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. M

    B Solar Wind Particles, - reaching into Earth's magnetic field?

    How many particles (approximately) from the solar wind reach deep into the Earth's magnetic field every second. Possibly measured in mass?
  2. C

    Lawn/Garden Wind Speed required to topple Patio Screen Support

    I want to install two retractable patio screens on my patio but there aren't any columns, so I'll need to install a post/column to attach the screens and guide rails to. My concern is making sure I install an adequate post for support during winds. If I can avoid it, I'd like to stay away from...
  3. G

    A The effect of perpendicular wind at channel inlet

    Hello I'm thinking of how to attack this problem. Outside a channel-inlet, wind is passing perpendicular to the opening with a wind speed of 9 m/s and a fan sucks in a certain amount of air into this channel so that the velocity in the channel is 3 m/s. When the outside air is 0 m/s I have no...
  4. J

    B Temperature of Solar Wind: Complexities of Measuring Heat in a Stream of Particles

    I read that the solar wind is a stream of particles, primarily electrons and protons, flowing out from the sun at speeds as high as 900 km/s, and at a temperature of 1 million degrees. Using the equipartition theorem, I calculate that a proton moving at 900,000 meters per second exhibits a...
  5. Umbrella curious

    Which Umbrella Base is Best for Windy Conditions?

    Which Umbrella base is the least likely to tip over, Round base, Triangle Base or Square base ? Trying to work out which is the best Umbrella base to have in the garden on a timber deck , Round base, Triangle Base or Square base ? I have noticed my round base Umbrella at home tips quite easy at...
  6. Grinkle

    Forces created by fixed tarp in the wind

    Consider a rectangular tarp with a grommet in each corner, and each grommet is tied to a pole in the ground with a short piece of rope, such that the grommets are basically fixed to the tops of the poles. The poles needn't be at equal heights and the tarp aspect ratio is not specific, in my...
  7. M

    How to calculate if wind through a funnel can open a check valve?

    Imagine a wind speed of 'W' (variable), rotating funnel of 'X' diameter that narrows and then conveys flow through a 'Y' diameter, 'Z' length pipe until it hits a 'Y' diameter check valve. What is the minimum cracking pressure needed of the check valve, provided the variables above? I am...
  8. Lotto

    How to calculate the wind force acting on a water drop?

    TL;DR Summary: I have a water drop falling with a constant velocity ##v##, since ##mg=\frac 12 C \rho S v^2##. Wind is blowing with a velocity ##u## only in a horizontal direction. What will be its force acting on the drop? I would use this equation ##F= \frac 12 C\rho S u^2##. When I want to...
  9. T

    B How does wind affect a turn for an aircraft?

    First, I understand how wind effects aircraft tracking. I can do the calculations involving wind correction angles, effects on ground speed, headwind or tailwind calculations, etc. I teach it in a college piloting program. I am wondering how the ground tract of turn is effected by the wind...
  10. O

    Why Does My Rewound Alternator with Copper Wire Not Generate Power?

    Hi, I am trying to rewind an existing Chinese alternator, it comprises of rotor with 12 magnets and 18 poles (stator), the original design produced virtually no power , aluminium windings have been removed and I have replaced with copper 20 gauge wire, 7 turns per pole, I spin it and nothing...
  11. G

    How to wind a 5K audio tube amplifier transformer?

    60 watt tube amp needs a 5k primary and 8 ohm secondary transformer. I have wound voltage transformers on my lathe many times. Audio transformer is no different. Online impedance transformer calculator says, 5k to 8 ohms in 25:1 ratio. Online info says, audio transformer should be 60w x 5 =...
  12. bob012345

    I The Effect of Wind on the Rate an Outside Spigot Freezes

    Suppose one forgot to protect outside water spigots against below freezing winter air. If there is a stiff wind, will, as I think, the spigot freeze sooner than if the air is calm at the same temperature? Also, wouldn't the case of calm air actually be more complicated to model because the...
  13. Al-Layth

    Calculating the change of a Wind Turbine's RPM due to Airflow as f(t)

    the tldr covers everything I think. I don't expect there will be an analytic solution here lol. but I don't even know where to even begin formulating this problem mathematically. I assume I should find an expression for the initial lift on the blades, multiply by 3 and then model it as a...
  14. electrodacus

    I Power available to a wind powered vehicle traveling directly downwind

    I will like the equation describing the amount of wind power available to a wind powered vehicle driving directly downwind. I'm interested in the ideal case so max theoretical power available to a wind only powered vehicle driving directly downwind. I do know what the equation is but I like to...
  15. Ahmed1029

    I Michelson–Morley experiment and the velocity of the ether wind

    How was it justified before conducting the MICHELSON–MORLEY experiment to assume that the sun was at rest with respect to the ether? Also, was the ether assumed to have the same velocity with respect to the Earth throughout space at one instant in time, or like wind, with different velocities at...
  16. crememars

    Wind drag problem with a ball hanging on a rope

    I drew a FBD but I feel like it's wrong because there are too many missing values. I tried this: Fy = 0 Tcosθ - Fg = 0 Tcosθ = mg T = (1.2)(9.8) / cos(25) T = 12.98 N Fx = ma Fwind - Tsinθ - Fdrag = ma Fwind - (12.98)(sin25) - Fdrag = ma I don't know how to find these missing values. I feel...
  17. N

    B Calculating Wind Turbine Torque - Get the Right Result!

