infrared S

Infrared Thermography

The  measurement of the surface heating  is  very  important  particularly  for estimating  the  thermal  load  at  large  Mach numbers.  However, heat transfer is also frequently estimated at small Mach numbers  because  it   is  possible  to determine   the  laminar-to-turbulent  transition   location  due  to  the  different heat   transfer   present  in  both  flow  states.  Today,  digital  infrared  cameras are   usually   applied   because  they  are  easy  to  handle  and  instantaneous temperature  measurements at  thousand of points are  possible with a sampling rate in  the kHz range.  Depending  on the sensor technology, these cameras are working  in different wavelength regimes,  namely:  the  short wavelength regime between 0.4 and 2--3 micrometer, the intermediate between 2--3 to 5 micrometer and  the long range between  8 and 12 micrometer.  In fluid mechanics the range between  2  and  5 micrometer  is  usually  recorded  as  high  resolution  indium antimonite (InSb) or mercury cadmium telluride sensors are available. These  sensors  have  excellent signal to noise ratio and are available with 14 bit dynamic range.

The  IR  measurement  technique still holds a lot potential for improvements. The Institute of Fluid Mechanics and Aerodynamics works on enhancements in the following fields:

  • Data acquisition in various temperature ranges
  • Calibration and noise reduction for accurate heat tranfer  measurements
  • Quantitative data evaluation and analysis
  • Simultaneous application with other measurement techniques like PSP, deformation measurement technique, and PIV