# Reynolds and Nusselt number in DoE

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

 June 26, 2013, 14:27 Reynolds and Nusselt number in DoE #1 New Member   Costin Ruja Join Date: Mar 2010 Location: Bucharest Posts: 22 Rep Power: 9 Good evening, After solving my DoE simulation (DX and CFX in workbench) i realised i also have to define as output parametres the Reynolds and Nusselt number.How can i do that in CFX-Post? I know i can see them in the solver log but i need them as output parameters in DX. Regards, Costin

 June 26, 2013, 18:38 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,065 Rep Power: 109 You will need to manually define variables for Re and Nu. The reported Re and Nu numbers in the solver should be taken as guides only - they are not calculated based on length, fluid property and temperature scales which are much use for most engineers.

 June 26, 2013, 22:33 #3 New Member   Costin Ruja Join Date: Mar 2010 Location: Bucharest Posts: 22 Rep Power: 9 Thanks ! I'll have to check it out first thing when i get to the office.

 June 27, 2013, 06:14 #4 Senior Member     Mr CFD Join Date: Jun 2012 Location: Britain Posts: 344 Rep Power: 8 Just a heads up. Incropera and DeWitt suggest the characteristic dimension in the Nusselt number should be taken as: Surface area divided by surface perimeter It doesn't explain why. However I like to think it's because: 1. The Nusselt number you will be using is likely to be an average Nusselt number based on the average heat transfer coefficient of a surface. And the way you get to the average heat transfer coefficient from a local one is by integrating the local heat transfer coefficient over the entire area. So taking the characteristic length as the surface area divided by surface perimeter makes sense (to me that is!). 2. Taking the characteristic length as the surface area divided by surface perimeter adds consistency. It means you don't have to worry about which length to take as the characteristic length if you had say a triangle, square, circle or any other shape as your heat transfer surface. I hope that helps.

 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 vinaykumar Main CFD Forum 5 June 21, 2011 08:39 y2k_o__o FLUENT 6 March 3, 2011 08:37 panos_metal FLUENT 0 January 7, 2011 07:37 Sammie FLUENT 0 October 24, 2007 07:10 Manuel FLUENT 0 November 6, 2006 08:23

All times are GMT -4. The time now is 16:25.