Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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What are the differences between an oblique wing and a swing wing? [duplicate]

How they differ from each other. How do they work. What is the structural differences. How do they help in reaching mach speeds and get better fuel efficiency. How does they both perform with max ...
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Does adding twist to wing always decrease induced drag and what are its effect on parasite drag? [duplicate]

I am doing an assignment and one question was the effect of twist on drag. The first two options are increased induced drag and decreased induced drag respectively. The third option is increased ...
POTATO MAN123's user avatar
1 vote
3 answers
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Do slats and leading edge devices increase lift at a constant AoA and airspeed?

I've seen mixed sources on this subject. Some say leading edge devices allow the wing to obtain a higher AoA, and others say it flat out increases lift. For me, the latter makes most sense, because ...
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Are oblique shocks formed at the leading edge-top surface of a wing?

Do oblique shocks form on the leading upper surface of a wing? I know bow shocks are formed there, but is that the same thing as I’m talking about? Oblique shocks would have to form there because the ...
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How much of the Virgin GlobalFlyer's L/D is due to laminar flow?

Despite travelling much faster than the Voyager, it has a significantly higher L/D. The latter seems to have two features that disrupt laminate flow, that are absent in the former. Namely the canards ...
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Drag breakdown of a typical civil airplane wing

How much of the drag produced by a typical GA/airliner/cargo plane's wing at cruise is induced, frictional, and pressure drag?
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why stabilator has a lower travel limit for down movements?

Within the POH of my aircraft, in a part titled "Control Surfaces Travel Limits", the manufacturer states: Stabilator: Up 18° --- Down 3° Why stabilator has a lower travel limit for ...
AIRWAYLOVER's user avatar
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When an oblique shock forms, what happens to the normal shock that helped it form?

What happens to the normal shock that helped the oblique shock form, in the first shock of a lambda shock? Oblique shock waves form because : "An oblique shock wave is a shock wave that, unlike a ...
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Computing the eigenvalues of the longitudinal dynamics _analytically_: is there a method to simplify the task, or must it be brute force?

I understand how to go about finding the eigenvalues and eigenvectors in principle, in order to distinguish the phugoid modes, but the first exercise in Lavretsky & Wise tells to compute those ...
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How do canards reduce the X-59's sonic boom?

X-59 As of 2017, the ground noise was expected to be around 60 dB(A), about 1/1000 as loud as current supersonic aircraft. This was to be achieved by using a long, narrow airframe and canards to keep ...
Abdullah is not an Amalekite's user avatar
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What determines the angle at which a shock will form?

What determines the angle that a shock will form? If you look at a lambda shock, you’ll see it isn’t straight up, but with an angle (both the front and rear part of the lambda shock). The second ...
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How to retrieve the thrust distribution over a blade using XROTOR?

What is the procedure for retrieving the thrust distribution over a propeller blade using XROTOR? I need the sectional (i.e., for each station) thrust coefficient values. I was only able to retrieve ...
floyd123's user avatar
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What's the efficiency between the duct and the fan blade?

I've heard many times that the smaller the gap between the fan blade and the duct, the better the efficiency/thrust is. Is there a formula or graph available to see how much efficiency is lost as you ...
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Do the oblique shocks at the trailing edge cause as much resistance as the ones on the surface of a wing?

Shockwaves formed on a wing will move backward until they reach the trailing edge, when they turn into oblique shocks and stop. When they're on the surface of the wing, it makes sense why they would ...
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Hexagonal Texture on RB211 Turbofan Intake

I was at the science museum in London, and was looking at the Rolls Royce RB 211-22B. This particular engine was, I believe, the sixth one ever produced. The surface texture of the fan inlet looks ...
natanijelvasic's user avatar
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Why weren't WWII piston aircraft able to fly at 500mph?

So, I just noticed that typical WWII piston engine fighter aircraft had a power to weight ratio of around 300W/kg, even at gross weight and altitude. This means that if we assume that an aircraft has ...
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1 vote
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Do boundary layers become thicker or thinner as you speed up?

What happens to the thickness of boundary layers as you speed up? I recently watched a video about the SR-71, in which it said “the inlet spike develops a significant boundary layer of air” when ...
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12 votes
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If a Cessna 172 is dropped from the sky, what minimum altitude is needed to safely land?

