POD analysis of turbulent convective heat transfer of pulsating flow in a channel with teardrop-shaped dimples using LES

This study investigated effects of flow pulsation on the heat transfer performance of the surface with teardrop-shaped dimples using Proper Orthogonal Decomposition (POD). Velocity and temperature data for POD was obtained from the Large Eddy Simulation (LES). LES was performed for the following conditions: teardrop-shaped dimples with 30 deg in-line arrangement, the Strouhal number of 0.3, half of peak-to-peak velocity amplitude normalized by bulk velocity of 0.2, and the bulk Reynolds number of 2.5 × 10⁴. The POD results revealed the first mode of velocity corresponded to periodic flow separation at leading and trailing edges of dimples, and the second mode to periodic swirling flow-separation behind leading side-edges of dimples. It was confirmed that the dominant periodic flow-separation over dimples was reproduced by using only the first and second modes. On the other hand, the periodic temperature variation caused by the pulsating flow was reproduced by the second and forth modes: low temperature fluid was periodically introduced into the dimples by the swirling flow-separation behind the leading side-edges of dimples.