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

LES of turbulent flow in annular pipe

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 6, 2016, 09:49
Default LES of turbulent flow in annular pipe
  #1
New Member
 
Francesco Garita
Join Date: Oct 2016
Location: Italy
Posts: 8
Rep Power: 9
fgarita is on a distinguished road
Hi everybody,

I am trying to set up a LES simulation using OpenFOAM 2.4.0 for a turbulent flow in an annular pipe. The solver I am using is pisoFoam and the turbulent model is dynamicSmagorinsky. The (structured) mesh is the one used by Lee et al. 2003, which was suitable for the LES they set up at that time.

My first goal is to reach the statistically-steady state, before doing any statistics. To do so I am monitoring two variables: volumeAverageUx2 and volumeAverageUy2 which means the volume averaged of the square of the velocity components normal to the flow direction (z-direction in my case). They should give an indication of the turbulent kinetic energy, as explained in this tutorial: http://www.ara.bme.hu/~lohasz/LEScou...nel_tut_v1.pdf . I should expect a peak of these variables and then an oscillation around a constant value when the statistically-steady state is reached.

The problem is the following: using the central scheme for the convective term (i.e. Gauss linear) the solution diverges after some time, depending on the initial condition. I also tried to use the MUSCL scheme and the same occurs. Even by fixing the maxCo to a small value such as 0.2, the schemes diverge (because the velocities become too large and the timestep very very small) The only scheme for the convective term which is stable is the upwind scheme. I tried to use the upwind scheme for the transition and then the CDS in the statistically-steady part, but the scheme diverges anyway.

The initial conditions used so far are: laminar parabolic profile unperturbed, laminar parabolic profile with 2 type of perturbations on top of it. I tried to adopt the initial condition used by Eugene De Villiers to my geometry but nothing improves. I also tried to use "perturbU.tgz" for "any ducted flow" that can be downloaded online, but I cannot graphically see any perturbation, despite my average Re_tau=147 is quite a common value.

Any ideas about how to tackle the problem? Do you think it depends on the initial condition, numerical scheme or maybe mesh? In the tutorial mentioned above, the CDS is used and no problems are met.

Thank you very much,
Francesco
fgarita is offline   Reply With Quote

Old   October 7, 2016, 10:10
Default
  #2
New Member
 
Francesco Garita
Join Date: Oct 2016
Location: Italy
Posts: 8
Rep Power: 9
fgarita is on a distinguished road
I found the problem. The crash was due to the OpenFOAM utility "funkySetFields" which changed my velocity BC at the wall from "uniform ( 0 0 0 )" to "zeroGradient".
It is enough to execute funkySetFields and then to change the BC in the 0/U file before running the simulation.
fgarita is offline   Reply With Quote

Reply

Tags
annular flow, les, turbulent flows

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
question regarding LES of pipe flow - pimpleFoam Dan1788 OpenFOAM Running, Solving & CFD 37 December 26, 2017 15:42
Periodic Pipe Flow LES; parabolic profile jrrelx FLUENT 34 August 13, 2015 18:58
LES of a turbulent channel flow stays laminar liu OpenFOAM Running, Solving & CFD 2 May 27, 2010 14:53
Turbulent flow in a cylinder pipe SeRGeiSarov Main CFD Forum 0 March 25, 2010 14:20
fluid flow fundas ram Main CFD Forum 5 June 17, 2000 22:31


All times are GMT -4. The time now is 10:56.