- Journal Home
- Volume 22 - 2025
- Volume 21 - 2024
- Volume 20 - 2023
- Volume 19 - 2022
- Volume 18 - 2021
- Volume 17 - 2020
- Volume 16 - 2019
- Volume 15 - 2018
- Volume 14 - 2017
- Volume 13 - 2016
- Volume 12 - 2015
- Volume 11 - 2014
- Volume 10 - 2013
- Volume 9 - 2012
- Volume 8 - 2011
- Volume 7 - 2010
- Volume 6 - 2009
- Volume 5 - 2008
- Volume 4 - 2007
- Volume 3 - 2006
- Volume 2 - 2005
- Volume 1 - 2004
Cited by
- BibTex
- RIS
- TXT
Error estimates for the Crank-Nicolson in time, Finite Element in space (CNFE) discretization of the Navier-Stokes equations require application of the discrete Gronwall inequality, which leads to a time-step $(\Delta t)$ restriction. All known convergence analyses of the fully discrete CNFE with linear extrapolation rely on a similar $\Delta t$-restriction. We show that CNFE with arbitrary-order extrapolation (denoted CNLE) is convergences optimally in the energy norm without any $\Delta t$-restriction. We prove that CNLE velocity and corresponding discrete time-derivative converge optimally in $l^∞(H^1)$ and $l^2(L^2)$ respectively under the mild condition $\Delta t \leq Mh^{1/4}$ for any arbitrary $M > 0$ (e.g. independent of problem data, $h$, and $\Delta t$) where $h > 0$ is the maximum mesh element diameter. Convergence in these higher order norms is needed to prove convergence estimates for pressure and the drag/lift force a fluid exerts on an obstacle. Our analysis exploits the extrapolated convective velocity to avoid any $\Delta t$-restriction for convergence in the energy norm. However, the coupling between the extrapolated convecting velocity of usual CNLE and the a priori control of average velocities (characteristic of CN methods) rather than pointwise velocities (e.g. backward-Euler methods) in $l^2(H^1)$ is precisely the source of $\Delta t$-restriction for convergence in higher-order norms.
}, issn = {2617-8710}, doi = {https://doi.org/}, url = {http://global-sci.org/intro/article_detail/ijnam/568.html} }Error estimates for the Crank-Nicolson in time, Finite Element in space (CNFE) discretization of the Navier-Stokes equations require application of the discrete Gronwall inequality, which leads to a time-step $(\Delta t)$ restriction. All known convergence analyses of the fully discrete CNFE with linear extrapolation rely on a similar $\Delta t$-restriction. We show that CNFE with arbitrary-order extrapolation (denoted CNLE) is convergences optimally in the energy norm without any $\Delta t$-restriction. We prove that CNLE velocity and corresponding discrete time-derivative converge optimally in $l^∞(H^1)$ and $l^2(L^2)$ respectively under the mild condition $\Delta t \leq Mh^{1/4}$ for any arbitrary $M > 0$ (e.g. independent of problem data, $h$, and $\Delta t$) where $h > 0$ is the maximum mesh element diameter. Convergence in these higher order norms is needed to prove convergence estimates for pressure and the drag/lift force a fluid exerts on an obstacle. Our analysis exploits the extrapolated convective velocity to avoid any $\Delta t$-restriction for convergence in the energy norm. However, the coupling between the extrapolated convecting velocity of usual CNLE and the a priori control of average velocities (characteristic of CN methods) rather than pointwise velocities (e.g. backward-Euler methods) in $l^2(H^1)$ is precisely the source of $\Delta t$-restriction for convergence in higher-order norms.