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

DNS turbulent initialisation

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 30, 2019, 11:12
Default DNS turbulent initialisation
  #1
Member
 
Nat K
Join Date: Oct 2017
Posts: 68
Rep Power: 8
nskelly is on a distinguished road
Hi,

I was wondering what methods are there to initialize a DNS flow field? I am looking at the flow within a cone and plate rheometer and I am unsure of what ICs or OF utilities are best for adding some sore turbulent intensity or perturbations. Currently, the only methods I have seen are perturbU, but this is restricted to channel flows.

Thanks
nskelly is offline   Reply With Quote

Old   October 1, 2019, 04:15
Default
  #2
Senior Member
 
Andrea
Join Date: Feb 2012
Location: Leeds, UK
Posts: 179
Rep Power: 16
Andrea1984 is on a distinguished road
Hi Nathaniel,

I have obtained an initial isotropic turbulent condition for LES with boxTurb. As the name suggests, the tool only works for box-shaped domains, and there is the additional caveat that the mesh has to have 2^n cells. For non-box shaped domains with a generic number of cells I usually do the following:

-generate a box with 2^n cells which encompasses the domain
-use boxTurb to generate a nice turbulent field within the box
-use mapFields with the cuttingPatches option to map the turbulent field to my actual domain

Hope this helps,
Andrea
Andrea1984 is offline   Reply With Quote

Old   October 4, 2019, 11:16
Default
  #3
Member
 
Nat K
Join Date: Oct 2017
Posts: 68
Rep Power: 8
nskelly is on a distinguished road
Hi Andrea,

Thanks for the reply. I read that using boxTurb is one method for initialising the flow. But I am a bit unsure of how the mapFields part works.

I want to look at the laminar-turbulent transition process. So how can I add the turbulent fluctuations to an existing simulation? The

For example:
If I want to run a simulation at Re = 2000 (where flow is in the transitional flow regime). Where do I put the the boxTurb field data? After some timesteps have solved or as the inital BCs?

Thanks
nskelly is offline   Reply With Quote

Old   October 5, 2019, 05:54
Default
  #4
Senior Member
 
Andrea
Join Date: Feb 2012
Location: Leeds, UK
Posts: 179
Rep Power: 16
Andrea1984 is on a distinguished road
I have never used boxTurb to superimpose turbulent fluctuations to an existing velocity field. The way I would use it is to generate an initial turbulent flow field and then run the simulation and let the "real" turbulence develop.

I am not sure this is the right thing to do in your case though, since you want to investigate transition and boxTurb is going to provide you with a fully turbulent initial flow field.

Andrea
Andrea1984 is offline   Reply With Quote

Reply

Tags
dns, initialise, turbulence

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
Hairpin vortices in turbulent channel flow using DNS Nitin Minocha Main CFD Forum 2 November 21, 2016 17:52
Turbulent or laminar flow yansheng STAR-CCM+ 4 July 1, 2016 17:53
spectrum: LES of a turbulent channel flow finally goes to turbulent liu OpenFOAM Running, Solving & CFD 6 November 1, 2011 01:00
DNS in Turbulent S.O.S. Urgent Hengky FLUENT 11 September 28, 2006 10:07
How to obtain turbulent K.E. from DNS data? Boying Lin Main CFD Forum 5 December 16, 2003 05:40


All times are GMT -4. The time now is 09:53.