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-   -   Creating A Constant Pitch Helical Line In Gridgen (http://www.cfd-online.com/Forums/pointwise/13890-creating-constant-pitch-helical-line-gridgen.html)

John Hinkey July 31, 2007 00:13

Creating A Constant Pitch Helical Line In Gridgen
 
I'm trying to create a constant pitch helical line on the surface of a database cylinder using Gridgen. I've tried several ways of doing this, but none of them give a true constant pitch helix - close, but not close enough for griding. Anyone out there have any experience doing this type of thing in Gridgen?

Thanks - John

John Chawner August 4, 2007 13:58

Re: Creating A Constant Pitch Helical Line In Grid
 
John,

One way to do this is as follows. All the steps can be done in a Glyph script or you can just generate the points in the script and do the rest interactively.

1. Using a Glyph script, compute points on the helix using the standard analytical definition of the helix (e.g. Wikipedia). Either create a db line from these points or export them to a segment file. Use a large number of points.

2. Create a 360 degree surface of revolution of the desired radius and length.

3. Use cylindrical projection (from the cylinder's axis) to project the helix onto the cylinder.

There also is probably a way to do this analytically. That is, create a surface of revolution and then create a line directly on the surface by computing the points on the helix in the surface's (u,v) space.

Hope this helps. If not, please contact our Tech Support at support@pointwise.com.

John Hinkey August 5, 2007 00:01

Re: Creating A Constant Pitch Helical Line In Grid
 
Thanks John -

Your good folks at Pointwise have already found some work-arounds for me. If anybody wants the details of these let me know.

- John


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