Learning Forum

[Vladimir]

I am trying to calculate flow of steam valve in Ansys CFX. Boundary conditions : at inlet - massflow rate and temperature of steam, at outlet - averaged pressure of steam; wall for all other faces ;relative pressure - 0.

After calculation i have that steam does not pass throught outlet. In solution log i have:" 

****** Notice ******                           |

" |  A wall has been placed at portion(s) of an OUTLET                 |

 |  boundary condition (at 100.0% of the faces, 100.0% of the area)   |

 |  to prevent fluid from flowing into the domain.                    |

 |  The boundary condition name is: Outlet.                           |

 |  The fluid name is: Steam1.                                        |

 |  If this situation persists, consider switching                    |

 |  to an Opening type boundary condition instead.  "

 

How could this happen ?

[Surya Deb]

Hi Vladimir,

This happens when there are re-circulation zones near the outlet. The vortices or re-circulations crossing an outlet will cause the CFX Solver to close part of the outlet with walls to avoid fluid from coming in from an outlet. 

A couple of remedies for this issue are:

1.) Extending the outlet further downstream or away from the regions of re-circulations.

2.) Using an Opening boundary condition .

I hope these will help.

Regards,

Surya

 

 

 

[Vladimir]

Hi Vladimir,

This happens when there are re-circulation zones near the outlet. The vortices or re-circulations crossing an outlet will cause the CFX Solver to close part of the outlet with walls to avoid fluid from coming in from an outlet. 

A couple of remedies for this issue are:

1.) Extending the outlet further downstream or away from the regions of re-circulations.

2.) Using an Opening boundary condition .

I hope these will help.

Regards,

Surya

 Surya, thanks you very much for your answer. I have find the solve of this problem on ResearchGate site. Apparently, error cause was initialization of the flow domain in an unbalanced thermodynamical state. If you interested you can look the  discussion by this link: 

https://www.researchgate.net/post/Why_Ansys_CFX_placed_a_wall_at_outlet