0
robibird

Wingsuit and Laminar Airfoil-explanation

Recommended Posts

...did a lot of airflow filming in 2005 - both ws and tracksuit. The advantage of airflow filming is, that you have 100% realistic conditions.

90% vortex lift when we talk just about the delta wing.

I just put a short video together, an extract of earlier R&D work. here you can see what happens with the airflow when it passes the leading edge.

check out:

http://www.skydivingmovies.com/ver2/pafiledb.php?action=file&id=5421

andi
www.pressurized.at

Edited to make url clicky ~ Craig

Share this post


Link to post
Share on other sites
I agree 100% with Robi that talking about laminar flow in the wing suit contest is borderline meaningless.

Having seen Robi kind of opened a “Pandora’s box” let us talk about other common misconceptions about wing suit design.

First let me say it is normal but erroneous to look at many airplane wing designs and try or think about implementing them in a wing suit. As much as we think we can fly like an airplane we are not airplanes: We do not have an engine and a rigid frame. However there are hints that we can draw from basic understanding of airplane fluid dynamics.

For instance if we analyze the sweep angle of a wing it is my opinion that only one right conclusion can be drown: A high sweep angle is not efficient in a wing suit. Of course Robi and Jari will disagree on this one because on many of their suits the arm wings have quite a bit of swept-back.

Swept-back wings were designed to address the issues related to supersonic flights. For the record few test pilots have died because engineers overlooked this problem even though the phenomenon was known before technology allowed for supersonic flights.

When approaching the speed of sound (770 mph), something peculiar happens: A sharp drop in pressure is generated aft of the nose of the aircraft. If this drop in pressure happenes in high humidity, a cloud is formed around the aircraft leading the very cool images of airplanes passing the speed of sound. This is known as the Mach cone. Why this happens is actually pretty simple. Any moving object generates sound waves that in general travel aft of the object at subsonic speeds. As the speed approaches the one of sound, those waves “collapse” into one, usually at the nose of the aircraft, and this sudden raise in pressure is also responsible for the “sonic boom”. Actually there is a second boom when the tail passes the shock wave but human hearing is not sensitive enough to detect the two and only one is heard. As the nose is “loaded” with high pressure, aft parts of the aircraft including he wings have much lower pressure. This higher pressure intuitively increases the temperature. Both the increase in pressure and temperature on the nose of the aircraft have detrimental effects on the wings namely an increase in drag that if compromises the whole leading edge it could result in total loss of lift.

Implementing a sweep angle on the wings allows for a reduction of this type of drag. I said a sweep angle and not just swept-back because a swept-forward will also work as in the case of the X-29 for instance. However a swept-forward design introduces some disadvantages like wing-tip twist, wing-tip-first stalls (which rob aileron efficiency more than any other stalls), not to talk about higher cost of manufacturing. The reason behind the sweep angle is to reduce the effect of compressibility responsible for the cone to approach the leading edge. So in theory the higher the sweep angle the higher the speed the code reaches the leading edge inducing a drastic reduction of drag, up to a point.

So why don’t all aircrafts have swept-back wings? In short because at lower speeds, the disadvantages are greater than the advantages namely less lift produced, more drag, “Sabre dance” (the pitch up close to the stall point), among others.

There is also IMO another disadvantage in having swept-back wings on a wing suit and this is the lower aspect ratio. Same goes for narrow leg stance, the aspect ratio is lower and all things being equal a wing with higher aspect ratio will produce more lift and less drag.

I also disagree with Robi with his analogy to the Space Shuttle. This “aircraft” is not an airplane per se and introducing such a design as a “normal” aircraft will get the person fired! The Space Shuttle is a compromise aircraft: it has to take off vertically strapped to some giant rockets, it has to orbit the earth, it has to re-enter the earth atmosphere reaching temperature that melt most metals, then it has to overcome Mach numbers over 20, and finally manage to land…and those things do not land pretty, they come in hot, having little flare power and nowadays NASA pilots do not even land them anymore leaving computers the job.

If we really want to “rob” ideas from aircraft wing aerodynamics in order to implement or evaluate them in a wing suit contest, then we should look at aircrafts such as gliders where in general high-aspect ratio straight wings are preferred.

