divergence detected in AMG solver pressure correction,fluent典型错误
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fluent有关内容集锦011 FLUENT的初始化面板中有一项是设置从哪个地点开始运算(compute from),选择从不同的边界开始运算有专门大的区不吗?该如何样按照具体咨询题选择从哪里运算呢?例如有两个速度入口A和B,还有压力出口等等,是选速度入口依旧压力出口?如果选速度入口,有两个,该选哪个呀?有没有什么原则标准之类的东西?一样是选取ALL ZONE,即所有区域的平均处理,通常也可选择有代表性的进口(如多个进口时)进行初始化。
关于一样流淌咨询题,初始值的设定并不重要,因为运算容易收敛。
但当几何条件复杂,而且流淌速度高变化快(如音速流淌),初始条件要认真选择。
如果不收敛,还应试验不同的初始条件,甚至逐次改变边界条件最后达到所要求的条件。
2 要判定自己模拟的结果是否是正确的,看起来解的收敛性要比那些初始条件和边界条件更重要,能够如此明白得吗?也确实是讲,关于一个具体的咨询题,初始条件和边界条件的设定并不是唯独的,为了使解收敛,需要持续调整初始条件和边界条件直到解收敛为止,是吗?如果解收敛了,是不是就能够差不多确定模拟的结果是正确的呢?关于一个具体的咨询题,边界条件的设定因此是唯独的,只只是初始化时能够选择不同的初始条件(指定常流),为了使解的收敛比较好,我一样是逐步的调剂边界条件到额定值("额定值"是指你题目中要求的入口或出口条件,例如运算一个管内流淌,要求入口压力和温度为10MPa和3000K,那么我开始叠代时选择入口压力和温度为1MPa和500K(假设,这看你自己咨询题了),等流场运算的初具规模、收敛的较好了,再逐步调高压力和温度,通过好几次调剂后最终到达额定值10MPa 和3000K,如此比一开始就设为10MPa和3000K收敛的要好些)如此每次叠代能够比较容易收敛,每次调剂后不用再初始化即自动调用上次的解为这次的初始解,然后连续叠代。
即使解收敛了,这并不意味着就能够差不多确定模拟的结果是正确的,还需要和实验的结果以及理论分析结果进行对比分析。
设置:初始值收敛值结果AMIX =0.0100;BMIX =0.0001 AMIX = 0.01; BMIX = 0.00 计算无误AMIX = 0.1000;BMIX = 0.0010 AMIX = 0.10; BMIX = 0.00 计算无误AMIX =0.20; BMIX = 0.01 AMIX =0.20; BMIX = 0.01 计算无误AMIX=0.2、BMIX=0.001 AMIX=0.2、BMIX=0.001 计算无误AMIX=0.3、BMIX=0.1 AMIX=0.3、BMIX=0.1 计算无误AMIX=0.4 AMIX = 0.40; BMIX = 1.00 静态log: WARNING in EDDRMM: call toZHEGV failed, returncode = 6 3 **,能带一样AMIX=0.02 AMIX = 0.02; BMIX = 1.00 计算无误AMIX=0.1 AMIX = 0.10; BMIX = 1.00 静态log: WARNING in EDDRMM: call toZHEGV failed, returncode = 6 3 **,能带一样AMIX=0.3 AMIX = 0.30; BMIX = 1.00 静态log: WARNING in EDDRMM: call toZHEGV failed, returncode = 6 3 **,能带一样BMIX=0.0001 AMIX = 0.40; BMIX = 0.00 计算无误以上参数设置,得到的能带图都一样,如下图:综上:设置AMIX=0.2(或0.3),BMIX默认(省事,等于1.0),可以保证计算过程无误。
还需进一步调整其他参数,算出正确的能带。
警告:算1QL弛豫、静态、能带时,都有这个提示:ADVICE TO THIS USER RUNNING 'V ASP/V AMP' (HEAR YOUR MASTER'S VOICE ...): You have a (more or less)'small supercell' and for smaller cells it is recommended to use the reciprocal-space projection scheme! The real space optimization is not efficient for small cells and it is also less accurate ... Therefore set LREAL=.FALSE. in the INCAR file对策:对于较小的晶胞(原子数小于20),设置LREAL=.FALSE.,计算结果比较精确。
问题:8-31-rke-steady-4-0.8运行至11000迭代步是报错“divergence detected in AMG solver: 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? Thanksin 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 theiso-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 too high?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 thanksTry 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 setting up the case, look closelyHi, 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 d idn’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 0.9. If over then 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?reduce underalaxtion 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.请求高手指点:循环流化床中非稳态气固两相流计算,使用欧拉双流体模型,K-E湍流模型,网格质量<0.55。