计算时出错（ＡＭＧ）

woliu

我是刚接触ＦＬＵＥＮＴ，在计算是出现以下错误：请指教以下：
absolute pressure limited to 1.000000e+000 in 146 cells on zone 2
reversed flow in 30 faces on pressure-outlet 4.

Error: divergence detected in AMG solver: temperature
Error Object: ()

这是怎么回事啊？

wangxyln

计算发散了，

hyacinth

Divergence in AMG solver :k

Posted By: Guillaume <baudryg@hotmail.com>
Date: Thu, 6 Jan 2005, 2:19 a.m.

Itry to study the turbulence inside a vertical cylinder. In a firsttime, I take the case of steady flow. The air is introduced axiallyfrom below, deflected by means of a small conical deflector and thanksto the geometry of the chamber the air goes up into the cylinder. Itake the ideal gas law, k-epsilon model, inlet and outlet pressure forboundary conditions.
My problem is that I have directly the message "divergence detected in AMG solver : k" when I want to iterate.
I try a lot of solutions I have find in this forum without any result.
Could anyone help me?
Thanks in advance
Checkyour hardware, especially RAM sockets. I have experience, that thiscould be initiated by some bad memory address sectors.
Ihad a similar problem, but with pressure correction. I found that I hadsome highly skewed cells. Once I corrected the highly skewed cells byadapting the iso-values of cell skewness my case began to iterate.Perhaps this may be your problem. First initialize the solution andthen go to contours grid and select equiangle skew and click compute toget you min and maxs. Having skewed cells of 0.9 or higher isn't good,as in my case. Hope this helps
I have check the skewed cells but it appears that in my case, this number is lower than 0.4 Is it to high?

divergence in AMG solver

Posted By: Steffen <st.reising@gmx.de>
Date: Mon, 22 Nov 2004, 6:38 a.m.

Hi.I have a simulation of a supersonic-valve running but the program showsme this message: divergence detected in AMG solver: temperature
I tried to rise the limits for temperature and other solution limits but nothing has helped so far
Does anyone what to do
thanx
Try to use more conservative Under-relaxation factor.
Ihad the same problem with a wing in a transonic flight. According to methe segregated solver is not suitable for the conditions with highcompressibility. Let me know if you succeed in using the segregated andhow... I suggest using the coupled solver,Your problem will vanish...Hope to hear good news from you soon. Luca
thiswill be something wrong with the either boundary condition or withmodel selection, generally if things are right fluent just convergesfine without any warning or problem. in my opinion these are the signsthat you are doing something wrong in settign up the case, look closely

Hi,I have the same problem, and could n't solve it by using the coupledsolver. Is there any other possible way. I am simulating office roomproblem. It seems very simple but on every stage it is creatingproblems for me. I am going to try to change the underrelaxation. letssee what comes up. Thanks
longago, one of my friend was doing CFD analysis of a kitchen,, usingcoupled solver, and he faced the same problem, for some time he didn’tget the converged results. Finally when I looked at his mesh. It seemedthe problem is with the mesh not with the solver settings. I suggestedhim to make mesh more finer, and viola it gave results in one run,without any problem. so moral of the story check your mesh.
My mesh is quite fine, but I will try more finer mesh. Thanks
then it shall converge ..anyway have you tried using segregated solver, how the results with that

Error: Divergence detected in AMG solver?
Posted By: frank
Date: Sun, 16 Jan 2005, 3:58 p.m.
What does mean and how do i fix it? I am runing a rosseland radiation model and it wont run past 1 iteration.
Frank
you are using the segregated solver, so you must reduce the under relaxation factor as you can.
Youcould have a grid issue concerning high skewness. This can be checkedby going to contours grid cell equiangle skew and select compute andcheck the min and max. You should be below .9. If over t5hen this couldbe your problem. It has happened to me a couple of times.
thanks a million i will try this...
frank
AMG solver: k divergence?

Posted By: Robert <r_carson22@yahoo.com>
Date: Sun, 9 Mar 2003, 11:23 a.m.

Howdo I remedy a divergence with this message. This is for scramjetcombustion in 2D with injectors on both the top and bottom. Is thereany way to look up error messages?
reduce underalaxtion factor.
Ihave tried reducing the underelaxation factors but the divergencepersists. Any other suggestions? Perhaps in the AMG solver Menu?
Itlooks like a problem with your boundary conditions, be sure they'recompatible with each other and consistent with the physics of whatyou're trying to simulate,
I think you'd better don't touch anything in the AMG menu, unless you know exactly what you're doing,
It is my opinion, if this could help.
Have a nice day,
Jkl.

转自http://cfdhvac.blog.hexun.com/4312418_d.html


[ 本帖最后由 hyacinth 于 2007-4-19 15:29 编辑 ]

cecil

把温度相关的物理量，松弛因子调整一下吧。

ljwin82

建议还是返回到网格吧
修改网格

woliu

谢谢各位的指导，我去试试！