I do agree with Robi when he says gravity is our only engine, there is very little doubt about that!
***********************************
EG Suits
***********************************

Share this post


Link to post
Share on other sites
What was the angle of attack on high performance segment? Since it's a sharp turn (reduced forward speed, increased fallrate), AoA could be high.

Do you think sculpturing the leading edge would increase L/D?
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Robi has stated in his second article on aerodynamics and wingsuit design why his wingsuit designs have swept back wings. It is not to mimic supersonic aircraft. It is because of strength issues.

However, when flying the V suits for performance the shoulders are rolled and the wings(elbows) pulled up to almost horizontal to the shoulders. Atleast that is what worked for me.

Kris.

Share this post


Link to post
Share on other sites
Quote

What was the angle of attack on high performance segment? Since it's a sharp turn (reduced forward speed, increased fallrate), AoA could be high.

Do you think sculpturing the leading edge would increase L/D?



Yeah...it was the one thing that the video does not show...the AoA on the performance flying segment. Wool is a great idea(until you(andi) posted it..I was only thing about how to solve the problem of videoing air flow over the wing)...I am going to put some streamers behind 30% of the phantom wings and fly at low AoAs and get video.

Exciting!

Kris.

Share this post


Link to post
Share on other sites
Quote

I am going to put some streamers behind 30% of the phantom wings and fly at low AoAs and get video.



Maybe you and Costyn should put some GPS's cameras, streamers and smoke on and film eachother in belgium...;)

Hans (aka gadget) also has his Pen-cam which can be velcro'd onto any part of your suit..

Getting you three together with all the toys is going to be awesome to watch!
JC
FlyLikeBrick
I'm an Athlete?

Share this post


Link to post
Share on other sites
Quote

I am going to put some streamers behind 30% of the phantom wings and fly at low AoAs and get video.



Cool. I'll do the same. Without and with the tubes, and at different AoA's.

More food for thought, better understanding of WS aerodynamics, better suits, better flying styles, more fun flying!!! ;)
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
If one of you can film the other (with streamers all over both arm and leg wings) directly from top while flying at >90% of your max L/D, and you confirm that AoA is <20 degrees by using GPS data (AoA = atan(Vy/Vx) - pitch), that would be EXTREMELY interesting.
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Quote

The data gathered in the tunnel using a rigid model was clearly discernable and reproduceable, however, the data collected on a human differed from the model and even more so from the data collected on a skydive.

It became apparent that the jumper is the biggest variable in the equation and flying in anything other than an optimal position for that person and suit will create vastly different results.



Well, that's more than obvious, there's no point in wasting windtunnel time on that. How did he collect data in windtunnel and how did he collect data on a skydive? How did he make sure that his AoA on a skydive was precisely the same as in windtunnel?

Flying at 70mph forward, 55mph down with the pitch angle 5 degrees, and 100mph forward, 40mph down with the pitch angle 15 degrees corresponds to AoA of 33 degrees and 7 degrees, respectively. Totally different airflows!

What was the maximum L/D he measured in real flights? How did he measure it?

And what was the whole point of his "research"? Was he trying to improve things?

Quote

the one thing that was evident was that in the optimum position for the suit(S-fly), the airflow over the suit showed where the aerodynamics could be improved or where it was very efficient.



So where "the aerodynamics could be improved or where it was very efficient"? Did he try to improve it? How?

Overall, what exactly did he achieve?
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
See Jarno...if we had yuri_base along this trip would be complete. :D.

Will try Yuri. But you convince Costyn to stick streamers all over his new suit :P. I don't mind sticking them on my current Phantom. I need to buy another phantom(my choice of medium sized suit) for my new skinny ass anyway. One of the other guys will have to do video.

Kris.

Share this post


Link to post
Share on other sites
Quote

Well, that's more than obvious, there's no point in wasting windtunnel time on that



Well one would assume that but to actually see the gross differences supported with empirical data collected in as controlled a manner as possible validates the assumption and provides hard data/numbers.

