Fig. 7

Timestep verification for 2D convection–diffusion equation: a backward Euler integrator: we select a time step of 3.12e-2, as it leads to an approximated convergence rate of 1 and an approximated error of 5e-4 for the selected state; b Runge–Kutta: we select a time step of 1.25e-1, as it leads to an approximated convergence rate of 4 and an averaged approximated error of 2e-5 for the selected state