Power spectrum of the fluid velocity perturbations within a small slice at the midplane for three runs: control (black, α_drive = 0), weak driving (green, α_drive = 10⁻⁴), and strong driving (red, α_drive = 10⁻³). ﹩| {\boldsymbol{k}}| ﹩ is given in code units (1/H). These spectra are compensated such that a power law with an index of −5/3 would appear to be flat. They are normalized by a common factor such that the mean of the control curve is unity. Using this convention, the absolute values of the power bear no meaning, but the relative power between the spectra is maintained. The weak driving and control runs have very similar spectra at small scales but differ on larger scales, which is consistent with small-scale motions being dominated by the presence of a thin particle layer.