Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star

Context. A realistic parametrization of convection and convective boundary mixing in conventional stellar evolution codes is still the subject ongoing research. To improve current situation, multidimensional hydrodynamic simulations are used to study interiors. Such numerically challenging, especially for flows at low Mach numbers which typical during early evolutionary stages. Aims. We explore benefits using a low-Mach flux solver demonstrate its usability astrophysical context. Simulations profile analyzed regarding properties mixing. Methods. The time-implicit Seven-League Hydro (SLH) code was perform helium shell burning based on 25 M ⊙ star model. results obtained with AUSM + -up were compared when non variant B -up. applied well-balancing gravitational source term maintain initial hydrostatic background stratification. computational grids have resolutions ranging from 180 × 90 2 810 540 cells nuclear energy release boosted by factors 3 10 , 1 4 dependence these parameters. Results. input range −3 –10 −2 . Standard mixing-length theory predicts velocities about 1.6 −4 if no boosting applied. show Kolmogorov-like inertial kinetic spectrum that extends further toward smaller scales variant. dissipation already converges lower resolution extracted entrainment rates boundaries zone well represented bulk Richardson law corresponding fitting parameters agreement published carbon burning. However, our needs be validated higher resolution. Further, we find general increase entropy may significantly contribute measured top boundary. Conclusion. This demonstrates successful application setup. Compressible phases nominal luminosity will benefit capabilities. Similar other studies, extrapolated rate helium-burning would lead an unrealistic growth it over lifetime zone. Studies luminosities different same needed detect possible impact radiation