Quote

How did he collect data in windtunnel and how did he collect data on a skydive? How did he make sure that his AoA on a skydive was precisely the same as in windtunnel?



From what I saw in the presentation, all data was collected electronically (AoA, speeds ,etc) first on the model,analyzed and used as a baseline to compare the human flight to, which was recorded the same way. For the actual skydives, he used a helmet mounted pitot tube and the same electronics he used to gather the data in the wind tunnel to determine that the data was as close as possible to what was done in the wind tunnel.

Quote

Flying at 70mph forward, 55mph down with the pitch angle 5 degrees, and 100mph forward, 40mph down with the pitch angle 15 degrees corresponds to AoA of 33 degrees and 7 degrees, respectively. Totally different airflows!

What was the maximum L/D he measured in real flights? How did he measure it?



He addressed these as well as other issues in his seminar with actual data readouts and since I don't have it in front of me, I am working from memory and I don't remember the specific answers to those questions. I know he would do a better job at describing his findings which is why if you're interested I'd recommend you contact him. Specifically if you plan on doing your own testing as it would save you from wasting a lot of time in certain areas.

Quote

And what was the whole point of his "research"? Was he trying to improve things?




Thats a good question. From what I understand, it initially started out as an assignment he was given and morphed from showing a military application to a scientific project to collect data on the wingsuit, ultimately I am assuming to further the military application. I am gussing that it has stalled at the scientific project as he stated that there are some variables in his research that need further scrutinization in order to obtain more precise data. I believe he is looking for funding to continue his research which is why he has given the presentation at the last 2 PIAs.


Quote

So where "the aerodynamics could be improved or where it was very efficient"?



Not sure I understand your question. Certain parts of the suit were indeed efficient aerodynamically and other portions of the suit it was evident that the airflow was less than ideal, hence where it could potentially be improved on.

I really recommend anyone interested in this to try and contact jean-Pierre as he has a great deal of information and can better explain what he did than I can based off of a 60 min seminar.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

Share this post


Link to post
Share on other sites
Quote

How can I contact him?



Sorry, I forgot to mention, I don't have his contact information. But I am sure it can easily be obtained from PIA. I'll check the stack of business cards I aquired at PIA to see if he gave me one.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

Share this post


Link to post
Share on other sites
Quote

here you can see what happens with the airflow when it passes the leading edge.



More thoughts after watching the video frame by frame.

1. Test can be improved. The threads are too long. Because of that, they don't just show local velocity vector, but rather exhibit their own complex dynamics where airflow at different speeds in different layers the tread bounces in, fights with the tension forces in the thread itself. This creates a confusing "dance" making an impression of higher vorticity than there really is. Shorter (<1 inch) and thinner (regular sewing thread) threads would reduce this undesirable phenomenon. Flow separation can then be seen by the angle threads make with the surface.

2. Re: AoA - During the turn, the high AoA is evident by looking at the front threads. (threads are straight at ~40 degree AoA). We have a momentary stall, so high vorticity is no surprise. After the turn, in final 2 seconds of the video, we can see AoA decrease and leading edge threads "stick" to the wing. Where the leading edge panel connects to the rest of the wing, the flow separation occurs. Not surprising either and immediately we see where the things can be improved:

wing should be made of one piece of fabric wrapped around arm (with some tailoring here and there to achieve fit, but with no separate leading edge panel) and the two ends of this piece sewn together at the trailing edge. Leading edge should be formed from inside the arm sleeve (using various means) to complete the target aerodynamic profile. Then we won't see this crazy dance. :)
3. Leading edge is very smooth and nice, what suit is that and is it modified in any way?
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Quote


Well, that's more than obvious, there's no point in wasting windtunnel time on that.


