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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How the wing creates lift? Why critical angle of attack is 16.5" for a supersonic jet and a kite?

I have seen many references on how the wings create lift, most of them overplaying effect of Bernoulli's rule. But nowhere has there been any consideration given to this important factor: Let's ...
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1answer
229 views

Why golf balls travel faster if they spin?

From the book I have been given to read I found that balls spin due to the centripetal force but i am confused about how exactly do the resultant force causes it to spin and move forward about the ...
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Bullets with aerospikes?

There is a concept used by ballistic missiles called a Drag Reducing Aerospike It is a flat disc deployed forward of the nose that... The aerospike creates a detached shock ahead of the body. ...
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2answers
87 views

Equal transit time fallacy and Newton's laws of motion

I've seen the equal transit time theory being used to explain aerodynamic lift [basis is Bernoulli's principle] several times. However recently I've been told that there is NO physical compulsion for ...
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1answer
107 views

Boomerang angular momentum

So I'm building a boomerang to fly 200 feet in order to do that I was told to increase the moment of inertia to increase the resistance from change in state, and I was told that it would increase the ...
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5answers
9k views

Why do archery arrows tilt downwards in their descent?

In the movies, arrows shot into the air rotate so that during the descent, the arrow head hits ground first. What is the source of this angular momentum? It would seem that the bow string exerts a ...
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22 views

Communication between two LEO satellites

Anybody have any idea about any mathematical model to allow communication between two LEO Satellites is possible in space, where two LEO satellites do not know their positions in two different polar ...
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2answers
522 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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Why is 55-60 MPH optimal for gas mileage of a passenger car?

My driver's education teacher back in high school said 55 MPH is optimal for gas mileage of a passenger car. Just last week, I read an article in a magazine saying 60 MPH is optimal. These numbers are ...
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1answer
35 views

Will a rocket accelerate faster if the air in front of it is sucked away?

Imagine a rocket with a super powerful vacuum pomp on top of it. These pomps or whatever should manipulate the airflow in front (or around) the rocket. What causes the rocket to accelerate quicker and ...
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44 views

Why do fans produce cold air currents when they spin? [duplicate]

This was basically an exam question on first year medical students in the Medical Physics class and I couldn't answer it based on my background and pertinent preparation. The topic asked the candidate ...
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3answers
68 views

Space Rocket Ionizing Its Path To Decrease Fuel Consumption [closed]

A beam(maybe multiple beams from ground crossing at, or just some very high alternating potential, something like focused haarp) on tip of rocket targeting at path of it, ionizing just the closest ...
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2answers
81 views

How is determined the shape of the wings of an airplane?

My understanding of the reason why a plane fly is summarized by the following figure: because the upper part of the wing is curved, the air above the wing has to flow faster than the wing below. This ...
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2answers
53 views

Roll angle for banked turn of an aircraft on a tilted plane

It is known that for a banked turn of an aircraft on a plane parallel to the ground, the roll angle $\Theta$ computes as $\Theta=\arctan(\frac{a}{g})$, with $a=\frac{v^2}{r}$ the centripetal ...
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2answers
70 views

When a tram brakes there is a huge volume of air getting inside the vehicle, if the windows are open. Why?

I have noticed this weird phenomenon. When a tram brakes with the windows open, there is a huge volume of air entering the vehicle. Much, much more air gets in when it brakes than when it accelerates ...
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1answer
64 views

Height formula of a sphere inside a pipe

I have a pipe with a ball inside it and a blowing air through it. Look this image: The air is blowing in the direction of $F_a$. $F_a$ Is the air force and $P$ is the weight force. What I want ...
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1answer
24 views

Spin on the rack

Bike mounted on hitch rack. Why wheels spin constantly while I drive? I can't find anything on the internet. The kids in the other cars love to watch them
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2answers
377 views

The demise of the Tacoma Narrows bridge was casused by aeroelastic flutter. But isn't that just a special case of resonance?

Much of the research I've done on the Tacoma Narrows bridge disaster of 1940 attribute the collapse of the bridge due to aeroelastic flutter - not strucural resonance. But isn't aeroelastic flutter ...
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1answer
96 views

If a high speed car or train enters a tunnel, will the aerodynamics effect slow it down and hence requiring more energy to maintain speed?

Speed and distance are two main determinants in this question. A slow moving vehicle or train entering a tunnel is unlikely to be affected by the presence of solid stationery object covering them. But ...
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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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3answers
114 views

Is a falling leaf an example of a chaotic system?

Let´s assume is a wind still day in autumn. When a little change is made in the initial motion of a leaf at the time it falls off a tree, the resulting path of motion of the leaf is very different ...
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10k views

Number of blades in a helicopter rotor

I was wondering how it is possible to determine what is the optimal number of blades in a helicopter rotor. I think that the length of the blade is involved as a longer blades would have to spin ...
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2answers
339 views

Is this simulation following real physics?

I am trying to simulate a game in Box2D(Physics engine). The game that I am trying to simulate is very simple and can be found here: http://www.makaimedia.com/#/speartoss What I want to know is that, ...
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2answers
82 views

Intuitive explanation for lower pressure above airfoil

From Bernoulli's principle we know for an incompressible fluid (constant density $\rho$) in a gravitational potential $\psi=gz$, that we can state the equation along a streamline from point 1 to point ...
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2answers
5k views

Exactly how much lift is needed to overcome the weight of an average person?

I am designing a "glider" of sorts, and I have some basic questions about the physics involved to get me started. How much lift is required to overcome the weight of an average person, say 150 pounds? ...
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2answers
135 views

Can the Arcaboard fly?

