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-   -   Polymer entrance BC (http://www.cfd-online.com/Forums/openfoam-pre-processing/62015-polymer-entrance-bc.html)

billy May 3, 2005 08:47

Hello, I am trying to simul
 
Hello,

I am trying to simulate the entrance of a polymer into a cavity (mould). I have defined an inlet and outlet. I am using interFoam to calculate the gamma function. For now, I am considering two Newtonian fluids (polymer / air).

My problem is that I don't know how to specify the BC at the inlet for the gamma variable. I would like to define a constant gamma value at the inlet (= 1.0, considering 1 polymer and 0 air). It is a constant source of gamma = 1.0. If I only specify the value at the inlet patch, the polymer is only dispersed in the cavity and this is not what I want.

Can anyone give me suggestions on how to overcome this problem?
Also if anyone is using OpenFOAM for similiar purposes, I would like to know. I can contribute with experimental validation and data.

eugene May 3, 2005 08:54

What do you mean "the polymer
 
What do you mean "the polymer is only dispersed in the cavity"?

Gamma=1 at the inlet is normally a sufficient BC for the 2-phase system. You have to be careful to keep a head of polymer at the inlet though. If the inlet runs "dry" (i.e. there is no polymer adjacent to the gamma=1.0 path) the solution may diverge.

henry May 3, 2005 08:54

Why do you think it is a probl
 
Why do you think it is a problem to specify gamma = 1.0 at the inlet? In principle that should be fine and the inlet flow you also specify should transport gamma into the domain.

billy May 3, 2005 09:12

Sorry, I think I did not e
 
Sorry,

I think I did not explain myself correctly.

----------------------------

Eugene:

"What do you mean "the polymer is only dispersed in the cavity"?"

What I mean is that I specify a value gamma = 1.0 at the inlet and I specify an inlet velocity (also of an outlet of course). The value of the rest of the cavity (mould) is set to 0.0 at time = 0 seconds since it is full with air. The solver runs and the results present a gamma between, for example, 0 and 0.25 for time = 1 second. I suppose 0.25 means that it has a 25% of polymer and 75% of air at that location. But this is not what I want. I want to simulate a constant entrance of polymer into the cavity. So gamma has to be constant and equal to 1.0 at the inlet at all times. Then I would track the interface (or flow front). I am using interFoam.

Henry:

How do I specify a transport gamma into the domain? This might be what I need to do.

Thanks in advance.

henry May 3, 2005 09:19

Specify a fixedValue BC for ga
 
Specify a fixedValue BC for gamma at the inlet with a value of 1.

eugene May 3, 2005 09:40

So after 1 second, the cells a
 
So after 1 second, the cells adjacent to the inlet have a gamma value of 0.25 and the rest of the domain has a value of 0? (correct me if I am wrong)

This simply means you haven't let enough time pass for the polymer to fill the cells next to the inlet. Remember this is not a donor-acceptor solver, there will always be a few cells with values between 0 and 1 at the surface of the polymer. You can track the front by looking at the iso-surface of gamma=0.5.

You mention an outlet boundary, I assume you have specified zeroGradient for gamma and U at this location?

hsieh May 3, 2005 11:01

Hi, Billy, Is this to simul
 
Hi, Billy,

Is this to simulate injection molding process? If it is, I will be very interested in knowing how you solve this using OpenFOAM. From time to time, we have to look at injection molding problems, and I do not know how to apply OpenFOAM to this type of problem, ie, viscosity of polymer is temperature dependent and it must be very time consuming to solve this problem using the full NS equation with interfaces.

Anyway, based on my experience with interFOAM, you have to initializ a couple of layers of cells near the entrace to gamma = 1. If you initialize the whole domain to gamma = 0, velocity = 0 and gamma = 1 "only" at the inlet, you generally run into problems.

Pei

billy May 4, 2005 11:10

"You mention an outlet boundar
 
"You mention an outlet boundary, I assume you have specified zeroGradient for gamma and U at this location?"

Yes for U, for the gamma I am not sure. I will check my model.

"Is this to simulate injection molding process?"

Yes.

I am trying with interFoam at the moment but I think I will have to create a new class (mouldFoam) to tackle the problem.

n_sathya September 30, 2006 10:08

hi i'm interested in using thi
 
hi i'm interested in using this for injection molding.
please let me know about latest development and how i can help

billy September 30, 2006 11:43

I think we have more people in
 
I think we have more people interested in this application. Maybe we can start a group and develop a new Foam class to deal with this case.

vikbergg June 18, 2007 12:38

I read that people are interes
 
I read that people are interested in starting a moldFOAM class to develop OpenFOAM so that it can do injection molding calculations. I'm extremely interested in contributing to this project. Can anyone let me know if it have been started, and what the current status of the project is? Thank you in advance!

billy June 22, 2007 06:56

I started a moldFoam class. Ba
 
I started a moldFoam class. Basically it is based on interFoam and I just added temperature transport to it. However, now I think it is better to reformulate it based on multiphaseInterFoam so it can simulate co-injection.

http://www.cfd-online.com/OpenFOAM_D...hment_icon.gif moldFoam.tgz

francesco_b January 15, 2008 12:10

Hi Billy, I have downloade
 
Hi Billy,

I have downloaded your moldFoam class, can you please post also a simple test case? I didn't understand how to treat the outflow BC in a case of polymer in a cavity, how to impose it? zeroGradient for U and gamma? How can I choose the outflow surface if the cavity is closed? (Am I missing something about it?)

Sorry for the number of questions, I'm very interested in this application.

Thank you in advance

Francesco

francesco_b March 12, 2008 12:08

Hi Billy, I've tried to com
 
Hi Billy,

I've tried to compile your solver but I've got some errors, mainly due to the movingmesh part of the solver.

Do you have built a version of the solver which works on OF 1.4.1?

Are you still working on this subject?
It would be interesting to hear, basing on your experience, if you think OF could be an adequate tool for molding and why.

I'd like to hear also someone else opinion.

Regards

Francesco

awacs December 29, 2008 07:57

Hi Billy, I'm interested in i
 
Hi Billy,
I'm interested in injection molding calculations too.I want to complile your moldFoam class which is based on interFoam.I have installed OpenFOAM 1.5.How can I add the moldFoam class to it?
Thanks for your help.

Best wishes.
Liu Jitao


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