Find location @ Line where a variable has a certain value

camoesas · March 29, 2010, 06:18

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

dvolkind · March 29, 2010, 07:13

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.

camoesas · March 29, 2010, 08:20

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

ghorrocks · March 29, 2010, 20:10

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.

camoesas · April 6, 2010, 03:51

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

brunoc · April 6, 2010, 12:02

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)

dvolkind · May 6, 2010, 01:52

It's probably too late, but I think extracting a polyline from a velocity contour plot is a good idea.

March 29, 2010, 06:18	Find location @ Line where a variable has a certain value	#1
camoesas Senior Member Join Date: Mar 2009 Posts: 138 Rep Power: 17	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

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March 29, 2010, 07:13		#2
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	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
camoesas Senior Member Join Date: Mar 2009 Posts: 138 Rep Power: 17	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
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	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
camoesas Senior Member Join Date: Mar 2009 Posts: 138 Rep Power: 17	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
brunoc Senior Member Bruno Join Date: Mar 2009 Location: Brazil Posts: 277 Rep Power: 21	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
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	It's probably too late, but I think extracting a polyline from a velocity contour plot is a good idea.