Abstract

Thermography is a common diagnostic for measuring spatially resolved surface temperatures. Extreme environments such as high-velocity impact testing employ thermography to probe fireball dynamics for modeling and simulation efforts. However, emissivity and related optical density are major roadblocks for accuracy. In this study, a variety of reactive projectiles are launched at 1300m/s and observed with single camera thermography from two 90° perspectives. The effect of flame shape on optical density and subsequently emissivity is compared between the different viewing angles. Trends indicate that asymmetric flames create varying optical densities between perspectives, resulting in up to 7% difference in reported median temperatures for the same flame. A maximum of 11% total difference is reported, with 6% due entirely to optical density effects. It is concluded that different viewing angles provide valuable insight into optical density and emissivity functions, and uncertainties of reported temperatures should account for this potential inaccuracy.

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