Turbulent heat and mass transfer through air curtains devices for the confinement of heat inside tunnels

The influence of flow instabilities on the efficiency of a twin-jet air curtain formed by a cold stream parallel to a hot stream was studied. Two cases were considered: the Reynolds number and mean flow velocity of both streams were set to 1000 and 3 m/s, respectively. The results obtained from 3D LES simulations were compared with experimental data and earlier LES numerical results using the FDS code. Energy spectra exhibit decay laws with − 5/3 and − 3 slopes. Instabilities with a characteristic Strouhal number of about 0.4 were detected. Kelvin–Helmoltz type instabilities play a more significant role than the Görtler type instabilities present at the wall for applications of plane impinging jets to ambience separation.