What are the drawbacks to "annular wing"/"super circle" aircraft?

[TechDIYaspirant]

TL;DR

Just looking for someone to shoot some holes in this (pun intended)

By annular wing I mean something what is seen in this video.


I'm fascinated by this design because it seems to lend itself to fluid entrainment and a greater lift profile for a smaller radius of wing. They are said to be quite stable.

 

[Vanadium 50]

"...you have to do it just right"
"...we almost lost it on takeoff"
And you want to use it for passenger flight?

For any technology change, you need to say what problem you are trying to solve and how much better the new design is. That's step one - once you do that, we can talk.

 

[Baluncore]

I'm fascinated by this design because it seems to lend itself to fluid entrainment and a greater lift profile for a smaller radius of wing.

A wing is designed to push air downwards as it provides lift, not to encourage entrainment. The sides of the circle seem to be a waste of material and fuel. It is more like a box kite than an airfoil. The tail plane has different characteristics to the main plane. That will lead to attitude changes with speed, a stalling or plunging flight.

How can engines apply thrust at the centre of drag?
Where will you place the ... how many engines?

What will happen when you want to turn?
Do you have a hangar high enough?
Will it be blown over when parked on the apron?

 

[Lnewqban]

Welcome!
Your main problems are: to overcome gravity always-vertical force and to keep control of the flying machine.
As the sections of the ring deviate from perpendicular to gravity, its useful lift gets reduced, but still add drag and weight.
The center of drag and mass of the wing is too high (big lever respect to the aircraft COM) for proper stability and maneuverability.

Perhaps reducing the wingtip losses could compensate for the above additional difficulties?

Please, see:
https://en.m.wikipedia.org/wiki/Closed_wing

 

[TechDIYaspirant]

Welcome!
Your main problems are: to overcome gravity always-vertical force and to keep control of the flying machine.
As the sections of the ring deviate from perpendicular to gravity, its useful lift gets reduced, but still add drag and weight.
The center of drag and mass of the wing is too high (big lever respect to the aircraft COM) for proper stability and maneuverability.

Perhaps reducing the wingtip losses could compensate for the above additional difficulties?

Please, see:
https://en.m.wikipedia.org/wiki/Closed_wing

I imagine squashing the ring into an oval whose shortest radius was perpendicular to downward pull of gravity would reduce some of the drawbacks you mentioned.

 

[Lnewqban]

I imagine squashing the ring into an oval whose shortest radius was perpendicular to downward pull of gravity would reduce some of the drawbacks you mentioned.

Exactly!
It has been done.
But then, you run into the new problem of the top surface interfering with the airflow over the lower wing, reducing its lift efficiency.
Note how biplanes where replaced with single wings when the resistance to bending of the light materials was increased with time.

 

[Vanadium 50]

imagine squashing the ring into an oval whose shortest radius was perpendicular to downward pull of gravity would reduce some of the drawbacks you mentioned.

I think you have to fess up to not being serious. You have not answered the question "what problem is this trying to solve?" much less "how much better is this design in solving it?"

Otherwise, you have a toy, not a tool.

 

[TechDIYaspirant]

"...you have to do it just right"
"...we almost lost it on takeoff"
And you want to use it for passenger flight?

For any technology change, you need to say what problem you are trying to solve and how much better the new design is. That's step one - once you do that, we can talk.

Well you caught me I didn't watch the video. I was just using the thumbnail as a visual reference. I've seen other model aircraft of the same design that seemed to have better performance but I'm not sure I can find it now. As to your questions I'll try to answer them as succinctly as possible below.

1. Problems
- wing tip vortices reduce efficiency, no wingtip, no wingtip vortices

2. Better.
- rings are stronger than lines, less strength needed lighter less dense materials, greater load capacity
- entrainment does not provide lift but airflow over surfaces does, less energy to move air over surfaces more efficient lift per unit of wing area.
- the sides of the ring can have control surfaces that replicate upright functionality of tail section, the offset of wings from perpendicular replicates the functionality of lateral function of the tail section (lift available at different points along the fuselage. (pics and description below. This potentially eliminates the need for a tail entirely saving weight, drag and failure points.