Long ago I wrote this in Aerodynamics II article
(http://www.phoenix-fly.com/articlesstvari/PF_Wingsuit flying and Basic Aerodynamics_2.pdf )
People tend to believe in anything, only if it looks cool enough. Wind tunnel testing certainly looks smart and cool, but beside getting some cool pictures there is so little you can achieve in practice, especially if the research is aiming to achieve something more than just to collect data for comparison between different rigs or components like helmets etc...
The VKB boys did that and provided us with data that just confirmed what was rather obvious: thin rig generates less drag than a bulky tick rig. What was nice in VKB Tunnel tes data was that we were able to see all the details and % of drag around two sets of gear...
Testing WS in the wind tunnel would be serious task even for organizations like NASA (in US) or TsAGI (in Russia). Even for them that would be a hard job w high cost and questionable results. For the moment, experimenting is the way to go here, since experiments are still one of main and most important tools in aerodynamics or hydrodynamics...

Edited to make url clicky ~ Craig
Robert Pecnik
robert@phoenix-fly.com
www.phoenix-fly.com

Share this post


Link to post
Share on other sites
Quote

See Jarno...if we had yuri_base along this trip would be complete. :D.

Will try Yuri. But you convince Costyn to stick streamers all over his new suit :P.



Well, I still have my Classic II and S6, I wouldn't mind sticking streamers on either of those. And yeah, it'd be cool to do some experiments. I'd be up for that!
Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News

Share this post


Link to post
Share on other sites
A high sweep angle is not efficient in a wing suit. Of course Robi and Jari will disagree on this one.
Swept-back wings were designed to address the issues related to supersonic flights.

I also disagree with Robi with his analogy to the Space Shuttle. This “aircraft” is not an airplane per se



There are some aircraft that use swept back wings to deal with weight and balance issue and they fly well below mach one. Supersonic isn't the only reason for sweeps. In these fixed shape airfoils the sweeps biggest disadvantage is the spanwise flow of air. I dont believe there is much span wise flow in wingsuits and the sweep helps us in keeping balance centered and pitch angle at the right degree.

The space shuttle could be considered a "lifting body" like the flying bathtub that started the data gathering for the concept. Come to think of it I've flown in flocks with people that could be considered flying bathtubs.

If we look at the bathtub and craft like the HL-10 we can see the closest mechanized flying application to our wingsuits.

Share this post


Link to post
Share on other sites
From discussion with Øyvind, it looks they used windtunnel data (among other things) to refine the pitch angle to achieve L/D=1.8 in real flight, the maximum of the L/D curve for G-3 they measured in the tunnel. Although initial L/D=1.6 test flight was impressive by itself, they improved that with the help of windtunnel.

With a lot of useless research going on in universities (see, for example, all this research on birds... interesting articles, but pointless), it seems some bored doctorate students in aeronautics might be interested doing some research in wingsuits. There's so much talent and money wasted there, it's not even funny.

Maybe I'll bribe some with Russian Vodka? :)
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

Share this post


Link to post
Share on other sites
Quote


With a lot of useless research going on in universities (see, for example, all this research on birds... interesting articles, but pointless), it seems some bored doctorate students in aeronautics might be interested doing some research in wingsuits. There's so much talent and money wasted there, it's not even funny.

Maybe I'll bribe some with Russian Vodka? :)



:) try Yuri, this may help us all!!
Robert Pecnik
robert@phoenix-fly.com
www.phoenix-fly.com

Share this post


Link to post
Share on other sites
Quote


Hello Mr. Eg,

may I ask your name please? Are you the designer of Eg suits?

J



The guy who posted that is the guy doing the R and D for Edgardo. Anyone who has ever been to any large boogie in the United States (where there are vendors) will know that EG himself could never type english that well.;) What EG is, though, is an incredibly hard working man. Positively the only person I have ever seen who would take your measurements, sew all night, and deliver your new jumpsuit to you the next morning at a boogie. I knew EG was going to build wingsuits eventually as early as 2003 at Rantoul.

I am anxious to see what these guys have to offer. The guy making the posts will be at the Flock and Dock. I am not sure if Edgardo himself will be there.

Share this post


Link to post
Share on other sites
I do know that there models were covered in electronics to measure lift, not sure how he did his angle of attack, I always thought if you get the attachment point of the harness right then to adopt "the position" would be enough, then the guy controlling the wind speed will put you in the middle of the tunnel, the pivot point of the harness stopping you from flying through the wall is the important part, but i see it in a vertical tunnel, he used a horizontal tunnel

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0