# Integration over portion of a surface

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 July 15, 2010, 12:01 Integration over portion of a surface #1 New Member   Joseph Tipton Join Date: Jun 2010 Posts: 14 Rep Power: 9 I would like to know if there is an easy way to calculate a function on a portion of a surface in CFX Post. For example, what would be the easiest way to integrate the wall shear stress in the fully developed region of a duct flow? So far, the only work around I can see is to run the simulation, observe the flow development length, modify the geometry to split the duct into two regions, and then rerun the simulation.

 July 15, 2010, 19:05 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,625 Rep Power: 105 Use a contour line to define your fully developed region on the surface, make a user surface defined by the contour, do the integration on the user surface.

 July 16, 2010, 09:08 #3 New Member   Joseph Tipton Join Date: Jun 2010 Posts: 14 Rep Power: 9 Thank you for the reply! I let my axial dimension be the contour plot variable, made several user surfaces for each level of the contour in the fully developed region, and then combined them in a surface group. I'm assuming that's the easiest method.

 July 18, 2010, 06:18 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,625 Rep Power: 105 If it works then it is all good.

 February 4, 2011, 18:43 #5 New Member   Join Date: Dec 2010 Posts: 26 Rep Power: 8 Is there way to apply this method to volumes?

 February 5, 2011, 05:53 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,625 Rep Power: 105 Apply what method? If you mean calculate functions on sub-volumes, then yes. Define a volume as a sub-region of the full domain and calculate the CEL expression on the defined volume.

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