50 Replies Latest reply on Jun 20, 2012 5:46 AM by Vahide Eshaghian

# how to fix airfoil geometry in SolidWorks?

Hello everybody,

I am new to SolidWorks and I would like to model a wind turbine in SW.

I have imported airfoil coordinates by using ''curve through xyz point'', now I plan to move the airfoil and loft it through a 3D curve.

My first question is that might airfoil geometry change by moving or lofting?

If yeswhat should I do to fix the airfiol geometry?

bahar.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello Vahide and welcome.

What does your imported data look like?  Are there 3d point and curves, just curves, etc.  Can you take a snapshot and post it?

Thanks,

Mike

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello dear Mike,

As it's shown below, the only object that could be observed is an airfoil in xy plane.

Regards

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

If that curve is on a plane cannot you extrude it if the airfoil isn't twisted?

• ###### Re: how to fix airfoil geometry in SolidWorks?

Yes, you're right but the airfoil should be twisted along a 3d curve!

• ###### Re: how to fix airfoil geometry in SolidWorks?

OK.  Do you have that 3d curve?  If so, does it intersect your airfoil cross section?  For a twisting direction (about an axis out of the page according to your curve) you need to have two airfoil cross sections.  You could then use guide curves for the desired path.

If it is just a straight twist and you were to know the axis of twist and that axis was perpendicular to the airfoil cross section, you only need two cross sections.

If you provide more detail with your response, I think we'll be able to solve it next go around.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Dear Mike,

I have the guide curve and it is a part of ellipse, but it does not intersect the airfoil, so I needed to move the airfoil first and then tangent it to the curve, at the end I copied it at the another side of guide curve.

I've done so, now the question is that, does SW change my geometry through guide curve?It seems that the blade is not smooth.

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

do a loft, convert the first airfoil to a new plane where you want it, then use the move\modify sketch to rotate the converted airfoil to its new position then loft between the sketches...whala...done!

put your file up here and we'll help ya

• ###### Re: how to fix airfoil geometry in SolidWorks?

Lenny, also the people at Dassault may kick you off of the forum if you take their voila and turn it into whala again.

• ###### Re: how to fix airfoil geometry in SolidWorks?

ok then SHAZAM!

• ###### Re: how to fix airfoil geometry in SolidWorks?

Lenny's approach is the best, if you know where it needs to be.  Can you post as he has suggested?

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide, I didn't see what the guide that you described looks like but I have two items of note.

If you won't want to move the guide closer to the profile, you can create a point in the profile and ad a peirce relation between it and the guide.

Second, if you only want the sweep to twist along the guide but not deform, then try making a sweep.   You can set options to twist along a path or keep the normal of the profile constant.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear John,

I've defined a coincident relation as you said. Do you mean sweep keeps profile constant? My profile which should keep constant is normal to guide curve at each section.

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

I've done that as Lenny said, but my question is that is it possible that SW change airfoil geometry during lofting?

I have imported a set of blades that has created by using circular pattern to Gambit and the blades volume is not similar!!

What might be the problem resource?

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

yes, you would have to put a new sketch at the proper location for the changed section at that point.

then pick the sections as you go and your airfoil will change shape.

think of it as making a balsa airplane model.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

If I understand correctly, you have two identical curves with which you have created a loft.  The loft isn't smooth however.  SW will change the airfoil geometry if the start points on the two curves are in a different location.  The green balloons on the loft allow you to change the start position.  It would be much easier to help if you could post your part.

• ###### Re: how to fix airfoil geometry in SolidWorks?

I recommend checking the curvature of the curve through points. Project to a planar sketch using convert entities and turn on curvature combs. The curvature should have no ripples and at most one reversal per side. I usually divide the airfoil into two splines and add a chord line.  It can be helpful to make the airfoil into a block for future checking or intermediate sections. Sweeps and lofts can get distorted in strange ways. Be sure to check the resulting intermediate sections using a split line or projected curve and compare to a copy sketch.

The best airfoils have a squared off trailing edge. This reduces drag and incrases lift. The sharp trailing edge can develop a wavy wake.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello everybody,

Thank you all so much for your attention and sorry for my delay.

Here is the geometry of my blades. Each blade section is an airfoil. The blades has created by using ''Loft"" in SW.

Now, the question is that may the airfoil profile change during this process?

I want to be sure that it does not change!

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

Lofts are not particularly good at maintaining their shape. A Sweep would probably be a better choice. You may need one or more guide curves to control the orientation of your profile as it follows the path..

Jerry Steiger

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi Jerry,

Can you elaborate as to why you think this would be an issue as long as your start and stop points would coincide on the same point on each cross section one would use to create the loft?  I have not seen any issues related to that, that is all.

Thanks,

Mike

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello everybody,

Thanks Jerry, but I thought sweep only works along a straight line, isn't it? My guide line is a 3d curve.

Dear Mike, do you mean everything is OK?

Regards,

vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi Vahide,

Rick's suggestion is accurate "Be sure to check the resulting intermediate sections using a split line or projected curve and compare to a copy sketch."

What you want to do there is to take a cross section of the loft at a point along your guide curve that is perpendicular to the guide curve.

That cross section at any point along the loft would have the same profile as your start and stop loft profiles.

You could also post the part.

Regards,

Mike

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear Mike,

Thank you so much for your helpful comment. I try to do that and will announce you.

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

Extrude only works along straight lines. Sweep works along any curve you like, although you usually have to be careful to keep from generating self-intersecting surfaces by having the offset to the inside larger than the minimum radius of the curve.

Jerry Steiger

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear Jerry,

I'm really wondered to hear that!

I tried it but there is a problem, I wanna to twisting the airfoil along the curve while keeping normal to curve. How can I model the last one?

