Heat transfer and associated coherent structures of a single impinging jet from a round nozzle

Abstract

The heat transfer arising from an impinging jet at a Reynolds number of 5000 is studied through Large-Eddy Simulation (LES), with special attention on the heat transfer dynamics. The obtained heat transfer and flow fields are decomposed and studied using proper orthogonal decomposition (POD) and extended proper orthogonal decomposition (EPOD). The heat transfer appear to be distributed according to a gamma distribution, in time, with location-dependent shape and scale parameters. The results obtained show that, over time, many locations on the impingement plate experience large over- and undershoots compared to the time-averaged Nusselt number distribution. The POD analysis show that the low order heat transfer modes, while having low relative intensity, are associated with distinct flow features. The flow features are identified by application of EPOD. The two dominant modes are associated with ring-like vortex structures organized concentrically around the impingement point. Reconstruction of the heat transfer field using the three first modes and the mean field show radially outward moving structures with a phase velocity of 0.23Ub.