Be your self do not depend in others to protect your points have you own personality
Aerodynamics thread
- Thread starter siegecrossbow
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Be your self do not depend in others to protect your points have you own personality
You, sir, need to work on your reading comprehension. I said no one can know the lift an aircraft generates JUST BY EYEBALLING IT. I hope this settles the discussion/misunderstanding/fiasco. Good day to you too.
vesicles
Colonel
If your goal is to attempt to replicate reality, then yes we are wasting time. However, let me ask you a question: why do you want to replicate reality when we already have an actual reality? Why going through all the trouble to make up something when we already have a real one?
Let me explain to you one more time. The goal for a model is to provide an interpretation for a phenomenon and to predict future event. This is how science progresses. You get a phenomenon that you cannot explain. Then you formulat a model that potentially explain that phenomenon. Then you test your model by performing experiments using the conditions set by the model. Then you modify your model based on the data you get from experiments until your model can correctly simulate the phenomenon. That is no way of saying that your model is fact and is reality. Absolutely NOT!!! It just mean your model still serves its purpose as a model. As soon as you begin to call your model a representation of reality, your colleagues will think you are delusional. Einstein would never say his theory of relativity is a representation of reality. He would say his theories can still interpret events as of now. Thus it is still a good theory. It is nowhere near reality. That is NOT why we come up with models.
SamuraiBlue
Captain
Completely off topic and gross miss understanding. Your representation of an atom is dumbfound version for simpletons since Heisenberg's Uncertainty Principle is too complicated to understand. Fluid dynamics is not based on quantum mechanics and does follow a straight forward principle that can be represented through mathematical equations with NO probabilities involved.
As for your question of how an atom looks like there are various electron microscope pictures like the one below.
Basically you are comparing Apples with a slab of meat.
vesicles
Colonel
We do theoretical work because a lot times we have no clue what is going on. Then someone has to develop a model. In the process of developing a model, we have to make assumptions. Many times, these assumptions that allow the model to work and to actually replicate an existing event and to predict a future event give people ideas about which could actually be happening. Then we design experiments to test these assumptions. If we get a positive data, then it is likely that the assumption in the model is correct. Then we learn a little bit more about nature.
Take the model of an atom again. In order to explain how atoms interact with each other, people came up with the orbit and sphere model. Once proven correct, people began to think "what if two atoms get together? Would that mix their orbits? Then a hypothesis is born: mixing orbits. Then quantum physicists used these assumption to develop models to see if the can predict the energy states in chemical reactions. The succeeded. Then people began to think this orbit mixing thing might hold some water. Then more modeling and experiments later, came the orbital hybridization theory. Now if the string theory is correct, then we have to throw out the orbit hybridization theory out of the window. Does that mean the orbit hybridization is all a waste of time? Absolutely NO! The theory has been useful in interpreting events. And it has helped us design chemical syntheis. And most importantly, it is a stepping stone in our quest to understand the universe. Without the orbital hybridization theory, we would not progress into something more advanced. That is the ultimate value of these models. They are steps to elevate us to a higher level. Every new model looks like an amazing achievement, by ultimately becomes a stepping stone for something even more advanced.
All in all, the take-home message is that you should never consider a model/theory a reality. Once you do that, you will stop improving. Let's face it. How would you ever improve reality??? Once you have that mentality, science stops progressing. So that kind of thinking is very dangerous. You should never think of any model any theory as absolute. Nothing is close to reality. That is what drives us to strive to improve and to get better.
Take the model of an atom again. In order to explain how atoms interact with each other, people came up with the orbit and sphere model. Once proven correct, people began to think "what if two atoms get together? Would that mix their orbits? Then a hypothesis is born: mixing orbits. Then quantum physicists used these assumption to develop models to see if the can predict the energy states in chemical reactions. The succeeded. Then people began to think this orbit mixing thing might hold some water. Then more modeling and experiments later, came the orbital hybridization theory. Now if the string theory is correct, then we have to throw out the orbit hybridization theory out of the window. Does that mean the orbit hybridization is all a waste of time? Absolutely NO! The theory has been useful in interpreting events. And it has helped us design chemical syntheis. And most importantly, it is a stepping stone in our quest to understand the universe. Without the orbital hybridization theory, we would not progress into something more advanced. That is the ultimate value of these models. They are steps to elevate us to a higher level. Every new model looks like an amazing achievement, by ultimately becomes a stepping stone for something even more advanced.
All in all, the take-home message is that you should never consider a model/theory a reality. Once you do that, you will stop improving. Let's face it. How would you ever improve reality??? Once you have that mentality, science stops progressing. So that kind of thinking is very dangerous. You should never think of any model any theory as absolute. Nothing is close to reality. That is what drives us to strive to improve and to get better.
vesicles
Colonel
You kidding, right? I was talking about subatomic particles, nucleus and electrons. An EM image shows a blob of electron rich region within an atom. It shows nothing about the subatomic particles, which was what I was talking about. NOT what an atom looks like, but what a subatomic particles look like. And check out the scale. It's 2 angstrom. You think an image of a blob of electron density, which is what EM measures at a scale of 2 angstrom, can tell you what nucleus and electrons look like???
