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Old   March 20, 2016, 06:45
Default free surface
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hossein
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Hi

I am trying to simulating free surface in moving container.
Unfortunately i have faced very weird problem, which water's surface is getting like it is evaporating.
So i make it more simple to find problem so i canceled the movement of container and it is just a cube contains water.

Surprisingly the problem occurs again. [below image]



why this occurs?

Also when I increase water height it doesn't occur.

Please help me ASAP
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Old   March 20, 2016, 19:51
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Glenn Horrocks
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If the free surface goes bezerk like this it is a sign that the free surface model is not well set up for your simulation. You will need to adjust the defaults to make it more stable. But exactly which setting you need to change is highly problem dependant, so I recommend you try all the settings and see which ones help you. I recall recommending you to do this check before - so it looks like you have not done it yet.

Quote:
Please help me ASAP
I will help you in my own good time. If you need urgent support then contact ANSYS support - that's what you pay them for.
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Old   March 23, 2016, 01:07
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I have tried various setting for free surface. what is strange, is that when i increase water height ,exceeding a exact height, this problem is not happening.!!!
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Old   March 23, 2016, 17:37
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Quote:
I have tried various setting for free surface.
Then you clearly have not tried the right ones. Which ones have you tried?

If the water height is increasing then you have a conservation problem. This can mean your convergence is too loose. Also this can be helped by switching your volume fraction coupling option.
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Old   March 27, 2016, 10:54
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Hi Hossain, try reducing the time step, I mean reduce it to ridiculously small amount. If you think your time step is already small enough, try using an adaptive time step and monitor your step, you will see how low it goes.
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