Aerodynamics thread

[Air Force Brat]

Well stated master delft, and Vesicles is a research scientist, and speaks in the "precise" language of science, there is NO room in research for idle "intuition", but accurate, repeatable, observation is the minimum standard for truth! but you are quite correct in referring to what the AFB does as intuition, I am quite "intuitive", but my intuition is always informed by observation? I have watched thousands upon thousands of landings, takeoffs, airshow performances and birds flying?

The Canadian Goose is the most faithfull model of aerodynamics in all of nature, the Buzzard very close behind?? LOL when I was a young man, we had a small farm, with a horse drawn corn planter, with a metal seat, converted to three point hitch, which my Daddy would pull behind our little ford tractor. Right in front of that seat was a Lever, which controlled the depth of the planter in the ground, (served as my first real joy stick), I made hundreds of low level passes down thru the cornfield, with a neat pull-out on each end, crop duster turn, and right back down on the deck, I still fly every piece of equipment I operate, and my onboard MK-1 flight director has served me faithfull for 59 years?? Yes its all between the EARS!

At some point my Dad told me to watch the Canadian goose, I recall him telling me as several were landing to watch them put down their flaps, they did, and then to watch them lower their landing gear. He then pointed out that they make a "take-off-run", and fly along in ground effect, running on the surface of the water as they gather airspeed to quickly climb away. Lielenthal and the Wrights gained their aerodynamic insight watching and observing nature??? not sure why Wilbur and Orville put the tail in front??? dummies???? but Lockmart has it straight!

Jeff Head's ole Pappy Lee had a great idea with the variable incidence wing on the F-8, and when that gorgeous A-7 came along with that beautiful gun, they dubbed her the "gunfighter", incidentally the A-7 has one of the best safety records of any jet fighter, and was a beautiful turnin burnin little fool!

 

[no_name]

not sure why Wilbur and Orville put the tail in front???

Lol I believed the brothers actually built the first canard aircraft.

 

[Air Force Brat]

Lol I believed the brothers actually built the first canard aircraft.

Yaaaaa! Dat Vaass my point!

 

[vesicles]

If there are limitations, what of it? If it's within a certain limit, it can be acceptable or work around it.

Every theory / model has its limitations. As I mentioned in my previous posts, one has to make many assumptions when developing a model (mostly to simplify the equations so that they can be solved), many of which are not realistic. This is a case-by-case situation. As someone working with these models, you need to understand these assumptions, i.e. limitations. These limitations can only be acceptable for certain amount of time. As you progress and continue to push the envelope, many of the limitations gradually become unacceptable as they seriously restrict how much you can push the envelope. thus these limitations must be corrected in order to come up with revolutionary designs. If we are stuck with "working around the existing models", we will never move forward.

Engineers and scientists have different mind set. Scientist want to look for deeper insights into nature while engineers want to avoid risk. So anything unexpected is risk, and risk must be resolved or workaround. The primary goal of any engineer is to meet the spec -- creating new theory, if it happens, is a side product, not goal.

As you guys correctly pointed out, I am a scientist and have been around scientists all my life, thus not familiar with how engineers think and work. However, from what Jeff showed us how his dad worked through the puzzling problems (posted a couple pages before), my guess is that good engineers also think like scientists. they would not be satisfied with their existing models. As shown by Jeff, his dad and his colleagues found out that existing aerodynamic models at the time would not work. the old theories that they initially used must be excellent theories at the time. Otherwise, they would not be using them to design their planes at the beginning. However, as they pushed the envelope to such an extent that the existing theories could no longer work for them. Instead of working around the limitations and working with what they had, they designed new experiments to modify the existing theories and eventually came up with new theories and new aerodynamic models. that's how our understanding of aerodynamics has progressed so much since the early days. I don't think the pioneers simply decided that they only wanted to work with whatever they had. they wanted to know why their existing models would not work and in the process discovered the limitations of their models and corrected them. Otherwise, we would still be stuck with flying wooden biplanes using the same aerodynamic models used by the Wright brothers...

"Intuition" is also used as the name of guessing at the solution of a problem based on a lot of experience. But you then need an experiment, or many experiments, to check on that intuition. Such intuition can save a lot of time and effort.

Well stated master delft, and Vesicles is a research scientist, and speaks in the "precise" language of science, there is NO room in research for idle "intuition", but accurate, repeatable, observation is the minimum standard for truth! but you are quite correct in referring to what the AFB does as intuition, I am quite "intuitive", but my intuition is always informed by observation? I have watched thousands upon thousands of landings, takeoffs, airshow performances and birds flying?

The Canadian Goose is the most faithfull model of aerodynamics in all of nature, the Buzzard very close behind?? LOL when I was a young man, we had a small farm, with a horse drawn corn planter, with a metal seat, converted to three point hitch, which my Daddy would pull behind our little ford tractor. Right in front of that seat was a Lever, which controlled the depth of the planter in the ground, (served as my first real joy stick), I made hundreds of low level passes down thru the cornfield, with a neat pull-out on each end, crop duster turn, and right back down on the deck, I still fly every piece of equipment I operate, and my onboard MK-1 flight director has served me faithfull for 59 years?? Yes its all between the EARS!

