Creating a wing surface from a set of airfoil datafile

[flutterboy]

Dear all,

I am an absolute novice to Unigraphics. I am trying to do something that I think should be very simple. I hope I can get some help for this.

I have around 1000 points which define the profile of an airfoil in a datafile. I need to do the following:

1. Import those points into Unigraphics

2. Connect the points to form a very very smooth airfoil profile.

3. Once this airfoil is obtained, I need to extrude it to a specified distance to obtain a wing surface. Then, export this surface to an IGES/STEP file.

So far, I think I could import the points into UG properly. I entered the SKETCHER environment and used the SPLINE -> Through points -> points from data file option to do it. As soon as the import was over, I obtained the airfoil curve. I am now not sure about how I can get the surface I want without messing with the smoothness of the airfoil profile. I actually tried Studio Surface 2x0 option but it made my profile very messy although I seem to have got the surface.

Can someone correct what I did and guide me through the steps 1, 2, and 3 above please ?


Thanks so much for the help in advance

With regards,
FlutterBoy

 

[JohnRBaker]

Unless you have to absolutely have a curve that passes THROUGH each and every point, you may get a better curve, and thus a better surface, if you were smooth the curve by doing a fit through those points. The reason I say that it because 1000 points seems like a lot and with that many points, often there will be some 'noise' that will result in something less than smooth and clean.


John R. Baker, P.E.
Product 'Evangelist'
NX Product Line
UGS Corp
Cypress, CA

http://www.ugs.com

 

[flutterboy]

Hi John,

Thanks for the quick response. So, if I can be satisfied with fewer points than 1000, then, can you tell me the best way to get the surface I want ?

Import data points from file -> Get the airfoil -> ... then what is the procedure to follow if my goal is to get a wing surface from that single airfoil curve.


Please let me know.


Thanks again,
FB

 

[JohnRBaker]

Does the set of points produce a single airfoil cross-section or multiples? If it's just one, try just extruding it. If it's more than one airfoil section, then Surface Through Curves.


John R. Baker, P.E.
Product 'Evangelist'
NX Product Line
UGS Corp
Cypress, CA

http://www.ugs.com

 

[flutterboy]

Hi John,

I have just one airfoil cross-section. I tried extruding it using the Extrude option in 'Modeling'. It did extrude my airfoil curve. But, I observed two things:

1. I seem to have got a solid and not a surface. I extruded a curve an not an area so I was expecting just a volume enclosed by the wing surface.

2. The original airfoil curve is very very smooth. I imported 700 points to get a spline out of it. However, after extrusion, this smoothness seems to have been gone. It seems to me like only fewer points of the original airfoil curve have been used during the extrude operation. I did not how to attach the .bmp I have of it to this message. If I did, I would have done it for your reference.

Please let me know if you have any suggestions based on what I wrote above.


Thanks in advance

Regards,
FB

 

[Dave K]

"1. I seem to have got a solid and not a surface. "

Change your modeling prefernce:
Preferences->Modeling
Change the body type to sheet.

Now extrude the spline(s) and you'll get a sheet body.

As for the smoothness after its extruded, try using the face analysis tools, which may show how smooth it is, better than standard shading. I like using reflections.
Analysis->Shape->Face->Reflections
Pick the sheets, and apply.


-Dave
Everything should be designed as simple as possible, but not simpler.

 

[cowski]

You extruded an open spline curve and the result was a solid body? That will probably happen if the start and end points are within modeling tolerance of each other. You can change a setting to ensure that you get a sheet body. In NX2 it is in Preferences -> Solid Modeling... change the output type from solid to sheet.

#2 could just be a visualization thing. Try regenerating the view after the extrude. If the view still bothers you, try a higher quality visualization mode. Preferences -> Visualization... Shade (tab) and change the tolerace (again the menu locations are for NX2). What you see on screen is a triangulated approximation to your input data, smooth curves with changes in curvature will make this more apparent than simple flat surfaces. The information is still in the model file, but the display is 'blocky' to speed up the graphics rendering.

There is a faq somewhere around here about posting pics (I can't find it now). Basically you have to post it on another site then link to it in your post.

 

[Xwheelguy]

flutterboy,

Be sure to analyze the splines you're using (use the curvature comb). Try to keep the number of segments as low as possible while maintaining the shape you need. Also, you might need to make your splines all 5 degree (versus 3 degree; cubic) or higher to help with surface complexity. You may have to refine your spline(s) even further to get higher quality surfaces. I would be surprised if you didn't have to add more spline profiles to end up with a clean surface. If you do, make sure they are similar in degree and segments. I am also of the same opinion that the number of points you used to define the spline seems a bit excessive, hence the refining advice.

Hope you're able to get it figured out.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.