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spork
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OmCheeto said:Can you answer my question?
I'll certainly try.
Where can I find Nikos's comments on the experiment?
Do you mean professor Nikos Mourtos?
OmCheeto said:Can you answer my question?
Where can I find Nikos's comments on the experiment?
spork said:I'll certainly try.
Do you mean professor Nikos Mourtos?
OmCheeto said:Is there more than one Nikos that worked on the project?
spork said:You're talking about someone that worked on the project?
(let's see how long we can answer a question with another question)
I don't know that you can read his opinions or comments about the project anywhere. I certainly don't recall seeing them. I'm quite certain he doesn't know how it works, and I guess it'd be a coin toss as to whether he believes it works.
Why do you ask about his comments in particular?
http://www.boatdesign.net/forums/pr...ctly-downwind-faster-than-wind-25527-10.html"10-26-2009, 04:43 PM
ThinAirDesigns ThinAirDesigns is offline
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San Jose State University Aero Professor and Stanford Phd Dr. Nikos Mourtos along with a team of students and advisors have taken on a project to construct and document DDWFTTW in a more thorough way than ever before. Their goal is to achieve a documented 2x windspeed DDW.
Follow their blog at www.fasterthanthewind.org
OmCheeto said:and now, fasterthanthewind.org, has no mention of his existence?
spork said:We set out to take this project on with a group of SJSU aero students. Dr. Mourtos was their professor - and agreed to the project. And that was about the end of it. One of the students took it upon himself to start working with us relatively late in the project. The others were effectively no-shows. Neither they nor the professor contributed in any way to the project.
Because we had accepted money from sponsors to accomplish a stated goal, JB and I saw to it that the project was completed.
But if it eases your concerns in any way - I strongly suspect he still exists.
2010 http://www.engr.sjsu.edu/nikos/MSAE/pdf/Shethal.F10.pdf"
Shethal Thomas Kodiyattu
OmCheeto said:But I did just find a paper written by one of http://www.engr.sjsu.edu/nikos/projectsMSAE.htm" students:
Unfortunately, it's a 125 page pdf
Depends on the time and their motivation. If they are highly motivated I might be able to demonstrate it and expect them to build their own on their own time while we move on. I like to cover the entire text in order and usually the all important high tech stuff needed now days comes near the end. I do plan to have them watch AT's U.tube presentations of ATPFTTP and UTRFTTR and at least build those things.spork said:Will you build a cart and demonstrate it in class?
The paper and ruler videos are not mine, but from someone who posts as "Michael C". My youtube channel contains some schematic animations:Fun Value said:Depends on the time and their motivation. If they are highly motivated I might be able to demonstrate it and expect them to build their own on their own time while we move on. I like to cover the entire text in order and usually the all important high tech stuff needed now days comes near the end. I do plan to have them watch AT's U.tube presentations of ATPFTTP and UTRFTTR and at least build those things.
chingel said:But then what is the correct way of thinking about the cart moving faster than the wind, and also the Yo-Yo and tumbleweed? What is the most intuitive and logical explanation?
Fun Value said:Right now it seems to me that maybe the most difficult part is the gear-box - one that changes direction from the plane of the wheels to a perpendicular plane so as to run the propeller. I thought I might find one at the local hobby shop, but they didn't have one. I guess I might have to make my own. Wonder if I can make it highly efficient.
spork said:We have never found that any given explanation is better than another overall. Each person that gets it seems to find one more intuitive while others claim that one makes no sense, and think another is more intuitive. Some are certain that none are intuitive, and that DDWFTTW is impossible.
One is that when you have two media moving at different speeds, and a device that extracts energy from the relative movement of those two media (by interacting with the media), then it is possible to construct such a device so it can continue to extract energy from the relative movment of the two media even when the devices speed is greater than the relative speed of the two media. The under the ruler cart, sailcraft like ice boats, and DDWFTTW carts, are examples of such devices. The limit of speed is related to how much the device slows the relative speed of the two media (if it slows the relative speed to zero, it can't extract energy), and when energy ouput to overcome the factors related to speed equals energy input.chingel said:But what are the explanations?
chingel said:The extracting energy from two different moving media doesn't really mean anything. It isn't really an explantion. It is like asking how a car works and then you get an answer that it extracts energy from a chemical reaction. Ok, but how?
It's all there is to say about where the energy is coming from.chingel said:The extracting energy from two different moving media doesn't really mean anything. It isn't really an explanation.
