# ICEM Edge Params Bunching laws

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 September 17, 2009, 08:20 ICEM Edge Params Bunching laws #1 New Member   Tyler Sloss Join Date: Sep 2009 Posts: 1 Rep Power: 0 I am trying to make an automated front end for some blocking based grids I am making in icem, because I have to do a lot of them, and want to make it so people not familiar with icem can make grids. I want to be able to update the number of nodes to use on certain edges based on their length, but have been unable to figure out how the bi-geometric bunching law works. Thank you for any incite or help.

 October 16, 2009, 09:33 Search the Help #2 Senior Member     Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,662 Blog Entries: 1 Rep Power: 36 Look in the help... You can type Bigeometric into the search... Look under Bunching laws for the description... Many of the other laws give the equations, but not this one. Bunching Laws BiGeometric The default bunching law. The two initial heights and ratios define parabolas in a coordinate system where the number of node points is the X-axis and the cumulative distance along the edge is the Y-axis. The parabolas are truncated where their tangent lines are identical; the spacing is linear between these points. If there are not enough nodal points to form this linear segment, a hyperbolic law is used and the ratios are ignored.

 August 21, 2011, 15:31 #3 New Member   Join Date: Aug 2011 Posts: 1 Rep Power: 0 Hello! I'm having the same trouble. For a parametrisation i also need information on the Bigeometric bunching law. But i find the help info somewhat incomplete. How exactly do the spacings and ratios define the parabolas? My first guess would be: The forumula for a parabola is f(x)=a*x^b with a=Spacing and b=ratio. Is this correct? I really need the correct definition. Thank you for help!

 September 13, 2011, 15:45 #4 New Member     Join Date: Aug 2011 Posts: 8 Rep Power: 7 Yesterday, I had the same problem. It´s not so difficult. BiGeometric distribution use for the initial and end bunching law two parabol-functions: y(x)=a+bx+cx². Using initial and end height and ratios, you can define this two parabolas. The second target is to know where both parabols have the same tangent. You can express this using two ecuactions, and getting the start and end point where to distribute the cells uniformly. Check the definition and think about it. PSYMN likes this.

 July 14, 2014, 08:43 #5 Member   Join Date: Nov 2011 Location: Germany Posts: 40 Rep Power: 5 i know this topic was discussed long time before, but i do not understand what you mean exactly. if i have the parabol function: y(x)=a+bx+cx² what are the variables a,b,c ? if i have two functions i become 6 unknown variables ... however 4 variables are discussed (spacing 1 and 2; ratio 1 and 2) i'm really confused at the moment ... kindly help

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