Vertically-integrated dust density distribution as a function of particle size for a disc with a gap carved by a 100 M_⊕ planet at 10 au (upper panels) compared to a smooth disc (lower panels). In the model shown here, the disc viscosity is set to α_visc = 10⁻³ and the local turbulence to δ_turb = 3.2 × 10⁻⁴. The colour bar indicates the surface density of dust in a given size range at a given radius. The three panels represent different times of the simulation (t = 0.2 Myr, t = 1 Myr, and t = 5 Myr). The black contours show different values of the Stokes number (St = [10⁻³, 10⁻², 10⁻¹, 10⁰]) for visual guidance.