A&A Supplement Ser., Vol. 124, September 1997, 597-614
Received March 14, accepted December 6, 1996
P. Morel
Send offprint request: morel@obs-nice.fr
Cassini, URA CNRS 1362 and GDR CNRS G 131, Observatoire de la Côte
d'Azur, Nice, France
The code CESAM is a consistent
set of programs and routines which performs calculations of 1D quasi-static
stellar evolution including diffusion and rotation.
The principal new feature is the solution of the quasi-static equilibrium
by collocation method based on piecewise polynomials approximations projected
on their B-spline basis; that allows stable and
robust calculations and the exact restitution of the solution not only
at grid points. Another advantage is the monitoring by only one parameter
of the accuracy and its improvement by superconvergence.
An automatic mesh refinement has been designed for adjusting the localizations
of grid points according to the changes of unknowns, each limit between
a radiative and a convective zones being shifted to the closest grid point.
For standard models, the evolution of the chemical composition is solved by
stiffly stable schemes of orders up to four; for non-standard models the
solution of the diffusion equation employs the Petrov-Galerkin scheme, with
the mixing of chemicals in convective zones performed by strong turbulent
diffusion. A precise restoration of the atmosphere is allowed for.
CESAM computes evolution of stars from the pre-main sequence
to the beginning of the 4He burning 
cycle.
In this paper a detailed description of the algorithms is presented.
keywords: methods: numerical -- Sun: evolution -- Sun: interior -- stars: evolution -- stars: interior