What is Wind: Definition and 857 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. J

    Airplane direction and wind direction

    Homework Statement I have an example problem I would like to solve and unsure how to graphically set up the problem. I would like to derive the answer by the component method of deriving vectors instead of law of sines/cosines. An airplane is trying to keep on a due west course towards an...
  2. J

    The Cooling Power of Wind: Reducing Car Hood Temps at 55 MPH

    If the hood of my at rest car is 106 degrees and I drive at 55 MPH, how much is the hood temparature reduced by the wind so created?
  3. T

    Why Is There Cold Wind? Investigating the Creation of Wind and Its Temperature"

    So awhile ago I was thinking about wind. Sometimes wind is hot but when I think of wind I usually think of cold wind. Wind seems to be fast moving particles and I know based on the kinetics theory of gases KE = \frac{1}{2}mv^2 = \frac{3}{2}kT Maybe, I'm making a wrong assumption but...
  4. anorlunda

    Can Wind and Water Sounds Be Distinguished in Nature?

    I just returned from a tenting trip. In a tent, one hears the sounds of night more plainly. I was struck by the fact that, try as I might, I can not distinguish the sounds of wind from those of running water. Specifically, Moderate winds (15-30 kt) in the forest. Moderate winds (15-30...
  5. C

    What psi can be achieved from a 60mph wind

    If I put vents on the hood of my car and drove at 60mph what kind of psi could be achieved? I don't care about what kind of technique is used just curious about what kind psi could be created. I apologize if I'm not asking this correctly but I have no background in fluid dynamics.
  6. B

    Deriving the expression for wind velocity around low pressure area

    Hi Can somebody tell me the steps and assumptions made in deriving the equation to calculate the wind velocity around a low pressure area ? (see the attachment fro Kleppner & Kolenkow). I tried to derive like this : Coordinate system located on Earth's surface with i direction towards E, j...
  7. S

    Finding the direction and velocity of wind using vectors question

    Homework Statement A person, traveling eastward at a rate of 4.0 km/hr, observes that the wind seems to blow directly from the north; on doubling his speed the wind appears to come from the northeast; determine the direction of the wind and its velocity. Homework Equations The...
  8. AJBMuir

    Why does a strong wind feel colder than a gentle breeze?

    This may be a ridiculous question, or we may be overlooking what is a simple answer but a friend and I can't come to a reasonable conclusion. Why does a strong wind feel colder then a gentle breeze? We have thought about the fact that this may not be the case at all and that the temperature of...
  9. C

    Direction problem; find angle to shortest path with wind

    Homework Statement A pilot must travel directly to a town 500 miles away in a directions 20 degrees east of south from her present position. There is a steady 40 mph wind blowing west to east. Her plane's cruising speed through calm air is 95 mph. Using vector, what must be the plane's...
  10. W

    Probability Wind or Rain if it's Windy?

    Homework Statement 30% chance of rain, 45% chance of windy, 62% chance rain OR wind. Assuming it is raining what is the probability that it is windy? Homework Equations P(wind or rain)= P(wind)+P(rain) - P(wind & rain) This does not work out the way I tried it... The...
  11. J

    Torque on shaft of wind turbine

    Today this guy at work told me that a 2MW wind turbine required 20K ft lbs on the main shaft at 20 rpm. I thought that I had recently read that a 750KW wind turbine might need 20K ft lb torque. I am not looking for exact numbers but which seems correct?
  12. F

    Calculate wind load using fluid impulse and momentum.

    I recently took a crash course that included some topics in fluid mechanics. I learned that you can use the concept of impulse and momentum the calculate the force of fluid, for instance a jet of water on a turbine blade. The equations used are: ƩFx = ρQ(Vx1-Vx2) ƩFy = ρQ(Vy1-Vy2) I...
  13. I

    Steady State Angle of a Pendulum with Wind

    I'm having trouble solving this problem. I'm trying to find the steady state angle of a rod with wind /fluid drag. Assume Cd, L, U, etc. are known. The viscous and form drag forces are a function of the angle θ so I don't have enough equations to solve the problem. Maybe there's some type of...
  14. M

    Directly Downwind Faster Than The Wind

    how can energy equations be applied in analyzing how is DDWFTTW- Directly Downwind Faster Than The Wind- system works? Thank you
  15. R

    Solar and geomagnetic field interaction with or without solar wind

    The usual story is that after a solar flair (coronal mass ejection) towards the Earth the Earth's magnetic field gets strongly deformed. It usually takes a few days from the solar event to when the Earth is impacted. But I wonder if there is also a direct interaction: If there is drastic...
  16. N

    Fixed Speed Wind Induction Generator

    Hi, I'm sure there is a simple answer to the following question that's got me thinking lately but I'm unsure (it's more of a hypothetical question out of interest and not homework). If a simple older type fixed speed wind induction generator was connected directly to the grid via a gearbox...
  17. G

    Creating controlled turbulence in a home-built wind tunnel

    Hi, I have built an 8' long wind tunnel for use in an experiment to test the effects of turbulence on several variables. However, seeing as this is an educational-level/novice wind tunnel with a fan rating of ~1800 cfm the wind speeds only really go up to ~10 mph. From my understanding, this...
  18. S

    What about current de-icing technology used for wind turbines?

