DGV - Doppler Global Velocimetry

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

• DGV gives velocity pictures.
• DGV can recover three-component velocity data.
• The spatial resolution of DGV is high (typically more than 200x200 = 40,000 data points per DGV data set).
• The technique is quasi on-line because of the fast data acquisition and straight-forward image post-processing.
  There is no need to track individual particles, only the scattered light needs to be recorded. This implies that very small particles (soot, dust, etc.) can be used.
• The method can be used in applications with poor optical access where methods such as LDA and PIV tend to fail.
• DGV can recover volumetric, three-component, time-averaged velocity data by translating the light sheets.

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 v_x. (For further details see Measurements inside a cold combustion chamber).

The principle behind Doppler Global Velocimetry

DGV Application Examples

• Phase-resolved measurements of engine exhaust flows
• Measurements in the wake of a car model
• Measurements inside an engine inlet duct
• Measurements inside a cold combustion chamber

Technical Details

• Laser Stabilization
• Light Sheet Optics
• DGV Camera
• System specifications