Study with computational fluid dynamics

[vario470 0]

hi,

Firstable, sorry if i don't write very well, i am french student ....

Currently i am studying skydiving ( wingsuit ) with a software called STAR-CCM+, i have some results, but I never have practiced this sport ....

Do you know what is the range of the incidence of a skydiver, is it betwin 10 degres - 25 degres ? or 15 degres - 30 degres ?

If you want i can post some results in 3D, to show you what i do !

Thank you very much
And Happy New Year !

[JohanW 0]

Up to 45 degrees.

Especially when flying floaty, near stalling the suit, glide ratio suffers and people fly very head high. Yes, we get vortex lift at best.

Frankly, I wish you luck in whatever you are trying to do, because a wingsuit is a very, very complicated object. And it generates rather more turbulence than lift.

If you get L/D higher than 3, your computations are grossly optimistic.

If you are specifically interested in wingsuits, you might try posting in the the Wingsuit Forum. Bring your asbestos underwear and be prepared to be called Yuri, while at the same time getting in major disagreements with that same Yuri himself. Some people like to crunch numbers, others are very, very bored and bothered with this.

Johan.
I am. I think.

[Costyn 0]

Hi,

Thanks for your interest. Please don't be too disheartened by Johan's post. He means well and doesn't want to scare you away, even though it may seem that way.
I'd be interested to see what you are working on, but it's true what Johan says, however much we want to believe otherwise, don't really get much real actual lift out of our wingsuits, it's mostly deflection which gives us our forward speed.

This little movie is quite telling in how quickly the laminar flow leaves the wing and it becomes one huge turbulence on top of the wing. Maybe this will help you in your research.

Cheers!

Costyn.

Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News

[KrisFlyZ 0]

Quote

This little movie is quite telling in how quickly the laminar flow leaves the wing and it becomes one huge turbulence on top of the wing. Maybe this will help you in your research.

Cheers!

Costyn.

I would be wary of accepting that video as gospel. Anyway, the Software he has access to can predict the airflow around a wing more accurately than the video.

To the original poster,

I'll help in anyway I can, just ask.

Would be cool to see what you find out.

Thanks
Kris

[kallend 1,619]

Quote

Quote

This little movie is quite telling in how quickly the laminar flow leaves the wing and it becomes one huge turbulence on top of the wing. Maybe this will help you in your research.

Cheers!

Costyn.

I would be wary of accepting that video as gospel. Anyway, the Software he has access to can predict the airflow around a wing more accurately than the video.

To the original poster,

I'll help in anyway I can, just ask.

Would be cool to see what you find out.

Thanks
Kris

I'd be very surprised if off the shelf CFD software can handle the kind of turbulent flow encountered over the top surfaces of a WS. These packages are not designed to do that.

...

The only sure way to survive a canopy collision is not to have one.

[Airowpoint 0]

Hi vario470,

Sound like a cool project. I have been wanting to do the same for a while. I have a license for ANSYS CFX http://www.ansys.com/solutions/fluid-dynamics.asp in my lab. I mostly want to show the burble/turbulence that forms behind us. The biggest problem is creating a realistic model and I haven't had any time to make a good one yet. I think the angle of attack is very small for normal flight. Maybe 5-10 degrees, it's hard to tell really. Have a look at some videos on youtube. And get someone to give you some GPS data of a flight for the glide ratio and speed.

Good luck and please show us some results!

Tristan
Will you answer "NO" to my next question?

[vario470 0]

Hi everybody,
I read a little bit what you wrote, but i just came back into my home and now it's 3 A.M in France, it's time to go to the bed. I will read this tomorrow and i'll post some pictures about what i do, thank you very much for your replies.

Here are enclosed some pictures with the personage, there is the surface mesh, and there isn't of backpack and helmet.
See you later,
Bye

[KrisFlyZ 0]

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I would be wary of accepting that video as gospel. Anyway, the Software he has access to can predict the airflow around a wing more accurately than the video.

I'd be very surprised if off the shelf CFD software can handle the kind of turbulent flow encountered over the top surfaces of a WS. These packages are not designed to do that.

[KrisFlyZ 0]

Nice!! Please add an object like the pack on the back of the person. We need that pack to live .

Helmet optional!!

[LouDiamond 1]

Vario, you might be in luck as I would point you to a fellow frenchman who could possibly help you in your pursuit. I don't know how to get a hold of him but his name is John-pierre Knapp. He could provide you with a good deal of actual data as he carried out several lengthy tests several years back. I have been involved with a government freefall CFD project for sometime and have had a few opportunities to place a wingsuit model in both a water flow chamber and in a wind tunnel. However, the data is not mine and a NDA prevents me from disclosing specifics. From what I can see, your meshes look well done,good job.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[kallend 1,619]

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I would be wary of accepting that video as gospel. Anyway, the Software he has access to can predict the airflow around a wing more accurately than the video.

I'd be very surprised if off the shelf CFD software can handle the kind of turbulent flow encountered over the top surfaces of a WS. These packages are not designed to do that.

I'll take your word for what the software can and cannot do.

The video is showing one configuration( straight arm ) and a very un airfoil like shape. There is also a very irregular edge after the leading edge(stop video at 20 secs)

Even so, at the end of the video, the tufts pretty much hug the first few inches of the wing.

Compare that shape to the one here
here. Seems like the tufts would hug a shape like this a bit longer.

As for the contribution of the top surface of a properly shaped wingsuit wing to lift, what do you think?

[Costyn 0]

Quote

The video is showing one configuration( straight arm ) and a very un airfoil like shape. There is also a very irregular edge after the leading edge(stop video at 20 secs)

Even so, at the end of the video, the tufts pretty much hug the first few inches of the wing.

Compare that shape to the one here
here. Seems like the tufts would hug a shape like this a bit longer.

As for the contribution of the top surface of a properly shaped wingsuit wing to lift, what do you think?

Okay I agree, the pressurized.at movie looks like he's flying a prototype which doesn't have a very smooth look to it. And yes, the V3 would probably do better. I'd love to see more video of wool threads on wingsuits. Tony told me he did a couple jumps with them as well, and he also saw the flow quickly became turbulent, the threads pointing forward instead of back. It would be cool if he could post some video if he has any. Tony?

Also, for this project it might be useful to get some GPS data from someone who does wingsuit BASE, max flight for 30 seconds, to get some good l/d data. It seems that people like Loic and Robi really do get a pretty good l/d, looking at the smoke trail they leave behind.

Cheers

Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News

[KrisFlyZ 0]

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What I think is less important than what can be measured.

However, on ANY airfoil under any flight condition the lift is the difference between the mean pressures on the top surface and the bottom surface, so you can't ignore one surface and hope to model anything useful.

Thank you, I could not have said it better. That is my point exactly!

[KrisFlyZ 0]

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Tony told me he did a couple jumps with them as well, and he also saw the flow quickly became turbulent, the threads pointing forward instead of back. It would be cool if he could post some video if he has any. Tony?

Cheers

Don't doubt that for a sec. IMO, Those tufts pointing forward argues the case for having a butt deflector. But that is my interpretation.

I am really keen on knowing from this CFD study, not on an absolute basis but comparing the results between different configurations for the given model over the same angle of attack range.

a) the Induced drag and how it varies with wing twist(anti-clockwise).
b) Flat wing vs a curved wing(spanwise).

etc.