    I saw those giant wind turbines stopped working in winter, since winter has most wind in four seasons. so, what good comes out of that? while at least 1/4 of time in a year that the wind turbines don't generate power. and wind turbines are so expensive with limited life time around 20 years...
  19. F

    Helical Twist Vertical Axis Wind Turbine - Generator Matching

    Hello I have designed a vertical axis wind turbine (Savonius) with a 180deg helical twist. It catches the wind really well but the wind power to electrical power conversion is really poor, it is currently only at 4% efficiency. I think the problem is the dc motor that I am using as a...
  20. B

    Vertical axis wind turbine design, torque help

    Hi i am currently doing my dissertation in which i am designing a vertical axis wind turbine design that is a modification of that of a savonius design. A major problem that i am having is being able to predict the torque value of torque for my design in order for me to then predict the...
  21. W

    Relative Velocity with plane and wind

    Homework Statement An aircraft flew due east fro P to Q at u1 km/h.Wind speed from south west was v km/h.On the return journey from Q to P,due west, the aircraft's speed was u2 km/h, the wind velocity being unchanged.If the speed of the aircraft in still air was x km/h, x>v,show by resolving...
  22. A

    How can I achieve 30mph in my homemade wind tunnel?

    Hey everybody, I have built a 7' wind tunnel. The test section is 7''x7'' and 24" long. The diffuser opens to 22''. I would like to achieve around 30mph through the test section. I am having trouble finding a fan that can meet that need. I have looked into using an electronic radiator...
  23. J

    How does surface size affect wind pressure on a sail boat?

    Hi forumers, I've got a question,and of course all proper answers are welcome, I think however a sailboat designer/engineer would quickly know what I'm talking about. I'd like to know what is the pressure/push of a 10 mph (16 km/h) wind on 12,000 sq.mt. surface ,and how to figure this...
  24. G

    Strain gage to measure drag in a wind tunnel?

    How would a strain gage be set up (on top of the model? around the sting?) to measure drag? I don't quite understand the connection between the force of drag and some sort of compression/tension force...? Thanks for the clarification.
  25. G

    Wind Mitigation and Building Facade

    I am working on an independent study that involves housing typologies and their adaptation to climatic conditions. I am looking at row housing and how their facades may become more adaptable and responsive to changes during storm conditions. My site is beach front and prone to hurricane/ cyclone...
  26. J

    Wind Turbine: Min. Wind Speed for 6MW Generator

    Suppose I've got a 6mw wind turbine with a very small wing span - 5 meters-, what would the minimum wind speed needed to activate the generator ?
  27. G

    Drag equation using wind to create 3d graph (Again)

    Hey guys, I am back again with a drag related question, earlier I posted a thread asking how I could incorporate wind into a drag equation of sorts to create a 3d graph that shows the trajectory of a projectile. The help I received helped me add head winds and tail winds, however I am now...
  28. G

    Drag equation using wind to create 3d graph

    Hey guys, I'm new to these forums so I am unsure if this is the right place to be posting this, but here it goes. I have been working on a drag spread sheet using OpenOffice Calc to predict where a potato will land when fired from a potato gun. I have gotten pretty far along, using...
  29. shinnsohai

    Designing a Wind Tunnel: Homework Assignment and Bernoulli Principle Explanation

    Homework Statement Recently I've been given an assignment Build a Wind Tunnel(That can generated wind speed of 20m/s) -Izzit the chamber(whole tunnel) must be sealed ? -The material of the wind tunnel must be transparent(something like plastic?)on the test section?? Homework...
  30. S

    Conducting a feasibility study on wind energy

    I'm in the final year of my bs. in mechanical engineering.For my senior project , I would like to conduct a study on the feasibility of harnessing wind energy for electricity in my country (I don't think it has been done here before and we have a power problem and a pollution problem). My...
  31. C

    Calculating Wind Turbine RPM from Generator Voltage Fluctuations

    Hello, I am trying to build a SIMULINK model in Matlab in order to determine the RPM of a wind turbine. Can someone please tell me how I can obtain the RPM of a wind turbine from the voltage fluctuations of a generator? Any good sites in the subject are also welcome. Thanks in advance.
  32. P

    Wind Load Calculations for a 50ft x 14ft Patio Cover at a 6 Degree Pitch

    this falls into civil engineering, but as we all know everything boils back to physics. and, i couldn't find any good civil forums to join. so, i have a basic Q but need help understanding some things. 1) i am building patio cover approx 50ft long x 14ft off the house. it has a pitch...
  33. C

    Effect of wind shear on noise propagation

    Can anyone recommend a source of information that quantifies how wind shear effects the propagation of sound/noise? I know the basics in that wind shear either bends sound waves upwards or downwards but I'm looking for something that helps calculate the effect.
  34. M

