Visualization of air flow using infrared thermography

A technique to visualize airflow using IR thermography is developed. A trace quantity of sulfur hexafluoride (SF6) gas is injected into the flow field to detect intensity patterns using a scanning IR thermography system with a single 8-13 mum bandwidth detector. Equations that relate the intensity patterns to volume-averaged temperature and SF6 mass concentration are presented. The visualization technique involves using a background surface at a known temperature different from that of the flow and image subtraction. The technique is demonstrated on free, impinging, and reattachment subsonic air jets, and is shown to be an effective means of visualizing flows at both elevated and ambient temperatures.