Convection In Massive Stars And Its Influence On The Structure And Evolution Of Stars

In massive stars, the convection in the interior is diferent from that of in-termediate and small mass stars. In the MS(Main Sequence) phase of small massstars, there is a convective core and a radiative envelope, between which is theradiative intermediate layers with uneven chemical abundances. Semi-convectionwould occur in the intermediate layers between the convective core and the ho-mogeneous envelope in massive stars. In the present paper, the Schwarzschildmethod and the Ledoux method are used to process the semi-convection andcore overshooting for15M⊙and30M⊙stars. Diferent entropy gradient is usedwhen adopting the Schwarzschild method and the Ledoux method which areused to confne the convective boundary and to calculate the turbulent quan-tities: s r=cpHP(d) when the Schwarzschild method is adopted ands r=cpHP(ad μ) when the Ledoux method is adopted. Core con-vective overshooting and semi-convection are treated as a whole part and thedevelopment of them are found to present nearly opposite tendency, more inten-sive core convective overshooting lead to weaker semi-convection. The infuencesof diferent parameters and the convection processing methods on the turbulentquantities are analyzed in this paper. Increasing the mixing-length parameter αleads to more turbulent dynamic energy in the convective core and prolongingthe overshooting distance but depressing the development of semi-convection.The hydrodynamic difusion process is used to model the convective mixing. Inthis two processes, we introduce one difusive parameter D, which is diferentfrom other authors introducing diferent parameters for the two regions. Theinfuences of the turbulent difusion process on the chemical evolution and otherquantities of the stellar structure are shown in the present paper.