Thermographic Detection of separated Flow

Characterization of Laminar Separation Bubbles Using Infrared Thermography

“…The increased fluctuations at reattachment were stated to be a result of turbulent characteristics of the boundary layer, and temporal oscillation of the reattachment location. The findings agreed with, and gave reasoning to, conclusions drawn in their previous study [23]. Moreover, using the temporal standard deviation of temperature fluctuations was shown to provide a viable estimate for both mean separation and reattachment on unheated surfaces with low thermal contrast.…”

“…In attempts to improve thermal contrast in the subsonic regime, external [21,22,25,26,[89][90][91] or internal [19,20,24,90] heating elements were often incorporated [82]. With the use of additional heating, both laboratory [19][20][21][22][23][24][25] and in-flight experiments [20,26] have performed successful detection of mean transition using infrared…”

“…Dollinger et al [23] used infrared thermography, surface pressure measurements, and oil film surface flow visualization to characterize separated regions on unheated airfoil and cylinder models. They used the temporal standard deviation of temperature fluctuations, or temperature fluctuation index (TFI), to characterize the separated region.…”

“…With recent developments in infrared camera technology, infrared thermography has been successfully applied in subsonic flows to identify boundary layer transition in both laboratory [19][20][21][22][23][24][25] and in-flight experiments [20,26]. Additionally, analysis of separating near-wall flows has been pursued, such as detection and characterization of laminar separation bubbles.…”

Evaluating airfoil behaviour such as laminar separation bubbles with visualization and IR thermography methods

“…As mentioned, in low Re flows, LSB forms due to the laminar flow separation and turbulent flow reattachment therefore detecting these areas utilizing IT allows the opportunity of detecting LSB characteristics on the surface of the airfoil [8]. A useful study related to separation detection using IT was reported [9] where the flow about a cylinder was studied and also investigated the separated flow area in deep stall condition over an airfoil using thermographic imaging, and temperature fluctuation to detect the separated flow. Simon et al [10] studied the laminar-turbulent transition on a flat plate using several heating methods and stated that overall internal heating was more suitable than others.…”