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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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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28 views

Wind blows to surface, how long legs I need? [closed]

Wind blows onto the surface normally at at speed of 20m/s. The frame (in vertical plane) has two supporting bars in the plane of the ground as shown welded rigidly. What is the length of horizontal ...
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18 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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1answer
36 views

How can I add a rounded trailing edge to an airfoil? [closed]

I have an airfoil coordinates file (NACA 65(4)-421) with a sharp TE. I need it to be rounded. It doesn't seem that there are any tools available to help with this, so I've tried making my own Python ...
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4answers
72 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 ...
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2answers
39 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 ...
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1answer
32 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 ...
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30 views

Ratio between power of chaotic and regular airflow

Turbulent field is created as a result of an impact of an airjet on an edge (the flow velocity is high enough). The field of velocities have a regular and a chaotic component. What I need is to ...
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123 views

Equation derivation for skipping rocks

oWhy can rocks skip over water? 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, one will fall in ...
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42 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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22 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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18 views

Explain an experiment: airstream between two hinged curved surfaces

Please, see the following video (the experiment starts at 3:40 and ends at 3:55): https://www.youtube.com/watch?v=7pB6q_bH35s&feature=youtu.be&t=216 The basic idea: given 2 curved surfaces ...
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25 views

How are shock waves related to sound, and are there equations describing its density, size, and pressure?

How exactly does one model a shock wave? I've done a lot of searching and have failed to find any equations where we're able to relate things such as its pressure, density, temperature etc. I've ...
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1answer
54 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
50 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 ...
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1answer
93 views

Is Magnus effect a corollary of Bernoulli principle?

Magnus effect is commonly explained using Bernoulli principle. However, taking the lift on a rotating cylinder as an example, the velocity difference is caused by the extra work done by the rotating ...
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1answer
68 views

How to obtain this equation for skipping stones over water?

I think I have a decent conceptual understanding of the forces at work when stones are skipped over water. My question pertains to the equation found in this [source][1]. Reproduced in Latex this ...
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1answer
40 views

Boundary Layer in aerofoil

I want to know how the top and bottom boundary layer interact at the trailing edge of an aerofoil (zero angle of attack) and what happens to the boundary layer after a small distance from the trailing ...
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4answers
68 views

How can a petrol car require less fuel at 55mph than a lower speed at the same rpm?

It seems to be widely accepted that somewhere around 55mph is the most economical speed to drive in a conventional petrol car. Recently I ordered an EV, and learned that (with the exception of at ...
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11 views

The torque produced in the rotor blades of an axial flow turbine

I want to ask about the torque experienced by a axial flow turbine, and how the torque is related to the ange of attack, or pitch angle of the turbine blades. (I'm new to technical terms, please ...
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1answer
31 views

How to calculate the actual drag force on a wing?

I want to calculate the actual drag force that a NACA 63-412 wing would experience at a given planform area and relative wind speed. Airfoiltools gives a drag coefficient of 0.01676 for the optimal ...
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2answers
53 views

How do you calculate/estimate hypersonic leading edge and skin temperatures?

At lower speeds (below Mach 5-ish), stagnation temperature (TAT) is a very accurate proxy for skin temperature. But at mid/high hypersonic speeds (especially in the thin upper atmosphere where mass ...
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28 views

Mass flow rate and force on moving disk

If I understood correctly, the force $F$ related to a given mass flow rate $\dot{m}$ through orifice area $A$ (or, say, on a disk of area $A$) is given by Newton's 2nd law of motion - assuming a ...
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39 views

Pressure-Velocity relation at a point in a flow

How can we relate pressure and velocity at the same point in a fluid flow? Why does pressure decrease with increase in velocity?
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1answer
185 views

Why does deflating baloon spurting through the air make circular motion? [duplicate]

When you inflate a balloon and then let it go again, it will fly through the air in an unpredictable motion. My kids (1 and 3 year old) love watching this. At some point my oldest asked how it worked ...
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22 views

In momentum theory, what happens if atmospheric velocity is larger than outflow velocity?

I am currently reading up on aerodynamics, essentially the actuator disk concept and momentum theory as it is described in e.g. Basic Helicopter Aerodynamics by Seddon and Newman. There they assume ...
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1answer
70 views

Why dosen't my boomerang return [closed]

My boomerang I built will only turn just a bit back towards me, but that's it, but why? Is it my design, I incorporated the recommended dimensions from the website I used, such as an 107 degree ...
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1answer
28 views

Airfoils contradict the law of the lever?

