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Doppler Global Velocimetry - DGV
DGV is a particle based velocity measurement system. Generally, in this technique a laser sheet is used to illuminate a flow region of interest. This illuminated region is imaged onto a digital camera through specially made absorption cells. This absorption cell has a sharp cut-off near the laser light frequency. As the scattered laser light is shifted in frequency due to the Doppler effect, the transmission through the absorption cell will also change. This converts the frequency change into an intensity change which can be more readily detected. The component of velocity, which is dependant upon the angle formed between the laser light sheet and the detection system. Therefore, the component of velocity detected can be changed by simply changing the light sheet or detector location. By replacing the system, three simultaneous components of velocity can be acquired over a two dimensional field.
This method can give a typical accuracy of 5 percent.[1]
Advantages include; Planar and simultaneous three components
Primary Limitations; Seeding and the techniques maturity.
[1] - given by the Nasa research centre at Langley. [http://mstb.larc.nasa.gov/tech/DGV.htm]
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