What is Wind: Definition and 858 Discussions

Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect). Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail.
Winds are commonly classified by their spatial scale, their speed and direction, the forces that cause them, the regions in which they occur, and their effect. Winds have various aspects: velocity (wind speed); the density of the gas involved; energy content or wind energy. The wind is also a critical means of transportation for seeds, insects, and birds, which can travel on wind currents for thousands of miles.
In meteorology, winds are often referred to according to their strength, and the direction from which the wind is blowing. Short bursts of high speed wind are termed gusts. Strong winds of intermediate duration (around one minute) are termed squalls. Long-duration winds have various names associated with their average strength, such as breeze, gale, storm, and hurricane. In outer space, solar wind is the movement of gases or charged particles from the Sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space. The strongest observed winds on a planet in the Solar System occur on Neptune and Saturn.
In human civilization, the concept of wind has been explored in mythology, influenced the events of history, expanded the range of transport and warfare, and provided a power source for mechanical work, electricity, and recreation. Wind powers the voyages of sailing ships across Earth's oceans. Hot air balloons use the wind to take short trips, and powered flight uses it to increase lift and reduce fuel consumption. Areas of wind shear caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and human-made structures are damaged or destroyed.
Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Dust from large deserts can be moved great distances from its source region by the prevailing winds; winds that are accelerated by rough topography and associated with dust outbreaks have been assigned regional names in various parts of the world because of their significant effects on those regions. Wind also affects the spread of wildfires. Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with cold temperatures, the wind has a negative impact on livestock. Wind affects animals' food stores, as well as their hunting and defensive strategies.

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  1. B

    Working out wind shear in dams & retaining walls

    Hey, got a bit of a problem; got a few questions on wind Shear in Dams & retaining walls. Can anyody help http://img296.imageshack.us/img296/9366/image0003xb2.jpg Thanks Andy.
  2. M

    Measuring Wind-Generated Waves: Ideas for Experimentation

    (I'm not sure if I posted this topic in the appropriate category. The project I'm discussing is for my school, but seems bigger and different than a homework question. If it's not the right section I'm sorry) I want to measure the relationship between various aspects of wind generated waves...
  3. P

    Thermofluids U tube manometer wind tunnel question

    1. Homework Statement Air at 20 degrees celsius and 100kpa is drawn into a wind tunnel. If the deflection h of a water manometer that is connected to a hole in the wall of the test section to measure the gauge pressure in the flow is 98mm. Calculate air speed in test section in m/s ignore...
  4. P

    Thermofluids Question wind tunnel u tube manometer

    Homework Statement Air at 20 degrees celsius and 100kpa is drawn into a wind tunnel. If the deflection h of a water manometer that is connected to a hole in the wall of the test section to measure the gauge pressure in the flow is 98mm. Calculate air speed in test section in m/s ignore fluid...
  5. T

    Can a Wind Turbine Improve the Efficiency of a Moving Car?

    If supposing we were to add a wind turbine connected to a generator to a moving car, would we be able to get the air flowing around the car to turn the turbine and therefore gain some energy? If it is possible, is it economical? if it is, is it practical? would there be a loss? would there be...
  6. I

    Wind Velocity: Findings & Insight Needed

    Having a little bit of trouble with this and not sure if my findings\thoughts are right and would like some insight. If a boat is traveling south at 10 km/h and a person on the deck measures the wind velocity to be 8 km/h east, would the actual wind velocity (velocity of wind relative to the...
  7. H

    Force of air resistance in wind tunnel

    Homework Statement I am working on making a small wind tunnel using a 20" fan. What i want to figure out is the force generated by the movement of air. I want to make the size of the tunnel shrink to help induce more velocity in the air (see picture). Homework Equations Bernoulli's...
  8. D

    Convection Wind Tunnel Power: Small Scale Plan for BC Property

    POWER FROM A CONVECTION LOOP: this is a scaled down version of the solar tower updraft system planned for austrailia, or the SHPEGS project with water/silica jell adsorption instead of ammonia absorption, or the water spray downdraft 'culvert on a hillside', proposed for hot dry...
  9. L

