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

Different flow patterns in CFX and Fluent

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 2, 2012, 15:24
Question Different flow patterns in CFX and Fluent
  #1
New Member
 
AMSharma
Join Date: Apr 2012
Posts: 12
Rep Power: 14
avi@lpsc is on a distinguished road
Hi Guys
I have some issues interpreting my results from two similar analysis, one in Fluent and other in CFX. Its a general compressible flow case of CD nozzle with supersonic diffuser attached to the exit of nozzle.
I will highlight the settings here:
Fluent: 2D axi case with density modeled as Ideal gas, Density based solver, 4 species properties given as polynomials, Pressure Inlet at Nozzle 33.5bar- Mass flow rate boundary imposed :8.65kg.s-Subsonic, Pressure outlet at Diffuser section attached to Nozzle exit 180millibar. Case Initialized with Pressure Inlet with lower value of axial velocity, Boundary layer in nozzle with Y plus approximately 10.Turbulence:SST K-omega, For this condition a converged solution shows the Nozzle mach Contour as - Full flow i.e no separation inside nozzle,No shock inside. (Maximum Mach Nbr: 8),

2. A similar case was ran in CFX with similar settings, Density: Ideal gas, Solver details : Default settings,Species Properties similar to Fluent,SST K-omega, Mass flow rate bc. A converged solution shows separated flow in nozzle and no full flow similar to Fluent results.

Grid Independent and Turbulence model study has already been conducted and all resulted in same flow pattern in Fluent i.e Nozzle full flow.

Similar GI study has also been done in CFX for with adapted grid in nozzle which shows separated flow with in nozzle.

So In a sense I am getting different results from two with similar simulations.I only uses density based solver of fluent for compressible flow problems. whether CFX solver is capable for this type of high speed flows. If it is,then what could be the possible reason for this differing results.

shall be thankful.
avi@lpsc is offline   Reply With Quote

Old   April 4, 2012, 08:44
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Are you sure the correct answer is no separation?
ghorrocks is offline   Reply With Quote

Old   April 5, 2012, 03:41
Default Differing Results Fluent CFX /Fluent
  #3
New Member
 
AMSharma
Join Date: Apr 2012
Posts: 12
Rep Power: 14
avi@lpsc is on a distinguished road
Thanks for reply.

1D cal. shows flow will separate inside the nozzle, but point here is that even I performed both simulations in 3D, same grid, property settings same. I am getting full flow in Fluent and separated flow in CFX. What would be the possible reason for it , whether PBCS solvers are able to handle shock formation and separation better than density based solver of Fluent. Major facility change will be done based on this analysis, so I need a solution for this different results.

Shall be thankfull
avi@lpsc is offline   Reply With Quote

Old   April 6, 2012, 03:37
Default
  #4
New Member
 
AMSharma
Join Date: Apr 2012
Posts: 12
Rep Power: 14
avi@lpsc is on a distinguished road
what for? ur also looking for answers to my query..
avi@lpsc is offline   Reply With Quote

Old   April 15, 2012, 19:05
Default
  #5
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
No, there is no general rule that PBCS solvers are better or worse at these type of flows.
ghorrocks is offline   Reply With Quote

Old   April 16, 2012, 12:45
Default
  #6
New Member
 
AMSharma
Join Date: Apr 2012
Posts: 12
Rep Power: 14
avi@lpsc is on a distinguished road
Thanks for reply..

Both CFX and Fluent DBS,PBCS are awesome. I have identified the problem.
avi@lpsc is offline   Reply With Quote

Old   April 17, 2012, 02:22
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
What was the problem? What did you do to fix it?
ghorrocks is offline   Reply With Quote

Reply


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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Multiphase flow modeling: CFX or FLUENT? Paul Main CFD Forum 8 January 24, 2012 10:25
CFX or Fluent for Turbo machinery ? Far FLUENT 3 May 27, 2011 04:02
Which software is better for channel flow with sedimentation effects. CFX or Fluent? mechovator FLUENT 3 August 30, 2009 10:41
Which software is better for channel flow with sedimentation effects. CFX or Fluent? mechovator CFX 1 August 30, 2009 08:21
multiphase flow, CFX or FLUENT? luis Main CFD Forum 6 October 5, 2006 14:24


All times are GMT -4. The time now is 13:12.