In this study, buoyancy components were introduced into turbulent fluxes such as Reynolds stress and turbulent heat fluxes, and the turbulent transport phenomena of combined convection were modeled by adding several buoyancy-induced components to the expressions of the turbulent fluxes. The turbulent transport mechanism of combined convection was also examined by applying a modified damping function, which is applicable to both the aiding and the opposing flows. The calculation target is a fully-developed turbulent combined convection between vertical smooth parallel plates, where the inertia force acts with parallel with or in opposition to the buoyant force. The wall is heated uniformly. The numerical computation was performed by combining two-equation turbulence models of different type, being applicable to both the velocity and the temperature fields. It was found from a series of computations that the model utilized simulates the heat transfer and fluid flow of turbulent combined convection physically. For industrial application, it is necessary to develop more appropriate and simpler turbulence models that are based on empirical knowledge than LES or DNS.