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

request

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

Reply
 
LinkBack Thread Tools Display Modes
Old   May 27, 2009, 10:18
Default request
  #1
New Member
 
rohollah
Join Date: May 2009
Posts: 2
Rep Power: 0
sadeghiroholah is on a distinguished road
Dear Colleague

With greetings, we are writing this letter of request as we inquire help in the following simulation which we have encountered in our research about solvent extraction settler.
A 3-D simulation of industrial gravity settler with 11m11m0.87m dimensions has been carried out. k-ε model for turbulence and MUSIG model for droplet size distributions were considered. For MUSIG model minimum size of droplet was 100m and maximum size was 2000m. Experimental data for droplet size distribution were used for inlet by a mean diameter of 180m. In this study, number of size groups were (5, 10, 15) and turbulence coalescence coefficient were (0.5, 0.3, 0.1, 0.01, 0.001). Bouncy coalescence coefficient were (0.5, 0.3, 0.1,0.01,0.001) and break up coefficient were (1, 0.5,0.3) for various simulation runs. In this simulation continuous phase density was 800 12kg/m3' type="#_x0000_t75">, poly dispersed phase density was 1000 12kg/m3' type="#_x0000_t75"> and volume fraction of continuous phase was 0.53. This simulation was carried out with various numbers of tetrahedral elements (300000, 400000, 500000, 600000). Upwind and high resolution schemes were used for various runs in simulations. Fluid time scale was controlled by physical time scaling. At the beginning, time scale was 1 sec. and gradually decreased to 0.1 sec. Mass flow rate for inlet, average static pressure and mass flow rate for outlet as well as free slip wall for free surface were used as boundary conditions.
Generally in all runs the following problems exist:
1- Maximum droplet size is reached after convergence, and there is this droplet size in the whole of calculation domain and phase separation is not normal.
2- Computation time is long (2-3 days) and convergence rate is slow

Your consideration is highly appreciated. I look forward to receive your positive response.
sadeghiroholah is offline   Reply With Quote

Old   May 27, 2009, 10:30
Default
  #2
New Member
 
rohollah
Join Date: May 2009
Posts: 2
Rep Power: 0
sadeghiroholah is on a distinguished road
Quote:
Originally Posted by sadeghiroholah View Post
Dear Colleague

With greetings, we are writing this letter of request as we inquire help in the following simulation which we have encountered in our research about solvent extraction settler.
A 3-D simulation of industrial gravity settler with 11m11m0.87m dimensions has been carried out. k-ε model for turbulence and MUSIG model for droplet size distributions were considered. For MUSIG model minimum size of droplet was 100m and maximum size was 2000m. Experimental data for droplet size distribution were used for inlet by a mean diameter of 180m. In this study, number of size groups were (5, 10, 15) and turbulence coalescence coefficient were (0.5, 0.3, 0.1, 0.01, 0.001). Bouncy coalescence coefficient were (0.5, 0.3, 0.1,0.01,0.001) and break up coefficient were (1, 0.5,0.3) for various simulation runs. In this simulation continuous phase density was 800 12kg/m3' type="#_x0000_t75">, poly dispersed phase density was 1000 12kg/m3' type="#_x0000_t75"> and volume fraction of continuous phase was 0.53. This simulation was carried out with various numbers of tetrahedral elements (300000, 400000, 500000, 600000). Upwind and high resolution schemes were used for various runs in simulations. Fluid time scale was controlled by physical time scaling. At the beginning, time scale was 1 sec. and gradually decreased to 0.1 sec. Mass flow rate for inlet, average static pressure and mass flow rate for outlet as well as free slip wall for free surface were used as boundary conditions.
Generally in all runs the following problems exist:
1- Maximum droplet size is reached after convergence, and there is this droplet size in the whole of calculation domain and phase separation is not normal.
2- Computation time is long (2-3 days) and convergence rate is slow

Your consideration is highly appreciated. I look forward to receive your positive response.
thank you for your attention
sadeghiroholah is offline   Reply With Quote

Old   May 27, 2009, 19:42
Default
  #3
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Hi,

This is quite a complicated simulation and there is no way we can give detailed help on the forum. However, the following general comments apply (I am going to have to write a FAQ on this, I can't count the number of times I have said this....)

1) Have you established you have adequately converged?
2) Have you established your timestep is accurate (ie small) enough?
3) Have you established your mesh is fine enough? The range of meshes you have checked sounds inadequate. Have a read of this for an outline (or even better read Roache's text on CFD accuracy) http://journaltool.asme.org/Template...umAccuracy.pdf
4) With multiphase and MUSIG simulations you have a heap of extra models to validate. Have you done a systematic validation of all the key parameters in these models?

Glenn Horrocks
ghorrocks 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
Installation OF1.5-dev ttdtud OpenFOAM Installation 46 May 5, 2009 02:32
Xwindows crash with paraview save srinath OpenFOAM Paraview & paraFoam 1 October 15, 2008 09:37
Request to provide information Sanjay Jain FLUENT 1 December 31, 2007 06:40
Request for Book online is equivalent to piracy Noname Main CFD Forum 20 July 4, 2005 18:39
Memory request Giovanni CD-adapco 1 September 10, 2001 12:21


All times are GMT -4. The time now is 07:28.