Wind Definition and 861 Threads

Hi guys something basic that I can't understand: if I have a wind turbine , rotating due to some wind with no load , and no mechanical or drag losses in the blades or in the mechanics (no drag at all, I know its impposible ,but still) , the forces on the blades, create a Moment that accelarate...

Hi, I am a little confused with the phase change that occurs in closed end wind instruments. According to http://newt.phys.unsw.edu.au/jw/flutes.v.clarinets.html, the phase does not change when the sound wave reflects off the closed end of the instrument. I thought that the phase changes by 180...

I am curious if an alternating solenoid coil needs to be wound with a single piece of wire from end to end, or - can each loop in the solenoid be made of a separate wire and stacked on top of the previous, as long as each termination is connected to the proper + / - terminal. Essentially - is...

Homework Statement Hi guys, I just wanted to verify my calculation of a reynolds number of a wind turbine. I understand that the reynolds number will vary in a spanwise direction along the blade due to changes in the characteristic length(chord width) and velocity(due to the tip speed...

I thought it is easy when I was watching all sorts of instruction videos. However, now I have Fisher and Paykel stator and rotor, and I cannot solve how rotor is suppose to spin. The magnets are so strong that I do not think any wind will be able to move it. When I received my parts, I had hard...

I have often wondered why conventional large wind turbines have evolved with their generators and gearboxes in the nacelle at the top of the tower where they are hard to reach and maintain. Despite this fact, I wish to believe that there may be benefits to a conventional horizontal shaft wind...

Hello guys! New here. Grade 11 student. I'm working on a project to investigate how roof angle relative to the horizontal vary with lift, according to Bernoulli's principal. The purpose is to reduce injury in storms. Problems are: Wind blows in all direction and I was thinking about...

ok I have a FFT filter ( lowpass and highpass), white, brown, and pink noise generators. How do I use all these things to make wind ,rain, and ocean noise ? I am told there is a way.

Hey guys, I am starting with the course for wind energy and although i have a pretty good knowledge until now , but I am still confused about somethings which i hope some of you will help me to clear :) Q1. Ok ... so why is there a twist in the blade? I mean wouldn't it be much...

Glad it's Friday? I will be if you can help me with this :D : I'm trying to understand an equation about calculating the power extracted by the blades of a wind turbine. I have spent a couple of hours going over it but still not making much more sense. I'm trying to find out why P =...

So I've had this question bugging me ever since I saw sound at physics class: How is it possible to match the resonance frequency of a column of air in an organ pipe and form a standing sound wave by simply blowing air into the column? The main reason I see this problematic is because I...

Good day! I was thinking of building a horizontal-axis wind turbine and testing various blade designs but i can't afford a generator to test the power output of each variation. Is it sensible/possible to get the output without a generator? Can equations in finding torque be used? Thank...

I am making a small vertical savonius type wind turbine and would like some general rule guidelines. I am using 14awg magnetic wire--70 turns (2"oval) and ceramic block 1" x 2" x.375" magnets. I am hoping to get the most power possible at lower wind speeds. Is there a rule that states a...

Why does the wind blowing on you as you drive with the window down feel cool? It's temperature should be the same as stagnant air if I wasn't driving. My guess is that it has to do with convection because the air has a velocity relative to the driver and there is a heat transfer coefficient of...

I am going to design 10 kw, Permanent Magnet, Direct Drive Wind Turbine Generator. The main problem is, how to determine the rotational speed of the Wind Turbine. This is important for me because I have to design the PMG and its rated rpm values...

http://iopscience.iop.org/1748-9326/9/5/055004/article http://www.bbc.com/news/science-environment-27406358# Activity on the Sun is sparking lightning strikes here on Earth, a study suggests. The finding was surprising, said Dr Scott, because it had been thought that an increase in the...

Hi, We had a company do a pointing error analysis on a proposed pedestal system, on which is mounted a two-axis (azimuth and elevation) 6 foot parabolic dish. I estimate the distance from the rotation axis to the apex of the dish to be roughly 43 inches. Among the error sources are errors due...