If an aircraft like a Cessna 172 is dropped from a helicopter, what absolute minimum altitude above the ground will be required to safely land the aircraft? CONDITIONS: Weather: Perfect conditions, ...
Gabe's user avatar
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Why aren't all fighter jets' engine intakes on top instead of forward?

Reading the question and answer to How does the Yak-130 fly with blocked engine inlets, I am now wondering why it - or any fighter jet - has forward engine intakes at all? The top and accepted answer ...
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Why are pressures equal across the slip line of a lambda shock, but density is not?

Why are pressures equal across the slip line of a lambda shock, but density is not? In this answer, it says this : The surface Σ is a slip line between zones 3 and 4. Velocities will be parallel ...
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How do boundary layers and shocks interact?

How do boundary layers and shocks interact? What difference is made with thinner and thicker BL's? I've recently been researching this topic, but at least for me there are no good search results on ...
Wyatt's user avatar
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15 votes
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How does the Yak-130 fly with blocked engine inlets?

In this Yakovlev Yak-130 youtube video you can see at 2:45 where it closes the inlets(something I've never seen before, I've only seen the typical engine inlet covers) and then it does a perfect take ...
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Why do the shocks on the upper and lower surfaces of a wing stop at the trailing edge? [duplicate]

Why do the shocks on the upper and lower surfaces of a wing stop at the trailing edge? When going Mach 0.82, the shocks on the upper (and lower) surface don't go the whole chord length of the wing. (...
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Why are bow shocks angled slightly downward at the leading edges of wings?

Why are bow shocks angled slightly downward on airfoils? In this picture if you look closely at the very bottom airfoil diagram, you'll see the "subsonic airflow" part is more below the ...
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Why do boundary layers become more turbulent as they flow over a surface?

Why do boundary layers become more turbulent as they flow over a surface? This question originated from this one. What makes the boundary become more turbulent as it flows over a surface/wing? My ...
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Why is a thicker boundary layer more turbulent?

Why is a thicker boundary layer more turbulent? I’m mainly referring to the effect of the varying speed over the boundary layer, and why it makes it more turbulent. I know it has something to do with ...
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Would air having an infinite speed of sound be ideal?

Hypothetically, if aerodynamicists had the opportunity to somehow raise the speed of sound in air to an infinite level so that air was no longer compressed, how would this affect aircraft related ...
usernamechecksout's user avatar
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Wind tunnel flow over surface vs. non-wind tunnel (atmosphere) flow question

If you take an infinitely thin sheet of metal and stick it out of the window of an airplane at exactly 0 AOA, will the surfaces of it become low pressure if you speed up? In a wind tunnel, there is ...
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Is air that is accelerating more turbulent?

Does air that is accelerating have more turbulence? It makes sense why air decelerating would make turbulent flow (e.x, the air during pressure recovery over the rear of an airfoil). Would speeding it ...
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Glider Flying Handbook page 5-6 error on effects of weight to stall speed?

I've been reading the FAA's Glider Flying Handbook, 2013 (FAA-H-8083-13A). Page 5-6 in chapter 5 states the following, but it doesn't seem right to me. The heavy glider has a higher stall speed and a ...
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Why does the density decrease equal the speed gain at Mach 1?

In this answer, it says : "At small Mach numbers, changes in speed cause negligible changes in density, but as Mach approaches unity, both are of similar magnitude. With Ma>>1 , changes in ...
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4 votes
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Why Critical Angle of attack doesn't change with an increase of IAS/TAS?

I am trying to understand this topic that is not letting me sleep. I am a private pilot and I am studying for the CPL, if someone could give me a simple explanation of this I would be very grateful. ...
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Why does density decrease most above Mach 0.3, and not as much below Mach 0.3?

Why does density decrease more above Mach 0.3, and not as much below Mach 0.3? From what I've heard, it isn't a linear relationship but why is that? Asked differently, what makes it a non linear ...
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Is my understanding of density/speed correct?

So I asked this question, and I wanted to know if my guess below was correct. I got an answer in the comments, but the reason for asking this question is because I was still a bit confused if my ...
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Does obstruction in one side of a Y/bifurcated inlet can cause asymmetric thrust?

