Flow and thermal characteristics of jet impingement on a flat plate for small nozzle to plate spacing using LES

Abstract

This paper presents a study of flow and thermal characteristics of jet impingement heat transfer by large eddy simulation (LES) using the wall adapting local eddy (WALE) viscosity sub-grid scale (SGS) model. OpenFOAM 4.1, a finite-volume based customized open source computational fluid dynamics (CFD) solver, is used for computations. Turbulent slot jet impingement on a solid flat plate for a small nozzle to plate spacing (H/B = 4, where H denotes the gap between jet and plate and B the slot width) and Reynolds number of 20000 is considered. The capability of the WALE SGS model is first evaluated by comparing the results of flow and heat transfer features including turbulence profiles with the reported experimental results and good agreements are observed. A secondary peak in Nusselt number (Nu) profile on the impingement plate is observed in accordance with the reported results. In order to gain a good understanding of flow and heat transfer characteristics, mean and r.m.s. values of velocity and temperature, Nusselt number (Nu), turbulent structures and iso-surfaces of various flow properties were analyzed in detail. Large coherent structures, flow acceleration and an augmentation in turbulence were correlated with the existence of a secondary peak in Nu profile. A detailed discussion on flow and heat transfer characteristics is presented in the vicinity of stagnation, impingement plate and wall jet regions.