DNS and RANS modelling of a turbulent plane impinging jet

The main objective of this paper is to study in detail the fluid flow and the heat transfer in plane impinging jets. Mean and fluctuating velocities and global parameters, i.e. the local Nusselt number, are analysed. The study is focused on a Reynolds number 20,000 (based on the bulk inlet velocity and the nozzle width, B) and dimensionless jet-to-surface spacing 4. As a first step, a reliable direct numerical simulation (DNS) has been performed. Then, the DNS results have been used as reference solution to assess the performance of several Reynolds-averaged Navier–Stokes (RANS) models. Namely, explicit algebraic Reynolds stress models and both non-linear and linear eddy viscosity models in conjunction with k − ϵ and k − ω platforms. Moreover, an overview of the numerical methods and the methodology used to verify the code and the simulations is also presented. Time-averaged DNS results have revealed that the main recirculating flow cannot be captured well unless the outflow is placed at least at 40B from the jet centreline approximately. This suggests that previous experimental data may not be adequate to study the flow configuration far from the jet. Consequently, conclusions previously published by the authors on the performance of the tested RANS models have been necessarily revised.