[Sufyan]

Hi CFD USERS:

I am simulating 3D droplet in a rectangular micro-channel.
I am facing a problem in drawing initial droplet shape in ANSYS FLUENT.

Droplet is not in spherical shape. I have got results for case of spherical shape droplet. The second case is more close to elliptical/Donut like.

height of channel < droplet size therefore it appears circular from top view but not from side view.

Is there any way to draw elliptical shape of initial droplet in ANSYS FLUENT.

It would be very kind if you help me.
Thanks

[CeesH]

The easy way to go is to initialize the droplet as a block and let it relax to its natural shape. Otherwise you may need some kind of initialization field function, that specifies the shape via a UDF or so. No experience with that, but I guess it's not impossible if you have a parameterized shape for your droplet - you can probably use define on demand with some if loop: if cell center is in the droplet boundary, initialize with droplet phase fraction =1 , otherwise 0.

[LuckyTran]

Another way without a UDF is to go to file => interpolate and read in a text file which contains the field values you want to initialize it with. Of course you have to generate this text file, presumably using excel, matlab, or something.

[Sufyan]

Originally Posted by LuckyTran

Another way without a UDF is to go to file => interpolate and read in a text file which contains the field values you want to initialize it with. Of course you have to generate this text file, presumably using excel, matlab, or something.

Thank you guys...

can you please elaborate it please. I read your comment many times but could not understand it completely.

[Sufyan]

Originally Posted by CeesH

The easy way to go is to initialize the droplet as a block and let it relax to its natural shape. Otherwise you may need some kind of initialization field function, that specifies the shape via a UDF or so. No experience with that, but I guess it's not impossible if you have a parameterized shape for your droplet - you can probably use define on demand with some if loop: if cell center is in the droplet boundary, initialize with droplet phase fraction =1 , otherwise 0.

Thanks dear. I am sorry. What do you mean when you suggest initialize the droplet as a block and let it relax to its natural shape. How to do that please explain..

thanks

[CeesH]

you can mark a specific region using adapt > mark cells.
Then go to solution initialziation> patch, to specify the volume fraction of the droplet phase as 1 in that region. This gives you a block of droplet in the middle of continuous fluid. Of course,it doesn't have the droplet shape yet, but if your surface tension is correct, it will take the correct shape in time.
It's a crude method, and takes some time to settle, but it works.

The other alternative is, as mentioned by LuckyTran, to use a UDF. there you can accurately specify which range of coordinates you want to include in the droplet, but you need to parameterize your shape: which coordinates lie within the droplet shape, and which do not.

[Sufyan]

Originally Posted by CeesH

you can mark a specific region using adapt > mark cells.
Then go to solution initialziation> patch, to specify the volume fraction of the droplet phase as 1 in that region. This gives you a block of droplet in the middle of continuous fluid. Of course,it doesn't have the droplet shape yet, but if your surface tension is correct, it will take the correct shape in time.
It's a crude method, and takes some time to settle, but it works.

The other alternative is, as mentioned by LuckyTran, to use a UDF. there you can accurately specify which range of coordinates you want to include in the droplet, but you need to parameterize your shape: which coordinates lie within the droplet shape, and which do not.

Thanks Sir,

It is very helpful. I am certainly going to try this one.

Once again, Thanks for your time and help.