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Doppler Global Velocimetry for the detection of velocity vector fields

Schematic set-up of a Doppler Doppler Global Velocimeter

Doppler Global Velocimetry is a relatively new technique for the investigation of flow fields, invented by Hiroshi Komine (United States Patent of the 24th April 1990, Patent number 4919536). In the last years this technique has become a promising flow field diagnostic tool for research and development tasks in aerospace and car industry.
At the PTB the Doppler Global Velocimetry based test facility is used to investigate flow fields in pipe configurations in order to get more informations about installation effects affecting the measurement of gas flow rates. In this facility three components of velocity can be acquired over a two dimensional field in only a few minutes.
Doppler Global velocimetry is a particle based measurement technique which uses a laser light sheet to illuminate the flow region of interest. This region is imaged onto a CCD camera through an absorption cell working as a frequency to intensity converter. As the scattered light frequency changes due to the Doppler effect, the light intensity in the CCD image varies and can directly be evaluated to measure one velocity component of the flow field. The component of velocity which is detected is dependant upon the angle between the incident direction of the laser light sheet and the observation direction of the CCD-camera. By the use of three different incident light sheet directions three components of velocity can be acquired over the cross section of the pipe.