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Goal: To reveal complex air motions within firelines
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The Inframetrics Thermacam SC1000 camera has
been applied in several diverse situations : |
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Three experimental burns took place during the International Crown Fire Modelling Experiment in June-July, 1997. During this experiment, the Thermacam was mounted on a 50 ft tower pointed towards intense, oncoming crown fires. It produced a sequence of high frequency (1/30 sec), high resolution (0.05-0.16 m) radiant temperature images, which have since been analyzed using the image flow analysis described below to derive wind fields and sensible heat flux.The 9 June burn was particularly successful, producing a high intensity crown fire that consumed the 150 m x 150 m forest Plot 6 in approximately 5 minutes. Analysis gave estimates of fire winds between 20 and 30 m/s, vertical heat fluxes The derived vertical velocities and radiance temperatures were used to derive heat flux profiles; these agreed with expected values, further corroborating the wind estimates. This work is believed to represent the first quantitative data set, albeit derived, showing the spatial and temporal structures of fire winds, heat flux profiles as well as derived vertical vorticity. |
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During WiFE, the Thermacam was mounted outside the left window of NSF's C130 research aircraft. The aircraft overflew and did pylon turns around wildfires at heights of 1500 to 3000 m above ground level, allowing the camera to view the fire for periods up to 20 minutes. The image flow analysis software was then successfully used for a quick-look analysis of the observed wind fields. Algorithms were developed to extract the aircraft motion, which was necessary before the image flow analysis could be applied. The combined image flow package with ego motion extraction represents a rather robust software system which allows the quantitative analysis of IR data from unsteady platforms. |
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In collaboration with Michael Reeder and David Packham (Monash), Clark participated in two field experiments in Australia during his sabbatical at Monash University. The first experiment was a test experiment of wheat stubble grass fires in preparation for Northern Territory grass fire experiments that took place near Darwin in June of 1998. Successful IR observations were obtained of both Australian spear grass and kerosene grass in the NT experiments. Preliminary analysis suggests that this region represents an optimal location to mount more comprehensive experiments in the future. |
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The collaborative research project between Clark, Coen, Radke (ATD) and Don Middleton (SCD) resulted in the development of an image flow analysis software package. Robust statistics and least squares minimization procedures were used to extract fire winds. This software was applied to the infrared (IR) video data taken during the International Crown Fire Modelling Experiment in Canada's Northwest Territories from June-July 1997 and is currently being applied to data from the Wildfire Experiment. and FROSTFIRE. The main assumption in image flow analysis is that distinctive features in the image can be assumed to retain their integrity from one frame to the next. In the case of the fires, we assumed that the IR temperature image was mostly advected with the wind over a period of 1/30 second. The procedure is then to consider a patch of data in the image and try to fit its motion to a local wind structure. An animation (AVI, 4.5 Mb) of these recovered winds reveals the complex motions within the fire. |
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Last Modified: 01 Oct 1998
