Spectral index distribution simulated substructured disks, selecting simulated disks with: 10⁻³⁵ ⩽ α ⩽ 10⁻²⁵, 10⁻²³ M_⋆ ⩽ M_disk ⩽ 10^−0.5 M_⋆, υ_frag ≥ 500 cm s⁻¹, m_p ≥ 150 M_⊕, and r_p ≤ 0 75 r_c. The heat map represents the spectral index distribution of the observed disks with the black dots representing each single observed disk. The black, blue, and red lines refer to the simulated results obtained for α_{0.89-3.1 mm} (black), the simulated results obtained for α_{3.1-9 mm} (blue), and the observational results (α_{0.89-3.1 mm}) (red). The continuous lines encompass the 30% of the cumulative sum of the disks produced from the simulations or observed. The dashed lines encompass the 90% of the cumulative sum of the disks produced from the simulations or observed.