Large-eddy simulation of jet in supersonic crossflow with different injectant species

The effects of injectant species on the turbulent structure and mixing state of jets in supersonic crossflow were investigated using alarge-eddy simulation. Hydrogen, helium, nitrogen, and ethylene were transversely injected into a Mach 1.9 airflow at a constant jet-to-crossflow momentum flux ratio. The time-averaged distribution of jet concentration was roughly the same for all the injectant species, but the large-scale structure of scalar fluctuation differed significantly. The probability density functions of injectant mass fraction revealed that the turbulent behavior of nitrogen and ethylene jets was highly intermittent. The velocity field was considerably different between the injectants, owing to the different injection velocities. The hydrogen and helium jets had a much higher velocity difference between jet and crossflow in the near field; thus, the observed turbulent intensities for these two injectants were much higher than those for nitrogen and ethylene. In addition, the spectral analysis of velocity fluctuations in the windward mixing layer showed that the scale of energetic eddies was larger in the hydrogen and helium jets than in the nitrogen and ethylene jets. These characteristics resulted in better mixing in the hydrogen jet than in the ethylene jet for the studied injection conditions.