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

Dynamic mesh & Negative volume in 3D

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

Like Tree13Likes

Reply
 
LinkBack Thread Tools Display Modes
Old   December 16, 2012, 10:31
Default
  #61
Member
 
Vidit Sharma
Join Date: Aug 2012
Location: Delhi, India
Posts: 32
Rep Power: 5
Vidit Sharma is on a distinguished road
Hi All..

Sir,
I am trying to rotate a 2D box or a 2D cup structure in Fluent using smoothing and remeshing. I am using tri mesh and as mentioned in Fluent Manual I am using smoothing and remeshing and also set the remeshing parameters from mesh info tab given in the remeshing menu. But the problem is that when i start simulation and it goes to first time step Fluent display "Updating mesh at time level N..." and here it stops and it happened alot of time and even waiting after a whole day it didnt worked. I also tried time step size from 0.01 to 0.000001 but it still show this problem.

Can you plz help in this case?

Thank u in advance
Vidit Sharma is offline   Reply With Quote

Old   February 19, 2013, 02:48
Default
  #62
New Member
 
Debanjan Deep
Join Date: Mar 2009
Posts: 14
Rep Power: 8
skyblue_mech is on a distinguished road
Hi Enry,
I am interested about the UDF since I have started to work on my moving mesh problem for a project this semester.
I shall be glad if you share the same so I can have some idea how to start with and how to write the UDF in my case.

Debanjan Deep
skyblue_mech is offline   Reply With Quote

Old   February 19, 2013, 02:50
Default
  #63
New Member
 
Debanjan Deep
Join Date: Mar 2009
Posts: 14
Rep Power: 8
skyblue_mech is on a distinguished road
Quote:
Originally Posted by enry View Post
I solved the problem. In case somebody is interested:
-UDF for the moving surface
-DEFORMING with re-meshing for fluid around moving surface
-DEFORMING with re-meshing for surface that is moving with fluid (i.e. re-meshing for surface that will be deformed because of moving surface)
-spring constant factor 0
-boundary node relaxation 1
-if there is a boundary layer, define a fluid-zone for the boundary layer, mesh it with map scheme, and in FLUENT define that fluid-zone as DEFORMING without re-meshing
-enable spring-on-all-shapes through the following command line: define models dynamic-mesh-controls smoothing-parameter spring-on-all-shapes yes

Bye.
Hi Enry,
I am interested about the UDF since I have started to work on my moving mesh problem for a project this semester.
I shall be glad if you share the same so I can have some idea how to start with and how to write the UDF in my case.

Debanjan Deep
meb likes this.
skyblue_mech is offline   Reply With Quote

Old   March 1, 2013, 00:58
Default 2D airfoil O Grid- negative volume
  #64
New Member
 
samrat himvanth nanduri
Join Date: May 2012
Posts: 23
Rep Power: 5
samcfd is on a distinguished road
Hi,

I'm carrying out a 2D pitching airfoil simulation using dynamic meshing with a "O" Grid. The dynamic conditions i have given were
1) airfoil - rigid body with UDF with pitching over X=0.25
2)interior - deforming with the min and max length scale from zone scale info
3) fluid -deforming with the min and max length scale from zone scale info.

The spring constant i gave was 0.001 and
convergence tolerance 0.0001
No of iterations 150.

The time step tat i used is 0.001.

After running the iterations and after about 500 time steps i'm getting the following error

negative volume detected
dynamic mesh update failed.
i have worked around with the spring constant and also with the time step nothing worked.
could someone help me out rectify this issue..
thanks in advance,
sam
meb likes this.
samcfd is offline   Reply With Quote

Old   March 1, 2013, 05:27
Default
  #65
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 77
Rep Power: 8
meb is on a distinguished road
Hello,
we can support your study with RBF Morph. I can help you with a test on your mesh if you want.



Quote:
Originally Posted by samcfd View Post
Hi,

I'm carrying out a 2D pitching airfoil simulation using dynamic meshing with a "O" Grid. The dynamic conditions i have given were
1) airfoil - rigid body with UDF with pitching over X=0.25
2)interior - deforming with the min and max length scale from zone scale info
3) fluid -deforming with the min and max length scale from zone scale info.

The spring constant i gave was 0.001 and
convergence tolerance 0.0001
No of iterations 150.

The time step tat i used is 0.001.

After running the iterations and after about 500 time steps i'm getting the following error

negative volume detected
dynamic mesh update failed.
i have worked around with the spring constant and also with the time step nothing worked.
could someone help me out rectify this issue..
thanks in advance,
sam
meb is offline   Reply With Quote

Old   March 3, 2013, 23:55
Default
  #66
New Member
 
samrat himvanth nanduri
Join Date: May 2012
Posts: 23
Rep Power: 5
samcfd is on a distinguished road
Dear Meb,

yes i can support...what input parameters do u require.


