Questions tagged [aerodynamics]

A subset of the [fluid-dynamics] tag concerning primarily forces such as lift and drag generated on bodies as they move through gasses or as gasses move through the body (typically air).

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3answers
89 views

Ceiling fans with just one large winglet?

I am from India and in India ceiling fans have generally three wings. Today while laying on my bed a question came in my mind. First of all, I know that if we use just a single wing at a time of same ...
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1answer
36 views

Do airplanes circulate the air sideways in flight?

When airliners fly through clouds it looks like they are circulating the air sideways. See Image. The wings are pushing the air flown through downwards, which circulates the air each side of the ...
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Righting moment of a flattened balloon

Would a flattened round balloon tend to orient vertically or horizontally, assuming neutral buoyancy? Does this shape provide a righting moment against pitch and roll? By flattened, I do not mean “...
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2answers
43 views

Can an airship tack?

A sail ship leverages the keel’s resistance to turning moments to allow a wind crossing a sail at an angle to tack, achieving a speed greater than the driving wind. But is it possible at all for an ...
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1answer
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Do helicopters and planes fly by different reasons?

In the case of the helicopter, it is pretty clear (well, for me) that it gets lift by pushing air downwards. And as a consequence, there is more pressure below its blades than above. But on the other ...
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2answers
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Can we Predict the Trajectory of a hypersonic missile?

I read in a newspaper that we can't predict the trajectory of a hypersonic missile and this property makes the missile undetectable. But I couldn't understand why can't we predict it's trajectory? ...
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1answer
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Are aerodynamic car rims really aerodynamic?

Especially new electric cars often come with aerodynamic wheels that look like a turbine with twisted blades. What is the point of this? I mean, e.g. in cycling they use just a simple disc wheel when ...
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32 views

Velocity induced by a straight vortex filament

Consider a straight vortex filament as shown below. At each point, there's a point vortex of strength $\it T$. Consider that a point $P$ is there on the outermost circle of flow induced by the vortex ...
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How to calculate strouhal number/vortex shedding frequency of the airfoil using mathematical approach?

As a part of my thesis, I am trying to find when the airfoil starts to flutter by changing pitch angles. I've computed the results in ANSYS Fluent. But now I've to calculate the same using a ...
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1answer
68 views

Effects of altitude on paper airplanes

If one were to fly a paper airplane at the Dead Sea (400 meters below sea level) and another identical paper airplane at the peak of Mount Everest (8800 meters above sea level) would there be any ...
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2answers
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Why do airplane wings have fins?

I was watching this video and it shows that adding fins on the wing helps the air get turbulent on the upper part of the wing, which forces the air to stay longer, and ultimately this helps with lift. ...
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1answer
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If an astronaut got stuck in the middle of a space station, can he propel himself towards a wall by blowing air out of his mouth?

Consider the astronaut as floating in the middle of the "Kibo" (ISS module) without him having any initial motion. The module has a diameter of 4.2 m (inner), and the goal is to reach any of ...
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1answer
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Why are turbines more effective than propellers on airplanes? [closed]

I have read this question: Why do turbine engines work? The compressor generates a certain volume of air at a high pressure. In the combustion chamber, this air is heated - this leads to a much ...
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2answers
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What is the purpose of the roll maneuver on a rocket?

I have watched several videos on both rocket launches, ballistic missile launches, even a really cool one by Northrup Grumman on launching a nuclear missile. (https://www.youtube.com/watch?v=...
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4answers
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Why are aerodynamic / streamlined shapes always stumpy at the front?

I'm building an autonomous boat, to which I now add a keel below it with a weight at the bottom. I was wondering about the shape that weight should get. Most of the time aerodynamic shapes take some ...
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1answer
52 views

What is the effect of “The Ground Effect” on a load bearing structure?

