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-   -   ICEM bunching law exponential 1 (https://www.cfd-online.com/Forums/ansys/98472-icem-bunching-law-exponential-1-a.html)

 sasa120 March 12, 2012 07:04

ICEM bunching law exponential 1

Hello everyone,

i want to analyse the influence of the mesh on the result. Therefor I created some meshes with different numbers of nodes.
For the O-Grid in the tube I want to keep the ratio constant and change the y+ value.
The Bunching law of the O-Grid is the Exponential 1 law. In the ICEM Help Engine I found the following equation to calculae the distance from the starting end to node i:

S_i = Sp1*i*exp(R*(i-1))
with
R= -log((N-1)*Sp1)/(N-2)

S_i is the distance from the starting end to node i,
Sp1 is Spacing 1,
N is the total number of nodes, and
R is the ratio

In my case N is 38 and SP_1 is 0.002mm.
So in my opinion S_38 should have the same value as the length of the edge wich is 22.5mm.

But when I calculate S_38 with the above-named equations the result is S_38 = 0.2429mm.

So what I wanted to do, is to change the total number of Nodes N and let the Ratio R constant. With these equations I wanted to calculate the new value for Sp1.

But there seems to be a mistake in these equation.

Can someone help?

 rikio March 21, 2012 11:59

S_i is the length of the ith segment, i.e., from the segment's begining to end, rather than edge's begining to ith node.

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