Remote noncontacting measurements of heat transfer coefficients for detection of boundary layer transition in wind tunnel testsAn infrared measurement system is used that consists of a laser heating source, an infrared camera for data acquisition, and a video recorder for data storage. A laser beam is scanned over an airfoil, heating its surface to a few degrees above ambient. An infrared camera then measures the temperature of the airfoil over a two-dimensional field, and these temperatures are stored as a function of time on a video recorder. The resulting temperature pictures are digitized and an iterative approximation algorithm is used to extract the heat transfer coefficient. The resulting values are normalized to the natural convection condition. The technique has been applied in low-speed wind tunnel tests and compared to well-established hot-film measurements which were made simultaneously to confirm the flow conditions. Heat transfer coefficients were determined using a linear scanning pattern, to indicate the position of natural and of artificially induced transition on an airfoil, at various wind speeds. The technique is shown to be sensitive to transition at low Mach numbers. The advantages of the technique are discussed.
Document ID
19880049272
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Heath, D. Michele (NASA Langley Research Center Hampton, VA, United States)
Winfree, William P. (NASA Langley Research Center Hampton, VA, United States)
Carraway, Debra L. (NASA Langley Research Center Hampton, VA, United States)
Heyman, Joseph S. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Subject Category
Instrumentation And Photography
Meeting Information
Meeting: ICIASF ''87 - International Congress on Instrumentation in Aerospace Simulation Facilities