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Title: Helical instability in an underexpanded jet with pressure ratio PR = 4

Description: Schlieren images captured at 1,000,000 frames per second depict an underexpanded free jet of air with a nozzle pressure ratio (nozzle stagnation pressure divided by ambient pressure) of NPR=4. At this ratio the jet is influenced by a helical instability mode which causes the 2nd, 3rd and 4th Mach disks to oscillate about the jet axis. Also seen are acoustic waves generated at the edge of the jet, and travelling away from it.

Credits: Adam Risborg and Julio Soria - Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC)


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Contributed By: Adam Risborg

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