IR-thermography studies of high-speed gas-dynamic flows

This study investigates the application of a specific infrared thermography technique to visualize high-speed flows by analyzing the emerging thermal distribution on quartz windows of a shock tube channel’s sidewalls ($24\times 48mm$). The interaction between non-stationary flow ($M=1.8-4.0$) and the streamlined channel walls results in energy exchange at the interface, forming a corresponding thermal load distribution due to the heat tangential conduction. These integral heat flux traces were captured using an infrared camera and quantitatively investigated. Panoramic infrared imaging conducted by a thermal camera with operating range $1.5-5.1\mu m$ and an exposure time of up to $500\mu s$ was combined and compared with a frame-by-frame shadowgraphy. The resulting radiation intensity integral maps were analyzed as a function of the incident shock wave Mach number, local flow-quartz interaction duration and heat flux magnitude, influenced by non-stationary boundary layer behavior. It is shown that the acquired inhomogeneous integral thermal patterns on the channel inner surfaces accurately correspond to the gas-dynamic structures of the flow according to their duration and intensity. The analysis underscores key local flow characteristics, including regions of deceleration and compression, stagnation zones, and rarefaction areas. Thermal maps captured from different observation angles ($\Theta \approx 0°,25°,36°$) revealed sidewall-specific heating patterns and composite images of overall radiation intensity. Experimental findings underline the feasibility of using this approach to investigate spatial–temporal characteristics of non-stationary flows via evolving thermal distributions on streamlined surfaces under conditions of non-stationary heat and mass transfer.