On the turbulent heat transfer in a square duct subjected to spanwise system rotation

Abstract

In this paper, direct numerical simulation is performed to study the effects of the Coriolis force on turbulent heat transfer within a square duct subjected to spanwise system rotation. In order to investigate the influence of system rotation on the heat transfer process, a wide range of rotation numbers have been tested. In response to the system rotation, mean secondary flows appear as large streamwise counter-rotating vortices, which interact intensely with the four boundary layers of the square duct and have a significant impact on the statistics of the coupled velocity and temperature fields. It is observed that at a sufficiently high rotation number, heat convection approaches a complete laminarization state near the top and side walls. The influence of large organized secondary flows on the transport of the turbulent scalar energy of the temperature field has been analyzed in both physical and spectral spaces. The effects of system rotation on the turbulent heat fluxes have been examined through a budget analysis of their transport equations. The role of near-wall streamwise-elongated turbulence structures on heat transfer is studied using a linear stochastic estimation approach. It is observed that the near-wall ejection events are amplified by the system rotation, resulting in a strong negatively-valued vertical turbulent heat flux in the near-wall region.