Mean and fluctuating velocity contours and acoustic characteristics of subsonic and supersonic jets

Subsonic and Supersonic Jets and Supersonic Suppressor Characteristics

“…In the subsonic mixing region the contours of constant pressure fluctuations were similar to those observed for sonic and subsonic jets as shown in Ref. 6.…”

“…6. On the axis of the nozzle the core length for these subsonic Mach numbers extended over the initial four diameters and downstream in the fully developed subsonic turbulent jet flow the axial velocity decayed as x~l, which was also observed in Refs.…”

“…These Mach waves are not present for air jets operated at room temperature with subsonic exhaust Mach numbers as shown clearly in Ref. 6 with the shadowgraphs obtained with a short duration spark source. In the fully developed subsonic turbulent jet the contours of the static pressure fluctuations for jet Mach numbers of 1.2 and 1.4 were similar to those observed with sonic and subsonic exhaust velocities.…”

“…Detailed surveys of the jet plumes were conducted with the small piezoelectric impact probe over a jet Mach number range of 0.6 to 1.4 and the contours of constant rms piezoelectric probe output are presented in Ref. 6. For subsonic Mach numbers of 0.6 to 1.0 the contours of the rms impact pressure fluctuations were quite similar with peak fluctuations occurring in a toroidal region located over an axial distance of approximately 3.5 to 6 diameters with the center of the region located approximately one nozzle radius from the axis.…”

“…This was the procedure used to obtain the variation of the overall acoustic power with jet velocity for constant mass flow rate in Ref. 6 and the results are presented in Fig. 25.…”