If you are not happy with such answers then you should not insist on explanations in terms of energy.chingel said:It is like asking how a car works and then you get an answer that it extracts energy from a chemical reaction. Ok, but how?
Two points being covered in my previous post:chingel said:The extracting energy from two different moving media doesn't really mean anything.
I think that the yo-yo case is somewhat intuitive since the outcome is what most people would expect. If you pull a yo-yo on the ground by pulling it's string horizontally, the yo-yo moves faster than the string. Then you could point out that if the ground didn't have any friction, then the yo-yo could would only move as fast as the string, so it's clear that the the yo-yo needs to interact with both the ground and string, which are the two media moving at different speeds in this example, in order for the yo-yo to move faster than the string. The energy input is the force times distance the string moves. The energy output is the gain in linear and angular kinetic energy of the yo-yo as it accelerates (plus losses due to rolling resistance, and friction, which end up as heat).chingel said:Ok, but how?
A.T. said:It's all there is to say about where the energy is coming from.
If you are not happy with such answers then you should not insist on explanations in terms of energy.
chingel said:Yes that's all nice and the only place it could possibly extract energy, but it doesn't explain anything, what, how? It is very unsatisfying. I cannot just go and start extracting energy from two different medias, I have to have some sort of a way or a mechanism of doing it.
I also have the same problem with the Yo-Yo. If the middle part is freewheeling, the Yo-Yo goes at the speed of the string, but when you connect it rigidly to the outer parts, it uses their energy to spin against the string and work itself up.
Maybe a better way would be thinking about it like some sort of a fulcrum? If the Yo-Yo is hexagonal for example, the ground is the fixed point of the fulcrum, the force is applied somewhere in between the ground and center of the Yo-Yo and since the center of the Yo-Yo is further along the lever it would move faster. But this would mean that the closer the point where the string applies it's force is to the ground the faster it would move
...but that is not the case with the Yo-Yo.
chingel said:Yes in the end the energy can only come from the wind, and since there are videos of it going faster than the wind, it does extract it somehow. What I would like to know is how does it do it, where does the energy come from when the cart is up to wind speed?
chingel said:Isn't it that the smaller the diameter of the center part, the faster the yo-yo goes up the string? But in the case of a fulcrum, the closer you are to the pivot point, assuming constant speed of the string, the faster the top of the lever moves, no?
Although the cart is moving at or faster than wind speed, the air accelerated by the propeller is moving slower than wind speed, and that air is slowing down part of the wind, and that is the source of the energy. All of this is from a ground based frame of reference.chingel said:Yes in the end the energy can only come from the wind, and since there are videos of it going faster than the wind, it does extract it somehow. What I would like to know is how does it do it, where does the energy come from when the cart is up to wind speed?
If the center part (and string) had zero diameter there would be no winding of the string, and the yo-yo would move at the same speed as the string.chingel said:Isn't it that the smaller the diameter of the center part, the faster the yo-yo goes up the string?
chingel said:The places where it ultimately must get the energy are undeniably correct since the cart is actually moving faster than the wind and has to get it from somewhere. But what happens at windspeed, how does it do it?
Take the triple case. Assume the string moves at +1 cm/s, then the yo-yo moves in the same direction as the string at +1.5 cm/s second (relative to the ground). From the yo-yo's perpective, the ground moves at -1.5 cm/s, the inner diameter moves at -.5 cm/s second (1/3rd the outer diameter surface speed), and string moves at -1 cm/s.chingel said:I would tend to think the smaller the diameter of the center part, the faster the yo-yo moves, because when the surface of the center part moves at 1 cm/s, if the outer diameter is twice of it it moves at 2 cm/s, 3 cm/s if triple etc.
As mentioned above, from a ground based frame of reference, the propeller's thrust slows down the wind, even when the cart is moving at faster than wind speed. Using the BB's stated advance ratio of .8, and max speed of 2.8x wind speed, then if wind speed is 10 mph, cart speed is 28 mph. From the cart frame of reference, ground speed is -28 mph, prop thrust speed is (-28 x .8 =) -22.4 mph, and wind speed is (-28 + 10 = ) -18 mph, and the air affected by the propeller is accelerated (-22.4 - -18 =) -4.4 mph. From a ground frame of reference, the wind speed is +10 mph, the cart speed is +28 mph, the propeller thrust speed is (28 - 22.4 = ) +5.6 mph, slower than the +10 mph wind speed. So the air affected by the propeller is slowed down by 4.4 mph.The places where it ultimately must get the energy are undeniably correct since the cart is actually moving faster than the wind and has to get it from somewhere. But what happens at windspeed, how does it do it?
chingel said:...how does it do it?
spork said:There are a bunch of ways to describe this, but let's take a simple kinematic approach first...
