|
[Sponsors] |
October 1, 2007, 08:22 |
r-refinement
|
#1 |
Guest
Posts: n/a
|
Dear Friends,
I am currently looking at r-refinement, wherein the nodes are moved according to the solution strengths. Currently, I am looking at a modified laplacian strategy employed by Marchant and Weatherill. In essence they make use of the following expression. r_o^(n+1) = r_o^(n) + delta delta = sum(w_i*(r_i - r_o))/sum(w_i) where w_i is the weights computed as w_i = k1 + k2 * dabs((phi_i - phi_o)/(phi_i + phi_o)). Here, phi stands for the solution variable, r the position vector and the summation is over all neighbours i of the point o. k1 and k2 are constants for noise damping and gradient amplification. Also, a slight modification of the aforementioned strategy is employed for boundary nodes. I have two questions. 1. What are the commonly used values of k1 and k2, and what is the basic idea behind selecting those ? 2. On the boundaries, how is the procedure modified, so as to also take care of the fact that it always lies on the boundary itself. I will be grateful if anyone with experience on these issues is able to help me. Thanks and Regards, Ganesh |
|
October 1, 2007, 11:12 |
Re: r-refinement
|
#2 |
Guest
Posts: n/a
|
In constant or nearly-constant regions, you would expect the grid to be isotropic. The node movement should reduce to an averaging formula, all weights should be equal. But there will be usually noise in the solution, may be due to limiters. Adding a k1 term which is larger than the magnitude of the second term due to noise would give nearly constant weights.
k2 seems to be just a scaling term for the gradients. I guess one needs to do some trial and error to determine good values for these. |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
[snappyHexMesh] Number of cells in mesh don't match with size of cellLevel | colinB | OpenFOAM Meshing & Mesh Conversion | 14 | December 12, 2018 09:07 |
[snappyHexMesh] Boundary layer in a pipe | Clementhuon | OpenFOAM Meshing & Mesh Conversion | 6 | March 12, 2012 13:41 |
[snappyHexMesh] snappyHexMesh won't work - zeros everywhere! | sc298 | OpenFOAM Meshing & Mesh Conversion | 2 | March 27, 2011 22:11 |
[snappyHexMesh] snappyHexMesh aborting | Tobi | OpenFOAM Meshing & Mesh Conversion | 0 | November 10, 2010 04:23 |
[snappyHexMesh] external flow with snappyHexMesh | chelvistero | OpenFOAM Meshing & Mesh Conversion | 11 | January 15, 2010 20:43 |