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Volume change and skewness angle problem

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Old   October 22, 2017, 22:38
Default Volume change and skewness angle problem
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Daniel
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Hey guys,

Wondering if anyone knows what to do when encountering low volume change (<0.01) and high skewness angle (>85deg). This has been occurring when I input the boundary layers on my ship mesh. I've tried with y+30 to y+80 but am still getting the problem. I've meshed the vessel surface about 0.05m~0.2m and very slow growth rate. I've attached snip shots of the high skewness angle cell and low volume change cell.

Sorry I cant show the full ship due to some confidential issues.

Any help is much appreciated
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File Type: png skew1.PNG (116.3 KB, 94 views)
File Type: png volume change.PNG (78.2 KB, 69 views)
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Old   October 28, 2017, 02:30
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it is rare in real industry geometry to have all cells satisfying the mesh quality guidelines and more so with the trimmer however what is important is that there are only a few and if there are lots that they are in areas that are going to have little influence on the solver which is quite common
if you are really worried then refine the mesh a bit locally to make them small and so have less effect or might eliminate them
the solver still works in bad cells but will drop from 2nd order to 1st order locally
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Old   October 30, 2017, 20:26
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Quote:
Originally Posted by ping View Post
it is rare in real industry geometry to have all cells satisfying the mesh quality guidelines and more so with the trimmer however what is important is that there are only a few and if there are lots that they are in areas that are going to have little influence on the solver which is quite common
if you are really worried then refine the mesh a bit locally to make them small and so have less effect or might eliminate them
the solver still works in bad cells but will drop from 2nd order to 1st order locally
Thanks a lot for the reply. Was really useful. What would be a good gauge to determine an "ok" amount of low volume change cells and high skewness angle? Usually I would get about 0.01% of cells not satisfying the mesh quality guidelines.

Hope to hear from you soon
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Old   November 1, 2017, 23:13
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there is no rule here - 1% bad will be fine if they are in out of the way places but 0.01% will be poor if where they will affect your results so use a threshold to display their location and decide
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