IR

   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: