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divergence detected in AMG solver


divergence detected in AMG solver:

标签:solvermeshdivergenceproblemerror 分类:专业交流 2009-12-01 13:27

问题:8-31-rke-steady-4-0.8 运行至 11000 迭代步是报错“divergence detected in AMG solv

er: pressure correction”(补充:每个工况均遇到此类情
况,原因尚未找到,暂时解决办法是将压力松弛因子从 0.3 改为 0.1); 解答:This error is reported when Fluent is not able to converge the

solution。The residuals are not converged。This error may come due to various reasons like improper mesh,improper boundary conditions , wrong material and improper solution settings。It is advisable to re check the entire case when one encounters this error。
以上老外对这个问题的回复,确实很多客户遇到过这样的问题,原因是多方面的,主要原 因集中在网格质量差和边界条件的不合理。 对于你的问题,如果之前都没有错误,到一定计算步才出现这样的问题,说明不是边条的 问题,问题可能出在局部的网格上面,你将压力松弛因子调小,增加跌代次数,减小了误 差,是解决问题的方法之一。 如果想彻底回避这样的问题出现,建议在网格上还需要下点工夫! 附:老外对类似问题的回复,你可以参考一下。

I try to study the turbulence inside a vertical cylinder. In a first time, I take the case of steady flow. The air is introduced axially from below, deflected by means of a small conical deflector and thanks to the geometry of the chamber the air goes up into the cylinder. I take the ideal gas law, k-epsilon model, inlet and outlet pressure for boundary 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 Check your hardware, especially RAM sockets. I have experience, that this could be initiated by some bad memory address sectors. I had a similar problem, but with pressure correction. I found that I had some highly skewed cells. Once I corrected the highly skewed cells by adapting the iso-values of cell

skewness my case began to iterate. Perhaps this may be your problem. First initialize the solution and then go to contours grid and select equiangle skew and click compute to get 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 Date: Mon, 22 Nov 2004, 6:38 a.m. Hi. I have a simulation of a supersonic-valve running but the program shows me 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. I had the same problem with a wing in a transonic flight. According to me the segregated solver is not suitable for the conditions with high compressibility. Let me know if you succeed in using the segregated and how... I suggest using the coupled solver,Your problem will vanish... Hope to hear good news from you soon. Luca this will be something wrong with the either boundary condition or with model selection, generally if things are right fluent just converges fine without any warning or problem. in my opinion these are the signs that you are doing something wrong in settign up the case, look closely Hi, I have the same problem, and couldn't solve it by using the coupled solver. Is there any other possible way. I am simulating office room problem. It seems very simple but on every stage it is creating problems for me. I am going to try to change the underrelaxation. lets see what comes up. Thanks long ago, one of my friend was doing CFD analysis of a kitchen,, using coupled solver, and he faced the same problem, for some time he didn’t get the converged results. Finally when I looked at his mesh. It seemed the problem is with the mesh not with the solver settings. I suggested him 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. You could have a grid issue concerning high skewness. This can be checked by going to contours grid cell equiangle skew and select compute and check the min and max. You should be below .9. If over t5hen this could be 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 Date: Sun, 9 Mar 2003, 11:23 a.m. How do I

remedy a divergence with this message. This is for scramjet combustion in 2D with injectors on both the top and bottom. Is there any way to look up error messages? reduceunderalaxtion factor. I have tried reducing the underelaxation factors but the divergence persists. Any other suggestions? Perhaps in the AMG solver Menu? It looks like a problem with your boundary conditions, be sure they';re compatible with each other and consistent with the physics of what you';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.


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