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

Translation of an airfoil

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 3, 2011, 14:06
Angry Translation of an airfoil
  #1
New Member
 
Join Date: Jul 2011
Location: London, UK
Posts: 6
Rep Power: 5
Phil_QM is on a distinguished road
Hi all

I am having problems with getting a NACA 0012 airfoil to translate vertically with harmonic motion. I have followed the ANSYS tutorials and tried to set my problem up in a similar way.

I am using a tet c-mesh you can see attached. I have a problem when my airfoil oscillates as elements seem to fold rather than remesh, resulting in a negative volume error.
This is shown in the second attachment, you can see at the top of the airfoil the elements are folding and on the bottom of the airfoil the elongated elements.

I am using define_cg_motion to oscillate the airfoil.

Thanks in advance
Phil
Attached Images
File Type: jpg C-Mesh1.jpg (96.7 KB, 18 views)
File Type: jpg C-Mesh6.jpg (81.0 KB, 17 views)
Phil_QM is offline   Reply With Quote

Old   November 5, 2011, 10:02
Default
  #2
Member
 
Zachariah Swetky
Join Date: Aug 2011
Posts: 36
Rep Power: 5
swetkyz is on a distinguished road
Would defining a UDF of the motion and applying it to Cell Zone Conditions > Mesh Motion > Translation work? I think this solves the same physics without the need for mesh adaptation.

-Zachariah
swetkyz is offline   Reply With Quote

Old   November 7, 2011, 07:54
Default
  #3
New Member
 
Join Date: Jul 2011
Location: London, UK
Posts: 6
Rep Power: 5
Phil_QM is on a distinguished road
How would I go about defining a UDF for this as I have been using Define_CG_Motion which I dont think is suited to this case.

Also how would applying a cell zone motion solve the same physical problem?

Sorry if my questions seem basic but I am fairly new to CFD.

Thanks Phil
Phil_QM is offline   Reply With Quote

Old   November 7, 2011, 10:18
Default
  #4
Member
 
Zachariah Swetky
Join Date: Aug 2011
Posts: 36
Rep Power: 5
swetkyz is on a distinguished road
According to the user guide, by using a Single Moving Reference Frame, the accelerations due to the motion of the frame are accounted for by the solver. This means that as long as your boundary conditions represent the problem correctly, the same physics will be solved.

As far as the UDF is concerned, my knowledge is limited. It seems to me that this is the only way to define non-constant motion for a moving frame is a UDF.

If this approach is too cumbersome, you may try implementing the non spring-based dynamic mesh method that removes cells once they become too small.
swetkyz is offline   Reply With Quote

Old   November 7, 2011, 17:03
Default
  #5
Senior Member
 
sail's Avatar
 
Vieri Abolaffio
Join Date: Jul 2010
Location: Always on the move.
Posts: 308
Rep Power: 7
sail is on a distinguished road
remeshing does not work on hexa cells. [Ref, Fluent guide]

to get some remeshing you need to mesh your bl and then some as hexa, and the farfield as tri. then set all the hexa domain as passive rigid body. there are quite a few tutorial for this on the web.

or, not using a c-type grid but a normal h-type, you could take advantage of the relayering option.
sail 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
Low Speed Airfoil Mancusi FLUENT 7 April 3, 2014 06:11
Natural convection in a closed domain STILL NEEDING help! Yr0gErG FLUENT 3 June 12, 2013 02:12
[GAMBIT] Meshing airfoil using .dat file problem creggie ANSYS Meshing & Geometry 10 June 27, 2010 19:24
Modeling Backflow for a 3D Airfoil (Wing of Finite Span) Josh CFX 9 August 18, 2009 11:31
Airfoil boundary condition Frank Main CFD Forum 1 April 21, 2008 18:36


All times are GMT -4. The time now is 02:25.