I was reading some posts on negative volumes. I am experiencing this phenomenon while trying to create a grid for Blassius solution (laminar BL velocity profile) and axisymmetric cone at 0 deg angle of attack. I am not able to post pictures of my grid, but can send it via e-mail to anyone who can help me. I use GRIDGEN to create the mesh, and when imported into Fluent, the grid check fails. I believe this has something to do with skewness (0.7 and above)? Please advise on how to correct the grid so it passes Fluent's grid check. Also, I am having numerous problems with Fluent's Boundary Conditions. There is no condition for "free-stream" or "frozen." Often, the code gives me wierd patterns near a boundary! I also get negative pressures and reversed flow from time to time!

ANY HELP WOULD BE GREATLY APPRECIATED...

Thanks

If you are using axissymmetry then the axis has to lie in X-axis. If it is not then fluent gives negative volumes eventhough the grid is good. To check this change the calculations into 2d instead of axissymmetry and check grid.

I hope I am correct.

I am not using axisymmetric boundary condition for this grid. It is a simple 2-D mesh with unequal grid spacing.

However, I contacted Gridgen technical support and they fixed my problem. The problem was that Gridgen was reading the block (3-D entity) in a left handed co-ordinate system. Fluent only recognizes a right handed co-ordinate system. Therefore I had to re-specify the i,j directions in gridgen before fluent would accept the grid. The command in Gridgen is: Block > Modiify > Respecify "eta" and "zeta."

Hope this helps anyone else who runs into a similar situation!

Hi friends the Gambit mesh that I generated for engine analysis is to do Dynamic meshing using fluent, but unfortunately the mesh is having highly skew elements and also negaine Volume elements how to overcome this? Pls help me in this Regards