Friction factor and heat transfer prediction of rocket engine cooling channels in numerical simulations with high roughness Reynolds number

In literature, it is widely recognized that surface roughness significantly influences friction and heat transfer. This effect is especially pronounced in additive manufactured components, which are increasingly important in the space sector. However, using numerical approaches to predict their performances is challenging because the correlations and the numerical models available for high roughness conditions have to be tuned with respect to the specific case. This study aims to benchmark existing modeling strategies and to compare the results against the experimental results of additively manufactured rocket engine cooling channels. To achieve this, the Spalart–Allmaras model equipped with the Boeing roughness correction was implemented in ANSYS Fluent and tested on various test conditions. The goal is to determine the best-fitting sand-grain parameter values that match experimental data in terms of friction factor and compare the heat transfer predictions regarding coolant temperature, wall temperature, and Nusselt number. Eventually, a correction of the turbulent Prandtl number was demonstrated to be needed. Data from literature and empirical correlations for high values of roughness Reynolds number are gathered and compared with the outcomes from this work, giving satisfying results.