And yes, my description of an atom is highly simplified. That is because I have no time to go into the details. And I was NOT discussing the subatomic particles in the context of fluid mechanics. I know nothing about fluid mechanics and never try to discuss it since I know nothing about it. I was discussing subatomic particles strictly in the sense of chemistry. Nothing to do fluid mechanics. And I have never mentioned fluid mechanics in any of my posts (well, I did mentioned my wife's uncle a an expert of fluid mechanics, but that has nothing to do with me). So don't put words in my mouth.
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I think you guys should all cool off.
What vesicles said is correct too, science is manly a theory; - and sure theories have progressed. The fact is, everything is a model and in many cases it is sufficient. Newtonian physics still widely used today and is the bases of fluid dynamics as we know it, is consistent with general relativity when C is small.
The fact still is, we don't know that much about fluid dynamics that correct results are only available after an actual experiment had been completed - or we would be designing perfect aerodynamic aircraft with a software package.
Vesicle is right, two sides of a coin will look different, but it is still the same coin.
It's just like you to distort facts and cherry-pick figures to try to make your argument look good. You're comparing LRIP figures for the F-35 to production figures for the F-22. Of course the F-22 will be cheaper for mass than the F-35, if you compare LRIP to production. Now, if you were actually doing an apples to apples comparison, you'd note that the F-22's initial LRIP phase cost 189 million in 1998 dollars. That's 273 million a piece in 2014 dollars, giving you a rough ratio of 17:10.
Besides that, the LRIP argument is extremely sound. The F135, as I've mentioned before, is just a derivative of the F119, except it gains a high bypass ratio, drops supercruise, and loses TVC. The F135 does boast higher T/W ratios than the F119, but the thing to note is that the F119's flat nozzles eat up about 1/6th of its total thrust. That means that once you factor out the F119's flat nozzles and use axisymmetric nozzles, the F135 has about the same T/W ratio as the F119, so the engines are essentially identical.
Yet the F135 costs $30 million a pop, making about 20% of the cost of the F119s, while the F119s cost only $10 million per engine on the F-22s, also making 20% of the total cost. Except for the LRIP aspect, there is no reason the F135s should cost so much, as the engines are not at all more capable than the F119s, hence the currently inflated cost of the F-35s is due to its LRIP / low-scale production status.
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As far as optimizing for WVR vs optimizing for BVR, the problem is that you're imagining that a single airframe can do everything. That is exactly why the F-35 project is having such grotesque troubles, because they're trying to make a small fighter take over the roles of more than 5 different aircraft (F-18, F-16, A-10, EA-6B, F-111). The thing is, a small, lightweight fighter doesn't need to be designed so that it can handle a BVR specialist by itself; by its very nature, as we've noted, smaller fighters are disadvantaged in BVR. Instead, you use other aircraft with different designs and functionalities to deal with the BVR phase of the engagement. Jammer aircraft, for instance, can degrade the effectiveness of enemy BVR systems so that they lose their advantage in BVR combat, while your own BVR specialists can screen off enemy BVR craft from being able to engage your WVR-oriented fighters.
The problem is that cost is a function of production rates and vice versa. The fastest way to increase production rates is to duplicate or scale-up existing production facilities, but the problem with that is that a given production facility is good to produce a certain number of engines and by not producing the full amount of engines you'll waste money.
Let's use an example. Say, you have production facility A, which is good for producing 100 engines a year for 5 years, and that production facility A costs 5 billion to build. Producing a full production run of 500 engines, your capital costs per engine is 10 million. Now, say you want to double your production rates. In order to do so, you duplicate it to get production facility B, which has identical properties. However, since you only have a limited order for 500 engines, after you hit 500 engines you're going to let the factories run idle. In this case, since your capital costs have doubled, but your output has remained the same, your capital cost per engine is now 20 million.
And as far as SF-A goes, while the SF-A is expected to be derived from the WS-15 core for reduced costs and the potential for retooling, there will likely be substantial differences between SF-A core and the WS-15 core. Take the CFM-56, for instance, on which the WS-10 was based. The CFM-56 was a commercial jet engine intended to power jet transports, but it was ultimately derived from the F100 engine. If sharing the same core should have given you substantial advantages in production and tooling, it took a hell of a lot of effort for the Chinese to reverse engineer the CFM-56 core into a fighter-capable turbofan which still doesn't have comparable capabilities to the F100 on which it was based.
Right, and I'm saying 1) that would happen sooner or later anyways once orders are fulfilled (which is why facilities are also designed to be adaptable to move onto new iterations so that they're not design locked when a product dies/becomes obsolete), and 2) some of that capacity can shift to fulfilling demand for variants in other uses (GTEs, high bypass variants, etc). An extension of that first point is that turbofan production expertise and skills are to a large extent generalizable, so you're not really losing returns on capital if you overproduce for one product, so long as demand is out there for the larger body of products that skill and expertise can produce. Building out that capacity addresses more than a single design.
I don't think the time China took to study the CFM-56 was about the production incompatibility between the F101* and CFM-56, but because of how much they hard to learn and because of how difficult it is to reverse engineer and learn metallurgical processes from final products. Also, as it stands right now, the WS-10 is probably superior to the F101 in its first iteration (since it sounds like the WS-10 is delivering higher thrust than the F101 at a lower bypass ratio).
And yes, it IS the F101 that the CFM-56 shares a core with, not the F100.
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