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Andreas Fischer, Lars Büttner, Jürgen Czarske, Harald Müller, Michael Eggert
Doppler Global Velocimetry with Laser Frequency Modulation for Precise Measurements of Velocity Profiles
Keywords: velocity field measurement, Doppler effect, frequency modulated laser diodes
A novel Doppler global velocimetry (DGV) method with laser frequency modulation is described which enables contactless measurements of the velocity in a plane of a flow. The measurement principle is based on the evaluation of a change in laser light intensity caused by a Doppler-frequency shift at the edge of a molecular absorption curve. The conventional DGV technique uses two cameras for referencing. As a result image misalignments occur causing high measurement errors. Using the novel DGV technique with laser frequency modulation, only one camera is necessary whereby misalignment errors can not occur and a lower measurement uncertainty is attainable. It is shown by experimental results that changes in light intensity do not cause a higher measurent error, if the modulation frequency has been chosen sufficiently high. The lowest uncertainty measured of the new DGV method was 0.02 m/s.
tm – Technisches Messen, Oldenbourg Wissenschaftsverlag
Print ISSN: 0171-8096
Volume: 73, 04/2006
Pages: 237 - 244