state advection–diffusion equation. The method uses a nonlinear approximation for both
diffusive and advective fluxes and guarantees solution non-negativity. The interpolation-free
approximation of the diffusive flux uses the nonlinear two-point stencil proposed in Lipnikov
[23]. Approximation of the advective flux is based on the second-order upwind method with a
specially designed minimal nonlinear correction. The second-order convergence rate and …