Car Goes Downwind 2.5 Times Faster Than the Wind

[John in CR]

That big prop sweeps a large enough area to capture plenty of wind energy to easily make that light and aerodynamic vehicle move faster than the wind...2.5 times as fast in fact. I'm sure most of that energy is used up by the wind resistance of the props motion itself.

Just think about how a plane putting out the same thrust goes faster relative to the ground with a tail wind than without, and then it might click for you. Your views posted in this thread make the plane example impossible too.

 

[nicobie]

This has already gotten too silly and boring.

I'm gone.

About time too.

 

[endlessplane]

Theory and Design of Flow Driven Vehicles Using Rotors for Energy Conversion
c2009
Mac Gaunaa, Risø DTU
Stig Øye, DTU-MEK
Robert Mikkelsen, DTU-MEK

http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/content

Tyler, did you bother to read the link?

Did you read it gonzo? Apparently not.

...it specifically stated GOING INTO THE WIND!!

The paper deals with both:
- directly upwind (section 2.2)
- directly downwind faster than the wind (section 2.3)

This is from the conclusions:

It is theoretically possible to build a wind
driven car that can go in the downwind
direction faster than the free stream wind
speed (using a propeller in the air)

 

[doctorGONZO]

Theory and Design of Flow Driven Vehicles Using Rotors for Energy Conversion
c2009
Mac Gaunaa, Risø DTU
Stig Øye, DTU-MEK
Robert Mikkelsen, DTU-MEK

http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/content

Tyler, did you bother to read the link?

Did you read it gonzo? Apparently not.

...it specifically stated GOING INTO THE WIND!!

The paper deals with both:
- directly upwind (section 2.2)
- directly downwind faster than the wind (section 2.3)

This is from the conclusions:

It is theoretically possible to build a wind
driven car that can go in the downwind
direction faster than the free stream wind
speed (using a propeller in the air)

How much cash did you invest in this scam?

Be honest.

 

[doctorGONZO]

That big prop sweeps a large enough area to capture plenty of wind energy to easily make that light and aerodynamic vehicle move faster than the wind...2.5 times as fast in fact. I'm sure most of that energy is used up by the wind resistance of the props motion itself.

Just think about how a plane putting out the same thrust goes faster relative to the ground with a tail wind than without, and then it might click for you. Your views posted in this thread make the plane example impossible too.

Big John, you must be really getting some GOOD stuff to smoke down there in cr.

Most of the science community, who, unlike you, rely on precise logic and mathematical accounting, require a claim to add up. You (all) keep on saying BUZZ WORDS and GOBBLY GOOK.

Scuze me if I dont believe a word you say.

 

[endlessplane]

Theory and Design of Flow Driven Vehicles Using Rotors for Energy Conversion
c2009
Mac Gaunaa, Risø DTU
Stig Øye, DTU-MEK
Robert Mikkelsen, DTU-MEK

http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/content

...it specifically stated GOING INTO THE WIND!!

The paper deals with both:
- directly upwind (section 2.2)
- directly downwind faster than the wind (section 2.3)

This is from the conclusions:

It is theoretically possible to build a wind
driven car that can go in the downwind
direction faster than the free stream wind
speed (using a propeller in the air)

How much cash did you invest in this scam?

It's a paper about physics, not about investments. Read it again, if you still have reading comprehension problems.

 

[doctorGONZO]

[/quote][/quote]
How much cash did you invest in this scam?
[/quote]
It's a paper about physics, not about investments. Read it again, if you still have reading comprehension problems.[/quote]


I have written my own paper about this ridiculous hallucinatory dream. My paper includes critically important factors which were OBVIOUSLY, sadly overlooked by previous comedy paper writers. My paper, including all critical factors, results in the acceleration beyond 1.0 wind velocity being impossible according the Newtonian Physics within the provisos of the OP.

