Zoom-in on the central region in Fig. 2 (black frame) where the donor is a C-rich star and q = 1, f = 80%, and η = 0.8. For R_d = 6 au and Ṁ₁ = 3 × 10⁻⁵ M_⊙ yr⁻¹, semitransparent yellow represents the 3D iso-density surface ρ = 9 × 10⁻¹⁴ g cm⁻³ and red corresponds to the surface ρ = 9 × 10⁻¹² g cm⁻³. The inner boundary of the simulation space is visible in dark red in the right part and the velocity field in the orbital plane is represented.