Convective Overshoot In Stellar Interior

The classical method on the convective overshoot is the non-local mixinglength theories. These theories are phenomenological method which are notbased on fluid dynamics. Recently, helioseismic investigations have showed thatthe profle of temperature gradient of the solar overshoot region is out of non-localmixing length theories, suggested that only turbulent convection models can leadto consistence, and pointed out the direct of studying convective overshoot.In this thesis, the the turbulent convection model has been studied, and itsapproximate solution and the asymptotical solution in overshoot region have beenobtained. The solar evolutionary models have been studied. It is found that thetemperature gradient profle, which results from the turbulent convection mod-el, near the base of the solar convection zone is consistent with the helioseismicinversion. The solar sound speed, density, and lithium abundance at the solarsurface can be signifcantly improved when the difusive overshoot mixing with aproper intensity is taken into account. The difusive overshoot mixing is adopt-ed in studying lithium abundance in open cluster. In the binary star HY Vir,the observations have been used to calibrate the intensity of difusive overshootmixing, and the properties of stellar models of HY Vir based on the turbulentconvection model and difusive overshoot mixing have been investigated. It hasbeen found that all the observations show that the best value of the parameterin the simple difusive overshoot mixing model is too low, which indicates thesimple difusive overshoot mixing model is not physically reasonable. In order tostudy the overshoot mixing, a turbulent model of convective/overshoot mixinghas been establish, the difusion coefcient of convective/overshoot mixing hasbeen worked out. It has been found that the difusion coefcient show distinctproperty in convection zone and overshoot region. The proper value in the newturbulent model of convective/overshoot mixing has been obtained by comparingtheoretical stellar models with observations.