A simple convection model for selfgravitating fluid dynamics Time-dependent convective energy transfer in protostars and nonlinear stellar pulsations

We describe a relatively simple time-dependent con- vection model that can be coupled to the equations of radiation hydrodynamics. We show that it behaves in a physically plau- sible way in protostellar collapse flows and is quantitatively correct for nonlinear RR-Lyrae pulsations and the Sun. To- gether with the equations of radiation hydrodynamics the model closely approximates the classical stellar structure equations with mixing length convection for a set of standard assump- tions.