Velocity fields in 2.5D simulations with boost factors b ∈ (10⁶, 10⁵, 10⁴, 10³) performed on the 512 × 256 grid. The velocity is normalised using the typical convective velocity u_conv as given by the scaling law shown in Fig. 6. The dashed and solid lines give the time-averaged radii of the Schwarzschild and convective boundaries, respectively. The simulations are shown at t = 0.5τ_th(b).