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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1answer
52 views

Could leading-edge dynamic stall occur for a tripped airfoil?

As far as I know leading-edge dynamic stall is characterized by the formation of a Leading edge vortex. This leading edge vortex forms due to the 'bursting' of the LSB (Laminar separation bubble). ...
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126 views

Sub-ideal Autorotation in Rotorcraft

I have another AuRo question for you. When a Helicopter autorotates (ideally) it is in the turbulent wake state and there is virtually no flow through the rotor disk (figure of Leishman attached). Now,...
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Has anyone tested or flown permeable wings to increase efficiency?

See this article: Aerodynamic Performance Improvements Due to Porosity in Wings at Moderate Re Was wing porosity ever tested/used for real aircraft? source: The aerodynamic efficiency parameter ...
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1answer
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What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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Would it be beneficial to have rotors AND propellers instead of a tiltrotor?

Would it be beneficial for tiltrotor aircraft if they had BOTH rotors and propellers, instead of the hybrid proprotors that are neither good propellers nor good rotors? Like imagine the V-22 Osprey ...
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Why do the ailerons of this flying wing work oppositely compared to those of an airplane?

I made this simple wing glider and put some ailerons on it. I thought that the ailerons in this glider would work the same way it works on airplanes, wherein the roll will be in the direction of the ...
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3answers
443 views

What is the maximum speed for regulation of sonic boom noise?

If fuel cost and fuel efficiency were not the issue, what is the maximum speed (air speed and ground speed) that business jets or airliners could travel at without exceeding the maximum noise and ...
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1answer
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Pitching Moments CG vs CP vs AC

Probably the question will be a little bit confusing but I'll try my best to make it clear. Due the position of the CP with respect of the AC, symmetrical airfoils don't produce pitching moments, but ...
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Are 0g pushovers in a C172 safe/legal?

I see YouTube pilots do it all the time, but I’m wondering how safe this maneuver really is given the fuel is a gravity fed system. Also, is it legal?
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What factors determine magnitude and orientation of induced velocity at propeller blade?

• Magnitude What factors determine magnitude of "Vind" (induced velocity)? • Orientation If we take analogy with induced velocity at wing,isnt "Vind" must be prependicular to Vr? • ...
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Is it fairly common for student glider pilots to have wing tip strikes, especially in gusty cross wind conditions?

Is it fairly common for student glider pilots to have wing tip strikes, especially in gusty cross wind conditions? I understand gliders are landed level, slow down and then the wing drops onto a wing ...
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Can boundary layer blowing increase transonic efficiency?

One of the problems faced by transonic aircraft is flow separation by recompression shock. Can the pressure drag that arises due to this flow separation be reduced by re-emerging the boundary layer ...
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Do black wings have better aerodynamics?

This news article links to a 2019 academic study: Thermal impacts of wing coloration on surface temperature during bird flight. Most of birds have dark upper wing feathers. Dark colors keep a sunlit ...
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How to calculate angular velocity and radius of a turn?

How can I calculate with known tangents of different angles and by rules of thumb? Which formulae should I use for fps and NM?
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For jetliners, how is a swept wing justified over a thin wing?

For a given speed, a swept wing is a fatter alternative to a straight, thin wing. But why? Does not the sweep lengthen the wing and make it heavier? Is the swept wing chosen for the extra fuel tank ...
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Relation between weight of the aircraft and mach number [closed]

Is there any formula that relates weight of the aircraft with mach number?
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Why aren't isentropic noses and tails used in supersonic aircraft?

An inside out paraboloid would theoretically produce isentropic compression for an inlet cone. But this question is about nose and tail cones on fuselages, and leading and trailing edges of wings. An ...
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2answers
170 views

What are the pros and cons of putting a propeller immediately before a slipstream pylon vs. immediately after

In the following situation with a slipstream pylon for a self-launching glider, what are the tradeoffs in sticking the propeller before vs. after the pylon? The wind turbine industry has the same ...
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2answers
176 views

How should I attach an aircraft model in a wind tunnel when testing wind gust/yaw stability?

Where should I attach the rod to the aircraft model when simulating wind gust /weather vane effect in wind tunnel testing? At the center of gravity, behind the CG, in front of the CG...?
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Is possible to stick two '2-blade' propellers to get multi-blade propeller?

Does propeller blades' airflow interfere with each other blades and decrease overall thrust? Should I consider high pitch propeller for this purpose? My purpose: I'm looking for a 20-inch four-blade ...
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1answer
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Induced drag reduction from tandem wing

Induced drag is proportional to the square of span loading. The normal method to decrease it would be to increase span. This, however, leads to an exponential weight increase. So, my question is, if ...
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5answers
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If the profile of a wing pulls a plane up, why can planes fly inverted?

I'm simplifying here, but every introduction to flying shows us that the profile of a wing leads to lower pressure on the upper side of the wing, hence the wing and the plane attached to it will be ...
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0answers
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How does gross weight affect helicopter autorotation?

The factors which affect helicopter autorotational aerodynamics include airspeed, gross weight, rotor RPM, and density altitude. The effects of these factors can be examined during a few phases of the ...
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1answer
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What are the advantages and disadvantages of the MiG-29's horizontal stabilizers (not what do they do)?

The MiG-29's tail axes are located fairly close to the leading edge, and rotate along an axis oblique to the chord. What are the possible consequences to this arrangement (e.g. actuator torque, ...
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Why does this Strikemaster have a textured leading edge?