The law of the lever says that "the less force you use, the more distance you have". It is often exemplified by referring to simple machines, but it should apply to all technical systems. But I do not ...
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1answer
44 views

Why does a parachute open up faster on Mars than on Earth? [closed]

I recently heard that a parachute opens up much faster on Mars than on Earth. Why is that the case? More specifically, during a NASA Edge TV program, one of the scientists working on parachute tests ...
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20 views

how much air pressure can be varied (in dapa) when an empty syringe's plunger is pulled in and out?

I'm new to the forums so please guide me appropriately if this is the wrong place to ask this question. When the syringe plunger is puller out ,a negative pressure is created at the nozzle....Isn't ...
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1answer
64 views

Am i trying to fly by pulling myself up by my hair? [closed]

I'm currently trying to build a multi-rotor of my own, and am testing it when i noticed that the lift that i am supposed to be getting is wayy less than what i am expecting. I have a rectangular body ...
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1answer
85 views

Finding turbulent velocity Fourier mode amplitudes from kinetic energy spectrum

A random vector field, such as a turbulent flow, can be decomposed into Fourier modes. Taking a snapshot in time (say an initial condition) we have that the randomly fluctuating component of the flow ...
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74 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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2answers
79 views

Where does the loss of kinetic energy of the wind flowing over an airfoil go?

When an airfoil is tested in a wind tunnel the speed of the wind behind the airfoil is less than speed of the wind in front of it. That means the wind loses kinetic energy. The reason for that is drag ...
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2answers
58 views

How does a supersonic flight speedometer work? [closed]

I'm sure today they can use GPS and radar, but I was pondering the queation when I saw a film clip of a vintage analog dial labeled in mach number. I'm supposing that the usual way of measuring the ...
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1answer
51 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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109 views

Helicopter, Tricopter, Quadccopter - what's really happening here? Are there generalized advantages on a small scale?

There have been, it seems, a proliferation of quad-copters commercially available. Amazon seriously tried to use them for deliveries. (Search Drone on their website.) The NFL uses one for cameras. ...
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1answer
148 views

Is this xkcd comic feasible? [closed]

I was reading through some xkcd comics, and I came across this one (http://xkcd.com/620/). In the comic, one of the main characters harnesses 91% his weight in order to be able to 'fly' with the lift ...
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1answer
52 views

What are the preferred height and diameter proportions for a rocket model?

I'm pretty sure, that if you make a rocket that's relatively small in height compared to diameter, it will most likely not fly very high and probably spin out of control. What about a rocket that is ...
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35 views

How much does grabbing a piece of a plane free falling change your survivial?

Just for context let's saying you are falling from a plane in free fall position at 56m/s(200 km/h or 120 mph) and you grab onto a wing which slows you down to 25m/s. You weigh 70kg. so ...
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2answers
43 views

What are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
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2answers
164 views

Boomerang physics and aerodynamics

I posted a question before on this website asking how to build a boomerang for a project which can fly at least 200 feet, so how would I increase the flight path. A user responded with: slow down the ...
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1answer
93 views

Thought Experiment: spinning ping-pong ball on International Space Station. What would Happen?

A ping-pong ball with a certain vector and rotation/spin in zero G, 1 atmosphere. If you did this experiment in a space station would the ball 'orbit in a circular fashion. or "Can you throw a ...
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1answer
31 views

Is there a way to convert CFM (rate of air moved) to kilograms of lift generated?

Is there a way to convert CFM as in a rate of volume of air moved to kilograms of lift generated?
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1answer
132 views

Boomerang torque and angular momentum

I'm building a boomerang for a project, but I've made it a goal for myself to have a boomerang which can fly at lest 200 feet, so how would I increase the flight path. Angular momentum increases in ...
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59 views

Books on experimental methods, fluid mechanics related

I need some good books on experimental methods, requirements are: Fluid mechanics related; Thermal, multi-phase etc. topics should be covered; Traditional methods are good, but it would be greater ...
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128 views

Why can't we fly? [closed]

Why can't we fly? It contradicts with our known laws of physics, but which one? Is it possible that once we know gravity better we would be able to fly using some sort of anti-gravity machines like ...
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1answer
58 views

When an aircraft flies over, glass window vibrates…Infrasound?

When an aircraft flies over, my big glass window vibrates, making a ticktack beating. Its frequency sounds low, less than 10 beats per second actually. I'm wondering about the mechanism of this ...
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Why are flight feathers asymmetric?

I've always heard that flight feathers were asymmetric because the shape generates lift, like an airplane wing airfoil shape. But, the feathers are not oriented with the shaft perpendicular to the ...
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86 views

Is more lift always better?

In the domain of aircraft, and more specifically powered flight, is there any case in which you wouldn't want the airfoil used to generate as much lift (and as little drag) as possible at a null angle ...