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. weirdoguy

    Velocity of wind based on the shape of a smoke trail

    Hi everyone. My high-school student got the following homework exercise at school which I have problem with: Smoke from the steam locomotive is carried by horizontally blowing wind. Shape of the smoke trail is shown in the attached figure. Using the drawing, determine velocity of the wind...
  2. J

    I Why does wind blow leaves in circles?

    Earlier today I realized that, when a strong gust of wind would blow through my area, it would pick up leaves off the ground and typically blow them in circular patterns, and typically the leaves would go in at least several complete circles before coming to rest back down on the ground. Why is...
  3. Ghostinthemachine

    Question: can we make wind during motion

    Why when I move my hand faster to long distance and apply force I get more air but when I move my hand fast to shorter distance I barely get any air
  4. J

    Wall to wall airfoil in a wind tunnel

    Does wall to wall airfoil produce downwash in wind tunnel ?
  5. A

    How to determine Wind turbine RPM

    How to determine rpm of rotational body such as wind turbine blades. Is there any relation of input wind velocity with the blade rpm? If the rpm formula in relation to input wind velocity is known then I can choose exact matching rpm for electrical generator for a given power output. As per...
  6. G

    To find the relative velocity of the wind as seen from a car

    Could I please ask for any help with the following question: Here's my attempt: (i and j are unit vectors in the directions of east and north respectively) (apologies that LaTeX is simply not working for me, I'll label the angles in each case T and P as shown in my diagram) Let the...
  7. G

    To find the true velocity of wind from relative velocity

    Please can I ask for help with the following as to where I'm going wrong. Book answer is 20 knots and 315 degrees My solution: In the below diagram I have sketched the two situations, k is the true speed of the wind. First question is, is my diagram correct? The velocity of the wind...
  8. Ennio

    I Solar wind velocity and corrections

    Greetings, how do - the velocity distribution of the solar wind at 1 AU - the velocity distribution of the solar wind in our line of sight look like? I have found the 400 Km/sec but no further information. Is it an average values? Is this radially on the sun the same? Links with graphs are...
  9. C

    Relative velocity of the wind making a flag move

    Here it is given that the flag flutters in the direction of wind w.r.t. to man. But why would the direction of fluttering of flag would change without any tangential acceleration. Is there a pseudo force acting on it. I think the direction if fluttering should remain same.
  10. rcgldr

    I Sail craft and apparent wind theory

    I created this thread for a separate discussion of apparent wind theory from the thread about sailboats providing their own wind, which is a bit mis-leading title, since the OP's question is about using a fan blowing against a sail to move the sailboat forwards. A quote of a post from that prior...
  11. G

    Find the velocity of the wind relative to the boat

    Could someone please help me see where I am going wrong here? During a race between two boats A and B there is a wind of 18 km/h blowing from due north. The resultant velocity if A is 12 km/h on a bearing of 060. Find the direction of the wind relative to A. My reasoning: (Relative to the...
  12. Vigardo

    Design loads for wind towers & jackets?

    Dear experts, I'm looking for some approximate (but reliable) design loads and geometry for wind turbine towers to perform a comparative FEA study. I don't need very exact data. I just want some load levels for different wind towers, e.g. for 5 or 10 MW on- and off-shore wind turbines, and...
  13. Sofina

    Meteorology Physics: Apparent wind problem

    Hello everyone. Sorry for the mistakes on my English on this post and on the H/W statements (it is translated by me). I have a homework problem on Meterology Physics, about a ship's Apparent Wind , and it is about the a) question and maybe i don't know well the theory to solve this problem. (I...
  14. Jess1980

    Pitch axis location of aerodynamic profiles of wind turbine blades

    Summary:: How is the pitch axis location of an aerodynamic profile decided? Hi, I drew a wind turbine blade in a CAD software. I used information on the pitch axis location I had on the various aerodynamic profiles I used to draw the blade. I understand that it allowed me to align the various...
  15. K

    How to use Weibull distribution when it comes to wind?

    I know that I'm supposed to use Weibull, but why does my teacher take the middle value, 5 m/s? Should one not integrate the formula and the use 4,5 and 5,5 as limits? This is what he has done: He then writes: makes a guess of an interval of 1 m/s and get: To be honest, I really don't...
  16. F

    B Sailboats providing their own wind

    I happened to be watching this cartoon and this one scene seriously bothered me... This... just feels like it wouldn't be a workable solution. Am I wrong? I can't say I perfectly understand how fans or propellers work, but I would imagine that by pushing air or water in one direction, equal...
  17. K

    Does a strong wind slow down your free fall?

    I was wondering do strong wind slow down or has any effect on the outcome of your free fall? Like slower down your impact or help you survive? Hypothetical, you free fall down height of 1,000 feet below are just rocks so hard surface (not water). Basically it should cause death. But let say...
  18. A

    Total work of a directional wind on a mailman

    Homework Statement: Mike the Mailman takes his oath seriously: "Neither snow, nor rain, nor heat, nor gloom of night stays these courageous couriers from the swift completion of their appointed rounds". Even though a blizzard is raging outside, he goes out to deliver the mail. He makes four...
  19. C

    What type of diagram should be drawn when applying Newton's second law?

