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

buoyancy source term in k-e model

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 20, 2008, 11:25
Default buoyancy source term in k-e model
  #1
Catherine Meissner
Guest
 
Posts: n/a
Hello, I try to activate the buoyancy source term in k-e model. But I am not sure how to do it correctly. I would be glad if someone could help!

I solve the temperature equation (TEM1) and use constant density so that the model should use the boussinesq approximation. Then I have to set 5 parameters according to the PHOENICS description BUOYA=0.0;BUOYB=0.0;BUOYC=-9.81;BUOYD = -BETA ;BUOYE = TEM1,ref The formular of the buoyancy term is given as Gb = ENUT * BETA * gi * {TEM1,i}/PRT(TEM1) everything is clear except the last parameter. Why should I give a constant temperature here? In my opinion BUOYE determines TEM1,i and this temperature is not constant!!! Can anybody tell my what BUOYE is? Thanks in advance,

Catherine

  Reply With Quote

Old   June 24, 2008, 04:25
Default Re: buoyancy source term in k-e model
  #2
Jalil Ouazzani
Guest
 
Posts: n/a
When using the boussinesq, you have first the classical source term in the momentum equation which is simply BuoYC*buoyd*(Tem1,i - buoye) (the buoye is a fixed reference temperature around which Taylor expansion of density has been made). Then you have the possibility of activating the effect of buoyancy in the k-e equations which use the term Gb (in this term there is no use of Buoye).
  Reply With Quote

Old   June 24, 2008, 04:34
Default Re: buoyancy source term in k-e model
  #3
Catherine Meissner
Guest
 
Posts: n/a
Hi Jalil, that makes thing understandable. This means if I define buoye then i get automatically a source term in the momentum equation? In my case the reference temperature (buoye) should vary with height. But I am not able to set this

  Reply With Quote

Old   June 26, 2008, 06:32
Default Re: buoyancy source term in k-e model
  #4
Jalil Ouazzani
Guest
 
Posts: n/a
Hello Catherine, I don't see the need to vary even in height the Tref but in case this is necessary, you can use your own source using either ground coding or inform (and in this case you will be able to vary all parmeters in your source term). It is quite easy to implement it. Jalil
  Reply With Quote

Old   June 26, 2008, 07:33
Default Re: buoyancy source term in k-e model
  #5
Catherine Meissner
Guest
 
Posts: n/a
Hi Jalil, it would be good to have tref varying with height if you consider the atmosphere. Tref is then the (potential) temperature in each atmospheric level. If you lift a parcel then you get different buoyancy effects in different heights. But in this case also BUOYD should be variable which is not the case. One way arround is indeed the inform for tref and to replace the whole buoyancy term in the momentum equation by this. But for BUOYD I am not able to give a Inform replacement. Catherine

  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
Source Term used in Eulerian Model(Two phase) Padian FLUENT 1 May 19, 2008 03:47
source term of buoyancy forces wanghong FLUENT 0 December 22, 2004 07:33
How to linearize the source term of the EBU model JadeMa Main CFD Forum 0 December 12, 2004 23:37
Problem: buoyancy source term for KE-EP model Andrey V.Ivanov Phoenics 0 May 23, 2003 03:50
buoyancy term discretisation sundar Main CFD Forum 1 June 7, 2000 07:54


All times are GMT -4. The time now is 10:53.