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

Dynamic mesh issue

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 12, 2012, 05:20
Default Dynamic mesh issue
  #1
Member
 
Dr. Moloy Kumar Banerjee
Join Date: Jun 2011
Posts: 71
Rep Power: 6
moloykb is on a distinguished road
Dear all,
I am trying to simulate the flow through a artery in the presence of stenosis with surface irregularities. The artery wall is assumed to oscillate with a velocity of sinusoidal variation. In order to define the motion of the wall I am using the Dynamic mesh feature of Fluent with the following compiled udf to define the motion of the wall.

#include "udf.h"

DEFINE_CG_MOTION(wave, dt, vel, omega, time, dtime)
{
vel[1]=-.0001*7.543*sin(7.543*time);
}
For the unsteady simulation I am using a time step size of 0.0001 sec and as a mesh method I am using Layering approach with a split and collapse factor of 0.4 and zone type as rigid body.
But unfortunately when I try to run the simulation it shows the error Update-dynamic mesh failed: negative cell volume detected.
Please help me.
Attached Images
File Type: jpg FFF.1.jpg (88.5 KB, 26 views)
moloykb is offline   Reply With Quote

Old   September 12, 2012, 10:21
Default
  #2
Senior Member
 
Join Date: Mar 2011
Location: Germany
Posts: 414
Rep Power: 11
cfd seeker is on a distinguished road
try reducing your time step size and also play with dynamic mesh parameters, also turn on smoothing
cfd seeker is offline   Reply With Quote

Old   September 13, 2012, 00:32
Default
  #3
Member
 
Dr. Moloy Kumar Banerjee
Join Date: Jun 2011
Posts: 71
Rep Power: 6
moloykb is on a distinguished road
Dear cfd seeker
thanks for your reply. I have already reduced the time step upto 0.000001 sec, but till the same problem exists.Regarding the parameters how to choose the proper value of those.
moloykb is offline   Reply With Quote

Old   September 13, 2012, 03:38
Default
  #4
New Member
 
Join Date: Sep 2009
Location: IIT Kharagpur
Posts: 10
Rep Power: 7
nimbus1947 is on a distinguished road
Try using triangular mesh and use re-meshing instead of layering.

If you insist on going with quad mesh try the following
1. Set the udf motion for the fluid (the quad mesh region)
2.Set the boundary as stationary.
nimbus1947 is offline   Reply With Quote

Old   September 13, 2012, 06:03
Default
  #5
Senior Member
 
Join Date: Mar 2011
Location: Germany
Posts: 414
Rep Power: 11
cfd seeker is on a distinguished road
Quote:
Originally Posted by nimbus1947 View Post
Try using triangular mesh and use re-meshing instead of layering.

If you insist on going with quad mesh try the following
1. Set the udf motion for the fluid (the quad mesh region)
2.Set the boundary as stationary.
which boundary to set as stationary?
cfd seeker is offline   Reply With Quote

Old   September 13, 2012, 06:17
Default
  #6
Member
 
Dr. Moloy Kumar Banerjee
Join Date: Jun 2011
Posts: 71
Rep Power: 6
moloykb is on a distinguished road
dear nimbus1947
how to set the udf motion for the fluid zone and what is the stationary boundary. Would u please elaborate something?
moloykb is offline   Reply With Quote

Old   September 13, 2012, 07:56
Default
  #7
New Member
 
Join Date: Sep 2009
Location: IIT Kharagpur
Posts: 10
Rep Power: 7
nimbus1947 is on a distinguished road
upload the picture of your full domain with boundary names.
nimbus1947 is offline   Reply With Quote

Old   September 24, 2012, 07:02
Default
  #8
New Member
 
CFD man
Join Date: Sep 2012
Location: Earth
Posts: 12
Rep Power: 4
fluentworkshop is on a distinguished road
Hi guys
Cell height of wall (in dynamic mesh zones) must not be zero.
or you must use another wall as stationary and also quad zone must be move with same udf.
fluentworkshop is offline   Reply With Quote

Old   September 24, 2012, 12:07
Default
  #9
Senior Member
 
Join Date: Mar 2011
Location: Germany
Posts: 414
Rep Power: 11
cfd seeker is on a distinguished road
Quote:
Originally Posted by fluentworkshop View Post
Hi guys
Cell height of wall (in dynamic mesh zones) must not be zero.
or you must use another wall as stationary and also quad zone must be move with same udf.
didn't get your point?
cfd seeker 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
SnappyHexMesh for internal Flow vishwa OpenFOAM Native Meshers: snappyHexMesh and Others 23 August 6, 2014 03:50
snappyHexMesh won't work - zeros everywhere! sc298 OpenFOAM Native Meshers: snappyHexMesh and Others 2 March 27, 2011 21:11
Dynamic mesh in Fluent to study tire in contact with road surface lihuang FLUENT 10 March 8, 2011 11:21
Extended version: Dynamic mesh fusij OpenFOAM 2 February 18, 2011 03:12
Gambit problems Althea FLUENT 21 February 6, 2001 08:05


All times are GMT -4. The time now is 21:23.