Windmill or Wind Turbine- powered boats: how many are out there, and are they viable?

Michael
You might find the linked paper of interest. It is what I expected to see.
http://www.wseas.us/e-library/transactions/fluid/2008/25-372.pdf

With intense velocity/pressure gradients you can get local cooling but the end result is slight temperature increase.

Anywhere that you have a temperature change you have some potential to do work but I cannot see how that can be done at present. It will having nothing to do with the lost 19 pound. That is on the wrong track.

Rick

 

Rick...That makes no sense...

The car analogy is ridiculous because it is not being supported by it's forward motion through another medium. The car would be still supported even standing still, so assigning a L/D for it is pointless. We are talking about a condition that arises due to a dynamic set of circumstances, namely the motion of a fluid that is not able to support it in a static mode. The one pound of thrust in my example is unable to support the 20 pound object without first pulling it through the air. So you still haven't answered where the difference in force comes from.

 

The lift is achieved by moving a large volume of air downwards to create a lift force. Exactly the same as a hydrofoil works. Only difference is that the hydrofoil will cavitate if pressure on the lift side is too low. With air there are small changes in temperature due to the rapid decompression and compression on the lift face but the net result is a slight gain in temperate. That is energy has been added to the airstream - NOT removed by the wing.

Rick W

 

Rick...I doubt that I can get you to understand that ....

...the wing is supported by the momentum transfered from the air to the wing, by intense bombardment of the underside by fast moving molecules. The lift side IS the underside, not the top, there is no such thing as suction, that is merely a term of convenience to describe a surplus of pressure in the underside. The lower pressure on top simply allows the higher pressure below to dominate.

BTW I am in Los Angeles at present, and it is late so I need to sign off for now. I hope some others will join in the fray and offer their comments so we can get some clarity here.

 

At no time have I mentioned suction. However it is the reduction in pressure on the lift side that provides the greatest component of the force on the foil. The wing has to be lifted from the bottom but that is by virtue of differential pressure. The main component being derived from the change in momentum of the air stream moving over the top surface and the Coanda forces rolling the flow downwards off the trailing edge. Take away the top surface and the foil is grossly impaired with much lower L/D.

Rick W

 

Rick
"..The main component being derived from the change in momentum of the air stream moving over the top surface and the Coanda forces rolling the flow downwards off the trailing edge..."
You really should stop reading websites that you don't understand the theory of what is being said. You do this endlessly yet you seem to think you understand it. The fact you constantly change tack because you're avoiding the question and/or don't understand it and your own reply, that you cut and paste in an attempt to "win" a debate.

You are you referring to what is commonly terms "circulation", the flow of air that is circulating around the foil. But that has nothing to do with what you're arguing about.

Air that is flowing over a surface, if curved (or at an angle) will create lift (drag too).

The air that is on the lower surface, that is facing the on coming air, has a higher pressure gradient. This increase in pressure is greater than the surrounding atmospheric pressure (further up stream and downstream), ie Patm + Pw (Patm being atmospheric and Pw being weather side).

On the Upper surface, away from the oncoming air, or the lee side, the pressure is less.

Why, because the lee side the air has a greater distance to travel than on the weather or under side (owing to the curvature of the foil). Hence, the air velocity over the lee side is increasing. It increases to satisfy Bernoulli's equation. In other words, the air is not "torn apart", so the air at the front of the foil, must "join up " with the air at the back, to do so, it increases in velocity.

The increase in velocity is mirrored by a decrease in pressure. PV/T = P1V1/T1, universal gas law, if memory serves (not done this for years..)

So the lee side, or upper surface has lower pressure and the weather side, or underside surface, has higher pressure. This creates the lift, since the upper surface is being "sucked up", or "pushed up" depending on how you view things.

The circulation is the Magnus effect. This was demonstrated by Magnus in the 1850s with a circular cylinder that is rotating, creates a force perpendicular to the flow of air. A ship was built with this concept by Flettner, using vertically mounted rotors. With the wind beam on, low and behold, she moved forwards.

 

Here's something that might explain why the old "distance travelled" arguments are just slop.

 

bil
I went through the clips again and pulled out another section that gives a closer view of the boat. Wind is quite light and travel is all very relaxed but the boat makes steady progress direct into the wind. This is about the minimum wind that I could get started in. Sometimes I needed to give the turbine a hand to get the initial speed of the blades through the air. Once you start moving the increase in apparent wind improves the turbine efficiency.

My next run is at least 3 weeks away. Maybe you will have some video of your own little boat to show what it can do before I get my next set of results.

Rick W

 

care to define what you mean by 'slop'?

I must say, if this is true, all my text books and my my old lecture notes are crap then....

