THE EFFECT OF TURBULENT PRESSURE ON THE RED GIANTS AND AGE STARS .1. ON THE INTERNAL STRUCTURE AND EVOLUTION

The expressions for the turbulent pressure, equation of state and ther modynamic quantities taking account of turbulent pressure are derived in the framework of the mixing-length theory of convection. The numeri cal computations indicate that the turbulent pressure in the region cl ose to the surface of a red giant or an AGE star can reach a value of 30-40 percent of the total pressure. A comparison of the evolution of a star with 7M. from the zero-age main sequence to the AGE stage adopt ing turbulent pressure with that of the neglected turbulent pressure s hows that the effect of turbulent pressure on the internal structure a nd evolution in the phase from the He-core burning stage to the AGE st age is significant. A similar investigation for the star of 2.8M. show s that the effect of turbulent pressure on the internal structure in t he same evolutionary phase is small. However, the effect of turbulent pressure on the evolutional track in the AGE phase is obvious.