High order compact difference scheme for elliptic equations with Robin boundary conditions
摘要
We propose a novel high-order compact (HOC) finite difference scheme for solving Helmholtz and diffusion–advection equations under Robin boundary conditions. Derived through successive variable elimination from difference equation systems, the method achieves fourth- and sixth-order convergence for the Helmholtz equation and fourth-order convergence for the diffusion–advection equation. Theoretical analysis establishes solvability and proves error estimates for all schemes. Completed Richardson extrapolation applied to the diffusion–advection solver yields fifth-order accuracy (wavenumber