In an airplane with Y/bifurcated inlet If for whatever reason one side of the inlet is obstructed would this cause to roll/yaw or the aircraft would stay stable. And in another setup, If instead ...
Gabe's user avatar
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Hexacopter Vn diagram/ flight envelope/ operational envelope

I am currently intern at a company. They are making agriculture hexacopter, now there is a confusion that does the hexacopter or multicopter have a V n diagram if yes how to make one what's the ...
Karandeep Singh's user avatar
1 vote
1 answer
308 views

Do speed and density exhibit a linear relationship?

Does speed and density scale linearly? Say you’re going 500mph, and speed up to 600mph. The density of the air will decrease. Now if you’re going 1000mph and speed up 100mph, does the density decrease ...
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Coordinate system in aircraft. Question about step between lines

Good day! Can you help me? I doing a restoration of the plane's geometry. I want to do restoration use a theory. But I have not information about step (size) between B.L. (W.L.) lines. As example - ...
Ruslan Pala's user avatar
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Critical angle of attack at high altitude

I remember hearing somewhere that at very high altitudes, the critical angle of attack for a given airfoil can decrease a bit. Is there any credence to this idea? Thank you
Terry's user avatar
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Camber Line equation and Thickness Distribution equation

I'm a high school student, not majoring in aerodynamics, so I'm struggling to understand the distinction between the Camber Line and Thickness Distribution equations. As I understand it, the Camber ...
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How can I calculate the surface area of a plane wing

I want to determine the surface area of an aircraft wing using calculus, specifically focusing on the cross-sectional area (thickness distribution) formula. Although I am unsure if there exists a ...
Dazai's user avatar
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Why do flat wings create a vortex/vortices?

I've been researching this for the past ~45 minutes, and I still can't find a solid answer. Why do flat wings create a vortex/vortices? In this answer, it says that the detached flow will create a ...
Wyatt's user avatar
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2 votes
2 answers
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Why is the pressure lowest towards the front of an airfoil? [duplicate]

According to this answer, the low pressure on top of an airfoil is caused by the curving away of the wing (what I interpreted it as). If you look at the lift distribution over an airfoil, you'll see ...
Wyatt's user avatar
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7 votes
6 answers
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How does the horizontal component of lift when flying at a bank angle cause the aircraft to follow a circular path?

I understand that when the aircraft is put into some bank angle, the lift vector now acts at that angle instead of directly against gravity, so we can pitch the aircraft up to increase AoA to increase ...
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Thrust needed to overcome parasite drag that increases with speed

Can anyone explain this passage from page 11-5 of the PHAK: “ For example, if an aircraft in a steady flight condition at 100 knots is then accelerated to 200 knots, the parasite drag becomes four ...
Terry's user avatar
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Does the bending air on a wing create one or multiple vortices?

As explained in the first paragraph of this answer, air will bend inwards on the top of the wing, and outwards on the bottom of the wing. This creates an inward flow component on the top of the wing ...
Wyatt's user avatar
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1 vote
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Why does the twin otter have wing fences?

Why does the twin otter have wing fences? Planes like the Cessna 172 don't have them, so why does the twin otter have them? (I know that it is used for STOL purposes, but how would wing fences help in ...
Wyatt's user avatar
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1 vote
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Am I correct with my thoughts of supersonic vs. subsonic flow?

So I'll just list a few things that I thought were correct. If there's anything I'm wrong about, I'd appreciate if someone could explain where I went wrong. In supersonic (vs. subsonic) flow, the lift ...
Wyatt's user avatar
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2 votes
2 answers
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If the RPM of the Gyro is increased due to high Vacuum Pressure. Will it increase rigidity and resist precession?

If the RPM of the GYRO of the Attitude Indicator or Heading Indicator is increased due to high vacuum pressure. Will it increase rigidity in space and resist any force applied and it will not precess? ...
Nish's user avatar
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In general, how much is V/V∞ ratio at upper wing surface?

Airflow on upper surface is always faster then freestream, in general, how much is airflow speed to freestream speed ratio(V/V∞, max values) at upper wing surface, are we talking about 1.1 to 2 or 2,3,...
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