[karachun]

Hello to everyone!
I have 2D test problem. I have rectangular domain with thin channel attached and pressure outlet at the end of it. Domain is filled with water by 50%. I use VOF model and ignore surface tension, flow assumed to be laminar. I apply fixed gravity in vertical direction and variable acceleration in horizontal direction. I managed to solve model with out mesh adaptation.
Now I want to add dynamic mesh adaptation to refine mesh near free surface, that rapidly change during time. Something similar to this video.
https://www.youtube.com/watch?v=AiDFNevhJ98
I want to adapt cells near free surface and coarse cells far from free surface.
I have created two Expressions to determine free surface condition
Free_Surface: AND(Volumefraction>0.4,Volumefraction<0.6)
Far_Away_From_Free_Surface: OR(Volumefraction<=0.4,Volumefraction>=0.6)
I run tool Adapt/Refine and use setting as showed on picture. When I press Adapt or Display I get error
Error: Expression evaluation failed
Error Object: #f
Look like I`m doing something wrong but I can not find error. My expressions look OK for me, they return Boolean values and cover all range of VolumeFraction without overlaps.
I have attached my .cas and.dat files in archive. My Ansys version is 2019R3.
Thanks in advance!

[vinerm]

The error is rather clear. The expression is incomplete. Since volume fraction could be of any of the phases, you also need to specify the phase in the expression.

[karachun]

Oh, I suppose that Volumefraction represent Secondary Phase VFraction, but this can word only in two phase flow. Thank you for reply.


But now I have searched Fluent Users Guide and don’t find examples of Volumefraction variable syntax. I try Volumefraction_water or Volumefraction(water) but Expression Editor don’t recognize these variables. Here water is name of secondary phase.


Can you prompt me where to search syntax example or how proper variable syntax look like?

[vinerm]

Fluent expressions are defined in a more formal manner. You have to specify phase="water" within the expression.

[karachun]

Now all working, thank you!
https://imgur.com/a/T6ZnY63

BTW I have found paragraph in User Guide about context specification.