3D hydrodynamic simulations of rotating, massive, main-sequence stars: a study of the interaction of core convection with rotation

We have been studying convection, mass entrainment, and mixing processes in the convective boundary region as well as the radiative envelope for a model star of 25 solar masses using the 3-D stellar hydrodynamics code PPMstar. We will report on the portion of this work that focuses on the effects of rotation of the model star. We will show the general features of core convection for this star from a high-resolution simulation on a grid of 2688³ cells using volume rendered movies. We study the star near the beginning of its life on the main sequence. Our simulations describe the entire central region of the star out to a radius of 2700 Mm, and the convective boundary in the initial state is at radius 1520 Mm. We have simulated a range of rotation rates, and angular velocities of 2.87 × 10^-5 and 9.06 × 10^-5 sec^-1 will be discussed. The convection flow is modified by the rotation in such a way that a region near the equator and near the convective boundary rotates faster than the solid-body rotation rate of the initial model. Redistribution of angular momentum in the core convection zone establishes a differential rotation profile, where the central region rotates slower and the outer region of the convection zone rotates faster. A simple mechanism for establishing this rotation profile in the convection zone will be described and illustrated using the 3-D simulation results. Angular momentum transport in the envelope surrounding the convective core is much more difficult to measure, although internal gravity waves are observed in this region. This effect seems to be very small, so that high grid resolution and careful data analysis are required to arrive at accurate estimates. Analysis of the rotating simulation results in terms of a 1-D model for the convection zone inspired by our simulations of non-rotating stars is also underway, and any recent results will be reported.