Laminar-Turbulent Transition Detection on a DU89-134/14 Airfoil at Low Reynolds Number and Low Temperature Using Cryogenic Temperature Sensitive Paint

Cryogenic Temperature Sensitive Paint (cryo-TSP) has been employed to investigate the flow topology over the DU89-134 airfoil at chord-based Reynolds numbers Rec = 2.5 × 10⁵ and Rec = 5 × 10⁵, and flow temperature of T = 233.15 K. Spanwise-averaged surface temperature distributions and their gradients were analyzed to determine the locations of flow separation, transition, and reattachment. Results indicate that in most observed cases, the flow is characterized by a separation-induced transition, which is concomitant with the formation of a Laminar Separation Bubble (LSB). In one case, the flow transitions directly to turbulence without prior separation, followed by a turbulent separation. This behavior is attributed to the formation of ice crystals on the leading edge of the airfoil.