Slices of surface density profiles for our fiducial inviscid Cartesian model (v = 0, blue lines) at a given time t₀ against the corresponding viscous models with v = v_num at t₀/2 (orange) and v = 2 v_num at t₀/3 (green). Solid and dashed lines correspond to t₀ = 224 and 748 orbits at R₀, respectively. The model with v = v_num evolves twice as fast as the inviscid simulation and the v = 2 v_num model evolves three times as fast, indicating a viscous contribution by the non-negligible numerical viscosity.