Chapter 4 Vortex detection - Computer Graphics and Visualization

Chapter 6. Applications
Figure 6.10: Bay of Gda«nsk; horizontal slice coloured with . White lines indicate
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e.g. the vortex near has no focus but a node critical point, without any
rotational component. Also, some elongated vortices have multiple critical points,
e.g. the one near where the critical points are outside the intuitive rotation
center. So, unfortunately, there is no one-to-one correspondence between critical points
and vortices, which makes this method less suitable as the only method for Þnding
vortex cores.
6.2.4 Vortex detection with curvature centres
Alternatively, we can apply geometric techniques for vortex detection, starting with
the curvature centre technique described in Section 4.3. Figure 6.12 shows the curvature
centre density (CCD) Þeld as a coloured height Þeld, along with the land geometry.
The colour of the height Þeld indicates the scalar value, to make it easier to
distinguish the peaks.
The results are unsatisfactory, but in a different way than in the previous application.
Here, the main problem is not too many false peaks, but too few; especially the
slow vortices are notably absent.
The main causes are probably that those vortices are too slow and too elongated.
Another cause could be that the curvilinear grid used in this data set causes the sampling
density to be non-uniform throughout the grid. As the current implementation is
limited to sampling at the grid nodes, the sampling density is lower in regions where
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