Computational Investigations of High-Speed Dual-Stream Jets

A series of coaxial dual-stream jets issuing into quiescent air was investigated using Reynolds-averaged Navier-Stokes calculations with linear two-equation and nonlinear two-equation explicit algebraic stress turbulence modeling. Comparisons of calculated mean flowfield development were made with experimental data. For all cases, a single axisymmetric convergent-divergent nozzle provided a Mach 1.5 primary flow. Three conical secondary flow nozzles with outer (secondary) to inner (primary) nozzle diameter ratios of 1.4, 1.7, and 2.0 were examined. For each configuration, three subsonic secondary flow Mach numbers (0.37, 0.60, and 0.90) were investigated. A single jet case was also investigated for comparison with the coaxial arrangements. Comparisons of calculated centerline jet velocity decay, velocity profiles in the developing jet region, and potential core lengths yield reasonably good agreement with experimental data. Experimentally observed potential core lengthening with increasing coflow nozzle diameter and increasing secondary flow Mach number is also observed in the calculations. Calculated turbulent kinetic energy fields are provided in order to further characterize the development of the turbulent jet flowfields. The peak kinetic energy magnitude decreases and the location of the peak moves downstream with increasing secondary flow Mach number and increasing secondary nozzle diameter.