Doppler Global Velocimetry (DGV) data in circular jets

A two-component Doppler Global Velocimeter (DGV) system has been improved through the use of vapor-limited iodine cells that have temperature-independent responses, along with non-polarizing beam splitters and lower f-number lenses. Two-component DGV velocity measurements have been obtained for a 1 inch diameter uniform circular jet flow at a nominal exit velocity of 60 m/sec, as well as for an annular jet and a swirling jet. These data generally agree with earlier point Doppler velocimeter (pDv) and hot wire anemometer results to within about 2-4 m/sec, and display a total variability from a smooth curve of ± 2-3 m/sec. Exceptions to this level of accuracy are noted in regions of significant secondary scattering, due to scattered laser light that is reflected off of the lip of the jet nozzle, as well as in regions of low smoke seeding levels, resulting in a low signal-to-noise ratios. A significant amount of the variability of the data from a smooth curve is due to the flat field correction