Infrared Thermography Measurements and Surface Flow Visualizations of a Laminar Separation Bubble over an Airfoil Model

The present work describes Infrared Thermography (IRT) measurements conducted on a NACA 0018 airfoil model to characterise the Laminar Separation Bubble (LSB) occurring on the suction side of the airfoil at low Reynolds number flow conditions. Surface flow visualizations with china clay were also conducted in the same flow conditions to provide a primary visualization of the extent of the LSB. The goal of this activity was the assessment of the degree of accuracy of different methodologies applied to surface temperature intensity measurements for the quantitative evaluation of the separation, transition and reattachment fronts of the LSB. This goal is achieved by superimposing these detected fronts over the dewarped visualization images obtained by a regular LWIR camera. The outcome of the comparison of the characteristic points locations with literature data and surface visualizations proved the suitability of the IRT and DIT techniques for the characterization of a LSB, particularly for reattachment position detected with the intersection point method.