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Venturi Airfoil

05/30/2010 1:40 AM

Another crazy idea that passed through my brain. As I understand it, airfoils generate lift when they decrease pressure above the wing, by speeding up the flow of air.

So... my idea here increases flow in a different method, by employing a venturi. That suggests to me that the pressure will reduce, and subsequently have lift, provided the drag is not too great. I realize there is a slightly larger surface area, but there is also a reduced thickness in the conventional wing chord section. Also, the need for tip winglets would be largely eliminated, and thus some efficiency gained.

I'm hoping some of you trained in aerodynamics can review this and tell me if you think it has any value. I can't find any references to such a design. Seen it before anywhere? I believe each design has strengths and weaknesses, and there would be applications somewhere that those strengths could be employed...

okay, the hockey game is back on, and philly is winning..woohoo!

(let me know if this is not clear)

Chris

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#1

Re: Venturi Airfoil??

05/30/2010 2:59 AM

Putting aside the airfoil lift vs. angle-of-attack lift debate, the concept suggested will have:

front compression, rear expansion, net force (lift) = "0"

Added structures will only increase drag.

IF you "cap" your wing idea, inject and ignite fuel at the appropriate spots in the flow, you now have multiple ramjets distributed over the whole wing. If your goal is faster and higher, the scramjet is the way to go.

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#4
In reply to #1

Re: Venturi Airfoil??

05/30/2010 10:38 AM

Hi mjb1962853,

I remembered about the scramjet when I was lying in bed after...

thanks

Chris

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#2

Re: Venturi Airfoil??

05/30/2010 3:30 AM

Hi Chris, Have a Quick View

Or here see 5 Glide slope control

There was at some point a glider air-brake system that raised little posts out of the upper surface - which is not unlike your design - but a the posts were lot smaller in scale than yours.

They were "devastatingly" good at breaking - but the system could fail only raising one side - which was "DEVAST-PRANG-ING".

Bernoulli's principal is - more or less - that the air must go faster because the distance is longer on the curved top, compared to the 'flat' under surface.

Messing with it on either surface is called "drag".

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#5
In reply to #2

Re: Venturi Airfoil??

05/30/2010 10:47 AM

Hi 34point5,

I knew there would be an increase in drag on the vert surfaces, but also a decrease in drag because the thinner wing section. so overall, a small increase in drag. There is also efficiency loss in traditional wings due to the tip vortex effect. I think that this design might minimize that, and therefore gain back the efficiency it lost as drag.

I know we have had lengthy discussions on aerodynamics here before (on cr4), and that the differential flow/pressure between top and bottom is only part of the equation. I still think that this will speed up the air flowing over the top, and therefore have a measureable effect. the question is how much...

As for 'braking systems', these are streamlined venturi shapes, designed to pass the air. All braking systems are designed to interfere with the airflow and create turbulence and drag. I do not think they are the same, or will have exactly the same effects.

maybe experimentation is the only way to tell.... but you know I like to dispassionately discuss technical questions like this, whether i'm right or wrong... thank you for your insights.

Chris

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#8
In reply to #5

Re: Venturi Airfoil??

05/30/2010 5:10 PM

Hi Chris, nice pic of a landing into a heavy multi-prop take-off wake.

The 'drag; of brakes is because they take power - as does a venturi.

I'm wondering what is behind your search. Shorter span? Lower take-off airspeed? You have had several like quests, it seems more than just your incurable curiosity.

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#15
In reply to #8

Venturi Airfoil??

06/01/2010 9:29 PM

I think the pic is a spray pattern of a crop duster.....

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#16
In reply to #15

Re: Venturi Airfoil??

06/01/2010 10:40 PM

Heeheeee.

Found this - it's a bit "TV drama" for the firts 3 minutes, then "training slow"; but goes to several concepts, including the transfer of momentum (I got a wrap on the knuckles for on Bernoulli's behalf earlier) manifest in the depression of wake.

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#3

Re: Venturi Airfoil??

05/30/2010 9:57 AM

Hi Chris,

Google for "Custer Channel Wing". It is an actual application of a venturi (okay, half-venturi) to generate lift. Oh, and apparently it works really well too.

Lord Vader out.

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#6
In reply to #3

Re: Venturi Airfoil??

05/30/2010 10:50 AM

Hi DVader1000,

I'm familiar with the Custer Channel Wing. I've got it on my favourites list. It is one of those ideas that worked well, but never had sufficient support to become mainstream. I don't get it.

and you are right.. it is a half venturi, which is exactly what I've shown.. but perhaps you are suggesting I should curve my venturii... I like it. harder to render and build, but may well decrease drag. (although, in fairness, the custer design also has the props blowing air through the channels, which directly increases the airflow too.)

Chris

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#7
In reply to #6

Re: Venturi Airfoil??

05/30/2010 12:29 PM

Structure change and the addition of an engine w/pusher prop makes the Custer Channel Wing different than proposed concept. The CCW should have a low pressure area over entire top surface of the wing channel due to the action of the pusher prop. While the CCW concept seems to have improved lift characteristics at low speed, I suspect it has not become ubiquitous because there are some significant practical limitations.

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#13
In reply to #3

Re: Venturi Airfoil??

06/01/2010 5:07 PM

That was a really interesting piece on the Custer Channel Wing.

Custer's concept of putting the airflow directly over the lifting surface I re-discovered when looking at a demonstration airfoil in the Brumigham UK technology museum, some 20 years back.

