Measurements of Instability in Supersonic Flow with Injection by Time-Resolved Flow Visualization
Experiments were performed in a Mach 4 Ludwieg tube to examine the transition process in flow over a sharp cone with boundary layer injection. Full-field images with nitrogen, helium and RC-318 injection reveal that transition occurs earlier with higher injection rates and with lighter injected gas. High-speed imaging at 290 kHz allows the measurement of wavelength and convective velocity by auto- and cross-correlation, respectively, in the cases with nitrogen injection. The wavelength is found to be approximately 8 mm with a convective velocity of 515 m/s, resulting in a frequency range of 60-70 kHz. These properties of the instability waves are roughly constant over all injection rates tested even though the thickness of the injection layer varies by a factor of two.
© 2016 American Institute of Aeronautics and Astronautics. Published Online: 2 Jan 2016. Thanks to Bahram Valiferdowsi, Ali Kiani, and Joe Haggerty for assistance with the models used in the present study. Additional thanks are due to Neal Bitter for insights into the transition process in supersonic flows. Bryan Schmidt acknowledges the support of Foster and Coco Stanback STEM Fellowship for his graduate studies.