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-   -   Gridgen node spacing (http://www.cfd-online.com/Forums/pointwise/11883-gridgen-node-spacing.html)

Vincent July 27, 2006 03:06

Gridgen node spacing
 
When I constrain the node spacing on both ends of a connector, the resulting distribution gives a maximum node spacing that is larger than the node spacing specified at both ends. I want to create a connector with a delta s of 2 on one end and 20 on the other end, and the maximum delta s on the connector should not exceed 20. So I need for instance a geometric progression starting with 2 and increasing to 20 on the first part of the connector, and a constant sizing for the rest of the connector. How can I do this without splitting the connector?

ag July 27, 2006 07:51

Re: Gridgen node spacing
 
You can put a breakpoint on the connector and use that to set spacings internally. Go to the "Redistribute" menu and look at the breakpoint functions.

John Chawner July 30, 2006 12:33

Re: Gridgen node spacing
 
ag's suggestion about adding a break point at the location where the point spacing reaches 20 and then remains constant is a good one.

If you don't want to have to constrain the location at which the spacing achieves a value of 20 (which you have to do with the break point idea), and if the number of grid points on the connector doesn't have to remain fixed at a specified value, there's a script on the Glyph Script Exchange (www.pointwise.com/glyph) that does pretty much what you want: given the spacing constraints and a maximum spacing allowed anywhere on the connector, it automatically adds points until those criteria are reached.

Also, strictly speaking, geometric progression won't work because it's a 1-sided function - you can only specify the constraint at one end.

adi.ptb July 28, 2016 11:30

Hi John,
I have two questions about geometric function for nodal distribution. my domains are all unstructured which their nodal distributions are hyperbolic tan. I tried to change the distribution to geometric function but when I select all the connectors and go to Grid--Distribute--function the geometric function was off. How can I turn it on? I had to go back and create the mesh from the beginning and used geometric function for connectors (in the defaults tab) but there wasn't any option for choosing the growth ratio. my second question is how can I control the growth ratio? because I wasn't able to find the growth ratio I moved on and used the "ConGeometricAutoDimension" glyph script and used it to distribute the nodes. Its a very good script, good control over the node distributions and also it has an option to set the growth rate. only one problem I could only choose one connector at a time and I have around 210 connectors and it took me a lot of time.
Thanks,

jchawner August 7, 2016 17:33

Hello ad:

Geometric Progression is a 1-sided distribution function meaning that you can only specify a spacing constraint at one end or the other - not both. I'm guessing that because you initially used TANH you have set a spacing at both ends. You'll have to unconstrain one (set it to zero) before geometric progression can work.

You also don't get to control the growth ratio. The things you control are: the first spacing, the length of the connector, and the dimension (number of grid points). If you also tried to set the growth ratio the problem would be over-constrained.


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