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

Standard initialization with an expected pressure

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 26, 2013, 17:08
Default Standard initialization with an expected pressure
  #1
New Member
 
Join Date: Mar 2013
Posts: 1
Rep Power: 0
APUT is on a distinguished road
I'm using the SIMPLE solver to find the area-weighted average of static pressure at the inlet of a laminar, steady-state, incompressible flow within a porous material. My boundary conditions are a velocity inlet and a pressure outlet.

From theory, I know what the pressure inlet should roughly be. However, if I try to initialize the problem with this theoretical pressure inlet, the solver gives me worse convergence and the pressure starts diverging at a high rate (though I did not keep running the simulation for long due to this initial observation).

If I standard initialize using the default values at the velocity inlet, the convergence trend is much more re-assuring and the values do not tend toward divergence. Also, hybrid initialization with default settings also gives me worse convergence.

Is there a better way to specify an expected solution at the initialization stage to speed up the convergence process? What are the exact steps?


Thank you!
APUT is offline   Reply With Quote

Old   March 27, 2013, 11:30
Default
  #2
Senior Member
 
OJ
Join Date: Apr 2012
Location: United Kindom
Posts: 475
Rep Power: 10
oj.bulmer will become famous soon enough
Often it takes a bit of experimentation to deduce the right approach for initialization strategy. As long as you get a converged solution, it doesn't exactly matter how you initialized it, but right initialization yields faster convergence.

In your case, in addition to standard initialization, you can also "patch" the inlet pressure to your inlet boundary.

Also, have a look at FMG initialization, wherein your geometry is meshed with virtually with coarse mesh and the Euler inviscid equations are solved. Be aware that FMG doesn't initialize turbulence quantities (k, \epsilon etc). So it is important to specify appropriate quantities at boundaries. The solution is then applied to successive meshes until the final fine mesh. Process takes few minutes but provides a good initialization.

Another way is to start having a coarse mesh solution as initial solution. This is possible in CFX, but not sure about FLUENT.

OJ
oj.bulmer is offline   Reply With Quote

Old   September 4, 2013, 02:18
Default
  #3
New Member
 
Jalay Shukla
Join Date: Aug 2013
Posts: 11
Rep Power: 3
jalay is on a distinguished road
i get smooth curve while going with hybrid initialization when i go for air in with standard initialization it continuously converge diverse ..
why this would be happening?
jalay is offline   Reply With Quote

Reply

Tags
convergence, hybrid initialization, initialization, standard initialization

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
Difference between pressure, absolute pressure and Total Pressure shaswat CFX 1 September 6, 2012 07:12
FSI: Pressure and Normal Force don't match with expected values Geraud CFX 6 August 21, 2012 16:34
Pressure Outlet Guage pressure Mohsin FLUENT 34 January 12, 2012 06:45
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 03:15
need a standard velocity and pressure distribution tommewang Main CFD Forum 1 August 9, 2003 11:41


All times are GMT -4. The time now is 18:04.