A subset of [tag:fluid-dynamics] 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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137 views

Can Bernoulli fly a car?

I need to settle an argument. How much influence, if any, does the Bernoulli principle have in sending a stock car traveling at 200 MPH sailing through the air when the air pressure unexpectedly ...
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2answers
518 views

Could a bladeless “Tesla Turbine” type air compressor be used as a high vacuum pump?

I have a wacky idea for a new vacuum pump, I'm trying to figure out why it shouldn't work. I'm interested in learning about Tesla Turbines, specifically when used in reverse as compressors or vacuum ...
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1answer
18 views

Gliders in a trailer

Everybody has heard I the old thought expirement of the birds in the trailer where the man hits the trailer the birds take flight and the trailer gets lighter. This has been disproven by the ...
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1answer
110 views

How does wind cause a wind turbine to spin? [duplicate]

How does wind cause a wind turbine (pictured) to spin? I cant find a good source on google to explain this to me. This question should help me understand better how a turbine is spun in a jet engine. ...
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1answer
97 views

How does gas spin the turbine in a jet engine?

I am confused about how the energy from the ignited gas spins a turbine in a jet engine, as pictured below                &...
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1answer
53 views

Speed limit to air travel? [closed]

Is there a hard limit on the speed of air travel on earth? That is, if you consider the way the human body reacts to gravity. Is there active research ongoing in this area?
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1answer
57 views

Why do papers fly off the wall when you run past?

Another example is walking past a book and the pages of the book will fly forward. When you run, why do you blow air to knock over papers off the wall or turn pages of a book?
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3answers
92 views

How does a boomerang behave in microgravity?

Let's say I have perfected a boomerang throwing machine - in Earth surface conditions the boomerang is always thrown the same way, and always returns to the throwing arm. And let's say I've sponsored ...
3
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1answer
209 views

How do propeller blades rotating through air accelerate it to provide thrust?

I have a good understanding of how a propeller works. An engine turns the blades resulting an increase in velocity. But how do the blades accelerate air to result in thrust?
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1answer
70 views

Is it possible for something to travel at supersonic speeds in a tunnel?

Is it possible for items to travel at supersonic speeds in a tunnel, as opposed to unconfined spaces? The particular scenario I had in mind was a bullet train travelling faster than the speed of ...
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2answers
154 views

Lift and drag coefficients on other planets

The question I'm trying to answer seemed simple: how hard would it be to fly on a planet with lower gravity but also thinner atmosphere compared to Earth. If the answer could hint me at how much ...
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1answer
88 views

Does air travel through a car when you are driving through air?

Air travels through different objects, but I am very confused because you see these pictures of cars doing wind tunnel tests and that smoke goes over the car to represent the cars aerodynamics. When ...
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0answers
126 views

How to calculate maximum wind speed in a funnel (Venturi Effect)?

It must be in an open area, so nothing forces the wind, just himself. Lets assume that the wind is blowing only one direction. I assume that at some point the speed will stop increasing and it will ...
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0answers
85 views

Position and Tension of Kite/Balloon Tether in Presence of Wind

I wish to solve for the position of a kytoon's (hybrid kite and balloon, with both aerostatic and aerodynamic lift as well as non-negligible drag) tether given the forces present on the kytoon and ...
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1answer
55 views

Looking at a falling person (vertically) from 60m to the surface, how much wind effect is going to be felt?

I am trying to work out horizontal ranges for a falling person from height (in 10m steps from 0m to 60m). I have used this site http://www.convertalot.com/ballistic_trajectory_calculator.html to ...
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0answers
21 views

Temperature and air flow - are they related?

If I open a window, does the air "changes" (e.g. the $O_2$ concentration) in the room more quickly if there was a temperature difference between inside and outside?
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3answers
1k views

Why does a sheet of paper fall slower than the same when rolled into a ball?

