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

Use homogeneous results as the initial guess for an inhomogeneous simulation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 3, 2014, 06:05
Default Use homogeneous results as the initial guess for an inhomogeneous simulation
  #1
Senior Member
 
RicochetJ's Avatar
 
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 291
Rep Power: 6
RicochetJ is on a distinguished road
Question

Hi, in an Eulerian-Eulerian multiphase simulation, will there be any issues using homogeneous results as the initial guess for an inhomogeneous simulation?

Background

I am performing a transient free surface simulation, where I have two continuous phases separated by a free surface. In the first instance there is nothing complex going on, i.e. no splashing, entrainment etc. So I'm modelling this as completely homogeneous (homogeneous momentum and turbulence). I want this to be my initial guess for the next part of the simulation.

In the next part of the simulation there will be gas entertainment, significant splashing etc. I will need to model the relative slip between the phases (water and vapour) to ensure adequate seperation, so will change to inhomogeneous for this portion of the simulation (I will provide an interfacial drag coefficient as required).

To reduce simulation time my idea is to run homogeneous, up to the point where I need to switch to inhomogeneous.

FYI I am using the mixture model to treat interfacial area density since the free surface model is too primitive in the inhomogeneous case (simply treats the IAD as the gradient of the volume fraction normal to the interface).
RicochetJ is offline   Reply With Quote

Old   December 3, 2014, 17:53
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,941
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
In concept using a homogeneous model as an initial condition for a inhomogeneous model sounds fine. Hopefully it is smart enough to map the variable fields to all phases - but I am not sure of this so you better check it.
ghorrocks is offline   Reply With Quote

Old   December 4, 2014, 06:29
Default
  #3
Senior Member
 
RicochetJ's Avatar
 
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 291
Rep Power: 6
RicochetJ is on a distinguished road
How would one test to see if this is true before I commit to timely simulations?

I'm thinking of doing the free surface bump tutorial in homogeneous, and then using it as the initial guess for the inhomogeneous run.

But since the flow phenemena is the same in both homogeneous and inhomogeneous I'm not sure what to look for to see if there is a difference.
RicochetJ is offline   Reply With Quote

Old   December 4, 2014, 09:10
Default
  #4
Senior Member
 
Join Date: Jun 2009
Posts: 313
Rep Power: 10
Opaque is on a distinguished road
Setup the inhomogeneous case with backup results at the start of the run (see output control or expert parameters sections). You will get a backup file written before it solves the first iteration.

You can post-process such file in CFD-Post and see if the initial condition is what you expected given the initial values file.

Good luck.
Opaque is offline   Reply With Quote

Old   December 4, 2014, 09:57
Default
  #5
Senior Member
 
RicochetJ's Avatar
 
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 291
Rep Power: 6
RicochetJ is on a distinguished road
Good idea! Thanks.

I'll reply with what I have found so people searching the forum can have an answer to this question.

Watch this space.
RicochetJ is offline   Reply With Quote

Old   December 26, 2014, 14:44
Default
  #6
Senior Member
 
RicochetJ's Avatar
 
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 291
Rep Power: 6
RicochetJ is on a distinguished road
Hi,

Just an update: you can use homogeneous results as the initial guess for an inhomogeneous run.

Just ensure the material names are the same in both homogeneous and inhomogeneous so it can assign the variable fields to all phases correctly.
RicochetJ is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
log file imani OpenFOAM Running, Solving & CFD 0 July 24, 2014 02:04
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 06:20
a problem with convergence in buoyantSimpleFoam skuznet OpenFOAM Running, Solving & CFD 5 February 19, 2014 05:30
Why RNGkepsilon model gives floating error shipman OpenFOAM Running, Solving & CFD 3 September 7, 2013 08:00
calculation stops after few time steps sivakumar OpenFOAM Running, Solving & CFD 7 March 17, 2013 07:37


All times are GMT -4. The time now is 20:57.