    Small wind tunnel for a model rocket

    I need to test a model rocket which will have average airspeeds around 200 mph. I am hoping to construct a plexiglass box about 9 feet long, 3 feet wide and 3 feet tall. For these dimensions and airspeed requirements it looks like I'd need a 160000 cfm blower. Is this something I can feasibly...
  10. G

    Building a Low Speed Wind Tunnel: Fan/Motor Size Considerations

    I am trying to build a low speed wind tunnel, and have a question. I understand that the contraction cone speeds up the air (proportional to the area ratio). What I am confused on is how does this "mechanical advantage" factor into sizing my fan / motor? I am planning on a tunnel with a...
  11. E

    How does wind acceleration affect the speed and direction of a sailboat?

    Homework Statement A sailboat is traveling east at 4.5ms-1. a suddent gust of wind gives the boat an acceleration a = 0.70 ms-2, 40 degress north to east. what are the boat's speed and direction 6s later when the gust subsides? Homework Equations V(@6s) = V(init.) + at The Attempt at a...
  12. K

    What is the force exerted on a flat roofed building by wind pressure?

    Homework Statement "Wind (density=1.29kgm^-3) blows over a flat roofed building of height 20m at 12ms^-1.The area of he roof is 100m^2.What is the magnitude and direction of the force exerted on the roof if the pressure difference between inside and outside is due solely to the fact that the...
  13. B

    Solar Wind Power: Can We Collect & Store?

    Is there enough power coming from solar wind to some how collect and store as energy.
  14. E

    Selection of material for wind generator

    sir i am tying to make a wind electricity generator, but i am confused about selection of material that i have to use for the project. can hysterisis loop help me? how? what the graph will show to me? please explain. the use of steal magnet will make my generator light and more efficient or...
  15. R

    Why is air always cold when it moves at high speeds?

    Why is it that air going at a high rate of speed always cold? For example, fans throws air at high speed and it's cold and when we, human blow air fast is always cold. WHY?
  16. M

    Wind Tunnel Testing Questions & Experiments

    Hello, Is there people amongst you who have ever dealt with Wind Tunnel testing? I cannot find a special section for experiments in this forum... I have a few topic to launch! Thanks...
  17. B

    How Does Blade Number and Wind Speed Affect Wind Turbine Efficiency?

    I'm doing an experiment (at A-Level) to see the efficiency of a wind turbine. I'm doing this by changing the number of blades and varying the wind speeds. I wondered if anyone had an equation that could look at efficiency? I have the current and the voltage (and wind speed). Sorry if I've...
  18. E

    How Does Wind Affect the Doppler Shift of Sound?

    Homework Statement A factory whistle emits sound of frequency f. On a day when the wind velocity is w from the north, what frequency will observers hear who are located, at rest, (a) due north, (b) due south, (c) due east, and (d) due west, of the whistle? What frequency is heard by a cyclist...
  19. D

    Pressure (force) from wind on a building

    Hello, I am trying to work with an equation I have for force from wind on an enclosed building. The equation is two parts, consisting of Qz which relates the the gound structure to the building qz = CONSTANT * CONSTANT * CONSTANT * CONSTANT * V^2 * CONSTANT V being the velocity You then...
  20. S

    Calculating Airplane Velocity with Wind: A Study

    Homework Statement An airplane is flying at [80.0, 50.0(degrees)] m/s when there is no wind. Then the wind begind to blow at [18.0, -20 (degrees)] m/s. a) if the pilot does not change the heading of the plane what will be the resultant velocity over the ground? b) In order to maintain...
  21. H

    How Fast Must Wind Blow to Lift an Aluminum Sheet?

    Homework Statement A sheet of aluminum of thickness .01 m lies in a parking lot. A wind blows over the top of the sheet. What is the minimum velocity that will cause the sheet to begin to rise: Assume the density of air is 1.18 kg/m^3 and aluminum is 2700 kg/m^3. Homework Equations...
  22. A

    Wind will affect the doppler effect?

