In a 1:1 mesh interface, which is explicitely set to GGI in CFX Pre, there are non-overlap fractions. This can be visualized in CFX Post. The non-overlap fractions appear especially in regions where the interface is highly curved.
How can this be explained? How to avoid this?
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The GGI intersection algorithm seeks for overlapping cells from the corresponding interface partner side within a certain tolerance. Thus, in highly bended parts of the mesh, always some cells in the neighborhood might be found which do not really touch or overlap with the cell face currently under consideration. This tolerance can be reduced with an expert parameter: ggi separation factor (default = 1) NOTE: In a 1:1 interface such a reduction is uncritical. In a non-matching interface with different mesh resolution on corresponding interface sides, this can lead to a situation where not any cell at all is detected on the other partner side. Some best practice hints: 1.) Try to avoid two sides of an interface separated by a gap larger than the local mesh resolution. 2.) In highly curved parts of an interface, mesh resolution should be fine enough so that neighbouring cell face normals have "similar" directions (e.g. angle < 10 deg) 3.) Mesh resolution on both sides of the interface should be of similar size. |
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