# Find location @ Line where a variable has a certain value

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 March 29, 2010, 06:18 Find location @ Line where a variable has a certain value #1 Senior Member   Join Date: Mar 2009 Posts: 138 Rep Power: 8 Hello! I want to calculate the boundary layer thickness on a plate. For this I have created several Lines vertical on the plate an now I want to know the altitude atop the plate where the velocity reaches 99% of Uinf for the first time. Is there any function that can tell me the coordinates of a certain variable on a Line? Thanks in advance

 March 29, 2010, 07:13 #2 Member   Dmitry Volkind Join Date: Jan 2010 Location: Chelyabinsk, Russia Posts: 58 Rep Power: 7 If Uinf is constant and Y is my plane normal and starts with zero at the wall, I would use CEL: MyFunction1 = v - 0.99*Uinf MyFunction2 = step (MyFunction1) Then I would make a plot MyFunction2 = f(Y) Axis segment where MyFunction2 = 0.5 is my boundary layer thickness +-tolerance It's the first thing that comes to my narrow mind, still I think there must be a better way.

 March 29, 2010, 08:20 #3 Senior Member   Join Date: Mar 2009 Posts: 138 Rep Power: 8 Hey Dvolkind, Thanks for your reply! I have tried your solution but its still not working. I get the Warning: "No Data exists for variable "my variable..." I am working on that keep you updated. cheers

 March 29, 2010, 20:10 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,824 Rep Power: 85 The problem with Dmitry's approach is it does not interpolate correctly between nodes. If you are going to do a lot of this I would export the nodal values along the line and do it either with a program or in excel/matlab/whatever. Then you will be able to batch a few of them together to do it more efficiently.

 April 6, 2010, 03:51 #5 Senior Member   Join Date: Mar 2009 Posts: 138 Rep Power: 8 Hey Glenn, Thats what I am about to do. Export all the data to matlab. However I thought maybe there is a easy solution for this first step in Ansys. Thanks Camoesas

 April 6, 2010, 12:02 #6 Senior Member   Bruno Join Date: Mar 2009 Location: Brazil Posts: 236 Rep Power: 12 Can't you just create an isosurface of 0.99*Vinf and then export this surface? When calculating the isosurface Post will interpolate values fine. (remeber to clip it to the are you're interested in)

 May 6, 2010, 01:52 #7 Member   Dmitry Volkind Join Date: Jan 2010 Location: Chelyabinsk, Russia Posts: 58 Rep Power: 7 It's probably too late, but I think extracting a polyline from a velocity contour plot is a good idea.

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