Doppler Global Velocimetry (DGV) is a velocity measurement technique capable of recovering planar three-component velocity data. The method relies on a direct measurement of the frequency-shifted light scattered by moving particles suspended in the flow under investigation (i.e. Doppler effect). Since the frequency shift is many orders of magnitude smaller than the frequency of the illuminating light itself, a narrow absorption band of iodine serves as a frequency-to-intensity converter in the form of an absorption cell placed in front of a CCD camera.
To date this rather new technique has been applied to a variety of flows found in turbomachinery components such as engine inlet ducts and combustion chambers. Increased use of this technology can be also found in the automotive development branch such as the measurement of the cylinder in-flow and turbo-chargers. Even phase-resolved measurements of engine exhaust flows are possible. The DGV hardware is not restricted to the measurement of internal flows; it is just as suitable for use in wind tunnel environments.
Some highlights of DGV
The figure shows selected YZ cross sections through the volumetric three-component velocity data obtained for the main zone of a combustion chamber. The contours indicate the out-of-plane velocity component vx. (For further details see Measurements inside a cold combustion chamber).
The principle behind Doppler Global Velocimetry
DGV Application Examples