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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223 views
Bicycle Wheel Drag in Slipstream
I was recently driving behind a car that had a bicycle mounted on a carrier over the rear bumper.
The bicycle wheels were not bound so they were rotating in the slip-stream of the car.
I wonder, the ...
4
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0answers
80 views
Why can't supersonic planes “just fly higher” to go faster while maintaining cost?
First post to this site, and I've got at most a high school background in physics - I really appreciate any answer, but I may not be able to follow you if you're too advanced.
I suppose this goes for ...
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2answers
226 views
Position of aerofoil force moment, center of pressure, aerodynamic center
I'm confused by wikipedia's page on aerofoils, the aerodynamic center, and center of pressure; it seems to contradict itself.
The airofoils page says the center of pressure is at the same position as ...
4
votes
1answer
112 views
Why do wind power plants have just 3 blades? [duplicate]
Why do wind power plants have just 3 blades? It seems that adding more blades would increase the area that interacts with the wind and gather more energy.
(Image from Wikipedia.)
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1answer
35 views
Equal Transit Time Fallacy
I learned, in grade school, that lift was generated via the particles on either side of the wing having to reach the other end at the same time. Looking back, that indeed has no physicality to it.
So ...
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2answers
4k views
How can airplanes fly upside down?
I've read many times, including here on this very site that the commonly known explanation of flight is wrong, and that airplanes can fly because the shape of their wings deflects air down. This makes ...
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0answers
38 views
Miniature F1 car Aerodynamics query [closed]
I'm participating in a competition called F1 in Schools where a team of 3-6 people have to run their own F1 team, and design a miniature version(210mm) of an F1 car which would be raced on a 25m track ...
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vote
1answer
141 views
How should holes in a Tesla turbine look like?
I think of building a Tesla turbine out of old hard drives.
Now I wonder how to cut ventilation holes in the platters.
On the internet there are a lot of different attempts on that matter. A lot of ...
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2answers
55 views
Are the hypotheses of the Bernoulli equation satisfied for a bird or airplane wing at low Mach number?
A previous question by David Zaslavsky was a request for a broad, "how things work" type of explanation of the lift of an airfoil. The answers given there are enlightening, but don't address a more ...
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1answer
91 views
Enginering question about F1 car
In formula F1 car, air coming infront of the car goes up with very high velocity as a result pressure difference is created which is very high from Bernoulli theorem.. The F1 car is very light so ...
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vote
2answers
72 views
Disconnected aileron/surface deflection in terms of speed?
Would a disconnected surface, especially aileron, deflect upwards as you slow down due to increased alpha? I figure out it is more likely to deflect upwards as you increase your airspeed, thus having ...
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0answers
48 views
Would there be any possibility for anyone to survive when a Boeing 747 crashes to pacific ocean with its normal cruising speed? [closed]
I know no case of anyone surviving when an aircraft of the size of Boeing 747 crashes to ocean with its normal cruising speed, but in physics sense, would there be any possibility of anyone surviving ...
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vote
3answers
1k views
Could a real-life X-Wing fly in Earth's atmosphere?
From an aerodynamic point of view, could a full-size aircraft of X-Wing design fly in Earth's atmosphere? Assuming you were free to add control surfaces here and there, could the wings in open ...
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vote
1answer
108 views
Inefficiency Comparison of Car Air Conditioning vs. Open Windows
On a recent long, hot journey in Spain, I was pondering which was the most efficient way of cooling the car. Which of these would be the most effective?
Switching on the air conditioning, thereby ...
4
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0answers
146 views
Why is it hard to breathe when cycling against the wind?
Sometimes when I bicycle against hard wind, I find it difficult to breathe. Others I have discussed it with have also noticed this effect.
A possible related phenomenon that I heard from an ...
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1answer
113 views
Is the total pressure coefficient always 1 in incompressible flow?
I have to do some calculations to get the drag from an experiment with a wake rake. In the equation I have to enter the total pressure coefficient $C_{pt}$, but in my calculations it seems to always ...
