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

Cyclic Symmetry - transient- axial turbine case.

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 13, 2013, 05:17
Default Cyclic Symmetry - transient- axial turbine case.
  #1
New Member
 
Gowrav Shenoy
Join Date: Feb 2013
Posts: 20
Rep Power: 4
Gowrav is on a distinguished road
Hi Everyone..
As a part of masters project, am doing flow analysis of axial micro turbine to evaluate pressure on blades.. my previous simulations resulted into singularity error while transferring result to FSI analysis.. i ve refined the mesh to fix this, which increased the mesh size now nearly 7 million elements. Which will occupy my computational resources and will eat lots of time than previous.
So i ve bn suggested to run the same with cyclic symmetry..
i am using 3d sliding mesh in fluent.. whether symmetry will work with that. ?
I am having 8 blades -symmetric- i have taken 1 full and 2 halves of adjacent blades for symmetric analysis. Is this correct way fr symmetry..
i am getting very low mass flow rate with same pressure in -pressure out bcs,, also i have not corrected pressures for symmetric analysis..
Kindly correct me where its going wrong. and share opinions to fix this.
Thanks in advance
Gowrav
Gowrav is offline   Reply With Quote

Old   April 13, 2013, 08:15
Default
  #2
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,914
Blog Entries: 6
Rep Power: 38
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
You are talking about periodic boundary condition to reduce blade count hence less no of nodes.

The number of blades for periodic case depends upon ratio of number of blades upstream and downstream. The main goal to have equal pitch on both sides. For example if you have 6 blades upstream and 12 downstream then you will select one blade from upstream blade row and two blades from downstream blade row.

It is possible that you don't get integral number for the ratio of blades from upstream and downstream row. In this case you have to approximate analysis. For example if you have 22 blades upstream and 41 downstream. In this case ratio is 1.86 and it is not possible to have exact no of blades upstream and downstream. Now you need to approximate. Assume you have 22 blades upstream (real) and 44 blades downstream (approximation)

Quote:
i am getting very low mass flow rate with same pressure in -pressure out bcs,, also i have not corrected pressures for symmetric analysis..
Kindly correct me where its going wrong. and share opinions to fix this.
Multiply mass flow rate by total no of blades (blade passages).

Last edited by Far; April 13, 2013 at 08:39. Reason: Adding something
Far 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
simulation Axial flow turbine using CFX dia aisa CFX 3 May 2, 2008 02:45
Global residuals in transient case mx Main CFD Forum 0 August 6, 2007 07:12
Free surface boudary conditions with SOLA-VOF Fan Main CFD Forum 10 September 9, 2006 12:24
GAMM Francis Turbine Case 8 mukkarum Main CFD Forum 0 July 12, 2003 00:30
Fluidisation transient case Vikas Kumar Main CFD Forum 0 April 24, 2003 03:29


All times are GMT -4. The time now is 14:09.