Recently, BBC news had a video that claimed to show a "real" hoverboard: As far as I can tell, there are 36 small fans on this device, and it seems to be flying just a few inches off the ground. ...
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2k views

Why does the higher pressure of air underneath an aeroplane wing keep it flying?

With aeroplane flight, the wings are shaped so that the air that goes over the top of the wing has to travel faster than the air that goes below the wing. This means that the air below the wing has ...
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1answer
36 views

what causes airborne bodies to tilt?

Imagine a Helium-inflated oblate spheroid floating still (A). Buoyancy force cancels gravity force on Y axis. Object is tied to ground with a rope. If a wind force is applied on X axis, why does the ...
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1answer
60 views

When does the shock occurred?

I'm between this 2 conditions that when does the shock occurred over an airfoil. When the speed of point of an airfoil reach to sonic velocity of environment. When the speed of point of an airfoil ...
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46 views

Plane landing into a tunnel

Typical action movies cliché is landing a plane in a tunnel or even a flight in a tunnel. Let's drop any doubts about supreme heroic piloting skills of the characters etc. and focus on aerodynamics. ...
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0answers
36 views

Why does the shock in viscous flow occur sooner than non-viscous one?

Why does the shock in viscous flow occur sooner than non-viscous one? If we want to discuss about drag, which one has bigger drag? This figure may help.
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4answers
2k views

Why airplanes fly: the final truth

The questions about the reasons the aircraft fly are frequent among scientist, since the high school until now, even if I work on the other side of fluid mysterious world (the Low Reynolds numbers ...
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4answers
2k views

Propellers and the Speed of sound

I was reading this website that described a novel wind turbine technology and it has this quote: In the mid-20th century, open propeller-driven planes with piston engines reached performance ...
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2answers
1k views

What would be an appropiate shape for a parachute?

I'm trying to design a parachute that minimizes the descent velocity, but I'm not sure what shape I should use. From what I've read, ellipse-shaped parachutes are too aerodynamic and minimize drag, ...
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1answer
102 views

Is it possible that viscous flow has a higher lift to drag ratio than inviscid flow?

I have a code for airflow around an airfoil. When I compare viscous and non-viscous flow at the same Mach number for a cruise, viscous flow has a higher lift to drag ratio than non-viscous flow. Is it ...
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2answers
2k views

What do bullet trails really look like?

In the movie The Matrix, during "bullet time" sequences, bullets are shown trailing evenly-spaced refracting blobs: http://2.bp.blogspot.com/_uypMqSrmflo/S18yZJPET_I/AAAAAAAAAGk/CDjoZaOLbwY/s400/...
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3answers
41 views

Modelling an Airplane Question

For an assignment of mine I am creating a very basic model of an airplane, where I choose to consider a fixed amount of parameters that affect flight and to disregard others which I find too difficult ...
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1answer
52 views

How does quadcopter's battery capacity relate to it's maximum flight time?

Suppose that we have a quadcopter weighing 3 kg (without a battery) and a battery (let it be Li-Ion type) weighing 2 kg. With this battery our quad can hover for 20 minutes until the battery runs flat....
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7answers
2k views

How do I figure out the effects of wind on flight?

For a school project, I'm trying to make an automated flight planner, considering mainly the differences in flight paths according to wind. Now I've heard that flying with/against the wind affects ...
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2answers
616 views

Energy from man-made tornadoes

Peter Thiel just paid $300,000 to Canadian inventor Louis Michaud who is working to construct useful "man-made tornadoes" or "atmospheric vortex engines" which could be components of future power ...
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1answer
286 views

Why Are Normal Shock Waves Unstable in a Converging Channel?

While learning about shock waves in an introductory Gas Dynamics course, it was revealed that normal shocks are unstable if formed in a converging channel. Even if the local conditions ostensibly ...
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2answers
1k views

Integrating pressure over a surface

Consider the 2D airfoil below. In engineering (and maybe physics) you will often see something like the following as an expression for the pressure force acting on a surface (in this case a curve ...
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1answer
649 views

Why do bowlers rub the ball before bowling in a cricket match?

Why do bowlers rub the ball before bowling in a cricket match? What is the science behind it? Is it because of friction?
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1answer
2k views

Paper plane between two fans - is this possible?

The setup: two fans facing each other, distance around 1m. Both are turned on. In between them, place a simple paper plane and according to this video, it will fly. https://www.youtube.com/watch?v=...
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1answer
52 views

What forces are involved in bending a freekick like that? [duplicate]

Look at this amazing, incredible goal (higher resolution at youtube). What are the possible forces that can conspire together to make the ball bend like that?
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0answers
64 views

Calculate ballistics using Pejsa method (bullet physics)

I'm not sure if it was already asked, but, could someone please explain the Pejsa method of ballistics, specifically the velocity and trajectory (no energy, wind or lead etc.) (just drop drift and ...
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1answer
85 views

Effect of paint on drag force [closed]

Aerospace engineering as well as automobile engineering gives a particular significance to the shape of a vehicle to enable proper and more effective transportation.What I want to know, is, about the ...
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1answer
93 views

Physical intuition for Lamb vector

In many aerodynamical descriptions involving vortex structures (e.g. the Crocco's theorem) there is a useful physical quantity called Lamb vector: $$ \vec{\omega} \times \vec{v} $$ where $\vec{\...
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2answers
431 views

Why does a propeller suck in air from the front?

A rotating but fixed propeller sucks in air from the front. What is the cause for this acceleration of air particles? Since propeller blades act like rotating wings, my best guess is that the blades ...