What is the Area Rule ACTUALLY?
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- Опубликовано: 31 май 2024
- Today we're talking in-depth about the Area Rule. What is it actually and why does it work? This rule has been a staple of aircraft design since the '50s, but online explanations tend to be lacking some of the more interesting specifics.
(0:00) - Intro
(1:20) - Simple Drag
(2:32) - Wave Drag
(2:58) - Transonic Area Rule
(4:11) - Supersonic Area Rule
(5:06) - Outro 
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How have i not seen this channel yet
Area ruling for supersonic flow the Mach wave angle, the angled plane, is really a cone. So, the cross-sectional area is the Mach wave cone, where it intersects the body of the aircraft.
The Concord would have a cone angle of 30 degrees for Mach 2 flight. Where the area rule would be optimized for its design cruise speed.
The reason why you have to smooth out the cross sectional area at an angle is to ensure that as much of the plane as possible stays behind the shock cone to prevent the shockwave from building up on various parts of the plane which will reduce wave drag. This causes the ideal area to be shifted rearward, it's for this reason that supersonic planes like Concorde feature wings placed further back and why their leading edges are sweptback to such an high degree. The area plot is not necessarily different when flying upside down as you simply take the angle of the shockave of whatever side of the plane you're basing it from. Since the Mach cone is symmetrical, the angle will be the same regardless of the plane's orientation.
Angle is the same, but the area cut is not (except for axisymmetric body). That is why series of area distributions is supposed to be obtained for each angle of orientation and then averaged over all of the angles. Early papers on area rule such as Lomax from 1955 explain it well.
Awesome vid. Just found your channel looking for a bit more in-depth info about area rule than the basic minimum I know. this was great, subbed!
well laid out very informative ... and concise ... nice job
Quaility work, as always.
4:34 if I'm not wrong using oblique cross section slicing for supersonic area ruling is an approximation, and you have to roll the cutting plane around the axis of forward motion while maintaining the angle, and average the cross sectional area.
A more rigorous solution would be to mesh the surface of the entire aircraft, and project a mach cone from every point, and see where the density of cone surfaces is high and reduce it. There's also the effect elsewhere in the comments where the airflow changing directions as it passes over the wings influences the cone angle
I’m an aerospace engineering graduate but by no means an expert. My intuition would tell me that the effect the Mach angle has is due to the fact that the velocity profile of the air (in essence, the cross section of the air as it moves around the aircraft) does not necessarily stay oriented perpendicularly to the centerline of the aircraft. That is, as velocity increases, the velocity profile of the air, as it moves along the aircraft, will skew diagonally due to the velocity differential between the upper and lower surfaces of the aircraft. This effect of the air’s cross section being further towards the tail on top of the aircraft means that the “area” you’re trying to modify must be oriented to match the velocity profile’s new diagonal orientation. I’m sure that equating the velocity profile’s diagonal skew to the Mach angle is not perfectly accurate, but it is probably close enough to use as a guideline for design. Please let me know if this isn’t accurate, thanks :)
Always great videos!
I think i just found the best channel ever. This is truly a gem. Earned a sub. But at 3:11, how do they have the same area plot? I dont understand how they are similar? If what way am I supposed to look at it?
Maybe you're thinking of the relation of the cross sectional area to the area plot in the wrong way? The left model has long, thin wings while the right model is like a football with an extra bulge wrapped around it's waist. The left model obviously has more surface area, and covers more area when viewed from above...but these are not the areas of concern for wave drag. Area rule only deals with how cross sectional area changes as you move from the nose to tail. If you ran the two models through a bread slicer (the tip of the nose being the first slice and tip of the tail being the last slice), each slice would have the same area as the corresponding slice from the other model.
Great video! Subscribed!
Great explanation!
Awesome video!
Beautifully Described! You could prolly teach a creature without opposing thumbs to paint Like Bougereau!
