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-   -   Help Regarding Segregation Model in FLOW-3D (http://www.cfd-online.com/Forums/flow-3d/63331-help-regarding-segregation-model-flow-3d.html)

Pathak April 5, 2009 10:25

Help Regarding Segregation Model in FLOW-3D
 
Hi,

I am using the segregation model in FLOW 3D and my alloy is A-356 (binary alloy of Al and Si with 7 wt% Si initially).

Well i have simulated the segregation model with the given benchmark problem if solidification of Ammonium chloride+water binary mixture and i have got satisfactory results for macrosegregation comparing with published results.

As i m using A-356 alloy now, and its properties are as follows:

TMELT (Melting Temperature) = 913 K
TEUT (Eutectic Temperature) = 850 K
CEUT (Eutectic Concentration) = 0.126
PCOEF (Partition Coefficient) = 0.13
All these parameters define the phase diagram for a given alloy.
So when i m trying to simulate the segregation, i am getting the solute concentration more than the eutectic concentration which is wrong.
I am not able to sort out why the solute concentration is going beyond eutectic concentration.
Additionally, i have some doubts about defining the reference concentration (CSTAR) and their corresponding Solidus (TS1) and Liquidus (TL1) temperatures.

According to the FLOW 3D documentation, the TS1 and TL1 should be defined according to the reference concentration (CSTAR).
So i m taking the reference concentration to be 0.01 and based on that my TL1 = 908 K and TS1 = 874.538 K.

one more thing i want to mention that in the binary alloy phase diagran the solidus line will become eutectic line when the concentration reaches (PCOEF*CEUT) i.e. the multiplication of partition coefficient and eutectic concentration.
So can i use any reference concentration or i have to use the reference whose magnitude is definitely less than (PCOEF*CEUT) because in that case only we will get the correct TS1 and TL1.
one can get these details after looking at the phase diagram of binary alloy.

If anybody has some experience with the segregation model please reply this post.

Thanks and Regards

NP


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