Hi all, newby here that could do with a little help. I'm doing a college project and need to work out the head wind speed in m/s that a vehicle would encounter at a various range of speeds in mph, for example a high speed train, so I can compile a graph of the data ranging from 10mph up to...

Homework Statement A wind turbine has a rotor (its rotating section) which has a moment of inertia I = 1.26 × 10^7 \text{kgm}^2. At peak output, with the rotor completing 0.25 \text{ revolutions per second}, the turbine produces a power of P = 3\text{MW}. The tips of the rotor blades sweep out...

Hi I have been looking for some simple equations that describe the turning moments on the rotor as wind direction changes. I know this can be relatively complex but I am looking for simplified equations. Has anyone got any information where I can find these? The wind turbine is a small...

Hi From what I understand as the rotor yaws, there are gyroscopic forces that act upon it and the magnitude of these depends on the speed of yawing (e.g. 10 degrees per second). What happens to the rotor rotational speed during yawing? Does it slow down? Is the aim to slow down the rotor...

Hi I am trying to create a model to simulate the motion of a weather vane. It basically looks at the wind direction and as the wind direction changes, the objects responds by trying to align itself parallel to the wind. First of all I am looking at the force perpendicular to the pivot...

Hi - I know someone must have thought of this already, so maybe you can help me understand. When I look at some of these modern wind turbines, the blades seem massively long. I see this lumbering set of blades moving slowly and I imagine that the bulk of the wind does not even touch the...

Hello everyone, the forum looks great and I have been reading it for a long time, but I have only registered. I am writing this post because I have to analyse two flow fields in a wind tunnel. 1) The first flow is generated from a helicopter blade, with Re=2000000, Mach=0.92 and...

Homework Statement At what rate does the solar wind carry kinetic energy away from the sun? Give your result first in watts, then as a fraction of the Sun's luminosity in photons, L=3.8*10^26 W Homework Equations KE=(1/2)mv^2 mass loss of sun- Msunloss=4πr2vρ The Attempt at a...

Homework Statement Homework Equations Constant acceleration equations: Δx = v,xi *t + 0.5*(a,x)*t^2 Δy = v,yi *t + 0.5*(a,y)*t^2 K = 0.5*m*v^2 U = mgh W,nonconservative forces = ∫ ∑ F dx Conservation of Energy: K1 + U1 = K2 + U2 ∑F = ma The Attempt at a Solution (Note that in my notation, I...

I am wondering if in a case where the air velocity comes from one face as shown in the picture. Can I assume the whole area going along the channel will be subject to the same convective coefficient? Thanks

Imagine a cylindrical space settlement. It spins about an axis to create pseudo gravity for residents, who will think that radially outward is "downward". The shape of this settlement is a toroid with a rectangular cross section. Air is pumped into make a habitable environment. Then...

[b]1. The problem statement: Slick is skiing down a 27 degree slope (above horizontal) into a headwind (parallel to the slope) of 8N. His mass is 78Kg. The coefficient of friction between the snow and the skis is 0.11. What is the resultant force? If the coefficient of friction...

Can a wind tunnel get up to scramjet speeds; ie. Mach 6-12?

I can't find anything I can make heads or tails out of so if you guys can help I thank you. I would like to design a wind turbine and be able to get as much power as I can out of each of it's coils. If I start with a magnet that is 1.1811" in Diameter and it is .125" thick with a grade of N52...

Hello there, A weather balloon is released, and its acceleration in the z-x-plane, a is governed by a buoyancy force, B, which is constant in the k-direction. gravitational acceleration, 9.81 m/s^2, in the k-direction, and FD, which is is like this: F_D = -D|\vec{v}|\vec{v} where D is some...

