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Error: Update-Dynamic-Mesh failed. Negative cell v

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Old   August 27, 2004, 02:49
Default Error: Update-Dynamic-Mesh failed. Negative cell v
  #1
kim
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Hi,

I am trying to illustrate the inclusion accumulation process on the nozzle's wall while liquid steel containing very small alumina particles flow through the nozzle(SEN of steel continous casting). The clogging always occurs when enough inclusions accumulate on the wall . As the accretion is grwoing up on the wall, the nozzle's profile will change and therefor affect the liquid steel flow in the nozzle.

I would like to calculate the nozzle wall's profile while accretion is occuring by using dynamic mesh method. The movement of nodes depend on the accretion rate resolved by DPM's udf. After hundreds of iteratiing, the results seem exciting. The shape of walls has been changed, some small bumps are produced on the boundary wall which could stand for initial clogging. However, as the calculation proceeds, error message "Error: Update-Dynamic-Mesh failed. Negative cell volume detected". I have tried several times to adust the parameters in panel "dynamc mesh". It seems that this it does not work.

In my case, the moving zones are nozzle's walls which are define by UDF of DEFINE_GRID_MOTION ().

I would appreciate it very much if you could give me some idea to overcome this problem.

Sincerely,

kim
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Old   September 1, 2004, 16:52
Default Re: Error: Update-Dynamic-Mesh failed. Negative ce
  #2
kamarul
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try to check in this web www.fluentusers.com and see whether there is any tutorial related to your problems.

best regards
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Old   March 1, 2013, 01:00
Default 2D airfoil O Grid- negative volume
  #3
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samrat himvanth nanduri
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Posts: 23
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Hi,

I'm carrying out a 2D pitching airfoil simulation using dynamic meshing with a "O" Grid.It is a structured mesh. The dynamic conditions i have given were
1) airfoil - rigid body with UDF with pitching over X=0.25
2)interior - deforming with the min and max length scale from zone scale info
3) fluid -deforming with the min and max length scale from zone scale info.

The spring constant i gave was 0.001 and
convergence tolerance 0.0001
No of iterations 150.

The time step tat i used is 0.001.

After running the iterations and after about 500 time steps i'm getting the following error

negative volume detected
dynamic mesh update failed.
i have worked around with the spring constant and also with the time step nothing worked.
could someone help me out rectify this issue..
thanks in advance,
sam
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Old   April 27, 2014, 17:03
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Hi everyone,

I am trying to simulate a piston motion in a lateral cylinder.

I defined a piston profile and profile simply consists of time-location data, such as:

(time
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
)
(x
1.2
1.225
1.25
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
1.275
))

When I give a constant move to the piston, I can solve the case; but when I define a profile like the above one, it gives negative cell volume error. It gives error when I give a periodic piston motion too. With periodicity what I mean is that piston moves-stops and moves again periodically. There is no oscillating motion.

What might be the problem. The case looks simple but I cannot solve it. By the way, my mesh consists of quad meshes and the case is 2D.
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