Accuracy and Application of Doppler Global Velocimetry to Complex Aerodynamic Flows

Abstract

Abstract : A two-component point Doppler velocimeter system using iodine vapor absorption cells has been improved through the use of vapor-limited cells that are insensitive to temperature variations. Also, use of a measurement volume of reduced size has improved the RMS results. Two-component velocity measurements have been obtained for a 1 inch diameter uniform circular jet flow at a nominal exit velocity of 60 m/sec, corresponding to a Reynolds number of 100,000. Similar data have also been obtained for an annular jet and a swirling jet. These data runs have been duplicated to judge the repeatability of these measurements, and also have been compared with single-component hot wire anemometer data for the same flow conditions. Mean velocity results are repeatable to within approximately 1-2 m/sec; the RMS velocity results are repeatable to within approximately 1 m/sec. Exit profiles of mean axial velocity data generally agree with hot wire anemometer results to within about 2-4 m/sec. However, the RMS velocity results are consistently 20-28% lower than the hot wire results everywhere but at the exit of the standard jet, where they are too high relative to the hot wire data. This is believed to be due to spatial averaging for the point Doppler velocimeter results, as well as to the method used to compute the RMS for some of these results. The two-component Doppler Global Velocimeter (DGV) system has also been significantly improved in the present work through the use of the same vapor-limited iodine cells that are not sensitive to temperature variations.