First let's imagine our cart was submersed in Jello and the prop has a very fine pitch (in other words it only tries to screw it's way through the jello by about 1 foot per rotation). So now we move this entire block of jello that the cart is in - but it's wheels are still rolling on the stationary ground. By pushing the jello forward, we end up pushing the cart forward too - and that makes the propeller rotate. So let's imagine that we gear the wheels pretty low so we have to push the cart forward 100' to make the prop do one full turn.
See what happens there? We push the jello forward 100', the prop makes one full turn, so the cart moves forward 100' with the jello *plus* the one foot its prop pulled it through the jello.
So if we do this over a period of one minute, the jello goes 100 feet per minute. But the cart goes 101 feet per minute (because it pulled itself forward in the jello). We're now going down jello faster than the jello - right?
rcgldr said:Take the triple case. Assume the string moves at +1 cm/s, then the yo-yo moves in the same direction as the string at +1.5 cm/s second (relative to the ground). From the yo-yo's perpective, the ground moves at -1.5 cm/s, the inner diameter moves at -.5 cm/s second (1/3rd the outer diameter surface speed), and string moves at -1 cm/s.
In the double case, the yo-yo moves at twice the string speed (relative to the ground) at +2 cm/s (relative to the ground). From the yo-yo's perpective, the ground moves at -2 cm/s, the inner diameter moves at -1 cm/s second (1/2 the outer diameter surface speed), and string moves at -1 cm/s.
rcgldr said:Yo-yo ... take the triple case. ... (wrong string speed numbers from yo-yo frame of reference)
My fault, the inner diameter speed and the string speed are the same, regardless of the frame of reference. The rest of the numbers were OK.chingel said:I don't understand.
The slower it moves. If the diameter is zero, the yo-yo moves at string speed. The larger the diameter, the faster the yo-yo moves as long as it doesn't slide. If the axle diameter is the same as the yo-yo diameter, then it can only move by sliding. If the axle diameter was greater than the yo-yo diameter (assume the yo-yo is rolling on rails to allow this), the yo-yo will roll to the left when the string is pulled to the right. In both cases, the closer the ratio of inner_diameter to outer_diameter is to 1, the faster the yo-yo moves (except if they're equal to 1, the yo-yo can only move by sliding).chingel said:Are you saying that the smaller the diameter of the middle part the faster it moves or the slower it moves?
No. It moves faster when the inner diameter tends towards the outer diameter.chingel said:In the under the ruler faster than the ruler example, the smaller the diameter of the middle parts of the wheels where the big wheel applies the force, the faster it moves,
No. It is the same. The blue wheel just allows to apply the force on top.chingel said:then it would mean that the effect is different from the lever example,
Sure you can. See the red dashed line indicating the leverage:chingel said:but why can't I view it as a lever
chingel said:I am having difficulty imagining that when you get the cart up to jelly speed and then engage the propeller, how does the force apply, how does it not use it's own energy to propel itself? I guess it's the same principle as the yo-yo, where the wheels are pivoting around the contact point with the ground, which I am having trouble grasping.
Wind power vehicles, also known as wind-powered land yachts, use a combination of wind energy and aerodynamics to travel faster than the wind. The vehicle's design allows it to harness the wind's energy and convert it into forward motion, similar to how a sailboat uses the wind to move forward.
The maximum speed of a wind power vehicle depends on various factors such as the wind speed, the vehicle's design, and the surface it is traveling on. However, some wind power vehicles have reached speeds of over 100 miles per hour.
Wind power vehicles are designed with a propeller that acts as a turbine. This propeller is connected to the wheels and helps to maintain a constant speed, even when the wind direction changes. The vehicle's design also allows it to adjust its direction to take advantage of the wind's energy.
While wind power vehicles can travel faster than the wind, they do have some limitations. They require a relatively flat and smooth surface to travel on, and their speed is dependent on the wind speed. They also cannot travel directly into the wind and require some wind to move forward.
Currently, wind power vehicles are primarily used for recreational purposes and land speed records. However, there have been some developments in using them for everyday transportation, such as in low-speed urban areas. As technology advances, it is possible that wind power vehicles could become a more viable option for everyday transportation in the future.