    Honestly I have no idea how to solve this. Can anyone help?
  20. P

    Wind Forces on Roof: Calculating Amount of Weight Needed

    For a project I need some dry workspace outdoors, so I build a wooden frame and covered it by a tarp. It's kind of like a carport with a A-roof where one side is 2,4m, the other is 3,6m. Angle of inclination is 30 degrees on both sides. Length of the building is 10m. The roof frame is placed on...
  21. Z0dCHiY8

    How much are wind farms useful to manage wildfires?

    The very idea is, to use wind turbines as guardian lines to slow Wildfires. 1. Power of Wind gets reduced (for needful direction) by such guardian lines. 2. Wildfire provides additional electricity. 3. those towers can be geared to spray retardants. 4. prescribed burns becomes more efficient &...
  22. R

    Can I store electricity from a wind turbine directly into a battery?

    Hello, This is an enquiry about the wind turbine electricity and battery storage. I am framing it based on my limited understanding. Please advise me. I intend to install and capture the wind energy through a small wind turbine at my home. The turbine shaft will be directly connected to the...
  23. Hassan Elkady

    Calculate Braking Torque in Wind Turbine Design

    How can I calculate the braking torque in wind turbine?
  24. T

    Vertical wind turbine with two concentric rotors

    Hello. For a long time, I wanted to build a wind turbine prototype that would have two concentric rotors. The design was inspired by an automotive torque converter, used with automatic transmissions. This device would have an external rotor that would be coupled to one generator and an internal...
  25. C

    At what wind speed will salt water "boil"?

    During hurricane Lenny in 1999, I was anchored on my sailboat in a protected cove in the Virgin Islands. The winds were about 60 mph with gusts to an estimated 80 mph where we were. I observed that during the gusts, the salt water would "boil", that is, totally evaporate the surface into a cloud...
  26. V

    How do you calculate wind speed using the Doppler effect?

    Problem Statement: The Doppler effect is routinely used to measure the speed of winds in storm systems. As the manager of a weather monitoring sta- tion in the Midwest, you are using a Doppler radar system that has a frequency of 625 MHz to bounce a radar pulse off of the raindrops in a...
  27. Marco Masi

    How much excess energy goes lost in solar and wind power stations?

    Since solar and wind power are fluctuating energy sources not all of it goes into the grid when the consumer power demand is lower than that actually produced. This is a well-known drawback of solar and wind energy that everyone talks about. What I never found is an assessment of how much of the...
  28. C

    Offshore wind power without subsidy

    News: The cost of offshore wind plant has been falling rapidly and now some projects in Holland are viable without subsidy... https://www.offshorewind.biz/2019/03/13/dutch-powerhouses-reveal-zero-subsidy-offshore-wind-play/
  29. A

    Cantilevered OSB Bending in the Wind

    Hope I am in the right subforum. I want to know how much a cantilevered sheet of OSB sheathing will deflect under wind load. I found the Moment of Inertia for OSB, but the units are in^4/ft. The bending equations I found use Moment of Inertia in units of in^4. The wind load will be uniform in...
  30. QuarkDecay

    Flow (liquid or gas) across a rotating surface's face

    << Mentor Note -- Two threads on the same question merged into one thread >> How does the maximum Power equation change if there's an angle to the way the wind falls into the wind turbine's blades? Example, when it falls vertically to the blades, it's Pmax= 8/27Sρu13 But if there's for...
  31. Kevin_787

    Wind tunnel calculations (making my own)

    Hey guys, I'm not sure this is necessarily a physics question, so if it's not I'd appreciate it if someone could point me in the right direction; but here goes. I've been giving some thought to building a wind tunnel lately, I realize this won't be cheap on any large scale, but I just want to...
  32. S

    Relative Wind Problem (Modern Engineering Mathematics, 5th)

    Homework Statement A cyclist traveling east at 8 km/hr finds that the wind appears to blow directly from the north. On doubling his speed it appears to blow from the north-east.. Find the actual velocity of the wind.[/B]Homework Equations Wind(relative) = Wind(Actual) - Velocity(cyclist)...
  33. 0

    Simple lift/drag measurements in a wind tunnel

    Hi everyone, I will be conducting wind tunnel tests of a NACA 0012 airfoil to obtain values of lift and drag in a low-speed wind tunnel (approx M = 0.1). I am looking for a really simple way of measuring these forces. Does anyone know of ways to achieve this? I am aware of force balance...
  34. Z

    Wind chill -- How is it actually measured?

    How do they measure wind chill factor?
  35. S

    Feasibility of stratopheric wind turbines?