    Dissertation help, wind turbine output

    This is a question that i am struggling to find any answer to on the internet. Doing some research for my 4th year honours dissertation. I have a wind turbine capable of producing a certain output at say windspeed of 10mph. Meaning that the wind is moving towards the turbine at 10mph...
  35. R

    Wind Tunnel Design Question Re: Test Section and Diffuser/Fan Size

    Hello, My name is Ryan and I'm a volunteer instructor with the local Royal Canadian Air Cadet squadron. I'm looking for ways to try and make the kids' aviation lessons more interactive and hands on, and so I've decided I'd like to build them a small wind tunnel, purely for flow visualization...
  36. H

    The force of wind blowing on a wall at an angle

    Homework Statement Say there is a wall with width w meters and height h meters. There is a wind with velocity v m/s blowing on the wall at a 45 degree angle. The collisions of the air molecules with the wall are perfectly elastic. What is the magnitude of the force on the wall? (The density...
  37. E

    6MW offshore wind turbine - build me 300x please

    Nice toy... :!) A recent offshore wind turbine. 6MW peak power, the rotor has 120m or 154m diameter :tongue2: The alternator rotates at the blades' speed, without a gearbox... With D=6.5m, it uses permanent magnets, its stator must be actively cooled, and the nacelle weighs 200t. Still...
  38. E

    Steel wind tower resistance to sunlight

    Hello, For my Mechanical Engineering project, I'm working on a wind tower. One of the specifications we have to respect is a 50 years resistance to sunlight. We've chosen inox steel as the primary material (after calculating the various constraints due to the wind the the rotor up on the...
  39. S

    A boat moving because of the wind

    Homework Statement A boat has a sail that has a surface S towards the wind. The wind blows at constant velocity u. Also given the density of the air, p. Find the velocity of the boat as a function of time. What will be the velocity of the boat after a long enough time? What exactly is this...
  40. 4

    Is Tower Height Crucial for Optimal Wind Power Generation?

    Hi, Why is hight of a wind generators tower so important? Given a 50-meter tower, at what wind 'power class' and at what 'power level' will wind power be considered economical (circa 2005)?
  41. bcrowell

    What are the effects of overblowing on wind instruments?

    Wind instruments exhibit overblowing: http://en.wikipedia.org/wiki/Overblowing Naively, I would expect that if one, for example, blew harder on a whistle, or blew at a different angle on a flute, the result would be as follows. You produce some noise spectrum, which becomes a different noise...
  42. J

    Can Astronaut survive within solar wind?

    Solar wind contains ion charges and electromagnetic field, will Solar wind affect action potential within Astronaut's nerve system? Does anyone have any suggestions? Thanks in advance for any suggestions
  43. T

    Wind speed calculation with an anemometer

    Homework Statement Hi everyone, I'm currently in my first year of college and today I tried to calculate the wind speed of a fan by using a home made cup anemometer. In our experiment we measured the time needed for 10 revolutions, on both of the speed settings of the fan. We then converted...
  44. M

    Effect of Blade Angle on Power Output of wind turbine

    Homework Statement Hi all! I am been working on an EEI. Basically I recorded the power output (P=VI) of a wind turbine with the blades at different angles. I went from 0 degrees (flat) to 180 degrees in 15 degree increments. Averaging the data I see a graph like this: Also, just to...
  45. L

    Need Help- Finding the tension and Force wind using Newton's laws

    Homework Statement A 1.20 g spider hangs on its thread from the branch of a tree. A horizontal win blows the spider and the tread to an angle of 35 deg from the vertical. Find the force of win on the sider and the tension in the tread. Diagram...
  46. J

    Plane's new velocity after wind from west

    1. Homework Statement A plane is traveling north at 200 meters/second; a wind blows from the west and accelerates the plane at 15m/s^2. If the wind lasts 10 seconds what is the plane's new velocity? 2. Homework Equations velocity = acceleration*time 3. The Attempt at a Solution v =...
  47. J

    Doppler effect with two moving objects including wind

    Homework Statement An observer is moving to the right. A source is moving to the left. There is a wind moving to the right. What is the observed frequency? I had a quiz and this came up. I'm not sure if I did it right. Homework Equations f'=f(v±(vl-vw))/(v±(vs-vw)) The Attempt...
  48. P

    A formula for calculating wind speeds?

    This is pretty simple,but finding the correct formula does not seem to be that easy for me. How could I calculate wind speeds with only having the distance an object moved over a certain amount of time and the weight of said object? For example,winds caused a 600lb object to travel 30...
  49. L

    Wind Tunnel Power Requirements

    I am designing a wind tunnel for my final year project. I am am now a little lost at the power requirements area. To select a fan, i understand that i have to overcome the pressure drops through out the tunnel by choosing a fan that has a higher pressure rise. So far i have figured out that i...
  50. J

    Automotive Wind-Powered Vehicle: New Idea & Input Welcome

    Hi : I am new here but have been thinking about this for a while. I am attaching a drawing to hopefully explain my idea. I think a crossflow fan mounted at the rear of the vehicle's roof ( Accross the width of the car's roof ) , protruding partially above it and setup to allow air flow through...
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