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

Spontaneous failure of moving mesh interface

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 15, 2010, 08:12
Default Spontaneous failure of moving mesh interface
  #1
New Member
 
Gareth
Join Date: Mar 2009
Posts: 24
Rep Power: 17
gareth__it_power is on a distinguished road
hello,
My problem is that interface between a moving and stationary part of my mesh seems to spontaneously start behaving like a wall, i.e. not allowing fluid across it. This may happen after the simulation has been running successfully for a relatively long time. I don't know what causes it.

A bit more background:

I am a Phd student and I am modelling a vertical axis wind turbine in 2D using uRANS. My domain is a large square, with a rotating circle in the middle which contains the blades.

The mesh is quads, and has been refined along the blade surfaces to give y+ around 1. I have also refined the mesh along interface (the boundary of the circle) with about 2000 cells along the interface. The timestep is such that one revolution takes around 1000 timesteps.

The mesh was built in Gambit, where I specified two zones; the moving and stationary areas. In Fluent I specified the rotational velocity of the inner circle, and the Mesh Interfaces (which I had to change from default Wall.)

When the simulation first begins it is fine, and it takes a while for the expected velocity fields to settle down and periodic behaviour to begin. At some point, it is impossible to predict when, the periodic behaviour ceases because fluid is no longer entering the circle, but is flowing around it.

I'd be very grateful for any suggestions, or to hear from anyone else who may have experienced this fault.

Kind Regards,

Gareth Uglow
gareth__it_power is offline   Reply With Quote

Old   August 26, 2010, 08:50
Default
  #2
New Member
 
Gareth
Join Date: Mar 2009
Posts: 24
Rep Power: 17
gareth__it_power is on a distinguished road
I seem to have solved the problem.

For some reason the diameter of the rotor or stator was changing slightly, causing a gap between the interfaces. This gap was interpreted as a very small wall.

I have now allowed a small, 1mm, overlap between the interfaces. The cell size in this region is about 1cm, so the overlap is small relative to the cells.

I'd be interested to hear from anyone else who has encountered this phenomenon.

Regards,

Gareth
gareth__it_power is offline   Reply With Quote

Reply


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
How to make boundary layer mesh moving with wall wayne FLUENT 3 June 12, 2008 00:23
Question on InterFoam moving mesh capabilities ziv OpenFOAM Running, Solving & CFD 0 April 23, 2008 10:11
ICEM CFD 5.1 Hex-Tet mesh merging failure bogesz CFX 1 January 29, 2005 07:46
C4 = 1 for Moving Mesh Xobile Siemens 2 January 18, 2005 06:22
Replace periodic by inlet-outlet pair lego CFX 3 November 5, 2002 21:09


All times are GMT -4. The time now is 16:12.