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One-Dimensional Scanning Approach to Shock SensingMeasurement tools for high speed air flow are sought both in industry and academia. Particular interest is shown in air flows that exhibit aerodynamic shocks. Shocks are accompanied by sudden changes in density, pressure, and temperature. Optical detection and characterization of such shocks can be difficult because the medium is normally transparent air. A variety of techniques to analyze these flows are available, but they often require large windows and optical components as in the case of Schlieren measurements and/or large operating powers which precludes their use for in-flight monitoring and applications. The one-dimensional scanning approach in this work is a compact low power technique that can be used to non-intrusively detect shocks. The shock is detected by analyzing the optical pattern generated by a small diameter laser beam as it passes through the shock. The optical properties of a shock result in diffraction and spreading of the beam as well as interference fringes. To investigate the feasibility of this technique a shock is simulated by a 426 m diameter optical fiber. Analysis of results revealed a direct correlation between the optical fiber or shock location and the beam s diffraction pattern. A plot of the width of the diffraction pattern vs. optical fiber location reveals that the width of the diffraction pattern was maximized when the laser beam is directed at the center of the optical fiber. This work indicates that the one-dimensional scanning approach may be able to determine the location of an actual shock. Near and far field effects associated with a small diameter laser beam striking an optical fiber used as a simulated shock are investigated allowing a proper one-dimensional scanning beam technique.
Document ID
20120012882
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Tokars, Roger (NASA Glenn Research Center Cleveland, OH, United States)
Adamovsky, Girgory (NASA Glenn Research Center Cleveland, OH, United States)
Floyd, Bertram (Sierra Lobo, Inc. Cleveland, OH, United States)
Date Acquired
August 26, 2013
Publication Date
January 5, 2009
Subject Category
Aerodynamics
Report/Patent Number
E-18268
Meeting Information
Meeting: AIAA 47th Aerospace Science Meeting
Location: Orlando, FL
Country: United States
Start Date: January 5, 2009
End Date: January 8, 2009
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 599489.02.07.03.06.02.02
Distribution Limits
Public
Copyright
Public Use Permitted.

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