An adaptive non-uniform L2 discretization for the one-dimensional space-fractional Gray-Scott system

This paper introduces a new numerical method for solving space-fractional partial differential equations (PDEs) on non-uniform adaptive finite difference meshes, considering a fractional order alpha is an element of (1,2) , 2) in one dimension. The fractional Laplacian in PDE is computed by using Riemann-Liouville (R-L) derivatives, incorporating a boundary condition of the form u = 0 in R\Omega. The proposed approach extends the L2 method to non-uniform meshes for calculating the R-L derivatives. The spatial mesh generation employs adaptive moving finite differences, offering adaptability at each time step through grid reallocation based on previously calculated solutions. The chosen mesh movement technique, moving mesh PDE-5 (MMPDE5), demonstrates rapid and efficient mesh movement. The numerical solutions are obtained by applying the non-uniform L2 numerical scheme and the MMPDE-5 method for moving meshes automatically. Two numerical experiments focused on the space-fractional heat equation validate the convergence of the proposed scheme. The study concludes by exploring patterns in equations involving the fractional Laplacian term within the Gray-Scott system. It reveals self-replication, travelling wave, and chaotic patterns, along with two distinct evolution processes depending on the order alpha: from self-replication to standing waves and from travelling waves to self-replication.