My position has been, and remains, IF THE KAR LEGITIMATELY PERFORMED AS CLAIMED, THEN NEWTONIAN PHYSICS MUST BE GROSSLY RE-WRITTEN FROM HEAD TO TOE. AND NONE OF YOU MUNCHKINS HAVE WRITTEN THE FIRST WORD TO GIVE A CONVINCING RE-WRITE TO NEWTONIAN PHYSICS.

All that any of you have ever done is to insult me like silly little bitches and tell me that I should sink into your silly hallucinatory dream. Sorry, cant do it. I dont ever do pot or LSD.

In this material world ruled by Satan, it is reasonable for me to demand of you to tell me where you have voted with your money, since money is what many of you honor above everything else.

 

[endlessplane]

I have written my own paper about this ridiculous hallucinatory dream....

Awesome. I suggest you submit it to the AAPT's American Journal of Physics:
http://scitation.aip.org/content/aapt/journal/ajp

You should specifically reference the AAPT's own analysis, and point out why it is wrong:
http://www.aapt.org/physicsteam/2013/upload/E3-1-7-solutions.pdf

 

[tomjasz]

Having seen the two wind powered record holders run at 116-120 mph, in half the windspeed, I am not so certain the physics will hold up. You boys might well be members of the flat earth society in the near future.

 

[John in CR]

Having seen the two wind powered record holders run at 116-120 mph, in half the windspeed, I am not so certain the physics will hold up. You boys might well be members of the flat earth society in the near future.

You're forgetting that those record vehicles don't travel downwind, so the wind resistance of the vehicle itself is what holds them back to a 2:1 limit. Traveling directly downwind the apparent wind flowing over the vehicle is far less than your record holders. They've already demonstrated 2.5:1, and based on the difference in the apparent wind I believe their statements about the theoretical limit 3:1 or higher.

 

[endlessplane]

Having seen the two wind powered record holders run at 116-120 mph, in half the windspeed,

You mean the Greenbird?

[youtube]TRFRQXPtXTs[/youtube]

The Greenbird record has been ratified by the same organisation as the Blackbird records:
http://www.nalsa.org/

In fact, the below video of the Blackbird, was shot by Richard Jenkins, the Greenbird pilot from the video above:

[youtube]5CcgmpBGSCI[/youtube]

I am not so certain the physics will hold up.

The American Association of Physics Teachers, American Institute of Physics, wind energy researchers from the Technical University of Denmark and MIT aerodynamics Professor Mark Drela are quite certain that there is no physics problem with directly downwind faster than wind.

 

[tomjasz]

I am a former member of NALSA and formerly owned and ran dirtboat.com I owned 3 slow boats. 2 Manta Twins and a Single. 50MPH 5 inches off the ground with wind and no brakes will make any boy smile from ear to ear. Best acid I ever dropped.
I have seen them all. But the most impressive was the first record holder built by two Americans without 57 sponsors. Iron Duck. Just two "cowboys" with a plan. Not unlike many of the dreamers here.

 

[liveforphysics]

My position has been, and remains, IF THE KAR LEGITIMATELY PERFORMED AS CLAIMED, THEN NEWTONIAN PHYSICS MUST BE GROSSLY RE-WRITTEN FROM HEAD TO TOE. AND NONE OF YOU MUNCHKINS HAVE WRITTEN THE FIRST WORD TO GIVE A CONVINCING RE-WRITE TO NEWTONIAN PHYSICS.

Newtonian physics IS for certain, 100% wrong in all cases in all ways.

All of classical physics, including Newtonian physics, superseded by relativistic physics and quantum physics. However, classical physics is a limiting case of the latter two theories, and it is often a very good approximation.

You may feel free to re-write anything you like, not that this is any violation of the all 100% wrong Newtonian physics model to begin with though.

I feel like a step backwards in your progress has been made, it seemed as though you had grasped the concept of harnessing energy from wind, and then using that energy to propel a vehicle already. Did your model of how energy/power transfer works change since the last month?