    Hello everyone, I am reading a book about wind power turbines and found a calculation. I tried it myself and the numbers doesn't match. Here is an image of the data and result. I don't get to the same torque. And also what do you think about the moment of inertia value? Before the data...
  18. P

    I Focussing on the Treadmill of Veritasium's Blackbird faster than wind

    Hi, Like many here I watched Veritasium's awesome videos on this*. And like many I found myself having to drag my mind into understanding why it works. The energy explanation makes the most sense to me. Derek explains that the fan is taking energy out of the existing wind - slowing it down -...
  19. larrylancaster

    Plane Traveling against the wind

    So the question was if a plane is going from point A (origin) to point B 400 km directly south of point A at 220km/hr north and there is a wind going 62 km/hr east to west, what angle should the plane orient to go straight from point A to point B? I got something lik 16.4 degrees. The second...
  20. F

    I General expression of wind force on a sail....

    Hello everyone, In trying to better understand how sailboats work, how they can sail upwind (not directly), how the go faster than the wind speed, I have been thinking about the magnitude of the wind force and its equation: $$F_{wind}= \frac {1}{2} \rho_{air} A v_{wind}^2$$ Instead of ##...
  21. K

    So who here has tried to make a homemade wind tunnel? My first attempt

    Hello all, i posted this on another forum but didn't get much response, I had an 18” centrifugal fan around around and wanted to see if I can push some real air to make a wind tunnel. I'm just a hobbyist, and like to build and modify cars, figured this would be something to look into. Looks...
  22. SchroedingersLion

    I The Plane in the Wind Puzzle: Does a Constant Wind Affect the Round Trip Time?

    Hi everyone. I came across the following brainteaser: A plane travels from airport A to airport B and then returns to A from B. There is no wind, both trips follow a straight line, and the plane flies at constant engine speed. Suppose now that a constant wind is blowing from A to B. Will the...
  23. jones1234

    I Estimating Vertical Wind Speeds: T_a, T_s, & P_a

    Hi all, I have some data from an automatic weather station, with recordings of both 2m air temperature and 2m air pressure and also the surface temperature. Is it possible to estimate vertical wind speeds between the AWS and the surface based upon this data? Imagine T_a = 15 degrees and T_s =...
  24. T

    I Changing the tone of a wind chime using slits or cuts

    I am trying to fabricate a chime or pipe gong and I want it to have a very low, sustaining tone. In viewing retail products (specifically, Hamacher Schelemmer online catalog item # 90774) I have noticed some products have a slit cut along the partial length of the chime to lower the tone. Is...
  25. O

    How do I calculate static and dynamic pressure for a wind tunnel lab report?

    how do I calculate static and dynamic pressure for the wind tunnel lab report, drag force, and lift force? Please, anyone? thank you.
  26. J

    Lawn/Garden Home project help please - max wind speed to tip over object

    Hi guys, thanks for helping me! I am working on a home project that includes a privacy shade for my backyard. I have a 6'x15' vertical shade attached to two portable posts that are held up right by four legs ("X" shaped footprint). the surface footprint of the legs covers an area of 46"x70". I...
  27. WhiteWolf98

    [Structural Dynamics] How to model a 3D wing as a 2D Wind Tunnel Model

    Greetings Good People, As the title suggests, I'm having some trouble getting to a 2D model. The process is to select an aircraft (or wing model), and model it as a 2D, 2DOF wing-tunnel model. The aircraft I selected was a Cessna 172. This had a tapered wing, which after some calculations and...
  28. chwala

    Find the velocity of the airplane if there was no wind

    Find the question and its solution below; Ok i realized that we could also use cosine rule here, in my approach i considered the sketch below; ##V_b= 18,125- (2×50×125×cos 135)## ##V_b=164.2## To find direction, i used sine rule; ##\frac {125}{sin α}##=##\frac {164.2}{sin 135}## ##α=32.56##...
  29. J

    How calculate lift/drag using static pressure taps in wind tunnel test?

    An airfoil section in a wind tunnel has many static ports/holes/taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface. In place A are static ports that read a pressure value of relative -100 Pa . This...
  30. jonagad

    Engineering Trying to design Wind Turbine Blades

    Hello, I'm trying to follow the instructions from the book "Aerodynamics of Wind Turbines"-Martin O.L. Hansen, to design a blade, the method it's the BEM accounting for the tip loss (Prandtl) and Glauert corrections, but I can't get it right, for the Cl (lift coefficient) and Cd (drag...
  31. A

    B The Mystery of Blackbird: Exploring Wind Power Leverage

    I see there has been threads about Blackbird and "Down Wind Faster Than The Wind" operating principle in general, and I see a good number of people (most?) in those threads seemed to pick up some understanding of how it actually works. So that's a good start and gives me hope. I had never heard...
  32. M

    Could the Wright Flyer take off without wind?

