|
[Sponsors] |
February 21, 2014, 17:49 |
Help!!! Cumulative error too High
|
#1 |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
Please can someone help me here? I'm simulating the backward facing step with and without the fully developed flow at inlet. My problem is i'm getting High value of the cumulative continuity errors, especially for the case with the fully developed flow. As a consequence the fields data are really strange see my post here.
In case of the fully developed flow i used the "setdiscreteFields" to map the inlet BCs. I'll upload my case,please take a look at it and see if you can find what i'm doing wrong, i tried everything and changed almost everything with no success. I changed also the mesh, varied the yplus value, the grid spacing (uniform and non uniform) used different programs to create the mesh but all in vain. here the zip with the case: https://www.dropbox.com/s/76zz543hb5p3808/BFS.zip Hoping someone would help me this time. |
|
February 22, 2014, 16:25 |
|
#2 |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
I tried to find out the culprit of the high cumulative error and the weird behavior of the field around the step, I simplified the mesh and i've considered a uniform mesh with the fully developed flow imposed at the inlet and the residual have a really strange behavior and i don't know what is the cause of it i started with the mesh at yplus 30 then i started to refine (x4) but i observed the same pattern.
I uploaded an image with the plot of the residual done with pyFoam. P.S how can i save the plots done by pyFoam? |
|
February 23, 2014, 03:44 |
|
#3 |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
I increased the cell number up to 400000 from around 12000, but th residuals have the save pattern. Now i'll try to change the initial condition and see if the problem lies there. Can the schemes or fvsolution settings be the reason of this?
|
|
February 24, 2014, 08:31 |
|
#4 |
Senior Member
Yuehan
Join Date: Nov 2012
Posts: 142
Rep Power: 13 |
I am faced with almost the same problem and I don't know why.
|
|
February 27, 2014, 10:18 |
|
#5 | |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
Quote:
I decided to simplify the mesh using an uniform with the same spacing in the x and y direction, then i increased the cell points and simulated it (up to about 500000 cells) and all of them had the same behavior of the residuals. The residuals tend to go down at each iteration then they explode when they are around e-5, they manifest an oscillatory behavior with a large amplitude and i'm still trying to find out the root of the problem, for sure the initial value of the velocity (being a fully developed flow or not) ans the mesh aren't the cause of it. |
||
March 4, 2014, 12:07 |
|
#6 |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
I refined the mesh, changed the geometry and considered different types of BCs but i couldn't trace the root of the problem. With paraFoam i can't see the vortex (with the streamline tool) and the residual after some time will go crazy. Please can someone help me here.
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
How to write k and epsilon before the abnormal end | xiuying | OpenFOAM Running, Solving & CFD | 8 | August 27, 2013 15:33 |
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3 | bookie56 | OpenFOAM Installation | 8 | August 13, 2011 04:03 |
IcoFoam parallel woes | msrinath80 | OpenFOAM Running, Solving & CFD | 9 | July 22, 2007 02:58 |
Could anybody help me see this error and give help | liugx212 | OpenFOAM Running, Solving & CFD | 3 | January 4, 2006 18:07 |
Multicomponent fluid | Andrea | CFX | 2 | October 11, 2004 05:12 |