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

A Guide Curve will control the twisting of the arifoil along the curve. I believe that the profile normally stays normal to the curve unless you specifically request that it not, by picking Keep Normal Constant.

Jerry Steiger

• ###### Re: how to fix airfoil geometry in SolidWorks?

Dear Jerry,

I've faced to a problem during drawing airfoil.

As it could be seen below there are two edges in trailing edge that should be merged to creat a closed group and also to import to Gambit.

I tried ''heal edges'' but it didn't work! What should I do to resolve it?

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

I don't understand what problem you are having. I see three edges; a top edge, a bottom edge and the trailing edge, which looks like it is an arc. Do you mean that there are actually two arcs? You can just delete one of them. Do you mean that you really need to have one curve for the whole profile? You can use a Fit Spline. This will replace your edges, arcs and splines with a single spline.

Jerry Steiger

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear Jerry,

Sorry I did not see your comment since now!

Yes, really I wanna to have only one curve for the whole profile. How can I use a Fit spline? I used ''curve through xyz'' to draw airfoil and then fited an arc at the trailing edge.

Best Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

Why do you need a single curve?

You can use a Fit Spline on your spline and your arc to get a single spline.

Note that a Fit Spline is not an exact copy of your original geometry. It can vary by an amount that you control with the Tolerance when you define it.

Jerry Steiger

• ###### Re: how to fix airfoil geometry in SolidWorks?

Dear Jerry,

What really I need is a curve that makes a spesific and constant angle to horizontal plane. So I intersect an oblique plane with a cylinder.

How can I control this feature in drawing a spline?

Thank you very much for your attention,

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

I tried sweep for my geometry, it worked correctly for keeping normal constant and also twist along path but it didn't worked for both together and gives below message:

''To make this option valid, the sweep must have a smooth path''

In the case I'm doing both piching and keeping normal should be considered. What should I do?

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Are you able to post your part?

• ###### Re: how to fix airfoil geometry in SolidWorks?

Yes how can I post it here?

• ###### Re: how to fix airfoil geometry in SolidWorks?

When you reply or edit an existing post, you have to use the advanced editor, which can be opened using the link in the upper right of the text editor.  It is labeled, "Use advanced editor".

• ###### Re: how to fix airfoil geometry in SolidWorks?

I don't know what Solidworks considers a smooth path, but the curve you want to use for sweeping the cross section is tangent to the cross section and SW isn't happy with that as it doesn't know what to do.

You have to have the beginning of your sweep curve have a larger angle to the cross section than what you have.  I'm not sure what you want it to look like exactly.

I don't typically use the sweep command to its fullest capacity either, but rather use lofts and boundaries, so my help is limited.

Do you have a picture of what it should look like at the beginning and end?

• ###### Re: how to fix airfoil geometry in SolidWorks?

Thank you dear mike for your attention,

I have to keep airfoil normal to guide line because of aerodynamic reason.

Yes, I have. Really the previous 3D blades that have been created by using loft bud it did not worked correctly!

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

The airfoil cross section isn't normal to the guide line you have.

• ###### Re: how to fix airfoil geometry in SolidWorks?

I mean the plane which airfoil lies in is normal to the plane of guide line. The airfoil chord (straight line from leading edge to trailing edge) should be paralell to the curve at the begining.

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

If you want a constant cross section, I don't see how you can do that.  Maybe I am missing something......

• ###### Re: how to fix airfoil geometry in SolidWorks?

What should I do?

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Please show a picture of your lofted solution or post that model so we know what you want the beginning and end conditions to look like.

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear Mike,

I've posted a figure of 3 blades past that's created using loft. Really I need to satisfy this criterions:

1- Airfoil would be normal to guide line at each section.

2- Airfoil section should twist around the guide line.

3- Intersection of airfoil and guide line should be at the leading edge point at each section.

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Not entirely sure what you are trying to achieve, but thought I'd have a stab anyway. refer attached

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear John,

Wow! I'm really wondered!

It seems that you draw a spiral for guide line,isn't it? Did you try it using the last guide line also?

And another question is that is seems the airfoil is twisting about guide line, is it? But in the sweep command, twisting option is not activated.

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Thank you dear John, your idea about using a spline was very good!

But there's a question how could I control spline that it makes a spesific, constant angle with respect to horizontal plane?

Best regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello,

A couple of things.  First, I moved your sketch to a plane that is perpendicular to your guide curve at the initial start.

Second, you are getting the "must have a smooth curve" error when you are trying to twist your sweep because when you select your 3d sketch, you have a horizontal line in the 3d sketch.  You need to change that horizontal line to a construction line.  Strangely, you can do a normal sweep with the 3d sketch without doing this though....

If you notice, John created his geometry by using a helix.  You can find sufficient assitance with SW's help tool to create a helix.

Let me know if this is what you are trying to achieve.

Thanks,

Mike

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hi dear Mike,

Thank you very much for your attention.

That's wonderful but there is a question that would airfoil be normal to curve at each section or not?

John's idea is very good, I tried it but the ideal curve for this case is one makes a spesific and constant angle with respect to horizontal plane. How can I control this feature in drawing a spline?

Regards,

Vahide

• ###### Re: how to fix airfoil geometry in SolidWorks?

Vahide,

If you could mathematically describe your curve, with a "x" order polynomial, you could determine a series of points in x and y and create a spline with those points.

Otherwise, unless you are guiding your spline with strategically located points, it will be non-deterministic.

The airfoil should be normal to the curve with the twisted sweep I posted.

Regards,

Mike

• ###### Re: how to fix airfoil geometry in SolidWorks?

Hello everybody,

My problem ith Gambit was resolved recently by correcting gemetry in SolidWorks. Thank you all advance!

Dear Mike, I'll try it surely. Thank you especially.

Best Regards,

Vahide