    Hello, I'm wondering if the 1903 Wright Flyer would be able to take off without wind supposing it had a longer takeoff track. Some people here in Brazil claim that there's no proof the Wright Flyer would be able to lift off under its own power. Generally, this revolves around the catapult...
  33. O

    How to wind a brushless motor (number of windings per stator)

    Hi folks, I'm searching for information/procedure and also calculations/equations on how to correctly wind a stator on a (general or DC 3-phase) brushless motor? I.e. how to wind a copper wire X number of times around the stators, and thus get the desired performance/force that is required...
  34. Kairos

    I Sound and apparent wind -- Any Doppler effect?

    If two cars are driving side by side at the same speed, their relative speed is zero but do they nonetheless perceive a sound Doppler effect from the other car's siren because of the apparent headwind generated by their speed?
  35. U

    Pebble accelerated by the wind with a starting velocity

    I first used differentials to find an equation for the displacement. $$6.0t^2+5.0t=13$$ and using the quadratic formula I got time ##t=1.1## I then got ##V_x## from ##6.0t+5.0=v_x=11.6## and ##V_y## from ##7.0t=v_y=7.7## The I got v from ##V=\sqrt {V_x^2 + Vy^2} ## $$\sqrt {11.6^2 + 7.7^2}...
  36. entropy1

    I Deterministic wind down of the Universe under MWI or Copenhagen?

    Is it correct to say: Under the Many Worlds Interpretation: If we rerun the universe repeatedly from the same state S(0), it winds down the same way each time, which is determinism; Under the Copenhagen Interpretation: If we rerun the universe repeatedly from the same state S(0), it may well...
  37. WMDhamnekar

    MHB Proof of known velocity of wind

    My attempt to answer this question: Let the actual velocity of wind is $\vec{v}=x\hat{i} + y\hat{j}$ where $\hat{i}$ and $\hat{j} $ represents velocities of 1KM per hour towards east and north respectively. As the person is going northeast with a velocity of 6KM/hr, his actual velocity is $...
  38. I

    Why do wind turbines pitch their blades?

    Hi all. I'm new to this forum and to wind turbine technology in general, and I watched one of these one-minute videos explaining why wind turbines pitch their blades but it doesn not make sense to me. Why don't you just get a bigger generator? You'd get more energy for the same blades, same...
  39. agnimusayoti

    How to Measure Very Small Differential Pressure in a Subsonic Wind Tunnel

    I assume that air have ##1 kg/m^3## density. Therefore, using Bernoulli equation, on upside and downside of my test object, there is a differential pressure ##\Delta P##: $$\Delta P=0.5*(v_2^2 - v_1^2)$$ From cases: (a) ##v_1 = 1 m/s## and ##v_2 = 2 m/s##, then ##\Delta P = 1,5 Pa## (b) ##v_1 =...
  40. MaratZakirov

    Rail Car with a Sail in the Wind

    I solve the following problem, there is a particle of mass ## m_p ## and velocity ## \vec{v}_p ## which collide with sail installed on rail car with mass ## m_c ## resting in the frame of reference associated with it before the collision. The cart is fixed on straight rails for which the vector...
  41. S

    Hurricane forces — Comparing the force from a 60 mph wind to a 120 mph wind

    The marker wrote that the answer is 4 and it's because m and v double. I don't understand how m doubles??
  42. D

    What modes of vibration contribute to the sound of wind chimes?

    I recently read a site dealing with tubular wind chimes. The author give some references that seemed to indicate that the sound we hear is the result of beam bending vibrations after the tube is struck. I'm not so sure about that. It is certainly true that striking the side of an open cylinder...
  43. brotherbobby

    Projectile motion with (constant) wind velocity

    Let me start be making a small sketch of the problem, shown to the right. If the range of the projectile on a still day ##R = v_{0x}T##, then on the windy day the range becomes ##R+2H = v'_{0x}T = (v_{0x}+v_w) T##. Since the maximum height attained by the projectile ##H =...
  44. hagopbul

    De-icing the wind turbines in Texas

    Summary:: how we can de ice the turbine in case of sudden frezzing like what happened in texas hello all : i was watching the news and saw the news talking about frezzing of wind farms in texas state , and losing about 35% of the energy due to that problem can we use the following methods to...
  45. K

    B How the Earth's Magnetic field deflects the solar wind

    On a previous thread (now locked) I was wondering about how, precisely, the Earth's magnetic field protects us from the solar wind. Posting this here because what I wrote in that thread is very wrong, and I think it's an interesting topic. I had a hell of a time finding good information. I...
  46. jovanovic_oliver

    B Understanding the Mass of Solar Wind and its Impact on Earth's Surface

    According to wiki sources "The average mass ejected is 1.6×1012 kg" I would like to know, what part of that falls to surface of the Earth?