    Homework Statement Is this true? the observed doppler shift for sound waves depends only on the relative motion of the source and the receiver. Homework Equations this is a concept-like question The Attempt at a Solution If no, doesn't mean, wind will affect the doppler effect?
  23. S

    Wind Turbine/Weather station interface

    Hello, I have a small 300W wind turbine (Aero4gen). I also have a weather station which datalog's the wind speed/direction, ect... at intervals of 5 mins also there is a solar radiation sensor (photodiode) (0 to 3 volts). Anyway, i will not be needing the solar radiation datalogging facility...
  24. P

    Calculating Velocity for Cannon Ball with Wind Velocity

    Hmm, i have this cenario, there is a cannon and it's target, separated by a distance d, not necessaraly in the same heigh. what i need is a function that gives the velocity needed for the cannon ball reaches the target. PS: consider the angle 45°, there is wind velocity, but not air...
  25. DaveC426913

    Aerodynamics of modern wind turbine

    I've been thinking about the wind turbine (horizontal turbine - like an airplane propellor.) that I pass on the way downtown and I'm realizing I've been taking for granted how it works. Seems to me it's exactly opposite of an airplane wing. Rather than forward speed generating lift, you have...
  26. G

    Solving Wind Speed Project Homework

    Homework Statement hello everyone, Im new to this forum but i really need some help doing a physics assignment. I am trying to use Newtons second law and the equation for wind resistance(click link) to determine the the angle made by a specific velocity. The link to the assignment is...
  27. N

    How Does the Solar Wind Impact Earth's Magnetosphere?

    Hi Group, Just wanted to find out : The solar wind particles are electrically charged and arrive at the earth with great speed, then get trapped by the magnetic field in the magnetosphere envelope round the Earth. Right...:biggrin: Now, what about quantity? please can you guys...
  28. F

    Force due to wind and rolling friction on van

    Homework Statement The graph shows the speed as a function of time for a minivan, coasting on neutral along a straight, level road, loaded with windsurfing equipment and towing a boat. The total mass is 2500 kg, weight= 5512lbs. Find the size of the force due to wind and rolling friction when...
  29. P

    Energy available to a wind turbine, Bern.'s eq

    HI folks, new to this forum.I posted this on a different thread, but this seems the better location... it's a conceptual question. I'm in a Fluid Dynamics class and need to make a presentation on Bernoulli's conservation of energy equation as it applies to wind turbines. I think I...
  30. P

    Energy available to a wind turbine

    HI folks, new to this forum. I'm in a Fluid Dynamics class and need to make a presentation on Bernoulli's conservation of energy equation as it applies to wind turbines. I think I understand the different energies involved here: kinetic(v^2/2), pressure(P/rho), potential(zg)... I want to...
  31. S

    How does a wind turbine in a tunnel affect the volume flow rate?

    Hi everyone…. I’m trying to evaluate the feasibility of putting what is essentially a wind turbine inside a horizontal exhaust shaft. I have a feeling that this would affect the volume flow rate through the shaft, but am having difficulty proving it. I have found plenty of textbook examples...
  32. B

    Low Speed Wind Tunnel questions

    I am building a small wind tunnel, and I have a few questions about it. First: The Fan I am using produces 800cfm and is 12'' in diameter, I am going to narrow it down to 6''. The calculated wind speed that I got was 74.5km/h. Can anyone back me up on this? Second: When I use scale models...
  33. E

    Does wind affect how far sound can travel?

    I feel that this may be a silly question, but, Does wind affect how far sound can travel? I know that the air temperature affects how far a sound can travel (does wind affect air temperature?), but what about wind? I tried to find an answer via google, but I haven't found anything...
  34. G

    Write a compound inequality to describe "fresh gale" wind speeds."

    On my homework is says "On the Beaufort scale of wind force, the term "fresh gale" describes wind speeds from 39 mi/hr to 46 mi/hr. Write a compund inequality to describe "fresh gale" wind speeds." Would an acceptable inequality be {S: 39 < S < 46} ?
  35. D

    Design Ideas for Wind Power Lifter | Manchester Twp.

    Does anyone have any good suggestions or design ideas. I have an idea in mind but outside input and help would be much appreciated. The site that has the project details is http://www.manchestertwp.org/teacher/mths/pwhite/Physics_files/physics%20oly%202006%202007/EVENT%205.mht .
  36. T

    How Does Rotor Diameter Affect Wind Power Output?