    1/2" kevlar rope has a breaking strength of 31,000 lbs and weighs 7.8 lbs/100 ft. = 116 kg/km So a a bit over metric ton gets you up to 10 km altitude. 2 metric tons at a 30 degree angle. Still gives you 25,000 pounds potential drag without breaking the rope. Working strength is...
  36. B

    How Can I Account for Wind Loading in Calculating Buckling Load on a Beam?

    Hi all, I have recently been asked to calculate the Buckling load on a beam (channel) carrying pipes, (Eulers critical load) this was no problem. Then i was asked to allow for wind loading.. I can not for the life of me figure out how to do this? Any tips for me? Thanks in advance
  37. K

    How to wind a DC generator coil?

    I want to make a dc generator and not sure my design will work. I will wind the coil on a donut shape disk and put 6 rectangular magnets on a disk rotor with North Pole face the coil. Please see attached pictures. Will this design works or have problems? Can I have one continuous coil or I...
  38. YMMMA

    SAT physics question -- Flag on a bicycle being ridden in the wind....

    Homework Statement A girl is riding a bicycle at 15 miles per hour due north. A steady wind is blowing at 15 miles per hour from the east. A flag mounted on the bicycle will be stretched out toward the (A) west (B) south (C) southwest (D) southeast (E) northeast Homework Equations Vector...
  39. S

    Airplane's motion relative to the ground involving wind speed

    Homework Statement Plane is 300miles E of chicago and it leaves flying east at 500mph. Wind is blowing 50mph south. What is planes ground speed? Where is plane 0.6 hours later when pilot expects to land in cleveland? Homework EquationsThe Attempt at a Solution This is how I set it up I want...
  40. O

    How to figure out the velocity and direction of the wind

    Homework Statement [/B] So here is my question: I asked you about a solution approach/solution for the following task: Two rail paths cross at an angle of 145 °. With a constant speed of 60 km/h, they just drive along their tracks, and each of them repels steam/smoke flags, which, among other...
  41. Vigardo

    Wind loads for circular cross-section lattice structures?

    Dear experts, How should I compute the wind loads for a Shukhow tower, i.e. a circular cross-section steel lattice structure? The structural members should be rectangular or circular. I´ve been checking EUROCODEs EN 1991-1-4 (2005) and EN 1993-3-1 (2006) without success. Is there any other...
  42. K

    Lift and Drag force in a Wind Tunnel

    Hello guys, I am trying to calculate the lift force and drag force in a wind tunnel at my school as a part of a project that i am doing. I am varying the length of the airfoils and trying to measure the lift force and drag force. I have 3-d printed 7 airfoils. However, I am not able to find any...
  43. jeffinbath

    B Why do modern wind turbines have 3 blades?

    Conventional Wind turbines now have 3 blades. I assume this is a matter of average air pressure. 1)Would a future wind turbine working on Mars with about 1% of Earth’s air pressure need to have many more blades? 2) Would all those Victorian windmills have been any more efficient with 3 sails...
  44. M

    How can i calculate the velocity in a wind tunnel

    Ive done some wind tunnel experiments for a wing design i made, the wind tunnel was set to 50% power and the incidence angle was increased from -2 to 14 at 2 deg increments, how do i calculate the velocity for each recording? I've done this before but I am just having a mental block on...
  45. S

    I The physics of sailboats tacking against the wind

    I've always been amazed by this, and as someone with a mechanical engineering degree, always a bit embarrassed that I don't understand this.
  46. B

    How to calculate the torque for a vertical axis wind turbine (VAWT)

    For my senior design project we are designing a vertical axis wind turbine (VAWT) and trying to increase efficiency by adding flexible parts to the blades. We are currently in the process of ordering a motor/generator where we can test our new model against the same model but with standard...
  47. S

    Calculating a push force using area, speed, and density?

    Homework Statement The doorway in the previous question measures 1.06 m x 2.04 m, and the wind blows parallel to the wall surface at 3.89 m.s-1. Calculate the force pushing the curtains out of the doorway. The density of air is 1.29 kg.m-3. Known data: A = (1.06m)(2.04m) = 2.162 m^2 v(wind)...
  48. J

    Automotive Wind Turbine on the grill of the car

    Hi, I'm currently in High school so I'm uncertain whether this could be feasibly possible. I read on another thread that Wind Turbine's produce too much drag to actually be beneficial to your car and energy. BUT, they all discussed the wind turbine being on the top of the car. I was thinking...
  49. deckart

    Wind Turbine Hydraulic to Electrical Conversion

    As a hobby for the last couple of years, I've been designing various theoretical wave and wind generator devices. One of the primary criteria is that the electrical power generation components have to be easily accessible. For wave power, electrical power generation has to be on shore not in...
  50. doglover9754

    Gas Usage in Cars: Effects on Environment

    My parents were driving over the weekend with the windows open and I came up with another bunch of questions. With the windows open, would you use more gas than with them closed? I figured that when the windows are open and wind is blowing in, the wind is pushing in the opposite direction that...
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