论文标题
有限元计算的自动变异稳定分析:瞬态对流扩散问题
Automatic Variationally Stable Analysis for Finite Element Computations: Transient Convection-Diffusion Problems
论文作者
论文摘要
我们使用自动变异稳定有限元(AVS-FE)方法建立了对流扩散初始边界值问题的稳定有限元(Fe)近似。瞬态对流扩散问题会导致经典FE方法中的问题,因为差异操作员可以在时空和时间上都被视为奇异扰动。不管潜在的差分运算符如何,AVS-FE方法的无条件稳定性都使我们在Fe近似的构建中具有显着的灵活性。我们采用了两种不同的方法来对对流扩散问题进行FE离散化:i)考虑使用有限元元素建立时间离散化的时空方法,ii)ii)一种线方法方法,在该方法中,我们在太空中采用了AVS-FE方法,而使用通用的Alpha方法则将时间域使用。在广义 - α方法中,我们将时间域离散为有限尺寸的时间步骤,并采用广义 - α方法作为时间积分器。然后,我们得出了获得的操作员的相应规范,以保证该方法的时间稳定性。 我们介绍了两种方法的数值验证,包括强调最佳收敛性能的数值渐近收敛研究。此外,本着Demkowicz和Gopalakrishnan不连续的Petrov-Galerkin方法的精神,AVS-FE方法还通过AVS-FE近似值的RIESZ代表估计了后验错误估计。因此,这些估计值所产生的本地限制的规范是我们提出多种数值验证自适应策略的空间和时间的错误指标。
We establish stable finite element (FE) approximations of convection-diffusion initial boundary value problems using the automatic variationally stable finite element (AVS-FE) method. The transient convection-diffusion problem leads to issues in classical FE methods as the differential operator can be considered singular perturbation in both space and time. The unconditional stability of the AVS-FE method, regardless of the underlying differential operator, allows us significant flexibility in the construction of FE approximations. We take two distinct approaches to the FE discretization of the convection-diffusion problem: i) considering a space-time approach in which the temporal discretization is established using finite elements, and ii) a method of lines approach in which we employ the AVS-FE method in space whereas the temporal domain is discretized using the generalized-alpha method. In the generalized-alpha method, we discretize the temporal domain into finite sized time-steps and adopt the generalized-alpha method as time integrator. Then, we derive a corresponding norm for the obtained operator to guarantee the temporal stability of the method. We present numerical verifications for both approaches, including numerical asymptotic convergence studies highlighting optimal convergence properties. Furthermore, in the spirit of the discontinuous Petrov-Galerkin method by Demkowicz and Gopalakrishnan, the AVS-FE method also leads to readily available a posteriori error estimates through a Riesz representer of the residual of the AVS-FE approximations. Hence, the norm of the resulting local restrictions of these estimates serve as error indicators in both space and time for which we present multiple numerical verifications adaptive strategies.