9.5 Measurement of the Wall Heat Transfer
223
range. Despite these limitations, infrared thermography tends to be systematically
used for heat transfer measurements because of their versatility and ability to provide
heat flux distribution over a body of complex geometry.
The infrared technique, which has a temperature resolution of a fraction of a
degree, is widely used to detect the laminar to turbulent transition region on a model,
making it a valuable tool for laminar flow research. Figure 9.29 shows a setup for
detecting the laminar to turbulent transition on a flat plate at Mach 1.6 where infrared
thermography and TSP were used in parallel. The IR and TSP images are compared
in Fig. 9.30, the flow coming from the left. IR detection is also used for transition
studies during flight tests (see Sect. 1.7.1).
(a) Detection part
(b) Emission part
Fig. 9.29 Test set-up for the detection of the laminar to turbulent transition on a flat plate at Mach
1.6 by using TSP (© ONERA)
(a) Infrared thermography
(b) Temperature sensitive paint
Fig. 9.30 Detection of the laminar to turbulent transition on a flat plate at Mach 1.6. Laminar
regions are in green (© ONERA)