Year: 2019
Type: article
Abstract: Renzini wrote an influential critique of “overshooting” in mixing-length theory (MLT), as used in stellar evolution codes, and concluded that three-dimensional fluid dynamical simulations were needed. Such simulations are now well tested. Implicit large eddy simulations connect large-scale stellar flow to a turbulent cascade at the grid scale, and allow the simulation of turbulent boundary layers, with essentially no assumptions regarding flow except the number of computational cells. Buoyant driving balances turbulent dissipation for weak stratification, as in MLT, but with the dissipation length replacing the mixing length. The turbulent kinetic energy in our computational domain shows steady pulses after 30 turnovers, with no discernible diminution; these are caused by the necessary lag in turbulent dissipation behind acceleration. Interactions between coherent turbulent structures give multi-modal behavior, which drives intermittency and fluctuations. These cause mixing, which may justify use of the instability criterion of Schwarzschild rather than the Ledoux. Chaotic shear flow of turning material at convective boundaries causes instabilities that generate waves and sculpt the composition gradients and boundary layer structures. The flow is not anelastic; wave generation is necessary at boundaries. A self-consistent approach to boundary layers can remove the need for ad hoc procedures of “convective overshooting” and “semi-convection.” In Paper II, we quantify the adequacy of our numerical resolution in a novel way, determine the length scale of dissipation—the “mixing length”—without astronomical calibration, quantify agreement with the four-fifths law of Kolmogorov for weak stratification, and deal with strong stratification.
Source: The Astrophysical Journal
Authors: W. David Arnett, Casey Meakin, Raphael Hirschi, Andrea Cristini, Cyril Georgy, Simon Campbell, Laura J. A. Scott, Etienne A. Kaiser, Maxime Viallet, Miroslav Mocák
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,499
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Australian Government, National Energy Research Scientific Computing Center, Durham University, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Partnership for Advanced Computing in Europe AISBL, Université de Genève, Barcelona Supercomputing Center, Government of Western Australia, Office of Science, Science and Technology Facilities Council, Australian Research Council, National Cancer Institute, Oak Ridge National Laboratory
Awards: G122673668, G1269417628, G1381339075, Durham DiRAC-2 petascale facility, G1468651527, G1571591014, DiRAC-2.5 - the pathway to DiRAC Phase 3, G2024759084, The DiRAC-2.5y Facility, G2126713887, G2368581224, G2843074508, G2918681272, G2955711198, G296705498, The convective boundaries in stars, G3240456572, G3295719173, G3363198467, STFC DiRAC Project Office 2014-2017, Cosmic Impact of Massive Stars: Convective Mixing and Mass Loss, DiRAC-2 Datacentric support grant, G419881185, G4251892262, G42916606, G432354605, G4498713678, DiRAC SMP Facility: The Structure of the Universe, INTERACTING SUPERNOVAE ARE POORLY-UNDERSTOOD ASTRONOMICAL EVENTS WITH GREAT POTENTIAL FOR EXPANDING OUR UNDERSTANDING OF HOW STARS EVOLVE AND DIE, A, G4831232377, G4848836895, DiRAC 2.5 Operations 2017-2020, DiRAC 2.5 Operations Bridging 2019 - Leicester, G5385953647, G5571342780, Late Phases of the Evolution of Massive Stars, DiRAC-2: Recurrent Costs for Complexity@DiRAC Cluster at University of Leicester, G5999448510, G6010405803, DiRAC Bridging Grant 2019 - Cambridge, DiRAC-2.5 DC - Operations 2017-2020, Resources for DiRAC2 at HPCs, XSEDE: eXtreme Science and Engineering Discovery Environment, Dirac 2.5 Operations, DiRAC2.5 Operations: The DiRAC Project Office 2017-2020, G7165083805, G7208848743, DiRAC 2.5y Bridging Funding - UCL, G7636747755, G7937591081, DiRAC Bridging Grant 2019, G8092745986, G825883484, The Virgo consortium for cosmological supercomputer simulations, Durham DiRAC-2 petascale facility support, DiRAC 2.5 Operations 2017-2020, DiRAC: Memory Intensive 2.5x
OpenAlex ID: W2896964679