[mohammadshumal]

Hi everyone
I want to simulate a 2D 90 degree bent. I have the sides as 1:1 periodicty.
my mesh is 1 element thick. i encountered this message
" ERROR #002100048 has occurred in subroutine SU_BNEXT. |
| Message: |
| All vertices for a fluid domain lie on boundaries. This is |
| considered to be a fatal error because control volume gradients |
| cannot be calculated, leading to serious discretization error. |
| |
| A common cause for this error is a mesh which is only one |
| element thick, without symmetry or 1:1 periodicity on the lateral |
| boundaries. If you have this situation, and the domain is |
| two-dimensional, please change the lateral boundary conditions |
| to symmetry or 1:1 periodicity. Alternatively, for |
| three-dimensional simulations, please ensure that your mesh |
| has at least two elements across. |
| |
| Execution is terminating. This error message can be bypassed by |
| setting the expert parameter 'boundary vertex check = f', but |
| be aware that doing so may lead to sigificant solution error.

I have run it successfully before.Now I added some expression to it.I want to have moving mesh and move the walls.
please help me

[ghorrocks]

The error message explains in some detail what the problem is. You have a domain which is only one element thick.

If you cannot work this out, please post an image of your model.

[mohammadshumal]

Hi Horrocks
thanks alot
yes.my domain is 1 element thick because I want to have 2D simulation.my problem is axissymetric so I should use periodicity as boundary condition.As mentioned in the text I use 1:1 periodicity but it doesnt work.when I changed it to symmetry the error was vanished.
I paste the image of it.
I appreciate your attention.Capture.PNG

[ghorrocks]

For a 2D simulation you need to use symmetry planes. For 2D with swirl you need to use periodic boundaries. The error message is suggesting your first try used a wall, which of course will not work at all and gives you an error message.

[mohammadshumal]

Originally Posted by ghorrocks

For a 2D simulation you need to use symmetry planes. For 2D with swirl you need to use periodic boundaries. The error message is suggesting your first try used a wall, which of course will not work at all and gives you an error message.

thanks alot
I have swirl at inlet(the flow enters with 60 degree related to radial direction)
so I need periodic.I tried automatic&GGI&1:1 for mesh connection,but none of them worked.
I solved this before without any expression for moving the wall.I think the error is not related to the expression
what should I do now?
please guide me

[ghorrocks]

What expression for moving the wall? What are you trying to do?

[mohammadshumal]

Originally Posted by ghorrocks

What expression for moving the wall? What are you trying to do?

Hi dear Glenn
Thanks for your attention
I want to move the walls under the impact of a target pressure.I defined two expressions as displacement(for moving the two walls)
I use specified displacement for mesh motion of the two walls(that two expressions)and stationary option for inlet and unspecified option for outlet and periodic sides.
why it works as I change the sides to symmetry?
what should I do