CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Creating Initial shape of droplet (elliptical)

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By CeesH

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 18, 2018, 05:01
Post Creating Initial shape of droplet (elliptical)
  #1
New Member
 
Muhammad Sufyan
Join Date: Jun 2012
Location: South Korea
Posts: 17
Rep Power: 11
Sufyan is on a distinguished road
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
__________________
SUFI
Sufyan is offline   Reply With Quote

Old   July 18, 2018, 09:28
Default
  #2
Senior Member
 
Cees Haringa
Join Date: May 2013
Location: Delft
Posts: 607
Rep Power: 0
CeesH is on a distinguished road
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.
CeesH is offline   Reply With Quote

Old   July 18, 2018, 13:53
Default
  #3
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,441
Rep Power: 53
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
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.
LuckyTran is offline   Reply With Quote

Old   July 23, 2018, 23:53
Default
  #4
New Member
 
Muhammad Sufyan
Join Date: Jun 2012
Location: South Korea
Posts: 17
Rep Power: 11
Sufyan is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
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.
__________________
SUFI
Sufyan is offline   Reply With Quote

Old   July 23, 2018, 23:54
Default
  #5
New Member
 
Muhammad Sufyan
Join Date: Jun 2012
Location: South Korea
Posts: 17
Rep Power: 11
Sufyan is on a distinguished road
Quote:
Originally Posted by CeesH View Post
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
__________________
SUFI
Sufyan is offline   Reply With Quote

Old   July 24, 2018, 06:17
Default
  #6
Senior Member
 
Cees Haringa
Join Date: May 2013
Location: Delft
Posts: 607
Rep Power: 0
CeesH is on a distinguished road
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 likes this.
CeesH is offline   Reply With Quote

Old   July 25, 2018, 00:27
Default
  #7
New Member
 
Muhammad Sufyan
Join Date: Jun 2012
Location: South Korea
Posts: 17
Rep Power: 11
Sufyan is on a distinguished road
Quote:
Originally Posted by CeesH View Post
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.
__________________
SUFI
Sufyan is offline   Reply With Quote

Reply

Tags
adapt region, droplet, fluent, microchannel, vof

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
chtMultiRegionSimpleFoam: maximum number of iterations excedeed. Nkl OpenFOAM Running, Solving & CFD 19 October 10, 2019 03:42
Suppress twoPhaseEulerFoam energy AlmostSurelyRob OpenFOAM Running, Solving & CFD 33 September 25, 2018 18:45
Segmentation fault when using reactingFOAM for Fluids Tommy Floessner OpenFOAM Running, Solving & CFD 4 April 22, 2018 13:30
chtMultiRegionSimpleFoam turbulent case Aditya Patil OpenFOAM Running, Solving & CFD 6 April 24, 2017 23:13
Micro Scale Pore, icoFoam gooya_kabir OpenFOAM Running, Solving & CFD 2 November 2, 2013 14:58


All times are GMT -4. The time now is 00:04.