Bulk velocity as function of loop position, z, and time for the four different values of the low-energy cutoff, a total energy of 10¹¹ erg cm⁻², and a spectral index of 3. The logarithm of the absolute value of the bulk velocity is shown, multiplied by the sign of the velocity. A value of one thus corresponds to an outflow of 10 km s⁻¹, minus one to an inflow of 10 km s⁻¹. Absolute values of the bulk velocity below 1 km s⁻¹ are shown as zero. The initial velocity of zero is shown in red, with subsequent timesteps, separated by 1.0 s, shown with rainbow colours from red to violet. The last timestep shown is at t = 20 s, when the beam was switched off.