6
votes
2answers
120 views
Could some design of a propeller be used in both air and water?
Propellers in water are smaller in diameter. They also move more slowly. On the other hand, aircraft propellers are larger in diameter, have narrower blades and operate at very high speeds. An ...
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vote
2answers
66 views
Concerning the curvature of an airfoil (shape)
I am wondering about the reasons for the shape of a turbine blade airfoil, see here
Do you know the reason for this shape? Usually, very large curvatures like this are to extract high lift from LOW ...
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1answer
48 views
Liquid oxygen how do they use it as fuel?
Rockets are said to be using liquid oxygen as fuel. How do they use liquid oxygen since it's just oxygen, it only helps in the combustion process. How can it be a fuel on its own?
2
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2answers
115 views
Whats the anti-torque mechanism in horizontal take-off aircraft?
In most helicopters there is the anti-torque tail rotor to prevent the body from spinning in the opposite direction to the main rotor.
What's the equivalent mechanism in horizontal takeoff single ...
3
votes
1answer
439 views
Air Turbulence and DIY laminar flow hoods
So for years on the mycology, plant tissue culture, and DIY laboratory websites there has been this ongoing debate on how to achieve laminar flow in a home built laminar flow hood.
Flow hood link!
...
2
votes
5answers
149 views
How does an aeroplane maintain balance during maneuvers?
I understand the principle behind flight, how the lift is generated etc. What I don't understand is when there are maneuvers made where the plane flies such that the wings are in vertical plane, how ...
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1answer
93 views
Surviving Free Fall with the Help of Mr. Bernoulli
What is the best strategy to survive a free fall naked out of a jetliner at cruising altitude (ignoring temperature)?
For instance, my strategy would be to streamline my fall so that my terminal ...
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vote
0answers
42 views
effect of internal forces to a glider's descent
This is a continuation of a previous question, with more thinking applied, thanks to a helpful comment.
Imagine a glider is airborne in a breezeless sky. The glider is 3 KM high, is traveling at 100 ...
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0answers
26 views
effect of internal force to a glider's descent [closed]
Imagine a glider is airborne in a breezeless sky. The glider is 3 KM high, is traveling at 100 KM / hr, and is descending at a constant rate of 10 m per min. The glider weighs 200 kg. The sole ...
2
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3answers
166 views
Why does an airplane need to climb during a takeoff even if it is in emergency situation?
Right after take-off (which means an airplane already exceeded V1) it is recommended that an airplane keeps climbing even when emergency occurs. Beside worries of crashing into houses and buildings by ...
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vote
1answer
91 views
What is the optimal weight for a golf ball?
I am 32 now, and have forgotten the basic physics formulas we used in school. I am sitting with a question that is bugging me.
I want to know, if I had to hit two golf balls of different weight, with ...
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0answers
40 views
Is the free-stream pressure the static or total pressure of the free-stream?
Is the free-stream presure $P_\infty$ the static pressure of the freestream or the total pressure?
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0answers
54 views
How large should a static pressure be during a windtunnel test in the wake rake.? [closed]
We did some experiments for an assignment and I'm getting some confusing results here. When I try to calculate the pressure coefficient it is about $-60$. When I looked at the measured static pressure ...
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2answers
242 views
What alternative shapes may a rocket heading into orbit have?
It looks like most rockets that head out of Earth, or even into orbit are pencil shaped (or nearly so). I would take this to mean there is some mass of air such vehicles push out of their way.
What ...
5
votes
1answer
88 views
Aircraft nose-up glide
In the pilot's introductory book "Stick and Rudder" it claims that a nose-up glide is possible. It doesn't state how, why or when. It implies it's possible to do and maintain a constant forward ...
1
vote
1answer
131 views
How fast does water fall in the middle of a very very thick waterfall?
Let me create a very artificial experimental set up. Take a bathtub the size of Delaware and suspend it a mile above the ground. Fill it with water (though I'm not sure to what depth - and it might ...
