CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Programming & Development

new radial equilibrium pressure BC for turbomachinery

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 3, 2013, 12:43
Default new radial equilibrium pressure BC for turbomachinery
  #1
Senior Member
 
Join Date: Mar 2010
Location: Cape Town, SA
Posts: 153
Rep Power: 8
Jonathan is on a distinguished road
Hi everyone,

this is my first attempt at a new BC for OF.

what i am trying to implement is the 'standard' radial equilibrium pressure BC which is used in many turbomachinery simulations. i.e., where the pressure at the outlet is governed according to:

\frac{\partial{p}}{\partial{r}} = \frac{V_{\theta}^2}{r}

I have a little experience with groovyBC, and have used it to set up an inlet velocity profile using lookup_tables, but now need to decide how to build the outlet BC. So basically, my questions are:

1) which would be easier - building the BC using groovyBC, or coding up a 'proper' new BC in c++ and linking to that
2) any hints as to how to go about this in either case - ie if coding one up, which BC existing BC to start with etc

how difficult do you expect this would be to implement in general (my c++ is coming along, but i am no expert as yet) and i am under a little bit of pressure to get it done

many thanks in advance
cheers
jon
Jonathan is offline   Reply With Quote

Old   April 4, 2013, 04:52
Default
  #2
Senior Member
 
Join Date: Mar 2010
Location: Cape Town, SA
Posts: 153
Rep Power: 8
Jonathan is on a distinguished road
hi guys !

any ideas? comments??

many thanks!
Jonathan
Jonathan is offline   Reply With Quote

Old   April 4, 2013, 13:09
Default
  #3
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 8
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
I have an old piece of code which was written in FOAM-1.5-dev.
The idea is quite simple:
1) construct a regular grid of points in cylindrical coordinates that covers the entire patch.
2) map velocity field on the regular grid
3) construct pressure field on the regular grid based on radial derivatives and a reference pressure at the hub
4) map back regular grid pressure on the patch

Hope this will be a good starting point for you, please let me know if you find some difficulties and do not hesitate to share the code once imported in current versions of OpenFOAM.
Attached Files
File Type: zip RadialEquilibrium.zip (11.6 KB, 24 views)
__________________
Cosimo Bianchini

Energy Engineering Department "S. Stecco"
University of Florence
Via di S.Marta, 3
50139 Florence - ITALY
Tel: +39 055 4796575
Fax: +39 055 4796342
Mob: +39 320 9460153
e-mail: cosimo.bianchini@htc.de.unifi.it
URL: www.htc.de.unifi.it
cosimobianchini is offline   Reply With Quote

Old   April 7, 2013, 17:08
Default
  #4
Senior Member
 
Join Date: Mar 2010
Location: Cape Town, SA
Posts: 153
Rep Power: 8
Jonathan is on a distinguished road
hi Cosimo,

thanks very much for your help and the piece of code. i will try to give it a go and see how i go.

i have been playing around with some code which lets the pressures over the patch fluctuate but constrains the integral of the pressure over the patch to a mean value, so the radial pressure gradients should come out in the solution, but will give your code a shot as well as it may give better results ...

i'll let you know how it goes!

many thanks
kind regards
jonathan
Jonathan is offline   Reply With Quote

Old   August 29, 2013, 11:40
Default
  #5
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 8
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
Did you get any good solution for the radial equilibrium BC?
__________________
Cosimo Bianchini

Energy Engineering Department "S. Stecco"
University of Florence
Via di S.Marta, 3
50139 Florence - ITALY
Tel: +39 055 4796575
Fax: +39 055 4796342
Mob: +39 320 9460153
e-mail: cosimo.bianchini@htc.de.unifi.it
URL: www.htc.de.unifi.it
cosimobianchini is offline   Reply With Quote

Old   August 30, 2013, 06:41
Default
  #6
Senior Member
 
Join Date: Mar 2010
Location: Cape Town, SA
Posts: 153
Rep Power: 8
Jonathan is on a distinguished road
hi Cosimo,

thanks for the post! the short answer was no - your c++ was a little over my head, and so i have been using a fixedMeanValue BC, and letting the flow solution figure hammer out the radial equilibrium, rather than enforcing it.

my results are comparable to those i get in Fluent, with the radialEquilibrium BC.

however, i have done quite a lot of c++ work in the last months, and depending on whether my supervisor wants me to follow that route, i might have to go back to it, in which case, your code will be my starting template.

best regards
jonathan
Jonathan is offline   Reply With Quote

Old   January 2, 2014, 03:31
Default
  #7
New Member
 
Zhiyuan Li
Join Date: Aug 2013
Location: Beijing
Posts: 9
Rep Power: 4
babala is on a distinguished road
Hi Cosimo,
I am trying to compile the code you have shared in Openfoam 2.2.1.But the Openfoam don't have a file named regularGridPolyPatch.H.
(regularGridFvPatch / #include "regularGridPolyPatch.H")
I even don't find regularGridPolyPatch.H in Openfoam 1.5.
Have you compile the BC in Openfoam 1.5 or other new versions? Do you meet this problem?

best regards

Zhiyuan
babala is offline   Reply With Quote

Old   January 6, 2014, 06:05
Default
  #8
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 8
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
The code for regularGridPolyPatch is part of the development I made for this radial equilibrium BC, you can find it in RadialEquilibrium.zip .
Hope you suceed in compiling the code and provide some feedback.
Regards,
Cosimo
__________________
Cosimo Bianchini

Energy Engineering Department "S. Stecco"
University of Florence
Via di S.Marta, 3
50139 Florence - ITALY
Tel: +39 055 4796575
Fax: +39 055 4796342
Mob: +39 320 9460153
e-mail: cosimo.bianchini@htc.de.unifi.it
URL: www.htc.de.unifi.it
cosimobianchini is offline   Reply With Quote

Old   January 6, 2014, 22:01
Default
  #9
New Member
 
Zhiyuan Li
Join Date: Aug 2013
Location: Beijing
Posts: 9
Rep Power: 4
babala is on a distinguished road
Hi Cosimo,
Thank you for your reply.Unfortunately, I can't find the code for regularGridPolyPatch in your development. There is only a head file named as regularGridFvPatch.H. Maybe you forget to compress the file into RadialEquilibrium.zip.

best regards
Zhiyuan
babala 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
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
Fluent natural ventilation pressure boundary condition pierresandre FLUENT 24 November 8, 2011 15:32
Setting Pressure outlet boundary for simulation of Radial impeller Mukund Pondkule Main CFD Forum 1 April 5, 2011 09:24
UDF to define or adjust pressure??? engahmed FLUENT 0 July 6, 2010 17:19
use of radial equilibrium press. in 2 phase flow James Willie FLUENT 0 May 2, 2005 11:26


All times are GMT -4. The time now is 20:42.