Laminar flow

The more I look into wing design, the more complicated it gets, it's a black hole of complexity...

. . . even a golf ball.

The properties of the medium change as the craft moves thru it. One would need feedback from all surfaces when turbulence begins. Then, the size and shape of the craft would have to change very quickly, to prevent that turbulence from growing and cancel what has developed. Maybe steerable micro lines? That would change direction, but not relative pressure and/or pressure ratios.

Perhaps a quick pattern recognition system and a quick surface pattern generation system.

Let's flip it. Is turbulence all bad? Would it be possible to tune it? Could we recover some of the energy lost to it? Or might we produce one turbulence to counter another? Could we manufacture a slip turbulence? Where we slip thru? A turbulence resonance?

Sometimes we can take advantage and gain from a obstacle. Has any looked from the opposite end? Maybe a certain level and character of the turbulence is the key.

It's just a napkin on the bar, I have no knowledge of such.

"Riblets" are a method of obtaining lower drag in areas where turbulent flow is unavoidable.

We used to have riblet gravy every Thanksgiving....

Aircraft in stable flight don't cause turbulence for themselves, they react to the external forces imposed on them.

Perhaps a clear definition of turbulence should be presented first. From Wikipedia:

"turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity"

To me, as a private pilot, professional flight engineer, and participant in several NASA airfoil studies and other studies such as wing tip vortices, I don't see how you could anticipate "chaotic changes" and then design active or passive aircraft systems to neutralize them.

Currently there are radar systems that give hints of turbulent areas in the atmosphere so that they may well be avoided when noticed. But as far as the actual aircraft participating in eliminating or even minimizing turbulence, I don't think our current understanding of fluid dynamics is capable of addressing it.

As always, I am open to correction, enlightenment, etc.

If you are able to calculate and anticipate the "chaotic changes" in turbulence or turbulent flow you will get a Nobel Prize!!!

You have rightly said that a "System for anticipating "chaotic changes" and designing active or passive aircraft systems to neutralize them" may not be currently available.

But if the technological revolution in the field of terrestrial telescope offers us hope for a wholly new concept in the field of aerodynamics too.

Strides in the technology of Adaptive Optical Elements and Systems for the creation of the terrestrial largest, most powerful, and most accurate telescope, to compensate for “The warm air rises, the cool air sinks; the winds blow; the Earth rotates; etc. All of these effects and more cause the molecules of our atmosphere to move and jitter around constantly. Astronomically, every observer must try and find ways to compensate for the trillions upon trillions of molecules interfering with every camera pixel attached to your telescope”. https://medium.com/starts-with-a-bang/this-is-how-astronomy-is-finally-defeating-its-greatest-enemy-earths-atmosphere-faa7f77a2ce0

Thank you, that is very well described and may well be part of a future or interim solution to minimize or eliminate turbulence that affects aircraft. But, it's one thing to alter optics and yet another to alter physical aircraft components while on the go, especially in terms of added weight and power requirements. These are always trade offs in heavier than air flight.

So here's where my thoughts go. Assume for a second that many of the UFO's being reported are really extra-terrestrial craft. If true the flight characteristics they describe are indeed proof that solutions to turbulence and other hazardous atmospheric events are possible; instant acceleration/deceleration, inertial changes that would pulverize the human body and mechanical systems, the ability to navigate in differing fluid densities effortlessly (air, water, space), etc.

I have no doubt that these "craft" would need to have some system that eliminates these hazards. I currently believe that involves some kind of field that encompasses the "vehicle"; maybe gravity altering. But that may be the ultimate solution with interim band-aids that could be instituted while the technology matures.

I think Gene Roddenberry of Star Trek fame, as well as other SF writers, have pointed the way, if not detailing the how. From my experience I think projected fields of some kind are the answer to the turbulence question and many others.

Adaptive optics in terrestrial telescopes do not predict or anticipate changes to the light path by the motion of the atmosphere. They measure and respond to the chaotic changes found in the atmosphere with a projected laser beam into that atmosphere. The adaptive elements compensate "on the fly" for the changes.

By definition, chaos cannot be predicted. If you could predict the change then it wouldn't be a chaotic change. Chaos theory does reveal patterns within a chaotic system that can identify more likely results but that is not a prediction.

Exactly. in terms of predicting where turbulence may manifest in the atmosphere as a whole. But discreet areas of active chaotic turbulence can be identified by some radars or by pilot reporting which, nowadays, allows aircraft to vector around those areas, or, presumably, allow anti-tubulence aircraft systems of the future to activate.

I presume that the use of the term prediction relative to (chaotic) turbulence means the actual movement within the identified area is not predictable.

But I nitpick.

"Aircraft in stable flight don't cause turbulence for themselves"

Actually, they do. Aircraft fly through a medium that is very smooth, except in very rare instances. The initial flow over the wing is laminar. It later becomes turbulent, and that is "new" turbulence, not present before the aircraft came through.

