Boundary-Layer Transition Detection on The X-15 Vertical Fin Using Surface-Pressure-Fluctuation Measurements

Lewis, Thomas L. and Banner, Richard D. (1971) Boundary-Layer Transition Detection on The X-15 Vertical Fin Using Surface-Pressure-Fluctuation Measurements. Technical Report NASA TM X-2466, Research Engineering, NASA Dryden Flight Research Center.

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Abstract

A flush-mounted microphone on the vertical fin of an X-15 airplane was used to investigate boundary-layer transition phenomenon during flights to peak altitudes of approximately 70,000 meters (230,000 feet). The flight results were compared with those from wind-tunnel studies, skin temperature measurements, and empirical prediction data. The Reynolds numbers determined for the end of transition were consistent with those obtained from wind-tunnel studies. Maximum surface-pressure-fluctuation coefficients in the transition region were about an order of magnitude greater than those for fully developed turbulent flow. This was also consistent with wind-tunnel data. It was also noted that the power-spectral-density estimates of the surface-pressure fluctuations were characterized by a shift in power from high frequencies to low frequencies as the boundary layer changed from turbulent to laminar flow. Large changes in power at the lowest frequencies appeared to mark the beginning of transition.

EPrint Type:	NASA Technical Memorandum
Keywords:	Surface-pressure fluctuations, Boundary-Layer transition
Subjects:	Aircraft/Project: X-15
ID Code:	820
Deposited On:	16 March 2006
Additional Information:	18 pages.