 

[doctorGONZO]

My position has been, and remains, IF THE KAR LEGITIMATELY PERFORMED AS CLAIMED, THEN NEWTONIAN PHYSICS MUST BE GROSSLY RE-WRITTEN FROM HEAD TO TOE. AND NONE OF YOU MUNCHKINS HAVE WRITTEN THE FIRST WORD TO GIVE A CONVINCING RE-WRITE TO NEWTONIAN PHYSICS.

Newtonian physics IS for certain, 100% wrong in all cases in all ways.

All of classical physics, including Newtonian physics, superseded by relativistic physics and quantum physics. However, classical physics is a limiting case of the latter two theories, and it is often a very good approximation.

You may feel free to re-write anything you like, not that this is any violation of the all 100% wrong Newtonian physics model to begin with though.

I feel like a step backwards in your progress has been made, it seemed as though you had grasped the concept of harnessing energy from wind, and then using that energy to propel a vehicle already. Did your model of how energy/power transfer works change since the last month?

If we assume that Special Relativity is true (and there are a great many sound arguments that it is profoundly wrong) then we must agree that at the very low energies and velocities of "everyday life" it reduces to a very nearly perfect approximation of classical Newtonian Physics. 22 MPH in the Blackbird famous run is not fast enough to cause a perceptible change from the Newtonian even if the most expensive and sensitive instruments were used to make the observations. Your reliance on the stale saying that classical physics is 100% wrong is indeed very nearly 100% WRONG! And if you claim to understand what you were saying, your statement cannot be understood as anything other than a deliberate fabrication.

The classical physics notions of Laws Of Motion, and Action ANd Reaction, and, Conservation Of Momentum, and, Transfer Of Momentum, are not perverted by Special Relativity or Quantum Physics regardless of whatever high energies and velocities are investigated. If you claim otherwise, you either have a fool's understanding of physics, or, you are deliberately trying to tell us things that are blatantly wrong.

You and the other munchkins in your klan seem to believe that at 1.00 windspeed the kar begins to suck energy out of the roadway to spin up the fan. I have patiently explained that that situation requires that the roadway must slow down as it loses momentum from feeding momentum to yo kar. So the relative speed between the roadway and yo kar must LESSEN. A lessened relative speed between yo kar and the roadway means that yo kar SLOWS RELATIVE TO THE ROADWAY. This is according to the principle of CONSERVATION OF MOMENTUM.

You are welcome to explain in specific detail how I am wrong. You (all) have been welcome to do so. So far, all that has has happened is a lot of smoke-blowing and name calling.

BTW I have faith in my ability to effectively analyze a physics situation on the basis of logic consistency and mathematics. Your (collectively) arguments have been extremely illogical, silly, and completely empty of any credible maths. So it does not matter to me if some other physicist or a herd has happened to fall into the ditch and reach a silly wrong conclusion.

None of your "papers" have been comprehensive. I have not read anything that included the most important factors. So it is no surprise that your "papers" have predicted the majicke emergence of momentum and energy out of thin air.

 

[tomjasz]

Ah the internets...

 

[Chalo]

doctorGONZO:

I too used to firmly refute the idea that a vehicle could run directly downwind faster than the wind. That's still true of sail, but the vehicles in question are not sail-driven. They are propeller-driven.

The power for the propeller, in essence, comes from the difference between the airspeed and the surface speed. Does this make more sense to you?

 

[endlessplane]

But the most impressive was the first record holder built by two Americans without 57 sponsors. Iron Duck. Just two "cowboys" with a plan. Not unlike many of the dreamers here.

Yes, Bob Dill and Bob Schumacher build the Iron Duck for relatively low cost compared to the Greenbird, and yet their record (116.7mph) stood for ten years. More info is here:
http://www.nalsa.org/speed_record.htm
http://home.comcast.net/~dolord/irondk.html
http://archive.sailingscuttlebutt.com/news/08/tt/bobdill.pdf

As Bob Dill points out in the last link, the cost for improving such records grows exponentially, so at some point low cost garage projects have no chance. There was an academic project trying to beat the Greenbird record (126mph), but I haven't heard anything for a while from them:
http://www4.lehigh.edu/news/newsarticle.aspx?Channel=%2FChannels%2FNews%3A+2010&WorkflowItemID=91ea9329-8178-49e8-b261-84b150ae3711

The DDWFTTW Blackbird was competing in a different category, and it was a rather low cost project (~10'000$ material cost), despite sponsors like Google.

