Comparison of Vortex Structures and Turbulent Heat Transport for a Single Jet and Multiple Jets in Crossflow

Abstract Large eddy simulations (LESs) were conducted for a single jet and five spanwise jets with a jet-to-jet spacing of 1.6D (jet nozzle diameter). The jet-to-crossflow velocity ratio was 3.3, and the Reynolds number based on the crossflow velocity was 2100. The verification study demonstrates that the present LES can reproduce the typical vortex structures of a single jet in crossflow and provide a good prediction accuracy. The principal finding is that the counter-rotating vortex pair (CVP) is formed only in a very short distance in the multiple jets and cannot evolve further owing to the significant constraint in the spanwise direction and strong stretch in the streamwise direction. The hanging vortex in the multiple jets is split into two disconnected parts, yielding an elongated cat-ear-shaped vortex on the lateral side of the upper jet body. A pulsating jet flow pattern forms in the space between the adjacent jets with a frequency of 32 Hz, which subsequently generates many small vortexes downstream of the jet. The absolute turbulent heat fluxes |〈u′T′〉| at the rear of the jet and |〈w′T′〉| in the border between the adjacent jets were larger owing to the generation of numerous pulsating jet flows in the space between the adjacent jets.