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January 22, 2013, 09:43 
Field Function for Surface Length

#1 
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anonymous
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Does anyone know if there is a field function for the surface length. I wish to plot pressure coefficient vs surface length on an aerofoil rather than axial distance.
Thanks 

January 22, 2013, 10:53 

#2 
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Ryan Coe
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You may be able to do this with a combination of vector field functions.
Another approach would be to write a field function with a polynomial that gives the location of the surface as a function of the orthogonal coordinates, and then reference that.
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Ryan 

January 26, 2013, 07:22 

#3 
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anonymous
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what if the surface is just a random collection of points and not a quadratic curve or something like that. is there a way I could use the coordinates of it somehow?
Thanks 

January 27, 2013, 11:03 

#4 
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Ryan Coe
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What type of airfoil is it? You should be able to come up with a function for the surface based on this.
Alternatively, you could just fit a curve to the coordinates.
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Ryan 

January 27, 2013, 13:04 

#5 
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anonymous
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It is a turbine blade the geometry can be found here:
http://wwwg.eng.cam.ac.uk/whittle/T106/Start.html I dont think I will be able to use an equation to determine the points. Is there not function that will get the points out of the geometry used in Starccm and make them avaliable. If I export the x and y coordinates of the geometry I can use excel to do it by finding the distance between each point and it gives a rough estimate I was just hoping that star would be able to do this for me thanks 

January 27, 2013, 13:12 

#6 
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Ryan Coe
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If it were me, and there were no way of finding the function used to describe the blade geometry, I would export the points and use matlab to fit a function (probably a cubic spline) to the surface.
You should be able to export the points by creating a table with the boundary of interest (the airfoil surface).
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Ryan 

January 28, 2013, 02:05 

#7 
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Ryne Whitehill
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I've requested this feature from cdadapco as well.
If you have access to fieldview, they do have a method to do it. STARCCM+ recently added in a "unwrapper" surface plot that is supposed to take a 3d surface and flatten it to 2d. Not sure if this could be used to flatten the surface out and then do a plot from that. 

January 28, 2013, 08:38 

#8 
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anonymous
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I do not have access to fieldview, is it a free program or would I need a licence.
Is Unwrapper only in the latest version of Starccm+ as I have 7.04.006 and when I search "unwrapper" in the help file nothing comes up thanks Last edited by badger1; January 28, 2013 at 09:46. 

January 28, 2013, 13:15 

#9  
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Ryne Whitehill
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Quote:
Its in 7.04. Not sure if it will do what you want, Ive only glanced at it. The help file page title is: Unwrapping, Unrolling and Projecting with Transforms Its under visualizing solution > transformations 

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field function, pressure, surface length 
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