I agree with AF Brat that "intuition" is a dirty word to me. I can't remember how many times we have been proven wrong by intuition... Intuition, a lot of time, can't be explained. It just comes to you. It's unreliable. I myself have been told that I am an intuitive person. I have been told by my mentors and colleagues that I have certain knack for noticing trends from seemingly random data. That's intuition, in my opinion. However, I have been proven wrong so many time when I attempt to extract meaning/trends from seemingly random data. So intuition may sound cool, but is completely unreliable. However, experience is another story. Every conclusion based on experience is supported by tons of observation. That's why experience is so important. That's why I believe that opinions from experienced aviators like AF Brat are invaluable.

 

[delft]

One of my professors "explained" that an airflow follows a surface "magically". ( Coanda effect ). I didn't think he was a good professor.

 

[Air Force Brat]

One of my professors "explained" that an airflow follows a surface "magically". ( Coanda effect ). I didn't think he was a good professor.

Well master Delft, I never realized what a poet my old man was, practical, pragmatic, forming a flying club and convincing 14 other guys, half who were not pilots?? that they wanted to buy an airplane, several did become pilots, and some are flying yet today?? myself being one who steals whatever flying I can find... some where in our many travels to the hayfield, hog-lot, cornfield, or alfalfa field??? stated, "some days you touch the control yoke, and that's all you feel???? on other days you feel the airplane from the core of your soul, all the way to the wing-tips," and yes old friend, it is magic, it is actually more spiritual than you might imagine.

To know and experience the joy of flying is to draw closer to my own Master Designer, and yes He is the one who gives us true Flight! To experience LIFE, in nature, in the Garden, in the Air, is to allow Him to show you the miracle of LIFE. Yes, I have delivered my own baby, and held her in my arms and watched the true Miracle happen, and no, theres nothing in this life that could possibly compare??

One of the many reasons I love aerodynamics, it is the beautiful science, the science of the poet!

 

[SamuraiBlue]

Hey you guys have you heard about the magic air flow regulator that will probably revolutionize aerodynamics?

It's called plasma actuator and was first proposed by the Russians in the 60's.
With it it will make unimaginable turns possible.

 

[SinoSoldier]

This may be a stupid question, but a dilemma I'm sure many aviation enthusiasts have pondered over, nonetheless.

Take a look at this video first:

Do you guys think the extremely high AoA, turning rates, and general maneuverability of the Su-35 can be attributed to its TVC, high TWR, airframe design, or perhaps an amalgamation of the three?

Do you think TVC is essential to be maneuverable in combat or can that be attributed more to the thrust-to-weight ratio. In other words, can a J-11D equipped with the notional 14-tonne engine pull off the same maneuvers as the Su-35S?

 

[Air Force Brat]

This may be a stupid question, but a dilemma I'm sure many aviation enthusiasts have pondered over, nonetheless.

Take a look at this video first:

Do you guys think the extremely high AoA, turning rates, and general maneuverability of the Su-35 can be attributed to its TVC, high TWR, airframe design, or perhaps an amalgamation of the three?

Do you think TVC is essential to be maneuverable in combat or can that be attributed more to the thrust-to-weight ratio. In other words, can a J-11D equipped with the notional 14-tonne engine pull off the same maneuvers as the Su-35S?

The OVT, High Thrust to Weight, and very Happy aerodynamics all contribute to the amazing performance of the Su-35, and No without OVT, the J-11 will lack the ability to be thrown around as the OVT birds are, even the F-22 is much more maneuverable than say the F-15 or even F-35. Now having said that the J-11 should have all the maneuverability and more than say an F-15, due to a superior flight control system and very happy aeros as well, but the lack of OVT does handicap the J-11, F-35, Typhoon, F-18, etc, etc, ...

Ovt is a game changer, and gives you the ability to "push" the airplane around its three axis, even lacking sufficient airflow to do so by virtue of pure aerodynamics, much of the very low speed kicking it around on this video is due to the controllability afforded by the thrust vectoring!

Let me add that fighter philosophy is changing, and super-maneuverability is no longer considered to be the game changer in a combat situation that it once was??? Much more emphasis is being placed on shooting the bad guy- BVR!

Future air combat will lack many of the accomodations and niceties we afforded one another in the past, such as the option to "disengage"??

 

[Pmichael]

Does the T-50 even has thrust vectoring?

I think it's pretty much accepted that thrust vectoring is just an effective way of losing all your energy. The combination of canards and

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vortex controllers is the more elegant way to archive similiar flight characteristics without dealing with heavier engines.

Not that extremely high AoA is really sustainable anyway.