It depends on volume but both the sheet and the sphere have the same volume. Does surface area play any role here?
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1answer
97 views

What are the biggest reasons that Cars get higher Land Speed Records than motorcycles'? [closed]

What are the biggest reasons that Cars get higher Land Speed Records than motorcycles'? It is because cars have a more streamlined frame than than motorcycles? But, from pictures, it seems that doesn'...
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2answers
2k views

What shape has the highest drag coefficient?

This image from NASA illustrates drag coefficients for several shapes: It is generally accepted that some variation of the teardrop/airfoil shape has the lowest drag coefficient. I was wondering ...
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1answer
66 views

How a paper plane(rocket) flies in air? what is science behind it? [closed]

What factors helps a paper plane to fly and can you explain how these factors help the plane to fly?
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0answers
179 views

Magnus effect, Coanda effect, and the Bernoulli principle: What is balancing gravity on a spinning sphere vs. a stationary screwdriver?

I've seen videos of golf balls and screwdrivers levitated by a focused air stream. Reading the comments of these videos (and others), I see explanations of the machanics at work and their cause and ...
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4answers
2k views

How does a converging-diverging nozzle not violate conservation of energy?

Disclaimer: I know absolutely nothing about fluid dynamics, and very little about physics in general. THis may be a really dumb question. Now, at subsonic speeds, converging and diverging nozzles ...
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1answer
106 views

Could a Jumbo Jet aircraft fly on paper wings?

My dad was an airline pilot and, during his training, his instructor told him that, in absolutely ideal conditions, (in practice obviously impossible) that the actual material composing the wing ...
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3answers
134 views

Will computer fan rotate slower if one makes impeller heavier?

Imagine that we replace plastic fan impeller with identical metal impeller (same form, heavier weight). Would maximum fan speed decrease? Common sense suggests that air resistance and bearing ...
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2answers
172 views

What's wrong with this argument that aerodynamic lift really does rely on Bernoulli? [duplicate]

There is a grade-school explanation of how a wing works that goes approximately like this (although I'm leaving out an erroneous bit): Because of the geometry of the way the wing meets the air, ...
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3answers
166 views

If gravity were to suddenly change, would the lift generated by a airfoil also change [closed]

If gravity were to suddenly change, would the lift generated by a airfoil also change? I realise that if gravity were to increase, then weight would also increase, leading to a change in the ...
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3answers
177 views

Why are vehicles not pitted like golf balls?

I have read that non-laminar flow reduces drag on blunt bodies. Given that, why is pitting not used on motor vehicles?
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3answers
141 views

Why do the tangent holes (like in pitot-static tube) feel the static pressure?

Why do the tangent holes (like in pitot-static tube) feel the static pressure although the static pressure is in the direction of the velocity of the streamlines not normal to the surface of the hole
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1answer
344 views

How much does air resistance affect the angular velocity of a golf ball?

I'm modeling the flight trajectory of a golf ball, and using angular velocity to calculate the Magnus force. Currently, I'm assuming angular velocity to be fixed throughout the ball's flight. How ...
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1answer
278 views

Could one fire a bullet with sufficient speed to leave the Earth?

Consider a gun or rifle fired directly upwards. My original question was what speed would be required to escape the Earth. The escape velocity from the surface of the Earth is the classic $$v_e = \...
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1answer
98 views

Does a ceiling fan sound louder when humidity is higher?

It seemed to me the ceiling fan is making louder noise(of cutting through the air) when the day is a bit damp/humid, especially after a rainy day/hour. Is this a valid observation? Can the increased ...
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6answers
2k views

Why is a beam reach the fastest point of sail on modern sailboats?

I've heard that a beam reach (perpendicular to the wind) is the fastest point of sail on modern sailboats, but I haven't heard a satisfying explanation of the physics behind the claim. Triangular ...
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2answers
964 views

Why bumble bee cannot fly aerodynamically? [duplicate]

I just saw this pic So I got curious and logged in on physics.stack first time, is it true? I am a math major and usually wander on mathstack but I would like to understand why Bumble bee cannot ...
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1answer
118 views

Balloon aerodynamics

In this recent anime that I have seen, there is a part where an atomic bomb is sent to the stratosphere in a box, by a helium balloon. As you can see in this picture of the set-up, there is a tube ...
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1answer
54 views

How is the kinetic energy of the wind transferred onto a lift based wind turbine?

