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Old   February 1, 2016, 05:07
Default Free surface- Sloshing
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hossein
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Hello,

I am trying to simulate free surface in moving (rotating) cube ( water -sloshing)

unfortunately convergence is terrible. and the free surface's behavior is not logical.

As shown in below image, at start of movement a hollow is creating in surface.




After some steps it acts properly,





but it again become completely wrong.



I really need help!
What is wrong?
I have checked all parameters.
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File Type: jpg 03.jpg (31.8 KB, 14 views)
File Type: jpg 02.jpg (35.2 KB, 14 views)
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Old   February 1, 2016, 06:42
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Glenn Horrocks
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First of all - make sure your convergence is tight enough, your mesh is high quality and your time step size is small enough. You won't get anything sensible unless you do this.

The default free surface settings in CFX are not always optimal. In fact in same cases it can generate large spurious flows adjacent to the free surface which generates artefacts like this.

I recommend you look at all the free surface modelling parameters and adjust them all and see what helps and what does not. Doe this on a small mesh for a small number of time steps - enough to see the problems you are seeing starting up. This means you will have a few dozen simulations to do, so script them up to run together. You will find there are a few parameters which affect the model you are doing and you can normally find some settings which work better than the default values.

I have done this a few times for free surface modelling work I did and it improved the model a great deal. But it is different for each model so you really need to find out what works for you.
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