|August 3, 2009, 03:55||
Periodicity momentum instead of axial momentum
Join Date: Aug 2009
Posts: 1Rep Power: 0
I'm new in the community and I've got a qustion about the use of periodic boundary conditions.
I'm trying to simulate a combustion chamber. Since the chamber is rotationally symetric I use just a piece of 4 degrees of the chamber together with periodic BCs. The mesh has 3-4 cell in the tangantial direction.
I'm solving the problem for steady state. Also the problem neither is influenced by the mesh quality (I have done a mesh study already) nor to a certain location in the fluid domain.
Also, by using symetric BCs the simulation is stable.
I suspect the periodic BCs to make the simulation instable.
The solution starts to get a angular momentum. Beginning from the outlet it propagats along the axis into the combustion chamber.
The solution then starts to get Mach-numbers of the order of 5-10.
If someone had/has the same problems and/or has a good idea for the solution, please let me know.
|August 3, 2009, 18:59||
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,282Rep Power: 88
In the real world, what is used to stop the flow rotating? You should put the devices in the model to stop it rotating. If you know the flow does not rotate then use symmetry boundaries and forget about the problems with periodic boundaries. Alternately you could put a directional source term in to damp the rotational component - but I would only do this after a thorough check of your simulation to see what is creating the rotation in the first place (ie, two wrongs don't make a right).
|Thread||Thread Starter||Forum||Replies||Last Post|
|SIMPLE momentum in cylindrical coordinates||TerraVici||Main CFD Forum||4||April 9, 2012 05:22|
|Pressure jump and momentum source||Tanya||FLUENT||1||June 4, 2009 15:22|
|Momentum Source in an accelerating frame||fakir||CFX||7||December 2, 2006 05:00|
|no enthalpy change across the momentum source||Atit Koonsrisuk||CFX||2||December 19, 2005 03:33|
|Nonstaggered Grids and Momentum Interpolations||S. Wang||Main CFD Forum||3||March 2, 2001 14:44|