I was at Duxford recently, and spotted a Jet Provost Strikemaster that had a rough texture applied to a portion of the leading edge of the wing. Why was this applied?
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Calculating CL and CD from Cp vs. x/c graph data? [duplicate]

I need to calculate CL, CD, CM coefficients for NACA 0012 airfoil at angle of attack 6 degrees and Re=7.5e5, Mach=0.05. I used Xfoil for getting the CP distribution, Cp vs. x/c graph and Cp-x-y data. ...
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1answer
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Is there any formula that directly relate density to altitude for a wide range of altitude?

I am working on a code to simulate a vehicle trajectory based on forces act on it in different altitudes, I need a formula that gives density in an altitude range between 0 and 40 km to obtain lift ...
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155 views

Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
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Why would a stretch variant need a larger horizontal stabilizer?

With the 787-10 stretch, Vedad Mahmulyin (a Boeing engineer) saved the company millions by implementing a software solution that negated the need to enlarge the horizontal stabilizer. Software again ...
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1answer
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So fast, it melts the ice off?

Approximately, how fast would an aircraft have to travel through freezing air to melt the ice off the wing, propellers, or rotor blades?
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What are benefits of unloaded wingtips?

What are aerodynamics benefits of using unloaded wingtips (zero lift)? does unloaded wingtip make inner parts of wing more efficient? (I know that unloaded wingtip reduces bending moment,so structural ...
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2answers
93 views

When does root bending moment start to become important?

I guess for small aircrafts ,hangliders etc root bending moment is not important at all,because it is relativly easy to achieve sufficient strength ,so their ideal solution will be eliptic..? Does ...
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The relation between Euler-angle rate and body-axis rates?

A paper about quadcopter dynamics and control shows the relation between Euler-angle rate and body-axis rates as: Q1: why are there $R_{v2}^{b}(\dot{\phi})$, $R_{v1}^{v2}(\dot{\theta})$, and $R_{v}^{...
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Does Smeaton's coefficient have a modern accepted value or it is dependent of the air density?

Does Smeaton's coefficient, k, have a modern value or it is dependent of the air density? Why is the accepted value of k so high? In various texts about the Wright brothers (see 1 and 2) one can read ...
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107 views

How do wing tip vortices that interact with the wing surface affect drag?

Often people say vortices are behind the wing so they cannot produce drag, I am not interested in those vortices behind the wing.... I am interested how wing tip vortices which interact with the ...
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3answers
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Does rolling or yawing affect the angle of attack?

If I'm on final in windy conditions and I need excessive rolling and yawing movements to stay on centerline and say, my pitch stays constant - does rolling or yawing change my AOA such that I could ...
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1answer
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How to find the angle of attack?

I'm trying to calculate the angle of attack (AOA) using aircraft some data. From what I understand the AOA is just the angle between the aircraft's forward unit vector (out the nose vector) and the x-...
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1answer
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Why do few small planes have reflexed flaps?

Reflex flaps capability is very common in flapped gliders, but outside of gliders I am only aware of the Maule which has this feature. https://aviation.stackexchange.com/a/37753/20394 shows the ...
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How much is thickness of air layer with zero velocity at wing surface?

How thick is the layer of air that is not moving(zero velocity) at the surface of wing, and can this be taller than the relative roughness height? Because everything that is inside this layer (V=0) ...
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1answer
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How pressure fields change around wing?

In the 3D case,downward turning is immediately above and below the wing is stronger than in 2D case,for the same lift.This is because more rapid dying off the pressure above and below the airfoil ...
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Is skin friction also pressure drag looking at microscopic level?

Roughness in boudary layer is taller than height of air which is not moving ,feel oncoming airflow in boudary layer, at front side must be high pressure at rear low pressure etc,so net force is to the ...
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Why are the Antonov An-124 horizontal stabilisers directly behind the wings?

With the wings being on the same plane as the horizontal stabilisers, turbulent air from the wings would interfere with the airflow over the elevators making them flutter. Surely putting the ...
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1answer
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Do raked wingtips reduce drag of a hang glider?

https://rakedwingtip.wordpress.com/ Do they realy reduce drag or improve performance? If so, how?
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How does the dihedral angle work?

I've been looking for this topic on the internet but I don't have enough concrete answers. Suppose we have a plane with dihedral and it has a suddenly swinging to the right (watching from the nose of ...
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1answer
136 views

Is there an ideal lift distribution for human-powered aircraft?

Is there an obvious, ideal lift distribution for human-powered aircraft? Eliptic or Bell(unloaded tips) distribution? For this who will tell Bell distribution,I have counter question ready,why dont ...
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1answer
163 views

Why does the Tu-134UBL have a sharp/pointed nose cone?

Russian/Soviet aircraft design has always intrigued me, and even more so when coming across this photo of the Tupolev Tu-134UBL with its pointy nosecone. Having looked up the performance ...
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What are differences between vortex, swirl, eddies and wake?

These terms seem to have the same meanings. Can anyone differentiate them?
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Wing dihedral in a biplane

Would a biplane be able to fly if the upper and lower wings were in opposite dihedral? Imagine a wing configuration similar to the fictional "X-wing" design from StarWars. What would be the ...
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3answers
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What determine hang point and bar position of hang glider?

1.What is relation between C.P., A.C., hang point,bar conection to made glider to fly well,when I lift hands from bar ,he will not pitch. 2.Does hang glider change stabilty from stable to neutral to ...
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Downwind Myth Question

I was reading a discussion about the "Downwind Myth" and a doubt arose: If we are taking off with a 50knots headwind, that wind component will be part of our dynamic pressure, and so in that ...

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