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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What really allows airplanes to fly?
What aerodynamic effects actually contribute to producing the lift on an airplane?
I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
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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 ...
13
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4answers
681 views
Why is exhaling more forceful than inhaling?
By blowing at pencil, a piece of paper, or another object up to fifty centimeters away, I can cause it to move away from me significantly. But I can't move an object toward myself by inhaling sharply ...
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1answer
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Did Felix Baumgartner produce a sonic boom during his jump?
I really got to thinking about this. The speed of sound is measured at 761.2 MPH at sea level. But how does this number change as air density decreases? The lack of air density is what allowed his ...
12
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3answers
593 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
376 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?
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4answers
874 views
How to sail downwind faster than the wind?
Recently a group set a record for sailing a wind-powered land vehicle directly down wind, and a speed faster than wind speed. Wikipedia has a page talking about it, but it doesn't explain exactly how ...
11
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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 ...
10
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4answers
801 views
Helicopter in an Elevator
You buy one of those remote control toy helicopters. You bring it into an elevator. The elevator goes up. Does the helicopter hit the floor or does the floor of the elevator push the air up into the ...
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1answer
335 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 ...
8
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1answer
2k views
Why exactly does a boomerang return back to the thrower?
I was always intrigued by the phenomena that govern the returning back of a boomerang to the thrower.
Even if it is dependent on various factors such as velocity, aerodynamics, wind resistance and ...
8
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2answers
431 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 ...
8
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1answer
387 views
NASCAR drafting at Daytona
This year, the racetrack at Daytona has been repaved. The track was always faster than other tracks NASCAR raced at and several cars in a "train" were faster than single cars or smaller trains. This ...
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Why does the air flow faster over the top of an airfoil?
I understand the common explanation of lift, which describes the airflow over the top of the wing as moving faster than the air below the wing. However, I don't quite understand why the air moves ...
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5answers
718 views
Why do blades of windturbine propellers as comp. to propellers of ships cover very different areas?
This is a thought I asked myself often, but never did real efforts
to get an answer. Barsmonsters question about number of fans of a
wind turbine made me think of it again
Why do blades of aircraft ...
6
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4answers
1k views
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 ...
6
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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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5answers
560 views
Turning an Airplane. What actually causes the circular motion in a banked (roll) turn?
Basically I'm wondering if this is correct. Which essentially says that you need a torque to get the nose of the craft to turn and that this is provided by the rear tail surfaces.
After trying to ...
5
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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 ...
5
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1answer
436 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.
...
4
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3answers
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How is the Joukowsky Transform used to calculate the Flow of an Airfoil?
As I read in The Road to Reality by Roger Penrose, the Joukowsky transform $$w(z) = \frac12\left( z + \frac1z \right)$$
after Nikolai Zhukovsky (transcribed in several versions from Никола́й Его́рович ...
4
votes
2answers
116 views
The visibility of air
For pilots of gliders or sailplanes, the 'thermal' is the most important phenomena of the air. A thermal is classically described as an upward flow of air caused by ground level heating of air that ...
4
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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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2answers
234 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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4answers
978 views
Why do aircraft inner wings lose lift when turning?
first question here, so please be gentle!
I'm reading an entry-level engineering course book and am currently up to discussion of aircraft design.
There's one particular statement that is unclear to ...
4
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2answers
877 views
What is the optimal design for a paper airplane? (Or, at least, how can you approach it?)
Having only really known two designs for paper airplanes since my days as a child, one which flies about eight feet and another which flies about ten feet, I have always wondered how people manage to ...
4
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1answer
209 views
Aerodynamics of two objects closely following each other
On bicycles.se a question came up about whether one cyclist drafting another causes the lead cyclist to be slowed down. A contributor suggested that the opposite might be the case, that the leading ...
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0answers
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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 ...
4
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0answers
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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 ...
4
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0answers
227 views
Why don't Turbojet engines use the De Laval Nozzle?
Why don't Turbojet engines use the De Laval Nozzle?
In fact, it seems that in a typical turbojet, the output nozzle contracts, not expands.
As the temperature of exhaust gases is high -- it should ...
3
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4answers
1k views
Is it really Impossible for Bumblebees to fly?
According to some source or other (I forget which now) it is theoretically impossible for bumblebees to fly by virtue of their size/bulk/aerodynamic properties. Is this old adage apocraphyal or true? ...
3
votes
3answers
215 views
Why is an Aircraft Runway NOT like a Teaspoon?
If the aircraft runway were like a teaspoon (by this I mean, flat in the beginning, then curving downwards and finally upwards), would it not work in favor of the propulsion of the aircraft? In spite ...
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3answers
401 views
Does wind speed things up or accelerate things?
This question may seem odd, but I can't think of anything better. So I'll go straight to the point.
Let's say there's a projectile in air going east, shot at a certain angle, with a certain speed. ...
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6answers
568 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 ...
3
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2answers
531 views
logarithmic wind speed profile
Under some atmospheric stability condition, over flat terrain, it has been observed for a while that the ratio between wind speed at height $h_1$ above the earth and the wind speed at height $h_0$ is ...
3
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3answers
325 views
Why trimming the mainsail gives a larger torque to head up
I am learning sailing on a 5m catamaran (Nacra 5).
I am familiar with basic aerodynamics and the physics of the sail and keel.
We learned that when sailing closed hauled, too tight a mainsail tends ...
3
votes
1answer
251 views
Tear drop shape
i heard that a tear drop shap is the most aerodynamic shape possible or the best is this true? If this isn't true what is since i need to make a fast ROV? Also since i need to have a propeller to ...
3
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1answer
446 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!
...
3
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1answer
203 views
Local Mach number for an airfoil
I would like to know how to calculate the local Mach number on the upper surface of an airfoil given the ambient temperature, the local velocity on the airfoil surface, the freestream velocity, and ...
3
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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 ...
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0answers
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Turbulence forming between the coaches of rail
is there any specific reason why rail coaches are connected by a rubber sheet; not of any other material ?
I watched a documentary on trains (Discovery Channel) which said it connecting coaches by ...
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 ...
2
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2answers
1k views
how does a helicopter get forward thrust?
Just passed a helicopter on my way to work. We have read in some detail how an airplane gets forward thrust and lift by deflecting air. How does a helicopter with horizontal fans achieve that ?
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2answers
564 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:
...
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4answers
187 views
What do spacecraft have in common with atmospheric aeroplanes?
Science fiction depicts spacecraft as both deep-space & surface capable. Is this feasible?
I would have imagined a vessel constructed for space travel to have little in common with operating ...
2
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2answers
111 views
How fast can toy helicopters change the turning direction of their propellers?
I saw someone do some tricks with a toy helicopter where he would turn it upside down for a while and it would still stay in the air. I thought it should have crash or at least not fly for very long ...
2
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3answers
189 views
Making a “heavier-than-air” craft float
How big would a hollow rigid object need to be to float, (not in water but in air) if all of the air was vacuumed out and the container sealed?
2
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3answers
683 views
Distance travelled in free-fall
When an object is in free fall, we have:
$a(t) = g - \frac{c}{m}v(t)^2$
where $g$ is acceleration due to gravity, $m$ is the mass of the object, and $c$ is the coefficient of air resistance.
How ...
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3answers
167 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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3answers
143 views
Effects on the lift of a Wing in a hermetically sealed torus
To help settle an office discussion could someone please explain why this is/is not possible.
Assuming that materials could be found that are light and strong enough for its construction.
If you ...
