Temporal profiles of some energetics-related quantities for several grid spacings, as differentiated by different colors. Energetics are consistently examined for a box, [ − (d/2 + 1.2b),(d/2 + 1.2b)] × [ − 1.2b, 1.2b], in which the three mutually exclusive constituents are the tube interiors, nonuniform layers, and exterior. Shown in (a) are the time derivative of the total perturbation energy in the box (dE_tot/dt, the solid curves), together with the instantaneous energy flux into this box (−F, asterisks). Further plotted in (b) are the instantaneous total energy in the interiors (E_int), nonuniform layers (E_layer), and the exterior (E_ext). All computations pertain to the S​_x pattern for a fixed combination of physical parameters [ρ_i/ρ_e = 5, ℓ/ℛ = 0.4, d/ℛ = 2.5, kb = π/30]. The computational domain size is fixed at [x_M = 12b, y_M = 10b].