I think maybe a wing that is open in the middle with parallel slats that has a pressure flap that opens to the upper wing surface that can inject air at the barrier layer when needed might improve laminar flow...so you would have an upper and lower wing surface held together with these flow channels that can adjust the rear space between the wing surfaces creating either a low or high pressure near the 3/4 wing depth where the boundary layer propagates on the upper wing surface....

So the air flowing through the split wing opening will create a suction at the boundary layer and draw the air into the internal air stream increasing lift and reducing drag...

One has effectively doubled the surface area of the wing. The contribution from form and profile drag as a result of that doubling needs to be considered.

I can recall Boing looking into this more than 30 years ago. I'm sure I have a copy of an article from an engineering magazine that describes using micro grooves on a wing surface to increase the attachment of laminar flow by around 10%. The original concept was based on a study looking at how sharks are able to accelerate so fast. I'll have to see if I can dig the article out.

Yeah I think I remember that, it turns out the sides of the fish were just flexible enough to deform with the turbulent waves, not helpful I would think over a few mph...

My memory was that it had to do with small grooves in the shark skin but it was a long time ago. I'll try to find that article.

https://daily.jstor.org/what-makes-fish-swim-fast/

..."Elasticity plays an important role too. Nobody has been able to measure the elasticity of fish bodies as they swim, but the consensus is that elasticity must help store energy and improve the efficiency of swimming.

Tingyu and co’s model provides some insight here too, by showing how elasticity varies with the force and power generated by the body. The researchers show how eels and mackerel must become elastic at different places in their bodies and at different points during each undulating cycle. “This observation is consistent with the findings of previous studies that suitable elasticity can save and restore energy to improve efficiency,” they say."...

https://www.technologyreview.com/2018/12/18/138543/we-finally-know-how-fish-swim-so-fast/

"When it comes to swimming, fish demonstrate an effortless grace and power that humans can only dream of. While the fastest fish swim at up to 70 miles per hour, no human has ever managed even 4 mph in water. Even the fastest submarines have a top speed of only 50 mph."

Well maybe it's more important than I first thought....

"Air has a density of about 1.2 g /litre, and water has a density of about 1 kg /litre. Air is therefore about 830 times less dense than water."

So a fish traveling at 70 mph in water would be experiencing the same forces as traveling 58,100 mph in air....? That doesn't sound right....in any case, 70 mph in water is impressive, and studying how this is achieved by the predators of the deep should shed some light...maybe

https://nymag.com/speed/2016/12/supersonic-underwater-travel-may-be-coming-soon.html

So a less dense bubble of gas enveloping the airplane....hydrogen? nah wait a minute, maybe the hydrogen would cling to the surface....

We could use hydrogen as fuel for the jet engines and have the fuel tanks slowly leak through vents at the front of the plane surfaces...What's the worst that could happen!?

https://www.nbcnews.com/mach/mach/these-new-designs-are-changing-look-airliners-surprising-ways-ncna745806

Viscosity is a factor as well, as is velocity and a characteristic length.

Reynolds number - Wikipedia

It is perfectly possible in principle to test an aircraft shape in a water tank when submerged by making the Reynolds Number the same for both the water case and the air case. When this is so, the shape will behave in the same way, irrespective of scale size of the models.

I've given up looking for the article I mentioned, looks like that folder got thrown out at some point. I have found however, several references on-line to this research, some relating to Boeing but also a thesis here.

Boing Boeing

Chaos is just a replacement word for unknown or un-discerned. Chaos, randomness and probability are polite lipstick for not knowing. Saves face. And ass.

Water drag was overcome with an interface of air. Hundreds of MPH under water. The air, interfaces the water(zero velocity) to the torpedo(100+MPH velocity) with little resistance or friction.

Something that can repel air molecules, and let empty space act as an interface might do it. With more study and knowledge, an EM frequency might do it. The proper terahertz tone might repel them, and we only have to repel the "skin", so not much power required. Maybe even powered by the static generated.

How does that static affect turbulence now? Does it?

"How do static charges affect an aircraft?

Aircraft accumulate electrical charges created by static electricity under various flight conditions and discharge of that electricity can generate radio frequency interference (RFI).

Static dischargers (wicks) are installed on aircraft to reduce the buildup of static charge on the airframe and radio receiver interference. During the flight, the aircraft becomes charged with static electricity."

https://flightsafety.org/amb/amb_jul-aug92.pdf

I wonder if the static affects the turbulence. Or if turbulence affects the static. I would think a charged molecule behaves differently than a neutral one. Have we done electrical experiments with turbulence? Does a charged surface affect turbulence? How about an alternating field?

...."The static electricity that accumulates on aircraft is proportional to the drag (so in turn to the frontal area of structure) and to the airspeed. It is the wind of moving through the air that rubs against the aircraft surfaces, and made greater by rain, snow and dust in the air.

A little background: Early aircraft of aluminum had little paint, whereas modern aircraft are entirely painted, and have much non-metallic composite structure. This greatly increases the static electricity. Paints have changed also and produce more static as they better resist ultraviolet fading and are better insulators. The surfaces that face the wind (forward) are those that the air rubs against more, and it is the rubbing that makes the electricity. It is called triboelectricity.

