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Figure 4.11: Error for Multigrid, DADPIV, and NDWO for Various Shear Rate, 32 Window.
Figure 4.11 hows that for the shear rates of 0.0625, 0.125, and 0.25 pixels per pixel, the NDWO
case has the highest error close to the wall, but the peak locking phenomenon causes the multigrid
and DADPIV algorithms to have a much higher oscillatory error at greater centerline velocities.
The traditional multigrid approach has comparable error to the DADPIV approach for shear rates
of 0.0625 and 0.125 pixels per pixel, but higher errors than the DADPIV algorithms for a shear
rate of 0.25 pixels per pixel. For the 0.25 shear rate, the DADPIV algorithm performs better than
the traditional multigrid algorithm and the NDWO method, averaging approximately 0.12 pixels
less total error than the multigrid method and approximately 1 pixel less total error than the
NDWO case. The peak locking phenomenon appears again at shear rates of 0.0625 and 0.125.
There may be peak locking at the 0.25 shear rate, but the measurement increments may be too
coarse to detect the phenomenon.
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