Top panel: clump radius (solid lines) and porosity length (dashed lines) in units of R_* as a function of the distance to the stellar center. In blue (resp. in red) are represented the profiles for the clump radius expansion law (4) (resp. Eq. (5)). The dimensionless clump radius at r = 2, indicated with a black dot, was set to 0.005, and the dimensionless clump mass to 4 × 10⁻⁷ (see Sect. 2.4 for normalization units). Bottom panel: clumping factor profiles for both expansion laws. The red (resp. blue) shaded region represents the shape of the clumping factor profile obtained for O (resp. B) supergiants by Driessen et al. (2019). Spectroscopically, these OB supergiants can be considered representing typical early- and middle-type stars.