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

steady/unsteady combustion???

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 13, 2003, 08:32
Default steady/unsteady combustion???
  #1
john
Guest
 
Posts: n/a
Hi all,

Could someone explain to me what steady and unsteady combustion is?

I mean when should the simulation be solved for steay state conditions and when should it be solved for unsteady conditions????

Cheers

John
  Reply With Quote

Old   June 13, 2003, 09:04
Default Re: steady/unsteady combustion???
  #2
prasat
Guest
 
Posts: n/a
I will be happy to help you out.

As in a laminar flow the fluid motion reaches a steady state.Therofre it is enough to simulation the Navier stokes equation steady term(without the unsteady or transient term). But in case of turbulence we nedd to solve the transient term also. You can apply the similar arguments in case of combustion. prasat
  Reply With Quote

Old   June 13, 2003, 09:55
Default Re: steady/unsteady combustion???
  #3
john
Guest
 
Posts: n/a
Hi prasat,

Thank you for your reply.

Does that mean, that if I want to simulate a furnace i have to do an unsteady simulation which causes large computation time, or is there an assumption I can use to simulate the furnace combustion with steady state formulation.

cheers,

John.
  Reply With Quote

Old   June 13, 2003, 10:40
Default Re: steady/unsteady combustion???
  #4
prasat
Guest
 
Posts: n/a
What type flow is it turbulent or laminar one. I guess that it will be turbulent only. so that means for simulation you have to take the unsteady term also. prasat
  Reply With Quote

Old   June 13, 2003, 11:32
Default Re: steady/unsteady combustion???
  #5
john
Guest
 
Posts: n/a
I don't know if you use fluent but in their turbulent combustion tutorial the solver is steady state.

If the flow is turbulent shouldn't the solver be unsteady?

This is the information I really want because if i know why they were able to solve in steady state maybe I too can, saving me a lot of time.
  Reply With Quote

Old   June 13, 2003, 12:18
Default Re: steady/unsteady combustion???
  #6
gorka
Guest
 
Posts: n/a
Hi,

If you use RANS (Reynolds Averaged Navier Stokes) approach for modelling turbulence it's not true that you must perform unsteady simulation. In fact, you should solve the unsteady problem only when the unsteadiness is caused by flow features (vortex sheding, time varying BC etc.)

Gorka
  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
hydrocarbon gases + Boron particle combustion nileshjrane OpenFOAM 1 December 13, 2010 07:20
Modelling Combustion in Porous Zone tanjinjack FLUENT 0 November 19, 2010 12:23
Hydrogen Air combustion in a combustion chamber popi CFX 7 July 11, 2007 18:40
Need Similar Combustion Tutorial as my model Arnab CD-adapco 0 May 24, 2005 18:23
steady/unsteady combustion??? John FLUENT 1 June 15, 2003 07:25


All times are GMT -4. The time now is 12:23.