A sensitive flow tracing technique applicable to remote rotating systems is described and demonstrated for the simple case of a disk rotating in air. The technique is based on the formation of a plume of silver iodide by reaction of iodine trace vapor, convected by the air flow relative to the disk, with silver foil attached to the surface. The plume is in effect an image of the flow made visible by the colored interference fringe pattern due to the optically thin silver iodide. By the use of a delayed iodine release technique described in the paper, this flow tracing method can be extended to remote geometries for which conventional methods may be unsuitable. The experimentally observed patterns are compared with computer generated patterns based on T. von Karman's analytical solution coupled with a numerical model for the three-dimensional transport of iodine vapor. The applicability of von Karman's solution is verified, and the usefulness of the experimental method for correlating speeds of air relative to the disk is demonstrated. (ERA citation 08:035250)
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