Influence of non-adiabatic model surface on transition measurements using the Temperature-Sensitive Paint technique in cryogenic wind tunnels

Tests were conducted at the cryogenic blow-down wind tunnel facility DNW-KRG in Göttingen, Germany, with the aim of investigating the influence of the thermal gradients on the model surface on onset of boundary layer laminar-turbulent transition. The laminar airfoil under investigation was tested at high Reynolds and both low and high subsonic Mach numbers. Boundary layer transition was detected non-intrusively by means of the Temperature-Sensitive Paint technique. The effect of the temperature drop occurring during a run at DNW-KRG on the stability of the laminar boundary layer was investigated. Various combinations of flow conditions and angles-of-attack were employed in order to investigate different stability situations. The influence of the temperature difference between flow and model surface on boundary layer transition development was examined. The unfavorable impact of the non-adiabatic thermal boundary condition at the model surface was identified to be dependent on the considered boundary layer stability situation