Aerodynamics thread

[Jeff Head]

The good old wind-tunnel has left more than one engineer "scratching his head" in this case is it a "double entender"???? Lee Head, scratching his HEAD??? sorry bub, I couldn't resist? and I really don't know what a double entender is, but it sounds good to the Brat, so lets just "Go with what ya Got!."

My Daddy's favorite saying when we had a "steer" rounded up that was trying to jump the chute, and HE EXPECTED ME To "hold what ya got" LOL

As much as he loved flying???? WOW! did he love to FLY, he loved farming just as much, we raised Beef Cattle, Hogs, Corn, Soybeans, and Alfalfa, he was a "Farmer"!

Brat, my Dad moved us out to a ranch when I was a young boy.

About 100 acres in a house he designed and helped build. In fact we three older boys (I was only nine or ten at the time) would go out every weekend and help build on the house, build fences, clear brush, etc. for the plan he had.

He loved that place...and he drove the 60 miles one way into work at Vought every day until long past when we were all grown. But he loved working out there and realizing his and my Mom's dream. And it was good upbringing for four boys too!

Cutting and hauling hay, taking care of the various animals, building and repairing fences...lots and lots of hard work. But also hunting, fishing, camping...swimming in the creek. As much as my dad loved his engineering work, His real talent showed in providing for and taking care of his family, and raising his sons. He was a God-fearing, honest, just man...who expected us to work hard and do our part...and holding our feet to the fire...but was also willing to show love and compassion to us...more than we deserved.

Several of the other ranchers around the area, once they got to know him and worked with him, always referred to him as Mr. Lee.

 

[nemo]

Actually, it seems to me that you "equation" boys, (sorry Equation, not You bruda), are missing the very clear science of "observation/experimentation", that is abundantly clear to those who are astutely observing the physical properties of the air-flow over the AIR-CRAFT.

You are counting your in-adequate equations as the end all, be all, when all real aerodynamicists, model/wind-tunnel, and ultimately build and fly to "PROVE" the theory of your concept?? that's why we build "proof of concept" models? then we have master scratch who not only does the math, he is able to apply it and to hypothesize from the math and his model, an accurate "picture" in his minds eye, of how that all plays out, and to "actualize" that concept?

I am completely inadequate in the math dept., but I have enough experience/experimentation under my belt to "visualize" airflow, as the aircraft passes "through" the air.

Brat -- you are able to 'visualize' airflow because the engineers designed the aircraft to have 'regular' airflow, and equations are one of the tools the engineers used to make sure the airflows are regular. And that's when aircrafts are designed to be stable -- nowadays aircrafts are deliberately designed to be unstable and use non-linear behaviors such as vortex generators to get better performances. I am not sure 'visualizing' will do any more, at least for design and engineering.

 

[vesicles]

Guys, we need to understand that there are so many limitations in models and equations, such as assumptions that you have to make in developing the most fundamental fluid mechanics models. Normally, you have to make so many assumptions to make equations solvable when developing a model. There is a joke in "The Big Bang Theory" about a square chicken in the vacuum. Sheldon Cooper also talks about his models having 20 something dimensions. Although these are jokes, they still capture the essence of limitations in theoretical work. No matter how fancy your model is, it may not even work in real world.

Models can approach the truth but can never be the absolute truth. that is why we need to constantly validate models by comparing them with real world observation. So observation or "visualizing" is absolutely essential to designing anything, including aircraft. We should not and must not argue with experiments, observation or "visualizing" when there is a difference between theoretical model and actual observation. When difference occurs, it is almost always the theoretical work that is wrong. Hence the saying "you can't argue with data". Guys like AF Brat are the foundation of any modeling and theoretical work. No matter how fancy your models are, the first step to validate your model is to talk with AF Brat. If he doesn't agree with you, your model is out. No question asked.

 

[nemo]

Guys, we need to understand that there are so many limitations in models and equations, such as assumptions that you have to make in developing the most fundamental fluid mechanics models. Normally, you have to make so many assumptions to make equations solvable when developing a model. There is a joke in "The Big Bang Theory" about a square chicken in the vacuum. Sheldon Cooper also talks about his models having 20 something dimensions. Although these are jokes, they still capture the essence of limitations in theoretical work. No matter how fancy your model is, it may not even work in real world.

Models can approach the truth but can never be the absolute truth. that is why we need to constantly validate models by comparing them with real world observation. So observation or "visualizing" is absolutely essential to designing anything, including aircraft. We should not and must not argue with experiments, observation or "visualizing" when there is a difference between theoretical model and actual observation. When difference occurs, it is almost always the theoretical work that is wrong. Hence the saying "you can't argue with data". Guys like AF Brat are the foundation of any modeling and theoretical work. No matter how fancy your models are, the first step to validate your model is to talk with AF Brat. If he doesn't agree with you, your model is out. No question asked.

Equations are nothing more than *repeatable*, *quantized* observations. As good as anyone's observation or intuition, unless it is made quantized and repeatable, it is not going to be good enough for anything other than experimental aircrafts. If you want to risk your own neck, fine, but it's too much to as others to risk theirs on your intuition. Hence you start from equations. If anything does not fit into the known equations, you try to avoid that situation from happening.