    Ok, doing a project at the moment and this is one of the issues I have to overcome; The information I have researched is as follows: If this is the case then a 88m diameter rotor should generate 2400kW? But the below diagram from the same page shows a 80m diameter rotor generates 2500kW...
  37. wolram

    Do Fish Break Wind? Investigating Digestion in Aquariums

    Do fish---- Break wind, when looking at them in aquariums i have never seen bubbles coming from that end, so may be their digestive system works differently.
  38. L

    Velocity of Wind: Calculate Direction & Speed

    The question said that the airplane turned west for 255km/h, and the resultant was 225km/h South 70 degrees West. I have to find the wind direction and velocity. How?
  39. D

    Solar wind + Weak magnetic field = No water?

    Is it possible that one day, the Earth magnetic field get so weaken that solar wind could strip off water from earth? I ask this because of this article which leads me to draw the parallel. http://www.geotimes.org/sept04/NN_solarstorms.html
  40. O

    Mythbusters Terminal Velocity Wind Tunnel

    Recreating the Mythbusters' Terminal Velocity Wind Tunnel - Need advice on Manometer Hello, I am trying to find the terminal velocity of a projectile. I am placing the projectile inside a clear tube and blowing compressed air inside the tube until the projectile is hovering at some height...
  41. S

    Trajectory, Wind Resistance, and Acceleration

    Suppose the force of wind resistance is proportional to the speed of the object and in the direction opposite of the object’s velocity. If you throw an object upward, when is the magnitude of the acceleration the highest? a.It is highest at the top of its trajectory. b.It is the highest...
  42. M

    Relative velocity question - plane and wind

    Relative velocity question -- plane and wind The distance between two cities A and B is l. An airplane travels back and forth between A and B, flying in a line, with velocity V relative to the air. (a) Find the total flight time, if the wind blows with velocity v, in a direction that forms an...
  43. A

    How to draw vectors of an airplane & SE wind diagram

    I can create/solve the math problem without any difficulties once I have diagram in place, but I am having trouble setting up the diagram so that I can visualize it. The questions is: A novice pilot sets a plane's controls, thinking the plane will fly at 2.50 x10^2 km/h to the north. If the...
  44. O

    Drag calculation in 3D, 'virtual wind tunnel'?

    Is there a (freeware?) program to calculate 3D lift and drag for simple flying bodies, e.g. ball, cylinder, cube, wing? There are programs to calculate lift and drag for foils (2D programs), e.g. javafoil of Martin Hepperle. Those programs could be used to study the flow in 2D only. E.g...
  45. B

    Wind Turbine Blades and Wind Speed Performance

    I wonder if anyone could shed some light or information about the subject I'm looking into. How will wind turbines with varied amounts of blades perform in varied wind speeds. E.g. the less amount of blades you have the better a turbine will perform at higher wind speeds? Any help on the...
  46. O

    Predicting Wind Speed based off previous data

    Hello all, My boss wants me to create a form of short term wind prediction based off a collection of long term wind data. I haven't taken a course in statistics so this is totally new to me. Basically, the data is organized by Year > Month > Day > Hour > Wind Speed with data stretching back...
  47. K

    Quiet Revolution: Can Our Wind Turbines Power Themselves?

    http://www.quietrevolution.co.uk/ I understand these things can spin, but what I'm questioning is whether they can really produce enough power to even power themselves? I mean, there have got to be a few hundred if not thousand LEDs on each one, as well as a control circuit to control the...
  48. E

    Measuring wind speed with ball and string Newtons 2nd law

    hello everyone, Im new to this forum but i really need some help doing a physics assignment. I am trying to use Newtons second law and the equation for wind resistance(click link) to determine the the angle made by a specific velocity. The link to the assignment is...
  49. O

    Average Wind Farm Size & Energy Production

    Hi, With all the wind farms being put into production recently, does anyone know what the average size generally is. I see they are generally between 10-kW to 5-MW, quite a difference, so I would think the large ones can only be used in certain places and need to be spaced apart more - but I...
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