I can see how the video above would not inspire much confidence having said all this so let's imagine the following:

1. wing rigidity similar to modern airlines.
2. fuselage centered within the ring.
3. ring squashed into an oval with shorter radius perpendicular to the ground so fuselage is connected to inner surface ring at two points opposite one another.
4. Rotate ring by 45 degrees along it's profile so that the rings connections with the fuselage are now at the following points from the tip to the tail at the first 1/4 length below and above the last 3/4 above. This means the ring/wing is swept back.

I would also add perhaps theirs also a version greatly scaled up which could eliminate entirely the tube and en-corporate cargo capacity into the wing itself (imagine two flying wings connected at their tips)

I've included a crude sketch to help for those less imaginitively inclined. Also in case it's not patently obvious, I'm no engineer so you patience with my crude understanding and obvious oversights is greatly appreciated.

edited for clarity

 

[TechDIYaspirant]

Exactly!
It has been done.
But then, you run into the new problem of the top surface interfering with the airflow over the lower wing, reducing its lift efficiency.
Note how biplanes where replaced with single wings when the resistance to bending of the light materials was increased with time.

What about a swept back design? Apologies for the crude sketch? Also see another post with attached pic for more detailed description.

 

[TechDIYaspirant]

I think you have to fess up to not being serious. You have not answered the question "what problem is this trying to solve?" much less "how much better is this design in solving it?"

Otherwise, you have a toy, not a tool.

See my reply to your initial post.

 

[FactChecker]

You make some broad claims that I doubt.
1) "greater lift profile for a smaller radius of wing": Not sure about this because so much of a ring does not have a normal pointing upward. It seems that the more upward force you want, the more you will flatten the ring into an oval. Then you approach a biplane and @Lnewqban's comments in posts #4 and #6 apply.
2) "rings are stronger than lines": stronger against which forces? Certainly, the sides of a ring tend to bend out and are weaker against those forces.

 

[TechDIYaspirant]

You make some broad claims that I doubt.
1) "greater lift profile for a smaller radius of wing": Not sure about this because so much of a ring does not have a normal pointing upward. It seems that the more upward force you want, the more you will flatten the ring into an oval. Then you approach a biplane and @Lnewqban's comments in posts #4 and #6 apply.
2) "rings are stronger than lines": stronger against which forces? Certainly, the sides of a ring tend to bend out and are weaker against those forces.

If at any point it appears that I am making a claim of any type please don't read it as such. I'm no engineer so my description of these problems is based on my rudimentary understanding of fluid dynamics and material science, as a result I'm not writing with precision but just with the language that seems to concisely convey my understanding.

I imagine this can be jarring to people who are use to rigorous formal statements of a problem. I stumbled on this forum through serendipity and thought it would be a good place to ask questions about problems I've wondered about and increase my general understanding of topics.

If I've mistaken the general intent of the forum, that is to say if it is intended strictly for scientifically formal discussions between industry professionals and academics I apologize and will look for a more suitable forum to inquire about my casual and amateur curiousity.

 

[berkeman]

I stumbled on this forum through serendipity and thought it would be a good place to ask questions about problems I've wondered about and increase my general understanding of topics.

PF is a great place to ask questions, especially about valid source material that you've actually read/viewed...

However, this is not a question in your OP:

Summary: Just looking for someone to shoot some holes in this (pun intended)

 

[TechDIYaspirant]

PF is a great place to ask questions, especially about valid source material that you've actually read/viewed...

However, this is not a question in your OP:

I'm not here to argue with you. But I'm genuinely curious to know the following.

How is someone who is not versed in the relatively rarefied field of aerospace engineering supposed to know before asking the question what is or is not valid source material?

The plane in the video flies does it not? Surely that is a sort of validation in and of itself. I've specified to the best of my ability when pressed throughout the thread. Apparently this is not enough to establish my bona fides.

I'm not an expert, I'm not even confident it is a good design. Hence the question:

"What are the drawbacks to "annular wing"/"super circle" aircraft?"

It appears to be a rather simple question to me. Maybe it is not though, in which case I would welcome any answer that might specify the misconception or further clarify the matter even if it is in regards to elementary precepts of aerodynamics. I hope it is apparent from my username that I do not consider myself above such basic pointers. Or If this thread is not worth your attention I will not regard your silence as a sign of your inability to clearly state an answer.

