Characteristic features of mixing of and heat transfer between a 2D counter-flowing wall jet and a main-stream flow were studied numerically. In the initial section of the flow above the working wall, an extended zone of recirculation flow appears after the reversal of the jet. A local increase in the velocity is observed between the upper wall of the channel and the separation zone. The size of the separation region and the flow intensity in it are defined by the value of the injection parameter. It is shown that there is an extended region of higher turbulence level above the working wall of the channel. This is due to the presence of a large recirculating vortex at mixing of the counter-flowing wall jet with the main-stream flow. The length of the flow recirculation zone increases with the injection parameter. Injection of counter-flowing wall jet into the main-stream flow causes significant enhancement of the heat transfer (the maximum increase in the heat transfer is as high as 6 times) in comparison with the flow in the channel under other identical conditions. With higher injection parameter, significant reduction in the heat transfer rate is observed (almost twofold).
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