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sudden jump of value at interface

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Old   July 11, 2011, 03:53
Default sudden jump of value at interface
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Hi, I am beginner in Fluent. my model involved interface. When I did my model in steady state, the velocity distribution seem nice as attached. However, when I did it in unsteady state, there was sudden jump at the interface. I totally do not have any idea to solve it. Pls help me. It is urgent. Any solution in solving my problem? Thanks for help.
Attached Images
File Type: jpg steady.jpg (38.9 KB, 8 views)
File Type: jpg unsteady.jpg (49.9 KB, 8 views)
File Type: jpg unsteady1.jpg (58.3 KB, 8 views)
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Old   July 11, 2011, 08:19
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Hi,
At interfaces we have non-conformal meshes and when you have considerable gradients near interfaces, you see such discontinuities. So, revise your gird, try to reach uniform grid.
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Old   July 11, 2011, 13:01
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Quote:
Originally Posted by Amir View Post
Hi,
At interfaces we have non-conformal meshes and when you have considerable gradients near interfaces, you see such discontinuities. So, revise your gird, try to reach uniform grid.
Dear Amir,

Thanks for your help. In order to reach uniform grid, do I need to refine the grid size or using other type of grid around the grid? Thanks for your help since I totally have no idea on it. Thanks.

Best regards
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Old   July 11, 2011, 15:00
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Quote:
Originally Posted by wlt_1985 View Post
Dear Amir,

Thanks for your help. In order to reach uniform grid, do I need to refine the grid size or using other type of grid around the grid? Thanks for your help since I totally have no idea on it. Thanks.

Best regards
Hi Raymond,

Actually, this jump is due to sudden size change across interfaces. Usually refining the grid and reducing size change can improve your result but you may need lots of cells to achieve that. Maybe you can change topology in order to reduce non-conformality and also size change. In addition, you can also use unstructured grid with proper size function.

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