Analysis of differential infrared thermography for boundary layer transition detection

Abstract

This paper presents an analysis of the differential infrared thermography (DIT) techn ique, a contactless method of measuring the unsteady movement of the boundary layer transition position on an unprepared surface. DIT has been shown to measure boundary layer positions which correlate weil with those from other measurement methods, and in this paper unsteady aerodynamics from a 2D URANS solution are used and the resulting wall temperatures computed. The results show that only the DIT peak can be anal ysed, but that this correlates weil with the boundary layer transition position. A small systematic time-lag of 1.5 ms cannot be reduced by using different surface materials, but the signal can be improved by using common plastics as a thin sheet on the surface.