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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7 views

Optimize toy airplane from a cocktail-straw and two paper rings

Thrown horizontally with small ring pointing forward (both rings oriented upwards at start). Both rings having same width (2.5 cm) and length 12.5 cm (small ring) and 2*12.5 cm (big ring). Paper fixed ...
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2answers
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Would dimples help a ping pong ball travel faster?

Dimples are used on golf balls to promote the formation of a turbulent boundary layer that stays with the ball longer as it travels through the air, therefore greatly decreasing the pressure drag ...
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How environmental factors affect aerosol transmission?

I am totally an amateur in this field, but I need this for my own multi-disciplinary project. I know this might be a basic question, and I actually did do some researches. I just want to make sure ...
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41 views

Lift on Airplane wing

Why commercial airplanes use long, slender wings? Isn't it to maximize lift, we make the plane's wings as wide as possible?
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1answer
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Pressure Drag on a 2D Aerofoil even when no Separation of the Boundary Layer?

So if a 2D aerofoil is subjected to potential flow, then there isn't a boundary layer separation at any point with the surface of the object, and hence pressure remains constant at the front and back ...
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1answer
46 views

How do birds fly forward (parallel to the earth)?

What is the physics of a bird’s forward motion? I know that a pressure difference in the air beneath their wings and above their wings can generate an upward force called lift. The velocity of air ...
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1answer
25 views

How to calculate Mars and Lunar payload if I have LEO payload? [closed]

I am working on a project and i need the payload capabilities of different rockets to LEO, mars and lunar orbit. Usually the LEO payload along with all other relevant data is given for all rockets. is ...
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$C_d$ is bigger at laminar or turbulent flow?

Bodies can be subjected to pressure drag or friction drag. But let's consider the overall drag coefficient $C_d$. My question is: $C_d$ is bigger at laminar or turbulent flow? This image represents ...
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1answer
38 views

Can the circulation around a wing be predicted (roughly) without the help of a computer? [duplicate]

This site already has several questions about how airplanes fly. Some of the answers do give useful insights, but the only real explanation I've found involves using a computer to solve the Navier-...
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How to calculate the positioning angle of a rocket for launch

I am building a model rocket. I want it to end up in a specific position. If I am taking into account the acceleration, starting position, end position, mass, and wind speed, how do I find the angle I ...
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Why does fluid pressure decrease as fluid velocity increases according to Bernoulli's principle?

I’m studying aerodynamics. I understand Bernoulli’s principle very well, I just can't wrap my head around why pressure decreases as velocity increases. Like the garden hose example: if you cover the ...
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How can I control the airflow in a car by open or closed window configuration?

What car window configuration will let air in by me and make / let it exit away from me. I have a large divider between front and back seats that covers much, but not all the plane between. People in ...
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Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust $F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
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Will the hose eventually become a straight hose? [closed]

A garden hose on the ground, water with enough speed flows out at its end. In the beginning, the hose is bent. Assuming only the force caused by bending and the friction force on the ground act on the ...
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2answers
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Why does the airflow at the leading edge of the wing curve toward the trailing edge of the wing?

Why does the airflow at the leading edge of the wing curve toward the trailing edge of the wing? Is it because the leading edge of the wing generates high pressure? High pressure pushes the air from ...
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How is the energy dissipated by drag split between sound waves and turbulence?

Consider an object of radius $R$ traveling at a constant, slightly subsonic or supersonic speed through a homogeneous fluid, in conditions of very high Reynolds number. Because the object experiences ...
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1answer
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“Trapping” boundary layer to reduce skin friction drag?

One of the propsed ways to reduce skin friction drag is by maintaining laminar flow. But to do this normall requires a low Reynolds number. But a low Reynolds number is in itself a recipe for extra ...
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1answer
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Wind tunnel experiment that measures lift (not the lift coefficient)?

Does anyone know of a wind tunnel experiment on a wing or airplane that measures the absolute amount of lift (not the lift coefficient); and demonstrates conclusively that the lift generate by a wing ...
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4answers
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Can a Styrofoam box bounce back into a moving van?

I just came across this video. A styrofoam box falls out of a moving van, bounces off the road and lands back in the van. How can the box land back so precisely inside the van?! Usually, I would ...
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3answers
100 views

Ceiling fans with just one large winglet? [closed]

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
42 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
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Can an airship tack? [closed]

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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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
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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
58 views

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
101 views

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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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
53 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
39 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
40 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
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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
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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
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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
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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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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
39 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
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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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