Speakers
Description
This study presents experimental results on non-stationary thermal and gas-dynamic processes emerging from the interaction of a plane shock wave (Mach 2.0–4.5) with axisymmetric blunt-cylinder models (sphere-blunted cylinder and a flat-nosed cylinder) in a shock tube channel.
The research employed combined high-speed optical and infrared diagnostics. Gas-dynamic structures were visualized using shadowgraphy through the channel's side windows (SiO₂) transparent to optical and infrared radiation. Non-stationary thermal fields on the model and channel surfaces were captured via panoramic thermography using Telops FAST M200.
The observed heated flow areas were: the flow behind plane shock wave (air); the flow behind bow shock wave; the flow behind contact surface (cold helium); the flow-wall interface (2 windows and the upper and lower walls); the axisymmetric model surfaces. Filters for different wavelength ranges were used to understand the radiation sources. Period of up to 100 ms post-interaction time was recorded.
A combined analysis of shadowgraph and thermographic data enabled the determination of characteristic times for various stages of non-stationary flow behind a plane shock wave and to investigation of the thermal processes accompanying the supersonic and subsonic flow regimes around the models.
The results demonstrate a direct correlation between gas flow evolution and thermal radiation intensity. For incident shock waves with M > 3, a supersonic flow regime with a detached bow shock wave persists for approximately 150 - 300 μs, transitioning to subsonic flow after 300-500 μs. Therefore, the maximum-recorded thermal radiation intensity from streamlined surfaces occurred within the first 500 μs, primarily in the boundary layer on the channel walls interacting with secondary shock structures and in the frontal stagnation zone of the models. Radiation from the heated quartz side windows decayed to background levels within 200-400 μs after shock diffraction. In contrast, the model surface exhibited prolonged cooling: thermal radiation from the nose region was detectable for up to 50 ms, and from the cylinder side surface for 30–40 ms (for M=3).
In summary, this work experimentally characterized thermal processes during non-stationary flow/body interaction. The application of synchronized shadowgraphy and thermography, complemented by advanced image processing, enabled the determination of characteristic flow regime timescales, identification of thermal emission regions linked to shock structures, and quantification of surface cooling dynamics.