If a train was made to utilize the ground effect, (or plane made to follow a rail) not to have any contact with the ground other than air, would the rail need to be so heavily built since the air is ...
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1answer
36 views

What is the Reynold's number of a plate moving through a fluid?

I read here that the equation of resistive drag $F = -bv$ can be used, assuming the particle is moving through a fluid at relatively slow speeds where there is no turbulence (i.e. low Reynolds number,...
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1answer
39 views

How does a bullet achieve its stability when fired?

As far as I know, darts, arrows, and airplanes have the center of gravity(CG) ahead of their center of pressure(CP) and often have fins at the rear to achieve stability. Contrary to these, bullets ...
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1answer
33 views

Vortex formation in an airfoil

How is a starting vortex formed when an airfoil (i.e cross-section of wings of a plane) starts to move?
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Is there a roof pitch angle for a hip roof that is most likely to withstand strong winds?

All other things being equal, what roof pitch (angle from horizontal) for a hip roof is likely to experience the least lift (or other relevant forces) and best withstand strong winds? Any of the ...
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What is a formal proof for Kutta-Joukowski Theorem in compressible flow?

Texts, such as Drela, Flight Vehicle Aerodynamics, indicate that the Kutta-Joukowski Theorem holds in compressible flow. Indeed, the KJT seems hold in linearized supersonic flow around a 2D flat plate....
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Calculating (transient) rate of cycles of practical thermodynamic engines (turbojet, multi-cylinder car engines etc..)

I tried to make a plan for a turbojet engine with my physics knowledge and I'm stumped in the first step. For any sustained real engine, I need to somehow take a fraction of the energy output and use ...
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1answer
45 views

Explaining Bernoulli's Principle

I'm trying to explain Bernoulli's principle (in the context of flight) to an audience that doesn't have a physics background. So I'd like to avoid mentioning technical concepts as much as possible. ...
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1answer
52 views

How fast do you have to travel to avoid freezing?

I was watching the show Snowpiercer on Netflix and it’s basically about about the last of humanity in a train that is constantly moving on tracks around the frozen earth. The earth temperature average ...
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1answer
16 views

Construction material and stack effect

In a stack, tower or chimney aimed at exploiting the updraught of air due to the stack effect, would the material that the stack is constructed from impact the flow velocity up the stack? Would the ...
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What does near field shear layer mean?

I'm reading a research paper and the abstract is as follows... Ignition initiation by a turbulent hot jet involves complex transport and chemical processes with disparate and sensitive time scales. ...
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0answers
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Model (or approximate model) of drone take-off forces?

I would like to implement a model of the force/uplift the floor makes in a multicopter take-off, but I don't find any info of this exact dynamic. Is there any paper that tackles this issue? Or any ...
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2answers
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What is the structure on SUV's top back edge? [closed]

I see a lot of SUV's that has the structure as shown in the picture .I am talking about the the top back edge (right above the back window). Wont't it worsen the streamlined design and causing more ...
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1answer
38 views

Why is pressure over the wing lesser than the pressure on the bottom? [duplicate]

Why is the flow above the wing faster than the lower one? Most people say it's because the pressure above is lesser than the bottom one But for the pressure to be low... The velocity must be high.So ...
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1answer
16 views

How can I hover the helicopter forward and backward? [closed]

I have a old toy helicopter which is currently not working. It has coaxial blades in order to lift it. It has a fixed shaft. Both blades have separate motor which helps them to rotate. I have very ...
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Need some help with shear stress

Just started getting into aerodyanamics/fluid dynamics and came across this paragraph. In it, it explains how layer a exerts a frictional force on layer b due to a velocity gradient but it also says ...
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1answer
27 views

Why are the soft sides of trucks sucked inwards at speed?

One would have expected there to be lower pressure on the outside of the truck because of the faster airflow - implying the sidewalls would be sucked outwards. Of course, there is some flapping and ...
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1answer
39 views

How do handheld folding fans create airflow?

