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[求助]
fluent非稳态计算两秒后出现不收敛，求指点，谢谢哦
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大哥大姐们大家好。 fluent非稳态计算喷雾蒸发，用的是dpm模型，为什么喷嘴工作2秒后才开始出现间歇性的不收敛呢？ 几何模型长为1米、直径为0.22米的圆柱，喷嘴设置在中间，网格数为10万，并对喷嘴附近加密；空气从喷嘴的一端以1m/s的速度流入；喷嘴为压力旋转喷嘴，喷嘴直径为0.001m，压力为1MPa，流量为0.002kg/s。前面2秒每步都能收敛，但2秒后间歇性出现不收敛，有遇到我这种情况的吗？求指导。 谢谢哦 |
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5楼2013-11-04 09:49:59
11楼2013-11-05 08:18:14
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说这么多还不如图说的方便，你算的什么样，模型，收敛曲线，把图放上来，另外，你对收敛的定义是什么，通过什么方式来判断。对于有的边界条件，收敛曲线是永远达不到你设置的要求，有的即使达到了也未必就是收敛结果，取决于你的初始边界条件，算法等很多方面。Fluent 里面是这么说的》 Note: There are no universal metrics for judging convergence. Residual definitions that are useful for one class of problem are sometimes misleading for other classes of problems. Therefore it is a good idea to judge convergence not only by examining residual levels, but also by monitoring relevant integrated quantities and checking for mass and energy balances. There are three indicators that convergence has been reached: 1，The residuals have decreased to a sufficient degree. The solution has converged when the Convergence Criterion for each variable has been reached. The default criterion is that each residual will be reduced to a value of less than , except the energy residual, for which the default criterion i,10e-6 . 2,The solution no longer changes with more iterations. Sometimes the residuals may not fall below the convergence criterion set in the case setup. However, monitoring the representative flow variables through iterations may show that the residuals have stagnated and do not change with further iterations. This could also be considered as convergence. 3,The overall mass, momentum, energy, and scalar balances are obtained. You can examine the overall mass, momentum, energy and scalar balances in the Flux Reports dialog box. The net imbalance should be less than 0.2 of the net flux through the domain when the solution has converged. In the next step you will check to see if the mass balance indicates convergence. 假如你的初始条件足够接近最终理论物理解，可以看这里 Sometimes, however, this criterion may not be appropriate. Typical situations are listed below. 1，If you make a good initial guess of the flow field, the initial continuity residual may be very small leading to a large scaled residual for the continuity equation. In such a situation it is useful to examine the unscaled residual and compare it with an appropriate scale, such as the mass flow rate at the inlet., 2，For some equations, such as for turbulence quantities, a poor initial guess may result in high scale factors. In such cases, scaled residuals will start low, increase as non-linear sources build up, and eventually decrease. It is therefore good practice to judge convergence not just from the value of the residual itself, but from its behavior. You should ensure that the residual continues to decrease (or remain low) for several iterations (say 50 or more) before concluding that the solution has converged. GOOD LUCK! |
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