Fluent：2D圆柱轴对称模型的不收敛错误处理

2016-09-25 by:CAE仿真在线来源:互联网

情况1:

话说上节千辛万苦的设置好了运行环境,没想到不到一秒,软件就说有无法收敛的错误,运行不了,到底是怎么回事呢?仔细看下了一下软件报错的两个问题:

1. 请在中心线设置轴的边界条件。

2. X-momentum AMG求解器中无法收敛。

对于第一个警告,无法理解,明明是设置了Axis的边界条件,为什么还会出现这个问题,没办法,上网Google第二个错误吧,终于发现了一位大神的提醒:One reason could be that the geometry is not correct. Do a Mesh->Check to make sure you don't get
Checking for nodes that lie below the x-axis.
WARNING: Invalid axisymmetric mesh: 6 nodes lie below the x-axis.
and
WARNING: Mesh check failed.
For axisymmetric, the axial direction should be x and radial is positive y. Even if the y starts with -1e-32, it will fail.
To fix this:
Use Mesh->Translate and move the geometry so ymin is +ve.

原来对于轴对称零件,轴的方向必须是x轴,我之前并没有检查这个,是不是这个原因呢,赶紧用Pro/E在建一个模型,这次将长边设在x轴上。

其他设置条件不变,再跑一遍,耶,成功!128次的时候收敛~

结果分析:

1. 将入口改为mass-flow-inlet,并设定质量流量为0.138kg/s,相当于2.2gpm,运行模拟得到速度云图

可以看到在层流情况下,越往外流速最慢,最外面一层速度为0,这个是符合层流的特点的;中间水流速为0.11m/s,这和水流速公式计算结果是一致的(v=Q/S= 8.3x10-3/(60*3.14159*0.02^2)=0.11)

情况2:

还有一种情况:

Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: vof-1
Error at host: floating point exception

The total mass flow at degassing BC is -1.#IND00e+00 (kg/s)

Error at Node 0: floating point exception

Error at Node 1: floating point exception

Error at Node 2: floating point exception

Error at Node 3: floating point exception

Error: floating point exception
Error Object: #f