# Surface integral on only part of a surface?

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 August 10, 2015, 06:08 Surface integral on only part of a surface? #1 New Member   Nate Join Date: May 2015 Posts: 2 Rep Power: 0 I'm trying to find an area weighted average (pressure and velocity) at the inlet to a duct which is drawing from a freestream environment. Let's say the duct is pointing directly into the oncoming flow. How would I extract the average pressure from just inside the inlet? If I create a "section" plane, it includes the entire external far-field in the integral (meaning the computed area weighted average is pretty much atmospheric conditions, not what I want). Is there perhaps a way to crop the section plane surface so it only shows contours and evaluates integrals on the region that I'm interested in? For clarity: here's results from an aircraft engine, effectively the same problem. How would they determine the average pressure and velocity right at the engine outlet? http://www.cfd.tu-berlin.de/~panek/cfd/jet2.png

 August 10, 2015, 17:42 #2 Senior Member   Join Date: Aug 2014 Location: UK Posts: 213 Rep Power: 13 hi..not cent per cent sure about this but some thoughts.. regarding velocity integral (assuming you're trying to achieve this using CFD Post in Ansys), using CELs and taking area averaged mass flow@inlet and dividing by the known surface area & area weighted average density@ inlet would generate the area weighted average velocity.. that probably could be a way.. about average pressure, again you have CELs for forces@inlet location and the resultant could be divided by known inlet area and area weighted average pressure could be observed.. i am sure there is a much better way to all this, in fact there are most definitely more specific CELs to achieve this but just something i could come up from top of my head..may be an alternative to crosscheck..

 January 23, 2022, 06:39 #3 Member   Join Date: Apr 2020 Posts: 76 Rep Power: 6 I am sure you have resolved this issue, nevertheless for the benefit of other members here is one solution: Create an iso-plane such that you limit the plane dimension to the area you want to investigate (this can be done by setting the coordinate limits), and then using the integral functions.