I noticed also that this concept of directing the airflow directly over the surface has been the subject of a patent from about 8 years ago!

I also understand that there are now further developments in hand regarding VTOL surfaces using a more innovative approach if,indeed, the authorities deem it to be innovative.

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#9

Re: Venturi Airfoil

05/30/2010 11:22 PM

The Bernoulli effect has been used to explain how wings develop lift since it is a simple concept to understand. Unfortunately, it only contributes a small amount of the lift needed to fly. The momentum transfer from the wing to the surrounding air generates most of the lift and requires the use of Navier-Stokes equations and computational fluid dynamics to compute it. Not an easy concept to explain or understand. NASA has a good site that covers the theory fairly well.

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#10

Re: Venturi Airfoil

05/31/2010 9:52 AM

The design would have too much drag to be useful, aircraft must me more streamlined to be successful. The channel wing has some really cool features...and its an old and more or less proven design to boot.

Balancing (or unbalanced) thrust side to side would have a dramatic effect on lift and stability. This would require new pilots with new skills. However, the biggest problem with it that I can see is that we have here a tool that has no particular use.

An perfectly good answer to a question which has not been asked.

Besides, Canadians have been building venturi effect aircrafts for years. The Avro "flying car" or "flying saucer" for instance works fine. But again, an answer to a question which has not been asked. The stability problems which famously plagued the design were eventually overcome, but the project died simply because there was no point in pouring more money into that hole with no real payoff at the end. At least the results and testing that was done is all still available if anybody wins a lottery and decides to open an aircraft factory to make such interesting toys.

I know that we use "model" aircraft with cameras on them in combat, would a venturi floated camera be useful? There are already fairly conventional aircraft which can fly really slow. The Canadian "Buffalo" used to land on football fields, for instance, and I once saw one land across the runway in admitedly unusual head winds. STOL is an accomplished fact with conventional aircraft.

Anyway, just rambing on here. However Cris, the fact is that the more I learned about aircrafts, the more I learned that what they teach people about how they fly is a vast oversimplification. The venturii effect is over-rated, the CF-104 for instance flew entirely on angle of attack alone. (It had no camber on it's so called wings and no venturi effect as a result!) For that matter the "Silver Dart" has no camber on its wings, and flies by scooping the air downwards to provide lift.

The guest's link above is a good intro to the subject.

Now, lets work on finding a use for this cool channel wing airplane!

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#11
In reply to #10

Re: Venturi Airfoil

05/31/2010 12:32 PM

Hi Yusef,

As always, you make a lot of sense. I think that the depressurization of the upper side is about efficiency & stability, but is not more important than the wing area + AOA. One has only to stick your hand out the window of a moving car to see that. I'm more likely to build an RC prototype than to actually go into business, which would provide some validity to the concept.

As much as I'm a rabid Avro fan, I don't think the Avrocar performed as expected. It worked well as a ground effect vehicle, but remember they did want to be able to actually fly with it, and it never did. (or perhaps it didn't reach that stage of development)

On a side note, we went to the Reynolds Museum in Wetaskiwin AB a couple of weeks ago, especially because they (not toronto) have built a full scale replica of the Avro Arrow... but we were told it is no longer on display (no room) and that it will have to wait the funds for a new building.

Chris

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#12

Re: Venturi Airfoil

06/01/2010 2:57 PM

CR4 ADMIN: Deleted Post #12 Spam: This post was deleted because it contained advertising outside the Commercial Space forum. Please review Section 14 of the CR4 Site FAQ about advertising.

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#14

Re: Venturi Airfoil

06/01/2010 9:06 PM

There are similar concepts that is already out there. It actually uses whats called ground effect, which Flarecraft uses.

p911

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#17
In reply to #14

Re: Venturi Airfoil

06/03/2010 6:43 PM

I don't think the "Flare craft" uses a similar technique at all. No venturii at all, only ground effect. It is a wonderful machine in its own right though, and should become a contender in the aerospace world. I don't want to rain on such a great idea, but I think the flare craft might be too expensive for a boat, and does not perform as well as an airplane, so, it is neither fish nor fowl, and its applications are limited. (As are all aircraft designs come to think of it.) I rather like its ability to glide over marshland, doing even less damage than a hovercraft, and I can see how handy such a plane would be for, say, inspecting pipelines in the arctic and ferrying people into unimproved or rocky docks.

Do you know other advantages, like is it more fuel efficient than a speed boat, or is it faster than a hovercraft?

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#18
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Re: Venturi Airfoil

06/04/2010 12:02 AM

You nailed its use on the head.

Flare craft has been around a very long time, about 20 years ago the ship yard I worked at had developed some of the proto types..If I remember right, I think its was headed up by Sikorsky's nephews or relative....

...and it has some dangerous handling characteristics, as far as costs, with what was put into it, the only thing we could see its use was for drug running, it was a boat and a airplane, yet it was neither.........but it couldn't out run a radio.

It looked cool.

It used fuel simular to a plane.....only more. seas have to be calm, thats why we were developing it on the great lakes/bays. Other than that the only other use is a prop in a Batman or 007 movie

p911

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#19
In reply to #18

Re: Venturi Airfoil

06/04/2010 1:59 AM

Aha, another answer to a question which has not been asked then! Darn! Oh well, there is no such thing as wasted research. I hear the "Spruce Goose" actually flew on its ground effect for a few hundred meters.

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#20
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Re: Venturi Airfoil

06/05/2010 1:26 AM

Kalinin K-7

With a few tweaks like putting an engine in each venturis?

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