Are Kuchemann carrots the same thing EXACTLY as Whitcomb bumps and if not, what exactly is the difference?
they are the exact same thing
there is only ONE patent prior to Whitcomb which you showed. NO prior evidence of the notion of area ruling before that that I am aware of. But that patent was for EXTERNAL features, that were droppable, and never resulted in a single aircraft nor practical application even to this day, and made no attempt to shape the airplane itself (relying primarily on the external pods to achieve the effect, which results in all sorts of secondary issues).
Whitcomb's work was also validated, and implemented. And thus Whitcomb gets the full credit. And not only did he use his idea to fix airplanes, he used it to fix wind tunnels as well.
Why does the plane in the thumbnail look like a boss out of an ace combat game
so where's the picture of the plane in the thumbnail?
In the thumbnail sir
at 4:11 : angled planed to determine supersonic area rule? In fact the area must be calculated for an infinite number of angled plane rotating around the direction of travel axis. This make much more sense... see explaination in NACA REPORT 1284. Theory Of Wing-Body Drag At Supersonic Speeds. By Robert T. Jones.
Why do so many young people find it necessary to try to discredit the ingenuity of American engineers and inventors? Simply discovering a thing is not the point. It is also being able to do something actionable and useful and translate that discovery into practical achievements. The American system is particularly good at this and deserves credit for leading the rest of the world in this respect.
...no. Ask any actual scientist or engineer, and they'll tell you they built on the discoveries and ideas that came before. And those discoveries and ideas? They were built on what came before them. Discovery is important. Application is also important. Optimisation is also important. It's simply wrong to suggest that discovering something doesn't matter.
De Laval invented the rocket nozzle as we know it. But Robert Goddard was the first to use it for a physical rocket. Guess what he called those nozzles? De Laval nozzles. Goddard did this because he used de Laval's ideas in his efforts. Among academia, there is actually a sense of giving credit where it's due. He didn't invent the nozzle design. So he credited the person who did. By suggesting that this video was discrediting Whitcomb's achievements, you're actually discrediting Frenzl, who discovered it almost a decade earlier *and* designed aircraft taking it into account. These aircraft were never finished, but the designs were made. And they would have been successful applications of area rule.
Your comment is truly accepted and appreciated my friend! Wonderful saying!
👏🏻👏🏻
What's the deal with the ANSA astronaut that keeps popping up doing the same thing over and over
👏👏👏
Supersonic area ruling is bad on combining *every* rotation of that planar slicing, not just one.
I feel like a engineer now lol
How work in wind mill
I’m not sure why you’re windmill is running near supersonic speeds but that could be an interesting problem
ya nerelere girdin aga
ANSA
Me P.1112, you're pointing to air intakes, not area ruling. your attempts at trying to steal credit from Whitcomb are lame.
that area rule sounds much too dumb to be an actual rule. Surely the equalization has to be angularly close? contribution from the wings can't just be countered by a dip at the top of the fuselage? it must be right at the foot of the wing
No, it can be on the top of the fuselage. Look at the 747: later versions had the hump on top of the fuselage extended to help with the area ruling despite it not being near the actual wings. This configuration counterintuitively gave it more cargo space with a net decrease in drag
@@ConHathy says who?
@@DanFrederiksen I learned about it in university but it has also been in "The Whitcomb Area Rule: NACA Aerodynamics Research and Innovation" by Lane E. Wallace. There is a widely circulated figure showing the area ruling and reduction in drag here (It says it comes from Aeronautics and Astronautics 1973, in my couple of minutes of googling I couldn't track down the original source of the figure but that would have been a NASA report): www.researchgate.net/figure/Boeing-747-cab-extension-subsonic-area-ruling-Source-Aeronautics-and-Astronautics-1973_fig82_349063662
@@ConHathy thank you. I notice that the extended upper version didn't come out until 1983 but it could still be experimental data before it was done. Wiki says the extended upper were on request from airlines though. And I note that the supposed benefit doesn't kick in until above the max cruise speed of the 747 at the time. So it could never benefit from it according to that data but if the data is real, it's interesting nonetheless. Would be interesting to see that experiment done again, perhaps in good simulation as well to explore the airflow and shocks, if the area rule is in fact in effect.