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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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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5answers
8k 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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1answer
30 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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42 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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1answer
75 views

How could Superman fly (using real world physics) [closed]

I have started a massive project on comicvine to see who would actually be the most powerful superhero in the real world with real physics. http://comicvine.gamespot.com/forums/gen-discussion-1/...
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20 views

About Von karman vortex shedding

Does Von Karman (vortex shedding) effect behind a flat plate, produces moment on that plate which? How to calculate this moment?
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3answers
62 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
63 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
52 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
64 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
61 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
23 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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1answer
85 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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3answers
110 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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2answers
75 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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1answer
34 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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0answers
44 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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1answer
50 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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3answers
38 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 ...
3
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1answer
99 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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1answer
51 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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61 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
74 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
83 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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1answer
174 views

Why is an airplane propeller so different from a boat propeller in shape? [closed]

Examples: Airplane propeller Source:http://www.sensenich.com Boat propeller Source:http://www.nauticexpo.com It is obvious that the airplane propeller is drastically different from the boat ...
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1answer
87 views

Boeing 737 Homework Problem [closed]

I have done the above problem, but have come out with a rather large surface area. Could someone point out my mistake(s)? Given/Assumptions: I assume $\sum F_y=0$ because it's level and straight. $$...
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1answer
43 views

Simulating supersonic flight in game

So this question about how to implement a good looking simulation of super-hypersonic flight of a rocket from launch point to orbit. I have an idea how to implement a good looking aerodynamic on sub-...
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0answers
47 views

How is egg shaped ball different from a spherical ball, aerodynamically?

I don't know whether this is the right place to ask this question or not but, how is an egg shaped ball aerodynamically different that the spherical ball? What advantages could one have over the other?...
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1answer
39 views

Power vs. Speed - Indoor rowing

In the sport of indoor rowing (and probably others) I know that to double your speed you must increase your power output by a factor of eight. I am wondering why this is the case. The indoor rower ...
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2answers
295 views

Are raindrops actually “shaped like tears” when they fall?

Raindrops are always pictured like this, people imagine they have this shape when they fall, but is this true? Doesn't this shape create too much drag? What shape do they really have? It would also be ...
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1answer
45 views

Aircraft Thrust to weight ratio contradiction with energy conservation

Usually, airliners have (Thrust/Weight) T/W ratio in the range of 0.2 to 0.8 and for steady flight W = lift My question is, for example, that Antonov 225 has Thrust/weight: 0.234 for max takeoff ...
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1answer
80 views

rocket vertical landing [closed]

SpaceX has published a couple of videos that show one of their heavy-lift rockets landing vertically in a highly specific location. How is it possible that they are able to control so many ...
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2answers
70 views

How to estimate wind speed from a pressure difference?

Does a formula (or a rule of thumb) exist to estimate the wind speed between a high pressure area and a low pressure area given the pressure difference between the two areas? Only the wind resulting ...
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2answers
126 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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1answer
34 views

Equal transit fallacy in viscous materials

Does the equal transit theory work in viscous materials? It would seem here that if one were flying through something like gelatin the particles would come together at the tail end of the wing.
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4answers
49 views

How do I figure out the totally airborne height for a given machine?

Technically "airborne" can just mean to move through the air, but I would like to know how high you have to be before you are entirely supported by air in a helicopter-like machine, as opposed to ...
3
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1answer
89 views

Why do throwing knives need to be balanced?

Indeed, unbalanced throwing knives are used, but I have read that balanced throwing knives are easier to use, because due to their geometric center being the same as their center of mass. Why would ...
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0answers
27 views

Lift provided to an aeroplane [duplicate]

We say that aeroplanes find lift due to an effect explained by Bernoulli's theorem. But isn't newton's third law of motion applicable along with Bernoulli's theorem? otherwise, an aeroplane wouldn't ...
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2answers
82 views

Conflicts between Bernoulli's Equation and Momentum Conservation?

The well known Bernoulli's equation states that $P+\frac{\rho V^2}{2}=c$ However, a simple momentum conservation considering $P_1$ and $P_2$ acting on two sides, and velocity changes from $V_1$ to $...
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1answer
180 views

How can we calculate the maximum height of a fountain? [closed]

There are two limiters in this question. First is drag of air. Second is the viscous forces of pipe.(belong to the tube where water hitts up) The question is how can we calculate the maximum height ...
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1answer
29 views

How drag force relates to velocity in the air?

As you know in the formula of drag $$F=0.5 *d*A*C*v^2$$ in different velocities we have different Reynolds number. and the Reynolds number relates to coefficient of drag. my question is how can we ...
10
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5answers
978 views

Do objects have a tendency to fall in their most aerodynamic position?

In one of my physics classes, we are using slow motion video to analyze the falling motion of an object and then find out the drag coefficient of that object etc. I noticed while doing this that if I ...
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1answer
77 views

What is the difference between the Method of Characteristics being formulated in terms of theta & alpha and theta & nu?

So I'm doing an MSc thesis involving the method of characteristics in rocket nozzles. My lecture notes have the MoC formulated such that the positive characteristics are defined as: C+ = Tan ( $\...
5
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3answers
544 views

Why don't surfboards fly out the back of a utility truck when driving on the highway?

I have never had it happen myself and every time I throw my boards (shortboards not malibus) in the back of someone's ute, with no cover on the tray, they always assure me they'll be alright( the ...
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2answers
115 views

Can a glider maintain a constant forward velocity component?

I have a puzzle which asks me to consider a (engineless) glider descending at a constant rate and flying at a constant forward velocity (in still air). The question asks how to derive sink rate, $v_s =...
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1answer
52 views

How does a nozzle behave differently at different velocities of flow?

A converging duct acts as a nozzle for subsonic flows while the same nozzle acts as a diffuser (decelerator) for supersonic flows? How does this actually work?
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3answers
134 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 ...