Envelope convection zone boundaries in an evolving 4.7 ﹩\;{M}_{\odot }﹩ star with initial metallicity Z₀ = 0.02 and the same initial metal proportions as in the best XEVOL age zero solar model. The figure shows the boundaries for every converged model in the time sequences. Three models are shown (see the text for details): T65KD10--4 (blue), with weak, short range turbulence below the He II convection zone; T150KD1K-3 (gray), with much stronger turbulence in the iron convection zone only (gray); T65KD30--4W5E-15 (red), with turbulence three times the strength of that in the blue model, plus weak, constant stellar mass loss (5 × 10⁻¹⁵ ﹩\;{M}_{\odot }﹩ yr⁻¹). Homogeneity is artificially enforced in layers cooler than 65,000 K (log T ⪅ 4.8).