A gas-flow tracing technique applicable to rotating systems boundary layer on a rotating disk

A sensitive flow tracing technique applicable to remote rotating systems for a disk rotating in air is described. 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 this flow tracing method can be extended to remote geometries. 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.