Large Eddy Simulation of multiple impinging jets in hexagonal configuration - Flow dynamics and heat transfer characteristics

Flow dynamics and heat transfer characteristics of multiple impinging jets are investigated numerically by the means of Large Eddy Simulation (LES). The experimental test case with 13 air jets at Reynolds number of approximately 20,000 impinging on the heated plate is simulated. A good agreement of LES results with the experiment was already demonstrated in our previous work (Draksler et al., 2014) by comparison of time-averaged flow parameters. Hence, in the present study LES simulations are used to investigate the dynamics and complexity of the instantaneous flow field and to thoroughly explain the local flow mechanisms associated with the heat transfer enhancement at the heated plate. Development of coherent flow structures is analyzed - their quasiperiodic propagation and disintegration on the heated plate result in a very heterogeneous but on average rather stable heat removal from the heated plate. It was shown that the heat transfer at multiple impinging jets is mainly governed by two mechanisms, a convective cooling by the tangential flow in a close proximity of the jet impingement point, and by intense quasi-periodic quenching caused by large-scale vortical structures.