QUANTITATIVE HEAT-TRANSFER MEASUREMENTS IN HYPERSONIC WIND TUNNELS BYMEANS OF INFRARED THERMOGRAPHY

A description of infrared thermography, as this is employed in a hyper sonic blowdown wind tunnel for the acquisition of high quality ''two-d imensional'' heat transfer data over aerodynamic surfaces, is given. I t is shown that the availability of an infrared scanning radiometer an d a standard digital image processing (DIP) system in the laboratory m ay provide the means for the performance of highly efficient (in terms of time and cost) heat transfer measurements, which exhibit accuracy levels comparable to those achieved by classical discrete point gauges , such as thin film surface resistance thermometers and thermocouples. The advantages of infrared thermal mapping over the classical techniq ues, not only in measuring heat transfer distributions over complex th ree-dimensional configurations and in locating and quantifying highly localized hot spots, but also in interpreting puzzling results observe d on simple configurations are illustrated by means of a series of exa mples. A discussion of the limitations of the technique is also offere d to indicate that most of such limitations are common to classical '' zero-dimensional'' Instrumentation as well.