LES simulations of an impinging jet: On the origin of the second peak in the Nusselt number distribution

The complex flow field of an impinging jet is investigated to understand the dynamics of vortical structures on heat transfer. The prediction of heat transfer by a turbulent impinging jet at small jet-to-wall distances is a challenging problem in CFD. In this study the flow and heat transfer characteristics of an orthogonally impinging cold jet on a heated plate has been investigated by large eddy simulations using structured grids. The LES simulations are performed with a dynamic Smagorinsky model in the finite volume based code FASTEST, using a second-order-accurate discretisation schemes for space and time. The investigations are performed at Reynolds numbers of 13,000 and 23,000 based on jet's diameter and bulk velocity. The dimensionless jet's outlet-to-target wall distance is two. The LES data help to understand the nature of turbulence in the stagnation zone and in the developing wall jet. Simulations help in understanding the reason of occurrence of second peak in the radial distribution of Nusselt number at the target wall. The dynamics of coherent structures and their influence on the heat transfer is also explored. (C) 2012 Elsevier Ltd. All rights reserved.