Experimental Investigation of Unstart in an Inlet/Isolator Model in Mach 5 Flow

Wagner J. L., Yuceil K. B., VALDIVIA A., CLEMENS N. T., DOLLING D. S.

AIAA JOURNAL, vol.47, no.6, pp.1528-1542, 2009 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 47 Issue: 6
  • Publication Date: 2009
  • Doi Number: 10.2514/1.40966
  • Journal Name: AIAA JOURNAL
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1528-1542
  • Istanbul Technical University Affiliated: No


The dynamics of unstart of a floor-mounted inlet/isolator model in a Mach 5 flow are investigated experimentally. The inlet section contains a 6-deg compression ramp, and the isolator is a rectangular straight duct that is 25.4-mm high by 50.8-mm wide by 242.3-mm long. Measurements made include 8-kHz schlieren imaging and simultaneous fast-response wall pressures along the length of the inlet/isolator. Unstart is initiated by deflecting a flap at the downstream end of the isolator. The shock system, induced by unstart, initially propagates upstream through the isolator at a velocity of about 35 m/s (in the laboratory frame of reference), then decelerates to about 20 m/s near the isolator entrance, and then accelerates to a velocity of about 74 m/s within the inlet. Throughout the isolator, unstart is seen to be strongly associated with boundary-layer separation. Once the inlet has unstarted, a high-amplitude oscillatory (periodic) unstarted flow ensues, for which the oscillation frequency is about 124 Hz. However, under some conditions, an 84-Hz oscillatory unstarted flow mode, with lower pressure fluctuations, is observed. Under other conditions, a nonoscillatory unstarted flow, with much lower pressure fluctuations, is observed.