Underwater Investigation of Stall Onset on an Elliptic Profile via Temperature-Sensitive Paint

Abstract

The onset of stall on an elliptic profile with 16% relative thickness was examined on a two-dimensional model investigated in the large water tunnel of Technische Universität Braunschweig. The model upper surface was equipped with a temperature-sensitive paint for the global, non-intrusive, time-resolved measurement of the surface temperature distribution. The model was also instrumented with a row of pressure taps to measure the surface pressure distribution. The results reported in this study focus on two chord Reynolds numbers and angles-of-attack around stall conditions. The flow was shown to remain attached for most of the profile chord length up to angles-of-attack of 11.5° and 13.0° at Reynolds numbers of 2.5 × 105 and 5.0 × 105, respectively, whereas a small increase of the angle-of-attack beyond these values led to massive flow separation. The spatial and temporal development of the thermal signatures of the separated flow structures was captured via temperature-sensitive paint at both pre-stall and stall conditions, including the time-dependent wall signature of stall cells. The experiments were performed at two chord Reynolds numbers (Re = 2.5 and 5.0 × 10^5) for a wide range of angles-of-attack (−4° <= AoA <= 30°), thus enabling the study of a variety of flow conditions, including laminar-turbulent transition and flow separation. The final contribution will provide the temporal development of the surface temperature at pre-stall, stall and post-stall conditions, and an evaluation of the onset of stall.