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2answers
192 views
Forces on an aircraft - thrust, lift, drag, weight
I'm extremely sceptical about the wikipedia page on aircraft flight mechanics. When describing 'straight climbing flight', it says:
lift is unable to alter the aircraft's potential energy or ...
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1answer
92 views
Propeller modelling
I need a (very) approximate model of a propeller on an aircraft.
My principal question is this: what would the relationship be between:
Propeller rate of rotation
Aircraft speed
Force generated by ...
4
votes
2answers
233 views
Why do cars gain lift while going at a high speed?
I've been researching the physics involved with spoilers and I've just been turning up the same information about spoilers giving the back wheels of a car more traction by acting as an up side down ...
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vote
2answers
150 views
Finding an equation relating the mass of a blade of a wind turbine to its velocity
I'm writing up my physics coursework and I thought I'd try and find an equation described in the title. This is my attempt:
Is it correct?
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2answers
89 views
Estimating drag due to wind - ribbon-shaped sail
In the countless calculations and discussions concerning the "space rope" I've never found any addressing its capability to resist winds.
Consider, as in most current works, it's a 1m wide ribbon, ...
12
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3answers
591 views
What causes an aircraft to roll when rudder is applied
When continuous rudder is applied in a typical light aircraft during straight and level flight at "normal" flying speeds and altitudes, the primary effect is that the aircraft will yaw to the left - ...
12
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1answer
375 views
Do modern Formula One cars produce enough down-force to drive upside-down?
For example, if they were driving at top speed through a long tunnel, could they transition to and stay on the ceiling?
2
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0answers
106 views
Control cable failure and critical flutter speed margin?
I'm a private pilot, and I have some questions to those who have knowledge of the aeroelastic effects and flutter phenomenon. I would like to talk a little about aerodynamic flutter onset speed and ...
2
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1answer
214 views
Limitations of drag equation
The magnitude of the air resistance for objects with Reynolds numbers greater than 1000 is given by the formula:
Why it does not hold for objects with lower Reynolds numbers? Can I use this ...
9
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1answer
333 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
79 views
Stability of balanced masses with different surface areas
Say I have this setup. The two round objects have equal mass and their centers of gravity at the same distance from the shaft. The objects only differ in that they have different surface areas ...
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0answers
131 views
Torque required to spin a disk along its diameter
How would I calculate (or simulate) this? I am only interested in the aerodynamic drag caused by the surface moving, not any other forces.
As far as I know, the only variables needed are the drag ...
8
votes
2answers
430 views
Does a wing in a potential flow have lift?
I have a hard time understanding whether or not a wing placed in a potential flow, assuming there is no viscosity and no friction with the wing, will produce a lift. I've seen several contradictory ...
11
votes
5answers
444 views
Is flying really easier on smaller scales?
In the book Playing with Planets, the author makes the following argument, pertinent to flying robots of the future:
As it is, an important law of physics says that smaller organisms fly much more ...
3
votes
1answer
132 views
What velocity must an aircraft achieve for its shock wave to transform to plasma?
A follow-up to After what speed air friction starts to heat up an object?
I understand there may be technological limitations at present ... but, is it theoretically possible for a body to travel ...
2
votes
1answer
288 views
Turning an airplane - coordinated turn and inclinometer (“the ball”)
I'm flying, turning in a stable orbit, i.e. at constant level with a constant angle of bank, at constant airspeed, with a constant radius of turn, as in the picture here (sorry it's my first post, ...
2
votes
5answers
388 views
How would you improve braking capability on a hovercraft?
Pretty much letting my mind free-wheel.
Assume a fleet of air-supported hover-craft were to replace cars/etc on the streets. Assume also that the present traffic-signals/pedestrian rules remain ...
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2answers
54 views
Can additional airfoil enable a commercial liner to reach 100km altitude?
Assuming that it's engines are incapable of dying out at 100km altitude, would mere addition of airfoil area enable a commercial liner e.g. B787 to reach that altitude?
