[IRP]

Dear all
I am dealing with a problem in Star-CCM+, about the impact of droplet on a surface.
Actually, I am going to provide phase source as a filed function in which whenever the surface becomes wet, permanently it stays wet.
in other words, i want to fix the flux (VOF) of a variable at a cell face, during the splashing of droplet.
I would be appreciated if anyone could help me to that what kind of filed function would be suitable in this condition (star- CCM+).

Thank you very much in advance.
Iman

[me3840]

I'm not sure if this is possible.

You could try making a field function off of the flow stop model. This is supposed to be for modeling freezing, so if you could get the droplets to 'freeze' then you could make a field function based on the relative volume fraction to do something.

You will not be able to fix the flux without doing user coding.

[IRP]

Thanks a lot for the kind comments. I think that the user coding should be very appropriate in my problem.
Could you be so kind and point me to some references or samples, in order to understand how to apply a fixed value of VOF using user coding in Star-CCM+?

I am dealing with this issue for a couple of months, I need your help for my case. So kindly help me out and give me urgent help I will be very thankful to you.

Indeed, I find a way in chapter 9 through
• An introduction to computational fluid dynamic: the finite volume method
H. K. Versteeg & W. Malalasekera
Which relates to the implementation of boundary condition.

At the beginning of this chapter, it gives the idea:
if we want to fix the flux of a variable at a cell face, can be done by introducing two overwhelmingly large source terms in the relevant discretized equation. For example, to set the variable Q at node P to a value Qfix the following source term modification is used in its discretized equation:

Sp = -10^30 and Su = 10^30 * Qfix

With these sources added to the discretized equation, we have:

(ap + 10^30) Qp = Sum (anb*Qnb) + 10^30 * Qfix

The actual magnitude of the number 10^30 is arbitrary as long as it is very large compared with all the coefficients in the original discretized equation. Thus, if ap and anb are all negligible the discretized equation effectively states that
Qp = Q fix
Which fixes the value of Q at P.

Many thanks
Iman

[me3840]

The user guide has an okay introduction to user coding, have you read that?

[IRP]

Again thanks for your good comment, I'm recently starting to read that one.