Hi, We are trying to estimate the likely maximum wave generated from wind blowing along an irrigation canal. We will subsequently estimate runup and the required freeboard to prevent overtopping. Our canal is ~ 5m deep, has 1:2 side-slopes and a 4.6m wide base. The canal is aligned with...

Homework Statement Any floating homogeneous balloon in a planar uniform wind current will always "tend" to present to the wind flow a section of maximal drag. 2. The attempt at a solution I have three possible solutions to this "problem": 1- Speed gradient justification: When an object...

This might sound like a ridiculous question and I am sure it is (they don't build them like that for fun) but why on Earth do they? I read an article that said the new PMG style turbines only require the shaft to be rotating at 16rpm to generate up to 8.6MW. Is there so much resistance that...

Homework Statement You’re a pilot beginning a 1500-km flight. Your plane’s speed is 1000 km/h, and air traffic control says you’ll have to head 15° west of south to maintain a southward course. If the flight takes 100 min, what’s the wind velocity?The Attempt at a Solution veffective south =...

Hey guys, so I'm building a mini wind tunnel and I would like to calculate the new RPM,HP and Torque since the propeller will act as a load and change the specs of the motor(note I'm using a air wrench as the motor as it's all I had around and have disabled the impact motion) the current specs...

http://en.wikipedia.org/wiki/GE_Wind_Energy The rotor swept area is 4657 m^2, and wind speed is 11.5 m/s. Produced power 1.5MW. I assumed that the air density is 1.2kg/m^3, and computed, that the theoretical upper limit for produced power would be 4.25MW. This was obtained by computing the...

Sorry to ask another question :/ Homework Statement Consider the change of momentum. A wind (of speed v) acts perpendicularly to a wall. Show that the pressure do to this wind acting of the wall is v2ρ, where ρ is air density. Hence show by suitable integration that the torque about the...

Hi, I am currently researching methods available for manufacturing a half-span wing model (approx 0.5m span, low sweep delta wing of varying cross section) to be used in wind tunnel experiments. A recent paper suggested the use of epoxy and micro glass beads injected into an aluminium mold...

First of all, I have read some of the previous posts that related to this topic, but they are closed. I am not looking to solve the world's energy crisis, but I was wondering if there was a way to harness some of the energy given off as friction from the drag of a car. I was looking at some of...

Question as the title above ! Could we use the wind turbine to compress the air into engine cylinder as the exhaust compression tubine does ? Thanks all for replying !

Homework Statement A ball of mass m = 300 g is connected by a strong string of length L = 80.0 cm to a pivot and held in place with the string vertical. A wind exerts constant force F to the right on the ball as in the figure below. The ball is released from rest. The wind makes it swing up to...

Say you're in a place either 15 degrees north or south of the equator where average temperatures are over 25C (77F), a large majority of days are either cloudy or rainy and there isn't any wind. You need 50Wh a day for your needs and the battery you have happens to have a capacity of 50Wh as...

Hello physics forum, I am currently trying to figure out how to pick a generator for a horizontal axis mini wind turbine based on specs. I plan on buying a DC motor to use as a generator with blades directly attached to motor shaft. My goal is for the motor to be most efficient at 25mph wind...

For high Rise Buildings,say above 30 floors,wind energy could be too ample to be wasted. So what kind of study has to be carried out in order to know the feasibility of installing Wind turbine above a building? What will determine the power output of this turbine?

Is there any significance in repeating a water tunnel study in a wind tunnel? If so, would the results be publishable or would it just be considered repetition of a previously published water tunnel study?

Homework Statement Modern wind turbines can convert up to 30% of the kinetic energy of the incoming wind blowing through their blades to electricity. Assuming that the wind at a proposed offshore location blows steadily at 20 knots, how much electrical power can be generated from a turbine...

Solar winds contain plasma, which are charged particles and carry Sun's magnetic field orientation, when those solar wind hits toward Earth, does anyone have any suggestions on how those plasma affects on Earth's magnetic field? and how this energy converts into different forms on Earth? Does...