14. Flow and forces around a wind turbine blade

By Henrik Bredmose. This session is about flow and forces around a wind turbine blade. In this video will be explained how to draw a velocity triangle for the flow around a blade section, how the aerodynamic forces drives the rotor around and how to calculate the lift on a blade section based on airfoil data.

[alishancharania]

I simply loved it when you superimposed the paper on the blade to explain your point. Wish the world had more teachers like you! <3

[anthonycrimin]

Thanks I finally get it. I couldn't figure out the vector diagrams until you used that simple paper cut-out!

[X_Vampire]

I got the concept, awesome idea to show the forces on the blade, thanks❤

[mmoci]

Excellent video, would be nice to have more such educational videos for beginners. For example explaining twist of the blade and so on...

[NickyDIY]

8:07 innovation of demontration, better than animation

[nasmboyd]

Thank you sooo much for this video. Soo simple and easy to understand 🔥🔥

[nyamjargalsaihan]

Is it possible to have a negative pitch angle in the low wind speed region? what effect does this create on the WT performance?

[muffin_simp]

In all of these velocity triangle explanations, the rotor rotation is drawn with an arrow opposing the tangential component of the lift force vector. The omega*r term is pointing to the left in all the drawings, and yet the lift vector's tangential component is to the right...which way will the rotor turn? It should be in the direction of the net tangential vector, not, opposed to it like it's drawn. I'm confused on nomenclature.

[ahmeds]

That's it. I am going to put DTU on my list for grad school.

[bimgim]

7:02 says lift is perp chordline, 8:34 says drag is perp lift, Vrel and drag act on same line, chord line and Vrel are not parallel, mistake? idk if 8:34 is an unstated assumption or if either timestamp is an error. thanks otherwise

[JesusRGutierrez]

What is the difference between a catapult an oil rig or wind turbine?
Design? Same winds different names different resource?

[takeshikovacsn]

Hello Mr.Bredmose thank you for this amazing explanation. I want to point out that at the beginning, in the velocity triangle, you call a' the axial induction instead it is tangential/swirl induction factor if i think I am right. Thank you.

[tarekelnabawy]

Wonderful thanks a lot for the last method you used to illustrate the real aerofoil by projecting it on a piece of
However I am afraid that the line that you have drawn is not the chord line, it can be only the chord line in case a symmetrical aerofoil and it seems that you have drawn a chambered again really appreciated !

[fahimummer]

Could you please show the formula for chord length?

[Fedroy]

Hi this is a wind energy problem .I would be very grateful if you could help me out in this problem."Given a wind speed of 8𝑚 /𝑠 and a blade tip speed ratio of 3. Calculate the blade chord angle at radius ratios 𝑅′ of 0.2, 0.6 & 1 for 1.An angle of attack of 0 degree 2.An angle of attack of 16 degree"

[gamgaraii]

Why don't we consider and calculate aerodynamics for 5 blades instead of 3?

[dmytronovycov]

bro i had to watch this like 20 times and i still didnt know what u were saying

[vincentrobinette]

My math skills aren't quite what yours are, so I have to ask some dumb questions. Let's suppose, the rotor is fixed pitch, such that I cannot feather them out knife edge to the wind, to minimize hub load. My small turbine has a tail vane, which always faces the rotor into the wind. Is the axial hub load less or more, if stopped completely, than if allowed to free-wheel? Is the hub load at the maximum when loaded to the optimum blade tip to wind speed ratio? Last question: From the calculations you presented, may I conclude, that the torque goes up on the square of wind speed, while the RPM goes up proportionately to the wind speed, thus, doubling the wind speed gives 8X the power? If that's true, high wind speeds could over run a permanent magnet alternator, causing it to lose control of the rotor, allowing it to basically free wheel. The torque of a permanent magnet alternator is limited by the field strength of the magnets.

[Taahmim]

I cant understand why people use the worst design in wind turbine?
Why generator is in the head?

[WRISELEY]

Parts of this lesson are somewhat helpful - but only if you already know how it all works. That's another way of saying that this basically shows us why most students coming out of college know almost nothing. Backing up and starting from the beginning, let's take the obvious language problem. I had to listem to him say things like "Air Foil Data" up to five times then catch it written on screen in order to realize he was saying something other than "Awfa". There's no point in trying to pass on knowledge, especailly intuitive knowlgedge to someone who speaks a different lanugage than the instructor. (And I comprehend foreign dialects better than most.) Also, mathematics does no good without a base of intuitive understanding of what it's based upon. So, the best you can say about this is -- it's nearly, but not totally, useless.