Large-Eddy/Reynolds-Averaged Navier–Stokes Simulations of Sonic Injection into Mach 2 Crossflow

摘要

Computational predictions of transverse injection of air, helium, and ethylene into aMach 1.98 cross owof air arenpresented. A hybrid large-eddy simulation/Reynolds-averaged Navier–Stokes turbulence model is used. A blendingnfunction, dependent on modeled turbulence variables, is used to shift the turbulence closure from the Menter k-!nmodel near solid surfaces to a Smagorinsky subgridmodel in the outer part of the incoming boundary layer and in thenjetmixing zone.The results showreasonably good agreementwith time-averagedMie-scattering images of the plumenstructure for both helium and air injection and with experimental surface pressure distributions, even though thenpenetration of the jet into the crossflow is slightly overpredicted. Predictions of ethylene mole fraction at severalntransverse stations within the plume are in good agreement with time-averaged Raman-scattering mole-fractionndata. The model results are used to examine the validity of the commonly used assumption of the constant turbulentnSchmidt number in the intense mixing zone downstream of the injection location. The assumption of a constantnturbulent Schmidt is shown to be inadequate for jet mixing dominated by large-scale entrainment.