The rotor blades of a lift based wind turbine are shaped like airfoils, so the wind flowing around them creates a lift force which in turn moves them around. From a thermodynamic viewpoint and like ...
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3answers
4k views

How do eagles fly slowly for a long time?

Eagles fly slowly for a long time. Many other species fly faster and move their wings faster. But eagles keep their wings steady, and move only their tail. How do they move slowly in the air, ...
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1answer
116 views

Why don't we build helicopter based space shuttles?

As seen in this video: the principle of the helicopter does work in space. So we could make a helicopter based space shuttle! It would be easier to navigate with it than with propulsors.
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1answer
40 views

Control surface effect

If we know the Center of Mass and the Center of Lift, and the position and rotation of some control surface, how can we calculate what control surface must be operated to change our path? lets say we ...
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4answers
876 views

Why is paper (or any tailless) airplane pitch stable?

To clarify my question further I'll use a practical example. Here is the simplest paper plane design I could think of - it is a rectangular thick drawing paper with a weight attached at the middle of ...
2
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1answer
305 views

How does a hovercraft hover, if it has low pressure underneath it?

I've read a few different explanations of how hovercrafts hover, and they all mention a low-pressure cushion of air. This confuses me though: If there is low pressure under the hovercraft, why doesn't ...
2
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1answer
105 views

Reynolds number of airfoil in a pipe

As part of a physics high school paper I am writing, I need to build a wind tunnel. As part of my calculations, it appears that Reynolds number is very relevant in aerodynamics (specifically for ...
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2answers
282 views

Do rotating non-circular projectiles also experience Magnus lift?

The Magnus effect has been studied on spherical projectiles such as golf balls, tennis balls, and soccer balls. The backspin of a golf ball leads to Magnus lift that opposes gravity, thus allowing the ...
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1answer
89 views

Speed of pressurized gas escaping into vacuum

Does speed of pressurized gas escaping through a narrow nozzle into vacuum depend on the pressure? I've asked a question on Space.SE regarding utilizing gas at extreme pressures for propulsion. My ...
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4answers
120 views

In aircraft design why are light materials preferred to heavy ones?

Especially given the relative cost between (say) steel and carbon composites. After all, I assume most fuel is consumed overcoming drag not accelerating mass. Once an aircraft reaches cruising speed ...
2
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2answers
99 views

Force on pilot ejecting at supersonic speeds?

Using the Rayleigh drag equation, and approximations for the air density, drag and frontal area of the pilot, and mass, at around 300 m/s (subsonic) a pilot might experience deceleration forces of ...
2
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1answer
317 views

Calculating wind force and drag force on a falling object

I'm trying to numerically integrate the motion of an object (say, a falling vertical cylinder). Here, there's a drag force: the wind "acting" on the body (presumably adding horizontal velocity) and ...
15
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2answers
480 views

Deriving equation for skipping stones over water

Why can rocks skip over water (stone skipping)? For instance, if you conduct an experiment where you drop both rocks from the same height, but give one considerable acceleration in the $x$-direction, ...
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2answers
116 views

Does air density influence a football player's ability to “bend” the ball?

Whilst reading an article on nasa.gov, there was a claim that I found interesting: At higher altitudes, the density r is lower producing a larger radius of curvature and a straighter path. The ...
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0answers
46 views

How big is the power loss of a downwind wind turbine due to turbulence created by an upwind turbine?

When a horizontal axis wind turbine is placed downwind of another horizontal axis wind turbine (distance between the two is minimal), then the downwind wind turbine has a lower power output because of ...
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3answers
489 views

Why does it seem as if big vehicles “attract” mine when I drive close to them?

When I drive a car at high speed and when I am near to another big car (like a van, or transport vehicle) I feel an attraction to or something push me toward the other big car. What's the physics in ...