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pass is subject to particles going in and out of the interrogation area, while the second pass
dramatically reduces this effect, as illustrated by the Figure 1.6. This process is known as First
Order Discrete Window Offset DPIV.
The second cross-correlation pass after shifting the
second image interrogation window by the previously estimated displacement provides a more
accurate velocity evaluation (Abiven and Vlachos, 2002).
Figure 1.6: First Order Discrete Window Offset
The second cross-correlation is preformed between two windows that contain the same particles.
The signal to noise is drastically increased during this operation. The iterative nature of this
process significantly reduces the effects of spatial averaging, which improves the resolution and
accuracy of system (Abiven and Vlachos, 2002).
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