 

[Pmichael]

Theoretical (CFD) and experimental validation (wind tunnel) of the aircraft model is an interrelated process of aerospace engineering.

Pilots are the last element of the developement chain because they are normally not flying or giving feedback until after the fly control unit provided the aircraft with artificial linear

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[Air Force Brat]

Guys, we need to understand that there are so many limitations in models and equations, such as assumptions that you have to make in developing the most fundamental fluid mechanics models. Normally, you have to make so many assumptions to make equations solvable when developing a model. There is a joke in "The Big Bang Theory" about a square chicken in the vacuum. Sheldon Cooper also talks about his models having 20 something dimensions. Although these are jokes, they still capture the essence of limitations in theoretical work. No matter how fancy your model is, it may not even work in real world.

Models can approach the truth but can never be the absolute truth. that is why we need to constantly validate models by comparing them with real world observation. So observation or "visualizing" is absolutely essential to designing anything, including aircraft. We should not and must not argue with experiments, observation or "visualizing" when there is a difference between theoretical model and actual observation. When difference occurs, it is almost always the theoretical work that is wrong. Hence the saying "you can't argue with data". Guys like AF Brat are the foundation of any modeling and theoretical work. No matter how fancy your models are, the first step to validate your model is to talk with AF Brat. If he doesn't agree with you, your model is out. No question asked.

I'm nearly speechless brother, but good manners and deep appreciation for this most generous kindness, moves me to tears, and to say thank you. Your observation would well apply to my "old man", (no, I Never called him that while he was alive), he should have been an engineer, but chose instead to fly, sadly I lack the Math??? but as you have well stated, sound engineering starts with a "vision", the Wright Bros. and Lilienthal observed nature, more specifically birds in their quest for flight, the drawings and mathematics followed those "visions", along with testing and trials and more testing??

Thank You for this most generous and gracious compliment, may God's richest blessings and grace cover you and yours my brother! I do love you guys, you each have my greatest affection and respect!

 

[vesicles]

Equations are nothing more than *repeatable*, *quantized* observations. As good as anyone's observation or intuition, unless it is made quantized and repeatable, it is not going to be good enough for anything other than experimental aircrafts. If you want to risk your own neck, fine, but it's too much to as others to risk theirs on your intuition. Hence you start from equations. If anything does not fit into the known equations, you try to avoid that situation from happening.

Please note that observation is NOT intuition! NO! NO! NO! Intuition is uneducated and unreliable guess without experimental support. That is not to be trusted and highly discouraged. Observation, however, is gathering of experimental data carefully and methodically conducted by experienced personnel. It is the golden standard of science. Every discipline of science starts with observation --> quantization --> validation of model using observation --> predicting future events using the model --> again, validation with observation. At any stage, if observation does not agree with the model, you modify the model because your model is no longer accurate in describing the event that it is intended to quantize.

So "if your observation does not fit into the known equations," you modify your equations to be consistent with observation! It simply means your equation is wrong, or you have ignored something important in your equations. If you limit yourself to the existing set of equations, we will never progress. The golden ruler is the observation, not models. By avoiding situations that do not fit the equations, you are ignoring the huge signs that tell you your model is wrong!

the process of "quantization" has serious limitations, as I describe in my earlier post. You should also know what steps one takes to decrease the amount of variables in an equation so that it can actually be solved. Thus, it can never be considered as the standard. Anyone who has done theoretical work should know these limitations and the limitations of modeling.

 

[nemo]

So "if your observation does not fit into the known equations," you modify your equations to be consistent with observation! It simply means your equation is wrong, or you have ignored something important in your equations. If you limit yourself to the existing set of equations, we will never progress. The golden ruler is the observation, not models. By avoiding situations that do not fit the equations, you are ignoring the huge signs that tell you your model is wrong!
the process of "quantization" has serious limitations, as I describe in my earlier post. You should also know what steps one takes to decrease the amount of variables in an equation so that it can actually be solved. Thus, it can never be considered as the standard. Anyone who has done theoretical work should know these limitations and the limitations of modeling.

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

 

[delft]

Please note that observation is NOT intuition! NO! NO! NO! Intuition is uneducated and unreliable guess without experimental support. That is not to be trusted and highly discouraged. Observation, however, is gathering of experimental data carefully and methodically conducted by experienced personnel. It is the golden standard of science. Every discipline of science starts with observation --> quantization --> validation of model using observation --> predicting future events using the model --> again, validation with observation. At any stage, if observation does not agree with the model, you modify the model because your model is no longer accurate in describing the event that it is intended to quantize.

So "if your observation does not fit into the known equations," you modify your equations to be consistent with observation! It simply means your equation is wrong, or you have ignored something important in your equations. If you limit yourself to the existing set of equations, we will never progress. The golden ruler is the observation, not models. By avoiding situations that do not fit the equations, you are ignoring the huge signs that tell you your model is wrong!

the process of "quantization" has serious limitations, as I describe in my earlier post. You should also know what steps one takes to decrease the amount of variables in an equation so that it can actually be solved. Thus, it can never be considered as the standard. Anyone who has done theoretical work should know these limitations and the limitations of modeling.

"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.

 

[Air Force Brat]

"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!