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-   -   inital conditions (http://www.cfd-online.com/Forums/star-ccm/75292-inital-conditions.html)

jopawipr April 21, 2010 08:33

inital conditions
 
Hey everybody!
I desined 3 eulerian phases(Dodecane(L),Dodecane(G) and Nitrogen).
At the beginning of my simulation there is just Dodecane(L) and Nitrogen.
So how can I define where the inital position of the phases are?
It's a 3dimensional simulation. The inital position just depends in z direction.
So for example:
z<=0.5 --> Nitrogen
z>=0.5 --> Dodecane(L)
Can anybody help me?
thank you very much!
Johannes

Vinicius April 22, 2010 09:20

Hi Johannes,

You have to create a scalar field function such as:

Initial Nitrogen:

($$Centroid[2] < 0.5 ) ? 1 : 0

Initial Dodecane:
($$Centroid[2] > 0.5) ? 1 : 0

at the Volume Fraction node, select it to composite and associate these field functions for each phase.

You can also use the $$Position field function instead $$Centroid. Be sure that you mesh has a good quality in this region, and if possible, try to have the cells aligned in the division line.

Regards,

Vinicius

jopawipr April 26, 2010 07:22

Thank you very much for your answer!

But for what is the "?" in the equation?
And the [2] is for the z-axis?

Best regards,
johannes

Vinicius April 26, 2010 07:25

The ? in the equation is the "if" condition, for example (condition) ? true : false.

The axis are x =[0], y=[1] and z=[2].

Vinicius

jopawipr April 26, 2010 08:10

thank's a lot!
a last question:
Does it matter i which order I define the three eulerian phases?
Cause i still get a failure when I define Dodecane(L) and Nitrogen with a field function. The initial condition of Dodecane(G) is 0 and constant...
Thanks, and best regards

Vinicius April 26, 2010 08:56

The order that you create the phases just define the order you might input the data in some fields, like volume fraction... What is the error that appears?


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