Computer Science
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........49k&link_type=abstract
Thesis (PH.D.)--YALE UNIVERSITY, 1993.Source: Dissertation Abstracts International, Volume: 54-06, Section: B, page: 3122.
Computer Science
9
Hydrodynamic Simulation
Scientific paper
By conducting realistic hydrodynamic simulations, stellar photospheric convection has been explored. Firstly, hydrostatic stellar models were constructed. Secondly, using the hydrostatic stratifications as initial conditions, time-dependent three-dimensional hydrodynamic simulations of stellar photospheric convection were conducted. Thirdly, a synthetic spectral line formed throughout the domain of the hydrodynamic simulations was calculated. By comparing the effect of simulated photospheric convection on the synthetic spectral line with the observable gross parameters of stellar convection, spectral line asymmetries, the validity of the hydrodynamic simulations was tested. Finally, the detailed analysis of the simulations provided better understanding of stellar convection theory. This study has achieved two goals: Firstly, the 'C' shaped line bisector for the Sun and the reversed 'C' shaped line bisector for an A5 star were reproduced. Furthermore, three different characteristics of convection which may cause spectral line bisector be reversed 'C' shaped, were identified. From the statistical properties of the solar simulation, we improved our knowledge on stellar convection. The simulation for shallow, inefficient convection, including radiative energy transport and ionization, showed the effect of ionization on the dynamics of convection. In addition, it was found that the radiative energy transport was important only at the top one pressure scale height in the simulation domain. Furthermore, we were able to test the ad hoc prescription of stellar convection theories, the mixing length approximation. The importance of the kinetic energy flux in the convection zone was confirmed, which was neglected in the approximation. The existence of several linear relations from the approximation was tested and confirmed. Therefore, even though the prescription is too crude, the approximation seems to be still reasonable tool in practical point of view.
Kim Yong-Cheol
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