Quote:
Originally Posted by meb View Post
Hello,
we can support your study with RBF Morph. I can help you with a test on your mesh if you want.
samcfd is offline   Reply With Quote

Old   March 4, 2013, 04:03
Default RBF Morph 2D benchmark
  #67
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 77
Rep Power: 8
meb is on a distinguished road
If you can share the mesh and movement info (i.e. movement type and desired range), we can do the test and publish here what we get using RBF Morph.

Best.

Quote:
Originally Posted by samcfd View Post
Dear Meb,

yes i can support...what input parameters do u require.
meb is offline   Reply With Quote

Old   March 4, 2013, 04:05
Default
  #68
New Member
 
samrat himvanth nanduri
Join Date: May 2012
Posts: 23
Rep Power: 5
samcfd is on a distinguished road
Could u pls send me ur maild id

Quote:
Originally Posted by meb View Post
If you can share the mesh and movement info (i.e. movement type and desired range), we can do the test and publish here what we get using RBF Morph.

Best.
samcfd is offline   Reply With Quote

Old   March 11, 2013, 11:07
Default Pitching airfoil range -45 deg 45 deg
  #69
meb
Member
 
Marco Evangelos Biancolini
Join Date: May 2009
Location: Rome - Italy
Posts: 77
Rep Power: 8
meb is on a distinguished road
Sorry for the delay (so many ongoing activities!).
You can do the job using RBF Morph. We did it on a 3d mesh. 2d currently is not a standard feature of RBF Morph; we can deliver custom builds that support it.

meb is offline   Reply With Quote

Old   November 18, 2013, 05:31
Post
  #70
New Member
 
P NAGA SURESH KUMAR
Join Date: Oct 2013
Location: HYDERABAD
Posts: 6
Rep Power: 3
PNSK is on a distinguished road
I think
1) Minimum length scale : 0.4 times average length scale
2) Maximum length scale: 1.4 time average length scale

i like to know how to rectify " Negative cell volume" error
PNSK is offline   Reply With Quote

Old   December 13, 2013, 05:40
Default
  #71
New Member
 
P NAGA SURESH KUMAR
Join Date: Oct 2013
Location: HYDERABAD
Posts: 6
Rep Power: 3
PNSK is on a distinguished road
Thanks for your answer mrestrepo30 because of it i solved my problem
PNSK is offline   Reply With Quote

Old   June 5, 2014, 15:11
Default
  #72
New Member
 
AZ
Join Date: Jan 2014
Posts: 14
Rep Power: 3
mjthomp3 is on a distinguished road
Quote:
Originally Posted by mahzironrazak View Post
Hi All

I am trying to simulate 3D flapping wing using fluent and i keep getting negative volume when i run the mesh motion. I used smoothing and remeshing. I have reduce the time step and still it didnt work. I also changed the remeshing parameters but no go. I read that for dynamic mesh "the translation in one time step should not be more than half the cell size adjacent to the moving boundary". what does that means? How can i get the cell size adjacent to the moving boundary? By the way how do i determine the correct value for dynamic mesh parameters :


1) Minimum length scale
2) Maximum length scale
3) Adjacent zone cell height

I used the data from mesh scale info (button)

Will increasing the density of the grid reduces the possibility of getting negative volume.

cheers
hey what dynamic mesh method are you using??
I am also doing the same but am curious on the method your using.....
mjthomp3 is offline   Reply With Quote

Old   June 5, 2014, 15:14
Default
  #73
New Member
 
AZ
Join Date: Jan 2014
Posts: 14
Rep Power: 3
mjthomp3 is on a distinguished road
Quote:
Originally Posted by meb View Post
Sorry for the delay (so many ongoing activities!).
You can do the job using RBF Morph. We did it on a 3d mesh. 2d currently is not a standard feature of RBF Morph; we can deliver custom builds that support it.


really neat video? Can you tell the steps to do it?
I was wondering, I have a 3D bumblbee MAV drone wing that i am doing research on. I was wondering how could I use the software you are mentioning in order to make it flap?
mjthomp3 is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ICEM] Generating Mesh for STL Car in Windtunnel Simulation tommymoose ANSYS Meshing & Geometry 48 April 15, 2013 04:24
Dynamic Mesh on Pintle type injector. herntan FLUENT 15 January 4, 2012 04:31
Dynamic Mesh Problem. Tom Clark FLUENT 9 July 7, 2010 07:56
Negative Volume Mesh MANOJKUMAR FLUENT 8 April 7, 2009 09:50
FSI & Negative Volume Mesh Mojtaba CFX 1 October 13, 2008 07:13


All times are GMT -4. The time now is 19:45.