Direct numerical simulation of turbulent flow in elliptical ducts

Direct numerical simulation (DNS) of fully developed turbulent flow in elliptical ducts is performed. The mean cross-stream secondary flows exhibited by two counter-rotating vortices which are symmetrical about the major ellipse's axis are examined. The mean flow characteristics and turbulence statistics are obtained. The variation of the statistical quantities such as the Reynolds stresses and turbulence intensities along the minor axis of the elliptical cross-section are found to be similar to plane channel data. The turbulent statistics along the major axis are found to be inhibited by the secondary flow transferring high-momentum fluid from the duct's centre towards the wall. The instantaneous velocity fields in the near-wall region reveal structures similar to the 'streaks' except in the vicinity of the major axis endpoints where significant reduction of the turbulent activity due to the wall transverse curvature effect is found.