Influences Of The Turbulent Stress On The Structure And Evolution Of Intermediate-Mass Stars

Convection plays a significant role in the stellar structure and stellar evolution. Now, researchers ignore the turbulent stress when they deal with convection. But In the stellar evolution later stages, the star has complete convective envelope, and the turbulent stress is enough big to gravity, so the turbulent stress can have the tremendous influence to the star structure and the evolution.In this thesis we have derived the evolutionary mold of star concerning turbulent stress and Rotation centrifugal force based on the mixing-length theory of convection. We Has calculated evolution of stars with 2.8m and 8m from H-burning stages to the AGB stages, analyzed sizes and effects of turbulent stress in the stellar interior in the different conditions of considering the rotation and not. Goal Is to study the turbulent stress to evolution influences of the star and the rotation star. The result indicated that the turbulent stress may be neglected In the nucleus burning stages,because stress is very small to gravity and the rotation centrifugal force; But for the red giant star and the AGB star, we find There is an small area which the turbulent stress gradient is several dozens time as big as gravitation in the envelope,in this area, the turbulent stress take the leading role,the mass outside of this area is driven out of star by turbulent stress.it cause mass loss,and explained well reason of the stellar wind produced at AGB stage.The research also indicated that, the turbulent stress change every stage's lifetime of the star with 8m;Turbulent stress also Causes the thermonuclear reaction of the He burning shell in AGB star not to be un-stable,and the occurrence of the thermal pulse greatly ahead of time,and very frequent. That this thermal pulse occurs ahead of time not only change the temperature, nuclear energy production and density in the He burning shell but also change the temperature, nuclear energy production and density of the H burning shell in the hydrogen and the stellar surface luminosity at the same time. Moreover, the turbulent stress also causes the convection the mixing action to strengthen, so elements abundance of the stellar interior and surface are all changed.The distribution of C and O in core are more uniform; .The abundance of H and heavy element in H-burning shell and neutron density and heavy element in He-burning shell are all reduced, but the abundance of the He is increased; To early AGB star,the abundances of elements of the stellar surface does not...