# UDF to Access Wall Normal Concentration Gradient

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

 May 6, 2009, 14:10 UDF to Access Wall Normal Concentration Gradient #1 Member   Daniel Tanner Join Date: Apr 2009 Posts: 54 Rep Power: 10 Sponsored Links I want to calculate and store the wall normal concentration gradient at my wall boundary. I have compiled my udf and it works correctly. However, I have some questions, below is a section of my udf for reference. ******************************************* /* Get Connectivity Data */ BOUNDARY_FACE_GEOMETRY(f,t,A,ds,es,A_by_es,dr0); /* Calculate Wall Normal Inter-centroid distance (dn)*/ dn = NV_DOT(A, (es*ds))/NV_MAG(A); /* Calculate Wall Normal Concentration Gradient*/ C_UDMI(c0, t0, 1) = ((F_YI(f,j,0)*F_R(f,j))-(C_YI(c0, t0,0)*C_R(c0,t0)))/dn; ******************************************* 1) I am unsure (though the difference is probably quite small) if it is better to use the inter-centroid distance in the wall normal direction ("dn" - as defined above) or "ds" as returned by the BOUNDARY_FACE_GEOMETRY macro to calculate the wall normal gradient (i.e., dpsi/dn or dpsi/ds). 2) To establish the concentration gradient is mass_fraction*density the correct term to use: F_YI(f,j,0)*F_R(f,j) - C_YI(c0, t0,0)*C_R(c0,t0) 3) I store these values at the centres of the cells (using C_UDMI) adjacent to the wall. Will this cause an error when contours of concentration at the wall are displayed in fluent, i.e., this would require the interpolation of the cell-centred values onto the wall and hence they would be different. Thanks...

 May 18, 2012, 10:35 #2 New Member   moon Join Date: Feb 2012 Posts: 24 Rep Power: 7 more informations please , i'm verry interrested thx

 May 21, 2012, 04:23 #3 Member   Daniel Tanner Join Date: Apr 2009 Posts: 54 Rep Power: 10 What questions do you have? If you have a UDF you are trying to create post it and I'll have a look.

 May 21, 2012, 11:14 #4 New Member   moon Join Date: Feb 2012 Posts: 24 Rep Power: 7 Yes Mr daniel , may you send me this udf please . thank you a lot

 February 18, 2015, 15:35 Help with the same problem #5 New Member   Nandish Join Date: Sep 2012 Posts: 5 Rep Power: 6 Could you please give more detail on your UDF.

 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 tom FLUENT 2 September 7, 2016 03:48 gawainhe FLUENT 1 December 24, 2008 20:00 D Krijgsman FLUENT 0 August 21, 2008 00:44 cxzhao FLUENT 0 April 27, 2005 21:20 Bastian FLUENT 0 July 21, 2004 04:52