Mach Number and Heating Effects on Turbulent Supersonic Jets

Abstract

Modern experimental techniques were used to obtain detailed aerodynamic and thermodynamic data for turbulent supersonic jets. Operating points from the work of Seiner et al. for heated Mach 2 jets were used as a starting point for the matrix of cases examined here using a geometrically similar Mach 2 nozzle. Two additional nozzles were examined having design Mach numbers of 1.36 and 1.63. For each Mach number, multiple jet temperatures were investigated. Jet measurements were first made with stagnation pressure and temperature probes for comparison to the previous experiments. The experiments focused on modern nonintrusive measurement techniques, including particle image velocimetry for mean and root-mean-square (rms) velocities, and rotationally resolved Raman scattering spectroscopy for mean and rms temperatures. Experimental results showed that as jet Mach number increases, the overall jet mixing rate decreases, as indicated by the potential core length, downstream mean velocities, and turbulence levels. Similar behavior was observed in the mean temperatures and rms temperatures. The suppression of turbulence as the jet Mach number increases is due to compressibility. For a fixed jet Mach number, increasing the jet temperature resulted in faster mixing by all measures. Peak turbulent stress levels, located along the lipline of the jet, demonstrated trends in individual stress components that differed depending on whether jet Mach number or temperature was varied, but indicated that the turbulence structure parameter was very similar when varying either jet temperature or Mach number.