Accession Number : ADA474770


Title :   Oscillations in a Forward-Facing Cavity Measured Using Laser-Differential Interferometry in a Hypersonic Quiet Tunnel


Descriptive Note : Interim rept. 1 Dec 2006-11 Dec 2007


Corporate Author : PURDUE UNIV LAFAYETTE IN SCHOOL OF AERONAUTICS AND ASTRONAUTICS


Personal Author(s) : Segura, Rodrigo


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a474770.pdf


Report Date : 11 Dec 2007


Pagination or Media Count : 151


Abstract : Laminar-turbulent transition is a pivotal factor for the design of hypersonic vehicles but the mechanisms that induce transition are not well understood. A laser differential interferometer (LDI) is a non-intrusive optical device that measures the optical path length difference between two laser beams. The LDI is a reliable calibrated instrument to assist the study of boundary layer instability-wave growth in hypersonic flow and has high sensitivity and frequency response. An LDI with a commercial balanced photodetector capable of detecting optical path length differences of lambda/21,000 from DC to 80 MHz was assembled and tested in the Purdue Quiet-Flow Ludwieg tube. Fluctuations in the subsonic region of a forward-facing cavity were measured with the LDI and compared to those detected with a Kulite pressure transducer at the base of the cavity. Predictions of self-resonating deep cavities were confirmed. The LDI was then adapted and transferred to the Boeing/AFOSR Mach-6 Quiet Tunnel.


Descriptors :   *LASER BEAMS , *HIGH SENSITIVITY , PRESSURE TRANSDUCERS , OPTICAL INTERFEROMETERS , INSTRUMENTATION , SUPERSONIC FLOW , BOUNDARY LAYER TRANSITION , OSCILLATION , LAMINAR FLOW , FREQUENCY RESPONSE , HYPERSONIC VEHICLES , HYPERSONIC WIND TUNNELS


Subject Categories : Lasers and Masers
      Electricity and Magnetism


Distribution Statement : APPROVED FOR PUBLIC RELEASE