
[Sponsors] 
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 bigeometric bunching law works. Thank you for any incite or help.


October 16, 2009, 09:33 
Search the Help

#2 
Retired from CFD Online
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,660
Blog Entries: 1
Rep Power: 38 
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 Xaxis and the cumulative distance along the edge is the Yaxis. 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: 8 
Yesterday, I had the same problem.
It´s not so difficult. BiGeometric distribution use for the initial and end bunching law two parabolfunctions: 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. 

July 14, 2014, 08:43 

#5 
Member
Join Date: Nov 2011
Location: Germany
Posts: 40
Rep Power: 7 
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 

Tags 
icem 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Where's the singularity/mesh flaw?  audrich  FLUENT  3  August 4, 2009 01:07 
fluent add additional zones for the mesh file  SSL  FLUENT  2  January 26, 2008 12:55 
ICEM  mesh near wing trailing edge  Joao Lourenco  CFX  5  August 30, 2007 17:20 
ICEM Extrude faces  Edge params.  Santiago Orrego.  CFX  0  June 19, 2007 12:08 
Star mesh import problem  chris1980  OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ...  20  May 8, 2006 01:07 