The video is not of importance except as a visual aid to identify very generally the type of wing design I'm describing and eliminate misunderstanding. It is not necessary to review it because I'm not interested in the particular performance characteristics of that model, the materials it is assembled from, the operators opinions about it etc. I hope this clears up any misunderstanding my use of the video may have given you.

 

[jrmichler]

I'm fascinated by this design

Then try searching aircraft annular wing. Lots of good hits, and it will give you the background to ask meaningful questions. Then we can give you some good answers instead of stumbling around trying to figure out what you really want.

 

[berkeman]

The plane in the video flies does it not? Surely that is a sort of validation in and of itself.

In addition to JR's good suggestions, one trick I use when trying to search for resources on a subject that I'm not very familiar with is to start with a Google Images search, and then maybe add more refining search terms as appropriate. That presents you with many parallel web page resources, and you can look at the URLs for each of the thumbnail pictures as you scroll down through the search results to decide which image/website to click into.

I generally don't click into general YouTube videos (the quality of the source varies too much), and instead look for university web pages and reasonable-looking engineering websites to try to find the best sources to post with my questions.

Hope that helps.

 

[Vanadium 50]

How is someone who is not versed in the relatively rarefied field of aerospace engineering supposed to know before asking the question what is or is not valid source material?

Respect.

"You watch this video that I haven't" is deeply disrespectful of other people. As it happens, at least part of the answer to your question "what are the drawbacks" are in the video you yourself posted. There's really so much we can do for someone who isn't putting any effort in.

You got some good advice from @jrmichler and @berkeman. That will get you father than complaining that you don't know much about this field but won't put in the effort to learn more.

 

[Benjies]

You got some good advice from @jrmichler and @berkeman. That will get you father than complaining that you don't know much about this field but won't put in the effort to learn more.

While I see the validity in all of your posts challenging the question, I see a lot of myself in the OP. I suppose it boils down to a question of what you want to see in this forum: sparse and limited engagement on posts that must be deemed worthy of engagement, or open engagement on posts from persons here to discuss a subject loosely. Both have valid stances and a balance likely needs to be met. I'm not entirely convinced the OP here asking a "prove it" question should be damned to stop asking questions.

Does PF wish to represent itself as a novel source of truth for all things physics? Does it want to engage with a wider community and discuss off-kilter topics such as the OP? I see a dichotomy here as one doesn't seem to serve the other: While in the brain of a student who's completed their masters in a subject can see a variety of reasons why the world should be interested in their subject, and scrutinize how exactly they should engage with the subject, those outside of this world simply can't empathize and either won't discuss with you at all, or will frustrate as they discuss in a manner deemed improper for the subject at hand. I'd site the OP as an example, to be frank.

Tonight I had a conversation with a friend about User Experience over a drink, and that space of technology development. I asked ignorant questions- framed my vision of UX from the perspective of network performance, and was quickly checked. The conversation went on, I was educated, and we proceeded with our nights. If a bystander with a PhD in computer science who worked at Google overheard us, regardless, it is the bystander's choice to either ignore the feeble attempt at tackling the difficult subject of UX, or engage with us imperfectly, at our level.Taking a step back and addressing the OP and this thread- oftentimes people are offset by "why not X" posts in aerospace design (and applied sciences in general) because the world has taken painful and expensive steps to converge on the solutions you see operating today. If there were any merit to an alternative design such as the one you are posing here, it would have already been built. A grandfather's tale to guide your questionings (or not questionings) of the science, but valid nonetheless.

Hope I haven't offended. Thanks all.

 

[anorlunda]

Does PF wish to represent itself as a novel source of truth for all things physics?

PF already made up its mind. Here is our mission statement.

Mission Statement:

Our mission is to provide a place for people (whether students, professional scientists, or others interested in science) to learn and discuss science as it is currently generally understood and practiced by the professional scientific community. As our name suggests, our main focus is on physics, but we also have forums for most other academic areas including engineering, chemistry, biology, social sciences, etc.

 

[Benjies]

While the question you've quoted was more a demonstration of an unattainable extreme, the mission statement to 'discuss as a person of the professional scientific community' would suffice to meet in the middle between this extreme and the opposite extreme of discussing openly. Understood, thanks.