Description

Visible and infrared (IR) observations of flame structure were made of the Frostfire controlled burn carried out 8-10 July 1999 at the Caribou-Poker Creek Research Watershed near Fairbanks, Alaska. The observations were taken from Caribou Peak, facing the burn area from the Northeast. A black and white camera with a filter centered on 510 nm was used to assess the feasibility of observing the C2 radical emissions band as a means of tracking flame structure. The C2 emission indicates regions of intense energy release in a flame. To our knowledge, this is the first attempt at obtaining this information in a field experiment. A sequence of images obtained from the black and white camera is compared with images taken with a standard color video camera. An Inframetrics Thermacam SC1000 FPA IR camera was used to collect infrared images of the fire, from which flame velocity information can be extracted. A sequence of images obtained from the IR camera reveals the temperature field in the rising buoyant plumes immediately within and above the large scale fire, estimated by the Thermacam at up to 900 oC. Estimates of large-scale velocities are derived from the IR images using the image flow analysis developed by Clark et al (1999). In this method, features in the radiant temperature field, most likely composed of glowing particles, are tracked from frame to frame (at 30 frames per second). Then, by accurately georeferencing the image and using an affine model fit, motion within the image plane can be obtained. It is expected that with further refinement of the methods for field conditions, these imaging techniques will provide useful data for evaluating three-dimensional models of fire spread.