Abstract
A two-component Doppler global velocimeter (DGV)system has been improved through the use of vapour-limitediodine cells that have temperature-independent responses, alongwith nonpolarizing beam splitters and lower f-number lenses.Two-component DGV velocity measurements have been obtained fora 1 inch diameter uniform circular jet flow at a nominal exit velocity of 60 m s-1, as well as for an annular jet and aswirling jet. These data generally agree with earlier pointDoppler velocimeter and hot wire anemometer results towithin about 2-4 m s-1, and display a total variabilityfrom a smooth curve of ±2-3 m s-1. This level ofaccuracy has been obtained for a system that uses a cw argonion laser and eight-bit CCD cameras and digitizers. Exceptions tothis level of accuracy are noted in regions of significantsecondary scattering, due to scattered laser light that isreflected off the lip of the jet nozzle, as well as in regionsof low smoke seeding levels, resulting in low signal-to-noiseratios. A significant amount of the variability of the datafrom a smooth curve is due to the flat field correction.
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