Infrared thermography techniques for boundary layer state visualisation

Abstract

Decarbonising power generation and aviation requires step changes in aerothermal technology. This necessitates working in large design spaces where boundary layer state and resulting loss and heat transfer characteristics are difficult to predict. Standard measurement techniques such as thin-film gauges and oil flow visualisation are intrusive and time consuming, so there is a need for rapid testing methods to diagnose boundary layer state and develop physical understanding. Infrared (IR) thermography has found wide use in aerothermal research and IR measurements of boundary layer state have been demonstrated in many experiments, however there is minimal literature on the best practices for fast and accurate measurements. IR transition measurements rely on temperature differences between laminar and turbulent regimes which are dependent on the thermal characteristics of the system. This paper shows how a 1D heat transfer analysis can be used to maximise the signal-to-noise ratio (SNR) of IR measurements. This can improve measurement quality and minimise complexity. Experimental validation is presented along with a demonstration of the value of IR in rapid testing.