Google provides no answers to this question. Google only tells how it cools but not how it it creates airflow. Could someone explain how handheld folding fans create an airflow despite only moving ...
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2answers
63 views

Why does a bow shock produce less heating?

A bow shock is a bow-shaped normal shock created around a blunt object flying supersonic. The shock itself - mach = 1 - can be very hot at hypersonic speeds. But the subsonic air behind is cooler, ...
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1answer
51 views

How does a fan work?

Why does a plane's fan push air backward instead of forward? And how does fan push air in any direction? shouldn't air molecules be pushed in the same plane as that of fans blade instead of going in ...
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2answers
47 views

Horizontal free fall speed vs vertical cruise flying speed [closed]

Assuming some random object (spherical cow/brick) reaches a speed v in free fall: if you pick this same object and you accelerate it horizontally up to the same speed v in the same type of atmosphere,...
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1answer
38 views

Why does the air flowing above the aerofoil moves faster than the air flowing below the aerofoil? [duplicate]

https://www.youtube.com/watch?v=UqBmdZ-BNig why can't it be the other way around that the air flowing below the chamber moves faster than the air moving above the upper chamber?
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1answer
39 views

Lift force on a rocket [closed]

How is the lift force is generated on a rocket? I've tried to find answer online but all efforts were in vain.
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2answers
39 views

How does pressure become velocity in a jet engine axial turbine?

All right. Here's what I understand about axial turbines: It is an axial compressor in reverse. An axial compressor forces air to flow in an increasingly tight space, where there is not enough ...
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2answers
32 views

Optimize crossbow [closed]

I'm currently building a crossbow and was wondering how I might improve the performance of it? I was suggested to fine-tune the rubber band more and maybe change the projectile maybe to a zinc alloy ...
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0answers
27 views

Simulating Rotor Blades for Quadcopter

I would like to simulate various shapes for rotor blades that will be used in a quadcopter. Which simulation software is used to understand how shapes, rotation interacts with the surrounding air? I ...
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2answers
43 views

Can a spinning frisbee have lift in still air?

Frisbees normally generate lift because their "wing" is moving through air, so what would happen if I just get the frisbee spinning without pushing its center of mass forward? Assume there is no ...
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2answers
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Is theoretically possible to have the laminar flow above $Re=10^7$?

The onset of turbulent flow ranges greatly, for pipe flow I came across the information that the onset of turbulent flow occurs at approximately $Re=10^4$, while for boundary layers on the airplane's ...
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2answers
72 views

Which of the following shows correct triangle law of vector addition? [closed]

This here shows an aerofoil of an axial flow compressor with velocities $V_a$ = air velocity and $V_e$ = velocity of blade.The resultant or relative velocity with which air strikes the aerofoil is $...
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1answer
97 views

Why do arrows not oscilate so much?

I am currently working on a flight simulator and I try to simulate every actions that applies on my plane. As you know, planes tend to orient themselves into the airflow direction, because of the "...
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0answers
28 views

Hydrodynamic force in complex form for fluid structure interaction

I am studying force being acted from a viscous fluid surrounding a cantilever cylindrical rod, the rod is vibrating and its velocity causes the fluid around it to flow in the plane perpendicular to ...
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0answers
25 views

Drag coefficient in a incline photovoltaic

i want to calculate the drag coefficient of a photovltaic that it's constantly changing angle. Is there a way to measure the Cd in any time? Edit: i want to calculate the Cd to have the Drag of the ...
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2answers
31 views

How can a certain velocity be used as unit of force in the lift equation?

My goal is to estimate the lift coefficient of a glider aircraft based on three properties: Climbrate [m/s] Turnrate [turns/minute] Speed [m/s] For this I'm using the lift equation: ...
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1answer
50 views

Question about a theoretical bee's power to lift

Given a theoretical bee with sufficient (not limited) wing power and material strength of the wing, but with realistic dimensions is it possible for it to lift a human? If not, what are the ...

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