This section is devoted to the discretization of the advection–diffusion equation and to the analysis of dispersion and diffusion eigencurves for different polynomial orders. The spectral/hp continuous Galerkin method considered closely resembles the formulation presented in [7]. Sec. 2.1 describes in detail the derivation of the semi-discrete advection–diffusion problem as applied to wave-like solutions, from which the relevant eigencurves can be obtained. The inviscid case (linear advection) is then addressed in Sec. 2.2, where the role of primary and secondary eigencurves is discussed from the perspective introduced in [9]. The viscous case is subsequently considered in Sec. 2.3, where eigencurves are shown to feature irregular oscillations for problems strongly dominated by either convection or diffusion.
