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adjacent connectors have different cell growth rates

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Old   May 16, 2017, 13:25
Question adjacent connectors have different cell growth rates
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tom pratt
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i am creating an structured mesh using pointwise v18.0. i have 2 roughly parallel connectors and i would like the spacings and growth rates to be exactly equal on both, to make a mesh which is structured and unskewed. i have tried to do this but unfortunately whilst number of nodes and edge spacing is identical on both, the grown rate is larger on one than the other leading to skewed cells.
i have no idea how to fix this! please help!
attached is a picture of one of the faces just to illustrate what i mean. the pictures are of either end of the face. suffice it to say that the cells in between are incredibly skewed.
thanks in advance.
example.jpg
example2.jpg

Last edited by tomp1993; May 16, 2017 at 13:29. Reason: added another image
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Old   May 16, 2017, 14:23
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Rick Matus
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What distribution function are you using? Is it the same on both connectors? Are there any break points on either connector?

Same questions for spacing constraints.
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Old   May 16, 2017, 14:43
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HI,
I'm pretty sure it is a simple geometric distribution, but in all honesty i am not really sure how to check or change this? i've moved to pointwise from ICEM and am used to being able to set the distribution function at the same time as setting the node number and edge spacings, although i cannot see the same option in pointwise?
and no, there are no splits in either connector, they both run from the bow to the stern of my geometry, one at the surface and one approximately around the outer edge of the boundary layer.
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Old   May 16, 2017, 15:18
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By default, new connectors in Pointwise are created with a hyperbolic tangent distribution, but various operations, like projecting onto CAD geometry can change that.

You can find detailed information about the distribution functions, break points, etc. in the Grid, Distribute panel. I recommend selecting the connectors and then going to Grid, Distribute. Look at the distribution functions and spacing constraints on each one and make sure they are the same. If they are the same, and the distributions still do not match, could you upload the two connectors as a Pointwise project file (.pw) here? I'll take a look and see what is happening.

One other factor to consider is that by default the distributions are based on arclength. If one of the connectors is straight and the other follows some curved path, the distributions will be different. This is because the spacing constraint is an absolute distance, but the distribution function is relative to the arclength. That happens frequently in ship hull grids. To fix that, go to Grid, Distribute, and select the Functions tab. Open the Spline pane, and change the spline variable from arclength to X (assuming X is the longitudinal axis of the ship).
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Old   July 13, 2017, 17:10
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You can quickly "fix" this issue by copying the distribution from one connector to the opposite connector. First, select both connectors and select Orient.. from the Edit menu. In the Orient panel, make sure the connectors are oriented in the same direction (indicated by a red arrow). Next select the target connector, and choose Grid->Distribute... From the Distribute panel navigate to the Functions tab, and expand the Copy From frame. Select the source connector, click the Copy Delta Values button, and click Okay.

A Glyph script that prompts you to select a target and source connector(s), orients, and copies either the delta values or the scaled distribution is attached--just rename the file's extension from *.txt to *.glf.
Attached Files
File Type: txt CopyGridPoints.txt (10.0 KB, 2 views)
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