As the aircraft flies through the air it rubs off electrons from the air and its particles. This electricity streams over the paint and plastic increasing in voltage before it can pierce through the insulating paint to the metal underlying or meets metal fasteners or structures, and be a part of the charge on the capacitor that is the aircraft.

A small twin engine commuter aircraft is a capacitor of about 1000 picofarads. A larger airliner may be about 3000 picofarads. Your body by comparison is about 100 picofarads. These are the capacitances that can be charged and can hold an electric voltage.

The formula for this is V=Q/C. Where V= voltage, Q = charge from air particles, and C = capacity of metallic structure relative to earth. At about 12,000 volts. the air begins to ionize and provides a discharge of the capacitor that is the aircraft body. The voltage drops and the cycle begins again.

As the aircraft flies through the particles of air and dust and precipitation, the force rubs off electrons and an electric charge accumulates to a higher and higher voltage . These captured electrons repel each other and accumulate at the extremities of the aircraft - the tips of the wings and tail. If untended the voltage rises to corona levels and then discharges in a stream of sparking. Then it starts to charge again.

But, it is normal that aircraft have “static wicks” installed to keep the voltage below corona and to continuously discharge the static electricity safely. It is necessary to add conductivity to composite (insulating) areas, either by wire or coating or chemical fabrication."....

https://www.quora.com/How-does-a-static-charge-build-up-on-the-surface-of-an-aircraft-showing-the-structure-and-distribution-of-electrical-charges-in-example-materials-such-as-metals-and-plastics

Since static electric charge is disruptive to communication, it is considered a bad thing...

Ok, then we need to split the air stream before it hits the plane. Interesting problem. Or a hydrophobic principle/method for air.

A nano forest surface might corral a layer of air, letting the stream interact with mostly air blanket, instead of the surface. Pores could ooze replacement molecules.

Perhaps some sort of a "skin" vacuum. Can't we make a much better vacuum with EM, than we can mechanically?

NASA did some experiments on boundary layer attachment via suction. The two show-stoppers were the weight of the system and clogging of the holes with dust and smashed insects. Surface contamination and manufacturability are problems with small grooves and nano texturing.

Keeping the channels clean is an issue. A scaled-up version of the concept is found in wing fences, often used to control lateral turbulent flow.

“it's one thing to alter optics and yet another to alter physical aircraft components while on the go, especially in terms of added weight and power requirements.”

Certainly not an expert in this area but there already are aircraft that modify its characteristics on the fly, automatically, and are quite efficient I think. I am not suggesting using feathers on airplanes but these components constantly adapt to changing pressures, flow, and air conditions. Curious to know about the efficiency of air flow over a falcon’s wing versus a typical high efficiency airplane wing.

Can you please provide a citation for any aircraft currently in service or in active full scale flight test that has the capability of changing its shape and, thus, its flight characteristics?

By that I don't mean aircraft with slats, flaps, ailerons, lift killers or other hardware commonly in use today with FAA approval.

I am aware of several research studies by NASA and other aeronautical research entities that are experimenting with such technology, maybe even in early active flight test. But I know of nothing even being considered for commercial deployment at the present time.

Thanks.

I can think of a few aircraft that changed their shape. This one is no longer in service but at one time I would see them daily.

Yes, that is an asymmetrical wing configuration performed during testing. This wing-changing capability would not actively or rapidly change to alter turbulence but a change in turbulence did happen.

The other planes I can think of are the B1-B and F-111. AFAIK Only the B1-B is still in active service.

I guess I should have included swing wings in my examples of old tech. The first production swing wing in wide use was the F-111 Aardvark, introduced to service in 1967.

And I suppose I also should have also included warp wings. The first Wright Flyers were warp wings. There were many more in early aircraft evolution. And there have been some recent proposals that would re-introduce warping.

I'm looking for anything that is "new", probably in terms of wing skin surfaces warping to adjust to differing flight situations. For example there was a NASA/MIT scale prototype of an aircraft wing made up of plates that could be mechanically manipulated to adjust the basic wing shape to fit diverse situations such as high speed (supersonic) cruise, slow speed maneuvering, landing, etc. That design got through wind tunnel testing but ended with no commercialization in the works as far as I know.

My point being that there are a multitude of ideas but damn few come to fruition.

The devil is usually in the details when it comes to a wing design moving to actual production. That's when you have to factor in things like a spar for structural integrity, fuel storage, electrical and/or hydraulic power networks to power whatever the morph tech might be involved. Maybe even an air source and channeling for an air blown (or suction) wing surface (which would likely involve a computational system and gating for manipulating the system through differing flight regimes). And then there's maintenance.

Oh, and not to mention surviving the FAA antiquated approval process.

....and training pilots to qualify to be able to fly it....yes any new plane that will be in commercial operation requires a certified pilot to fly it...

And then there's that!!

Looks like the shark skin effect is still being investigated here.