The effect of the shock-wave intensity on the boundary layer transition in the viscous interaction is analyzed by means of (both experimental and numerical) density gradient fields and (numerical) mean and fluctuating velocity fields. Moreover, a relevant sensor used to detect the transition is the wall temperature: in fact, the temperature is increasing during the transitional regime (from laminar to turbulent) of the boundary layer.
In the experiments, the detection of the boundary layer transition region is performed by using several techniques whose results are compared and cross-checked to accurately determine the transition process on the flate plate. So, these techniques are:
- Schlieren visualizations. These pictures are obtained by an high-speed camera (Phantom V710) located on the side of the wind tunnel, and 60,000 images are recorded at 35 kHz frame rate.
- IR (Infra-red) thermography measurements. The arrangement is constituted of a FLIR SC7000 camera (size image: 640 x 512 pixels with 1 pixel equal to 14µm; lens of 50mm; integration time: 2ms and frame rate: 100 Hz) and of a IR window mounted on a sidewall of the test set-up.
- TSP (Temperature Sensitive Paint) measurements. The arrangement is constituted of a UV-lights source located in one side of the test set-up and of a camera placed in the other side. The flat plate is entirely painted excepted near the leading edge in order to not modify its shape, because the bluntness effect is sensitive on the transition location.