DNS Study of turbulent heat transfer in an elliptical pipe flow subjected to system rotation about the major axis

Abstract

Turbulent heat transfer in an elliptical pipe flow subjected to spanwise system rotation about the major axis has been studied through direct numerical simulations (DNS). The influence of the Coriolis force on the turbulent heat convection has been analyzed through analyses of the first- and second-order statistical moments of the temperature field in both physical and spectral spaces. The mean temperature, turbulent heat fluxes, pre-multiplied spectra of temperature fluctuations, and coherent thermal structures of the rotating flows are compared against those of the non-rotating flow. It is observed that the secondary flow pattern is sensitive to the rotation number and has a significant impact on the transport process of thermal energy and on the value of the Nusselt number. Through a budget analysis of the vertical turbulent heat flux, it is revealed that the profiles of the budget terms are symmetrical about the minor axis and the turbulent production is the primary source term in a non-rotating flow. However, as soon as the system rotation is imposed, the profiles become asymmetrical and the Coriolis term starts to dominate the turbulent production process as the primary source for turbulent heat flux at a moderate rotation number. Examination of the coherent thermal structures within the flow further reveals that the Coriolis force acts to reduce the vertical turbulent heat flux on the pressure side of the pipe.