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-   -   about error in CFX-pre and the model in workbench (http://www.cfd-online.com/Forums/cfx/22272-about-error-cfx-pre-model-workbench.html)

erick March 9, 2006 01:25

about error in CFX-pre and the model in workbench
 
Hi, my dear friends.

In my simulating, I saw the following notice in CFX-Pre: "A wall has been placed at portion(s) of an outlet boundary condition ( at 39.3 % of the faces, 38 % of the area) to prevent fluid flowing into the domain. The boundary condition name is outlet1. the fluid name is air at 25℃. If this situation persists, consider switching to an opening type boundary condition instead. "

I wonder the model is mot made correctly.Could you help me to check? Many thanks.

The model is a pipe with two open-ends as outlets and a hole in the middle of the bottom as inlet (unit: mm) (1)Make the pipe. In plan ZOY, from [(z,y)](-8,4) to (8,1), draw a rectangle then take line (-8,4),(8,4) as axis to REVOLVE 360 (2) Make inlet(a hole). In XOZ palne, draw a circle, center of the circle is (0,0), diameter is 1, Then EXTRUDE, IMPRINT, NEXT. Is it right?

Waiting for your answer, Thank you in advance.


eike March 9, 2006 03:22

Re: about error in CFX-pre and the model in workbe
 
Hi Erick

Are you sure, that you received the notice in Pre and not from the Solver? Because it looks like a warning from the solver, that fluid wants to go into the domain through your outlet. But if you define your outlet as an outlet this is prohibited. To avoid this, the solver creates a wall at the outlet.


erick March 9, 2006 03:48

Re: about error in CFX-pre and the model in workbe
 
Dear Mr. Eike,

I am sorry. The "notice" is in CFX-solver. The pressure in Inlet is 0.2 MPa. Maybe the model is not correct? Please help me. Thanks.

Erick

Rajit March 9, 2006 21:01

Re: about error in CFX-pre and the model in workbe
 
In general you get this reply when your boundary is not put at the appropriate position.like immediately after a bend.

consider moving the boundary to the appropriate poistion because the fluid is trying to recirculate back into the domain and your Boundary condition is outlet, which wont allow it to do.

change it to a opening boundary condition which will allow the flow to recirculate if you cannot change the location of the outlet.

If possible consider using velocity at the inlet and pressure at the outlet because this is more robust.

Hope these are helpful Thanks Regards Rajit

erick March 10, 2006 01:28

Re: about error in CFX-pre and the model in workbe
 
Dear Mr. Rajit,

Thank you for your helping.

Pressure at Inlet is 0.3 MPa(Abs.) So, I think the air will flow out "Outlet". If I change Outlet to Opening, the Notice may disapper. But how about the result.

Please help me.Many thanks.

Best Regards Erick

Rajit March 12, 2006 19:28

Re: about error in CFX-pre and the model in workbe
 
What is that you will have to look at the outlet?. What is your outlet condition now?.

No it won't change the results of the simulation.you are just making the simulation more robust.This is how i have presumed things in my simulation.

Regards Rajit


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