Reads like a guy trying to make a name for himself, by use "particle physics", as opposed to streamlines, to explain an otherwise accepted theory of foils.
All he is doing is replacing "stream line flow" with force on a stream line flow "particle"...it is the same. Just repackaging the theory into particles of air. Still uses the difference in pressure between the upper and lower surface, so, again, what do you mean by 'slop'?

Is this a theory you subscribe to yourself?

Rather poor science when using a computer simulation.

PS
when he makes statements thus:
However, the fact is often overlooked that
Bernoulli’s equation applies only along a streamline.
There is no explicit relationship between the
pressure and velocity of neighbouring streamlines.

Just shows that the author does understand Bernoulli's theorem correctly nor its application. Bernoulli's theory can be summed as:
"The total energy of each particle of a body of fluid is the same provided that no energy enters or leaves the system at any point. The division of this energy may vary, but the total remains constant". Where does Bernoulli say ahh..the pressure gradient between stream lines is thus..? It doesn't! Poor paper really, nice try, but if that came across my desk for marking, 4/10.

 

I looks faster than the 4kmh your graph provided! One thing I did notice that the wind was off a little to one side. Which makes me think of another point. Does it say on the Aeolus racers website whether the wind was directly against or not? It seems too much of a coincidence that the wind would align directly on two days with their sea wall at Den Helder. Unless of course the sea wall was crescent shaped or something and they chose different starting points according to the wind. (I will check this up on Google Earth).
Yes, I suspected that like the Aeolus racers, yours would not be self-starting either.
By "my boat" I assume you mean the one designed by Windmaster. Well, I haven't built it yet, but I may have it ready. I'm not sure whether it would be a fair comparison though, because it is so small and yours is about 21ft? I think the Windmaster one could benefit from longer hulls.

 

I expect they chose the location for the consistency of the wind. In every run you see the turbines are facing ahead. Also consider that the apparent wind angle will shift more to the front at higher speed.

My turbine is self starting when the wind is above 15 to 20kph. However there are times when the breeze can be felt but not enough to get the turbine spinning. Giving it a flick can get it going and the little extra apparent wind speed is enough to keep it going.

Rick W

 

Sloppy argument.

You might also like another definition (due to Ambrose Bierce):
Positive - wrong at the top of one's voice.

Maybe you should have questioned them when you had the chance.

Try searching for NASA + wing theory + misconceptions.

I don't need arguments by analogy and hand-waving calculations for my work.

Have fun!
Leo.

 

Leo
"..Maybe you should have questioned them when you had the chance..."
I take it form this, that you questioned the validity of all those previous text and reference books (of which there are many) yourself and arrived at the same conclusion as the author, but many years ago, as you have clearly had the chance? Care to show me your work citing this, prior to the author above? Or are you a new convert to this splitting of hairs theory with an obtuse alternative interpretation of Bernoulli's theorem?

His paper has nothing to do with the old "distance travelled" arguments. All he is trying to do is say streamlines get closer to a curved surface owing to a change in local pressure...yeah..so what...nothing new here. Just a different way of presenting the same data.

As i noted above, all he is trying to say to is that Bernoulli's Theorem one cannot use a "splitting" analogy. These analogies are only used for clarification/explanation to students who start to study aeronautic/hydrodynamics. Since no where, as noted above, does Bernoulli refer to "splitting" nor stream lines in his Theorem. Babinsky's starts with his assumption, by everyone, that a fluid particle is split, as he assumes that what everyone else assumes. Which of course it is not....as there would be one almighty bang if that were the case!! Nice free energy though

"...I don't need arguments by analogy and hand-waving calculations for my work.."
Than you are better than Einstein, Schrodinger et al....my my

Have fun!

 

bil
I just picked up on your first line. If you do the timing of the boat past something in the background you will see it takes maybe 12 seconds to transition the length of 7.2m. So it is well under 4kph in that shot; really no more than ghosting.

I have attached a video of the same boat in its normal guise. It is a relaxed 12kph with the engine running around 150bpm. Admittedly the engine is quite impressive, he has done 12 hours on a trike holding around 160 to 170bpm so 150bpm is an easy pace for him. I think he holds the world record on a faired trike - just under 500km in 12 hours.

So you can see that turbi-prop technology has a way to go before it is at all impressive. I am hoping to jag some ideal weather for the current set up so I can at least set a target that might be a challenge. I am thinking I might try something like a 3km course with upwind, downwind and reaching.

Rick

 

There's no need for me to even consider that aspect in my work. My aero work is mainly with the numerical solution of the linearised lifting surface equation. To me it's just another integral that's tough to calculate accurately.

Sure. So spoon-feed them pap if that's your style Tell them about "Lift Demons" too. That'll get their attention because it could be about characters in WoW .

What a truly queer thing to imply. There's no need for me to resort to hand-waving or analogies when setting up and inverting large matrices.