Detection of Unsteady Boundary Layer Transition Using Three Experimental Methods

Kurzfassung

Transition measurements were simultaneously performed using hot lm anemometry, pressure analysis, and differential infrared thermography (DIT) in a pitching airfoil wind tunnel test. The principles of the three detection methods will be described and results will be presented for the unsteady transition locations detected on the DSA-9A rotor blade airfoil at M = 0.3 and Re = 1.8 x 10^6. Test cases with periodic ramping motion will be compared to cases with sinusoidal oscillations. The influence of surface heating (necessary for the DIT measurements) will be analyzed and the effects of varying pitching amplitudes and frequencies on the transition detection will be discussed. Furthermore, different post-processing strategies of the DIT infrared images will be investigated and compared to the results obtained with hot film anemometry and pressure analysis.