New model for turbulent heat transfer accounting for radiation convective coupling in RANS framework

In high temperature participating flows, radiation tends to be the most relevant heat transfer mechanism. Radiative heat transfer differs from conduction due to its peculiarity of being non-local. This non locality causes counter intuitive interactions with turbulent temperature field and conductive heat transfer.  While some theoretical knowledge has been gathered regarding the mechanism underlying these interactions, standard models have not yet been adapted to these recent findings. In particular, solving the RANS equations relies on the modeling of unclosed terms, one of which is the turbulent heat transfer. This quantity is severely modified by the presence of radiative heat transfer, leading to erroneous temperature predictions if standard models are employed. Therefore, this work provides the inclusion of radiative convective coupling in the modeling of the turbulent heat transfer. The proposed model consists in a first order approximation of the fluctuating radiative field which is expressed as a linear function of temperature fluctuations. This concept is applied to modify the existing standard two equation model and tested against various DNS cases. The results show very good agreement both in terms of average temperature and turbulent heat transfer.