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a.etesam March 30, 2009 03:10

Hi Dear Friends
I am trying now to simulate flow over an ogee spillway and i want to see the Air in the flow but in my simulation i have 2 warnings:
1- warning **
** turbulence options require **
** a non-zero molecular viscosity **
** ifvis reset to zero **

2- warning **
** selected data request for **
** turbulent energy **
** cancelled **
** ifvis < 2 **

i cant see the fraction of air in my simulation. why? any body can help me? Thanks:confused:

stefmascio March 30, 2009 08:15

hello Ali,
from these warnings it seems that you haven't set the viscosity of your fluid. Try to set the viscosity in the "fluid" panel and the messages should disappear.

About the problem of seeing the air: have you switched on the "air entrainment" model?

a.etesam April 1, 2009 05:35

Hi stefmascio
my fluid is water and when i choose airentrainment, F3d choose 1 torbulance model(RNG).in this case is necccary i set the fluid viscosity?
Thank you very much:)

stefmascio April 1, 2009 07:12

the fluid viscosity is required whenever you activate any viscosity model (non-newtonian, newtonian, ...).
Water is viscous, so you should activate at least the newtonian viscosity and put the water viscosity in the fluid properties.

The air entrainment model need viscosity, and then it should work both with no turbulence (laminar) or turbulence. It depends on wich version of F3D you have.
But one thing is the viscosity, another thing is if the fluid is turbulent or not.

a.etesam April 1, 2009 17:40

I am using F3D ver9.0 . As default when we active Air entrinment model , the turbulent model will active.when we deselect turbulent model we can see that Air entrainment will inactive.why do you say we can use Air entrainment model for both state (laminar & turbulent)?

stefmascio April 2, 2009 02:37

I'm not sure, but as you have noticed with 9.0 you can use the air entrainmnent model only if the flow is turbulent. The extension to laminar flows is a more recent improvment (probably since version 9.2, if I don't remember wrong).
Is your flow laminar? Do you know the Reynolds number of your flow?

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