# mean velocity through area

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 February 6, 2014, 10:31 mean velocity through area #1 New Member   Deutschland Join Date: Dec 2013 Posts: 4 Rep Power: 3 Hey guys, is there any possibility to calculate a mean velocity through an area (not a plane), see figure. I have an solution, but this is very very uncomfortable. I export a data file with the velocity values in normal direction to that plane. I have to import this file in Matlab and over an script file i can filter the values outside my area. with the velocity values of the area i can calculate my mean velocity. is there any possibility to draw a polyline on my plane normal to the flow direction that describes my area A in CFX? http://www.directupload.net/file/d/3...n5hf9x_png.htm thank you guys

 February 6, 2014, 10:59 #2 Member   Kevin Hoopes Join Date: Oct 2010 Posts: 40 Rep Power: 7 I would try a user surface in CFD-Post. You could use your matlab script to generate a csv file in the right format that you could then use in CFD-Post. This would create a surface just like any other surface in CFD post that you could use all the functions on. It seems straight forward from the help, the only trouble would be getting the connectivity information, but matlab has some triangulation functions that can help you there.

 February 6, 2014, 11:07 #3 Member   Join Date: Nov 2011 Location: Germany Posts: 40 Rep Power: 5 hi, did u test the usage of user surface for ur problem ? in CFD-Post guide chapter 10.1.11.1 is the area of interest always on the same position ? ### edit ### sorry for the repetition ... i did not update the site and saw the post of khoopes after i posted reply ... and finally i found no way to delete the post

 February 6, 2014, 17:56 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,954 Rep Power: 85 Can't you calculate the mass flow rate over any arbitrary surface? There is built in calculator in CFX-Post to get that. And if you know your density you can get velocity from that.

 February 6, 2014, 18:10 #5 Senior Member   Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 498 Rep Power: 11 Just thinking off the top of my head, and I assume you have the area in your model and it is not aligned with the coord system or is of odd shape/alignment: 1) In CFX post you can create an expressions: Normal X*Velocity u Normal Y*Velocity v Normal Z*Velocity w 2) Create a vector variable with components of each of the above expressions. 3) Calculate area average of the vector magnitude If your area is aligned with the coord system, then there is no need to create the above, as I hope you know.

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