Infrared Thermography

The measurement of surface heating is particularly important for the estimation of thermal load at high Mach numbers. However, heat transfer is also often estimated at low Mach numbers, since the position of the laminar turbulence transition can be determined due to the different heat transfer in both flow conditions. Nowadays, digital infrared cameras are used because they are easy to use and with a sampling rate in the kHz range, they allow instant temperature measurements at thousands of points. Depending on the sensor technology used, these cameras operate in different wavelength ranges, typically between 2 and 5 microns or between 8 and 12 microns. In fluid mechanics, the range between 2 and 5 micrometers is usually measured by high-resolution indium antimonite (InSb) or mercury-cadmium-telluride sensors. These sensors have an excellent signal-to-noise ratio and are available with 14-bit dynamic range.

There is still a lot of room for improvement in IR measurement technology. The Institute of Fluid Mechanics and Aerodynamics is working on further developments in the following areas:

• Data acquisition in different temperature ranges
• Calibration and noise reduction for accurate heat transfer measurements
• Quantitative data evaluation and analysis
• Simultaneous use with other measurement methods such as PSP, deformation measurement technology and PIV