowest equal order pair finite volume element discretization is achieved by enriching the velocity space with local functions that do not necessarily vanish on the element boundaries. Finally, some numerical experiments that confirm the predicted behavior of the method are provided.     

A stabilized multi-level method for non-singular finite volume solutions of the stationary 3D Navier–Stokes equations

This paper proposes and analyzes a stabilized multi-level finite volume method (FVM) for solving the stationary 3D Navier?CStokes equations by using the lowest equal-order finite element pair without relying on any solution uniqueness condition. This multi-level stabilized FVM consists of solving the nonlinear problem on the coarsest mesh and then performing one Newton correction step on each subsequent mesh, thus only solving a large linear system. An optimal convergence rate for the finite volume approximations of nonsingular solutions is first obtained with the same order as that for the usual finite element solution by using a relationship between the stabilized FVM and a stabilized finite element method. Then the multi-level finite volume approximate solution is shown to have a convergence rate of the same order as that of the stabilized finite volume solution of the stationary Navier?CStokes equations on a fine mesh with an appropriate choice of the mesh size: ${ h_{j} ~ h_{j-1}^{2}, j = 1,\ldots, J}$ . Finally, numerical results presented validate our theoretical findings.     

非定常Stokes方程的稳定化全离散有限体积元格式

本文研究非定常Stokes方程的有限体积元方法,给出一种基于两个局部高斯积分的稳定化全离散格式,并给其有限体积元解的误差分析.