# Strange averaging in directMappedFixedValue BC

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 June 24, 2010, 08:28 Strange averaging in directMappedFixedValue BC #1 Member   Tobias Holzinger Join Date: Mar 2009 Location: Munich, Germany Posts: 46 Rep Power: 9 Dear All, while trying to derive my own BC from the direct mapped BC, i was wondering why there are two different averaging possibilities: Code: ``` if (setAverage_) { Type averagePsi = gSum(this->patch().magSf()*newValues) /gSum(this->patch().magSf()); if (mag(averagePsi)/mag(average_) > 0.5) { newValues *= mag(average_)/mag(averagePsi); } else { newValues += (average_ - averagePsi); } }``` Any Idea about the streching if the average differs to much? Have FUN!

September 7, 2012, 05:10
#2
Senior Member

Florian Krause
Join Date: Mar 2009
Location: Munich
Posts: 103
Rep Power: 9
Quote:
 Originally Posted by woody Dear All, while trying to derive my own BC from the direct mapped BC, i was wondering why there are two different averaging possibilities: Code: ``` if (setAverage_) { Type averagePsi = gSum(this->patch().magSf()*newValues) /gSum(this->patch().magSf()); if (mag(averagePsi)/mag(average_) > 0.5) { newValues *= mag(average_)/mag(averagePsi); } else { newValues += (average_ - averagePsi); } }``` Any Idea about the streching if the average differs to much? Have FUN!
Hi guys,
I am successfully using the mapped BC for LES of turbulent flow through a 90deg bend, with the mapping region located in an (extended) straight inlet section. I switched on averaging of velocity to obtain my desired bulk velocity.

While running the simulation, I assumed that OF always computes the new velocities according to the above else statement, using the difference between the desired average and the current velocities. Then I checked the corresponding code and I'm also a bit confused by the same the if statement, specifically by the condition and the first correction method.

Any ideas?

Thanks,
Florian

Last edited by florian_krause; September 7, 2012 at 05:29.

 Tags averaging, boundary conditions, directmappedfixedvalue

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post huwei CFX 3 February 22, 2015 14:09 tar FLUENT 11 March 22, 2014 11:52 cspectre CFX 2 December 6, 2009 06:30 iko FLUENT 3 July 3, 2008 05:55 Jaap Hoffmann Main CFD Forum 1 August 4, 2003 04:57

All times are GMT -4. The time now is 09:28.

 Contact Us - CFD Online - Top