Convergence analysis for second‐order accurate schemes for the periodic nonlocal Allen‐Cahn and Cahn‐Hilliard equations. (27th July 2017)

• Record Type: Journal Article
• Authors: Guan, Zhen; Lowengrub, John; Wang, Cheng
• Is Part Of: Mathematical methods in the applied sciences. Volume 40:Number 18(2018)
• Page Start: 6836
• Page End: 6863
• Publication Date: 2017-07-27
• Subjects: convergence analysis -- energy stability -- higher order asymptotic expansion -- nonlocal Allen‐Cahn equation -- nonlocal Cahn‐Hilliard equation -- second‐order numerical scheme; Mathematics -- Periodicals; Technology -- Mathematics -- Periodicals; 519
• DOI: 10.1002/mma.4497
• Languages: English
• ISSNs: 0170-4214

Abstract

Abstract : In this paper, we provide a detailed convergence analysis for fully discrete second‐order (in both time and space) numerical schemes for nonlocal Allen‐Cahn and nonlocal Cahn‐Hilliard equations. The unconditional unique solvability and energy stability ensures ℓ 4 stability. The convergence analysis for the nonlocal Allen‐Cahn equation follows the standard procedure of consistency and stability estimate for the numerical error function. For the nonlocal Cahn‐Hilliard equation, because of the complicated form of the nonlinear term, a careful expansion of its discrete gradient is undertaken, and an H −1 inner‐product estimate of this nonlinear numerical error is derived to establish convergence. In addition, an a priori W 1, ∞ bound of the numerical solution at the discrete level is needed in the error estimate. Such a bound can be obtained by performing a higher order consistency analysis by using asymptotic expansions for the numerical solution. Following the technique originally proposed by Strang (eg, 1964), instead of the standard comparison between the exact and numerical solutions, an error estimate between the numerical solution and the constructed approximate solution yields an O ( s 3 + h 4 ) convergence in ℓ ∞ ( 0, T ; ℓ 2 ) norm, in which s and h denote the time step and spatial mesh sizes, respectively. This in turn leads to the necessary bound under a standard constraint s ≤ C h . Here, we also prove convergence of the scheme in the maximum norm under the same constraint.