Fluent：2D圓柱軸對稱模型的不收斂錯誤處理

2016-09-25 by:CAE仿真在線來源:互聯(lián)網(wǎng)

情況1:

話說上節(jié)千辛萬苦的設(shè)置好了運行環(huán)境,沒想到不到一秒,軟件就說有無法收斂的錯誤,運行不了,到底是怎么回事呢?仔細看下了一下軟件報錯的兩個問題:

1. 請在中心線設(shè)置軸的邊界條件。

2. X-momentum AMG求解器中無法收斂。

對于第一個警告,無法理解,明明是設(shè)置了Axis的邊界條件,為什么還會出現(xiàn)這個問題,沒辦法,上網(wǎng)Google第二個錯誤吧,終于發(fā)現(xiàn)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.

原來對于軸對稱零件,軸的方向必須是x軸,我之前并沒有檢查這個,是不是這個原因呢,趕緊用Pro/E在建一個模型,這次將長邊設(shè)在x軸上。

Fluent13實戰(zhàn)一:2D圓柱的定常流動(Troubleshooting篇)

其他設(shè)置條件不變,再跑一遍,耶,成功!128次的時候收斂~

結(jié)果分析:

1. 將入口改為mass-flow-inlet,并設(shè)定質(zhì)量流量為0.138kg/s,相當于2.2gpm,運行模擬得到速度云圖

可以看到在層流情況下,越往外流速最慢,最外面一層速度為0,這個是符合層流的特點的;中間水流速為0.11m/s,這和水流速公式計算結(jié)果是一致的(v=Q/S= 8.3x10-3/(60*3.14159*0.02^2)=0.11)

情況2:

還有一種情況:

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