Airfoil Blades (Rookie questions)

[zack wanambwa]

Hello everyone

am still planning on starting work on my first project so am still green on most issues.

I have some questions regarding the airfoil. most designs I see on otherpower.com, have the windmill facing the direction the wind is coming from, right? What force contributes to the rotation of the blade? is it the drag, lift or both?

Also, the wind seams to hit the blade in a direction perpendicular to the chord length of the airfoil shape!

Thats a bit confusing coz i thought the wind should come in from the sides, and the drag produced should cause the rotation. Can someone please shed  some light on this issue.

[tecker]

 The drag facilitates rotation as the wind hits the miter of the blade surface and flows over the trailing edge of the blade . I know you've seen turbine  blades loping along in a really Lite breeze . The rotation pushes the leading edge of the foil into the wind and the foil splits the oncoming air forcing the air to speed up on top and slips past the air on the bottom this creates lift and the blade rushes forward to fill up the vacuum . So its selection C Both

[clflyguy]

Zack,

This stuff has been covered too many times. Please use the "Google search the board"

function at the upper right of the page for a more in depth explanation, since what

I'm going to tell you is just the quick and dirty.

  The wind doesn't hit the face of the blade perpendicularly, it hits it at an angle

because the blade has what is known as "pitch". This serves to make the leading edge

of the blade encounter the wind a millisecond or two before the trailing edge does.

The side of the blade facing the wind is flat, the other side has an airfoil

shape. When wind hits the blade it's split between the two sides, causing a high

pressure on windward side and a low pressure on the leeward side. High pressure

air (forward flat side) is deflected by blade angle (pitch) towards the trailing

edge. Low pressure air (back curved side) must speed up (it has slightly farther to

go) to catch up with with its brother air molecules that it was so rudely separated

from by the leading edge. This "stretching" causes the low pressure or "lift" on the

curved side of the blade. Since the blade has pitch, that low pressure air (think

suction) is imparting a bit of force on the blade, inducing it to move in the

direction closest to the low pressure that it can, as limited by the turbines shaft.

  The flat (forward facing) side of the blade contributes to the rotation also by

imparting (due to pitch) a direction change in the local air mass which causes a

deflection pressure against the face of the blade, which again is moderated by

the turbines shaft.

  As far as wind coming from the side... Uh-uh, think about it, the forces would

cancel each other out.

    Read, then read more,     -Gus

[Ungrounded Lightning Rod]

Look for "apparent wind" "angle of attack" "lift" etc.

[edy252]

hi,

as others have said, you can easily find detailed info about this topic by googling....(i know i've learned about it this way!)

regarding the side of the airfoil facing the wind : you have to think about the airfoil as it spins....it's as if ur moving fast in one direction, you would think that the air is moving in ur opposite direction...the same thing happens with the turbine's blades....when they rotate, the velocity of the wind RELATIVE to the airfoil is what counts....in other words, if the turbine is at a full stop, the best position for it to start is letting the leading edge face the air flow....hope i made things a bit clearer

[zack wanambwa]

Thanks alot guys!! Really made things clearer.