Wake vortex formation and its role in turbulent heat transport in jet in crossflow.

Although extensive experimental and numerical investigations have been performed for a jet in crossflow (JICF), the formation mechanism and vorticity source of its wake vortex are still not well understood. In the present study, large eddy simulations were conducted to analyze the wake vortex structures for a JICF with a jet-to-crossflow velocity ratio of 3.3 and a Reynolds number of 2100. The proper orthogonal decomposition analysis and the numerical smoke experiment reveal that jet sheds a significant amount of vorticity into the wake vortex. Also, the vorticity generated near the bottom wall of crossflow is pulled into the wake vortex due to the higher wall-normal velocity. Therefore, the wake vortex of JICF originates from both the jet and the bottom wall of crossflow (not just either of them). Furthermore, the role of the wake vortex in turbulent heat transport was examined. The wake vortex with a large vorticity ( | ω z + | ≥ 1.3) contributes to 49% of the total heat flux in the vertical direction, although its occurrence ratio is only 26%. Hence, the wake vortex with a large vorticity plays an important role in the turbulent heat transport in the vertical direction. [ABSTRACT FROM AUTHOR]