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

Bad pressure distribution in pump

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 1, 2013, 05:41
Unhappy Bad pressure distribution in pump
  #1
New Member
 
Marek
Join Date: Feb 2013
Posts: 6
Rep Power: 4
oringo is on a distinguished road
Hello everyone,
I use CFD to calculate radial force in cetrifugal pump. I made geometry of old "test stand" used to calculate radial force. I have data from scientific research (capacity, static pressure in inlet and outlet). I want to confront them with CFD results. My problem is I get bad results, which are not connected with scientific data, eg. force decreases with capacity lower than in BEP (0,5*Qn), so it's not physical. It looks that I get bad pressure distribution.
see the pictures of model:
http://www.picshot.pl/public/view/full/301733
http://www.picshot.pl/pfiles/301734/volute.jpg
Blue colour are interfaces, red are rotating walls in stationary domain, purple - LE and TE. Volute geometry is very simple-similar to rectangle.
When I print forces in Fluent when residuals are about 2e-3 I get eg 200N, but when my residuals are about 1e-3 the force can be twice lower. It looks that pressure distribution is not stable(?), but residuals are quite stable. Usually I can't get converge lower than 1,5e-3 for second order upwind. I used k-e, k-e realizable, k-w SST but it not helped. In inlet I use BC mass flow inlet and in outlet outflow. I tried also use pressure BC in outlet and inlet, but I didn't get capacity which I should get.
I've meshed impeller domain in TurboGrid. Minimum orthogonal quality is 0,15. I made volute grid in ICEM (hexa) and it has min quality 0,45. So mesh is acceptable. Hub and inlet_and_shroud domain were made in Ansys Meshing. I tried 2 grids, bigger has about 4,5 mln nodes and it not helped.
I don't know what am I supposed to do?
Are my interfaces in bad position (see the pictures)? Should I place them in other place or way? Impeller diameter is 268 trailing edge diameter is 264 and tongue diameter in volute is about 290.
Why I get pressure distribution completety not connected with scientific data.
I'd be very grateful for help because I don't know what should I do....

BW,
Marek

Last edited by oringo; March 1, 2013 at 09:13.
oringo is offline   Reply With Quote

Old   March 1, 2013, 16:42
Default
  #2
New Member
 
Join Date: Nov 2012
Posts: 3
Rep Power: 4
mix_mentzos is on a distinguished road
I think that concerning the BC it is better for inlet Velocity or mass (the same) and for outer Pressure.
mix_mentzos is offline   Reply With Quote

Old   March 2, 2013, 11:38
Default
  #3
New Member
 
Marek
Join Date: Feb 2013
Posts: 6
Rep Power: 4
oringo is on a distinguished road
Thanks for advice. I've moved interface of impeller farther into volute and now it looks better even with low quality mesh
oringo 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
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 02:15
pressure distribution and friction factor Tajul FLUENT 2 March 16, 2006 05:51
Problems of Duns Codes! Martin J Main CFD Forum 8 August 14, 2003 23:19
pressure gradient term in low speed flow Atit Koonsrisuk Main CFD Forum 2 January 10, 2002 11:52
Effects of gravity in pipe - pressure distribution Anthony Wachs FLUENT 2 July 25, 2001 07:07


All times are GMT -4. The time now is 19:49.