# Negative Volume

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

 August 30, 2007, 05:51 Negative Volume #1 saurav pathak Guest   Posts: n/a can anyone kindly explain me what is meant by "negative volume" in a mesh?

 August 30, 2007, 06:43 Re: Negative Volume #2 rt Guest   Posts: n/a degenerated elements, reverse or inconsistence node ordering

 August 30, 2007, 08:23 Re: Negative Volume #3 Ahmed Guest   Posts: n/a How volumes are calculated? the scalar triple product of vectores formed from the sides of a cell, the formula is found in any linear algebra book, play a bit with the numbers and see by yourself how could you get a negative volume. Some times the cell you are calculating its volume is not deformed at all, but its vertices are numbered clock wise, in this case remeshing is the only solution to this nasty problem

 August 30, 2007, 11:01 Re: Negative Volume #4 Anantha Guest   Posts: n/a It depends.. If you are using commercial tool like ICEM, you have the option of 'invert block' to get rid of this problem.. though the mesh will look perfect for eyes, we will get negative volume error because of the reason as said by Ahmed and some times you can fix it up by this block inversion method.

 August 31, 2007, 07:34 Re: Negative Volume #5 Charles Guest   Posts: n/a All of the above comments are true, but sometimes, when dealing with nasty geometry, hexahedral meshes can simply get folded, which will also show up as a negative volume. Imagine taking a rectangle, and twisting one edge through 180 degrees. So negative volumes can't always be solved by re-ordering. You may need to look a it to see if the cells make physical sense.

 August 31, 2007, 13:18 Re: Negative Volume #6 Joe Guest   Posts: n/a I'm assuming this is a structured or hex mesh. If all the volumes are negative, then your system is left handed. Reordering the indicies will fix that - easy. If just a few of the volumes are negative, then you have crossing grid lines - much harder. You need to find the location and source of the problem to fix this. Sometimes smoothing the mesh will an elliptic solver will work. But most of the time there is an underlying problem with your database or grid structure.

 September 1, 2007, 11:26 Re: Negative Volume come back #7 jorge Guest   Posts: n/a I have ansys turbogrid 10 in workbench environment, but this send a error when i want to do a mesh.(negative volume). I read many post about this(These advice move the master control points)but the problem is not solved. Help me.Please. Jorge

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Ganesh FLUENT 13 January 22, 2014 05:11 AlmostSurelyRob OpenFOAM 3 June 24, 2011 13:06 gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11 paean OpenFOAM Running, Solving & CFD 0 November 14, 2008 22:14 Rasmus Gjesing (Gjesing) OpenFOAM Native Meshers: blockMesh 10 April 2, 2007 14:00

All times are GMT -4. The time now is 22:11.