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

Regarding mesh movemsnt in I.C Engine cylinder

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 16, 2004, 09:05
Default Regarding mesh movemsnt in I.C Engine cylinder
  #1
Ashwini kumar Mishra
Guest
 
Posts: n/a
Dear CFX user, I am working with a project on Piston & valve movement for 4 stroke IC engine using CFX-5.6. I am trying to make the piston and valve movemnt by generating codes. Though I able to get the piston and valve movement but not at at desired level. Reason is the mesh elements provide negative volume and get crashed after covering a distance up to about 30 % of cylinder height. Could any one CFX user guide me the right way to sort out the mentioned problem.Whether i should opt for mesh elements like Hexa with unstructured or so. Please mail me with proper solution on amishra2k@yahoo.co.in Thanks & Regards Ashwini Mishra
  Reply With Quote

Old   February 16, 2004, 17:21
Default Re: Regarding mesh movemsnt in I.C Engine cylinder
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi Ashini,

The moving mesh feature of CFX5.6 is a beta feature only so it is not perfect. It will be a fully supported feature in 5.7 when it comes out, however.

I found to mesh large mesh deformations (like that found in IC engines), you have to draw your initial mesh at top dead centre. This then means you have to draw a mesh which still gives a decent mesh when stretched out to bottom dead centre. You can't do this with tet elements, so you need to mesh across the cylinder plane with either tris or quads, then extrude that mesh down the cylinder axis with a very fine mesh. This makes the mesh at TDC have a very large aspect ratio, but this is unavoidable without cell addition/deletion.

It's a tricky meshing operation, but it is the only way of doing it. I have considered interpolating to a different mesh half way through the stroke, but have not tried it yet and it will just add to the already significant degree of difficulty.

Good luck! Glenn
  Reply With Quote

Old   February 17, 2004, 08:52
Default Re: Regarding mesh movemsnt in I.C Engine cylinder
  #3
Gloria Gaynor
Guest
 
Posts: n/a
Hi there,


Glenn is right.


I worked once generating only one grid and moving it along time (or crank angle, whatever) but I spent a huge time to find the optimal mesh to make myself able to finish one entire engine cycle. Another way is to make several grids, as Glenn also stated, each grid to its specific position and interpolate them as long as you proceed with the solution. However, this could be really a pain in the a** to do it in a HEXA mesh. I saw some time ago someone who made scripts automatizing this operation in ICEM Tetra. But, of course, I'm sure he also spent a lot of time working on this automatization task.
Take care, Gloria Gaynor
  Reply With Quote

Old   February 19, 2004, 11:05
Default Re: Regarding mesh movemsnt in I.C Engine cylinder
  #4
Jörn Beilke
Guest
 
Posts: n/a
You can re-invent the wheel and use cfx or you can just use starcd which is used by most automotive companies to run this type of calculation. There are some good articles about this topic on www.adapco-online.com

  Reply With Quote

Old   February 19, 2004, 13:30
Default Re: Regarding mesh movemsnt in I.C Engine cylinder
  #5
Bob
Guest
 
Posts: n/a
Glenn, quick question as I don't understand the geometry. Do you have to deform the whole mesh to generate the piston cyle, or could you translate the mesh around the piston, deforming the mesh in areas away from the the piston (assuming the piston is where the majority of the mesh would be ?). Just wondering if this would make like any easier ? when we did some moving mesh work around a complex shape, that was the approach we had to take. Bob
  Reply With Quote

Reply

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
[ICEM] Generating Mesh for STL Car in Windtunnel Simulation tommymoose ANSYS Meshing & Geometry 48 April 15, 2013 05:24
Flow past a circular cylinder mesh Turbulent Main CFD Forum 8 December 9, 2012 05:19
[snappyHexMesh] 2D Cylinder mesh problems with Snappy ivan_cozza OpenFOAM Meshing & Mesh Conversion 37 June 4, 2012 16:49
[ICEM] Unstructure Meshing Around Imported Plot3D Structured Mesh ICEM kawamatt2 ANSYS Meshing & Geometry 17 December 20, 2011 12:45
Convergence moving mesh lr103476 OpenFOAM Running, Solving & CFD 30 November 19, 2007 15:09


All times are GMT -4. The time now is 07:23.