 

[stepheneb]

None of your "papers" have been comprehensive. I have not read anything that included the most important factors. So it is no surprise that your "papers" have predicted the majicke emergence of momentum and energy out of thin air.

Did anyone already share Mark Drela's paper from 2009?

Dead-Downwind Faster Than The Wind (DDWFTTW) Analysis: http://blueplanettimes.com/wp-content/uploads/2010/08/Drela-DDWFTTW-Analysis.pdf

He's an aerodynamics professor at MIT and the author of XFOIL http://web.mit.edu/drela/Public/web/xfoil/.

FWIW, Drela's paper is not how I came to understand what's going on.

The only thing more impressive than the length of threads discussing this topic (and the length of this thread is infant-sized compared to some) is the work JB and team have done making a real person-carrying full-size vehicle demonstrating the physics.

There's something very special about this particular problem/demo that makes it very interesting from a cognitive/learning/frame-of-reference POV.

 

[Frank]

Dr G, a number of papers have been referenced. Perhaps you should demonstrate how they are incorrect?

 

[Drunkskunk]

I am on of the dumbest people on ES, bo help me to understand this in terms a dumb person can understand.

In no wind, the blackbird won't roll because the wind resistance on the propeller is the same from the front and the back, and is the same resistance to moving the rest of the body.?
But with a 10mph tail wind, the pressure is now Higher behind and lower in front of the propeller, and the average resistance is higher than the resistance to the rest of the body, so the wind turns the propeller, which turns the wheels and moves the blackbird forward.

That makes sense up to 10mph. 1:1 wind/vehicle speed. Now if I understand this right, the wind is still blowing, and even though the wind speed is now neutral to the vehicle, because the propeller is being turned by the motion of the wheels, there is still higher pressure behind the propeller than in front, so the vehicle is still able to accelerate to higher velocities.

If I'm getting what is going on here, then the vehicle should be able to travel up to the speed where the amount of energy difference between the front and rear of the propeller is the same as the difference between the front and rear of the rest of the vehicle.

 

[Grey beard]

I've looked at the film of this vehicle a few times. We have a large prop connected mechanically to the wheels. We are to assume we have no outside forces except for a 10mph breeze. The vehicle is at a dead stop. The only energy is the wind acting on the prop. When the wind acts on the prop pitched as this one is, it has a want to turn in a anti/counter clockwise motion, yet it defies all aerodynamics and starts turning in a clockwise direction. Again, the vehicle is stationary. The only energy is the wind. The only means to harness it is the prop, and the prop begins its rotation in the opposite direction that aerodynamics dictate. So, I call buII$hit.

 

[endlessplane]

When the wind acts on the prop pitched as this one is, it has a want to turn in a anti/counter clockwise motion,

That is correct. The aerodynamic torque is counter clockwise (looking from behind).

...yet it defies all aerodynamics and starts turning in a clockwise direction.

It doesn't defy aerodynamics. There is more aerodynamics happening here than just aerodynamic torque. There is also an aerodynamic force that pushes the whole thing forward and creates a torque at the wheels, which turns the prop clockwise against the aerodynamic torque.

Look at this video at 6:00, where they demonstrate the self-start with a small model:

[youtube]nudBjrOF3LE[/youtube]

The only means to harness it is the prop, and the prop begins its rotation in the opposite direction that aerodynamics dictate.

It slows down the true wind relative to the ground, so it harvests wind energy.

 

[liveforphysics]

I've looked at the film of this vehicle a few times. We have a large prop connected mechanically to the wheels. We are to assume we have no outside forces except for a 10mph breeze. The vehicle is at a dead stop. The only energy is the wind acting on the prop. When the wind acts on the prop pitched as this one is, it has a want to turn in a anti/counter clockwise motion, yet it defies all aerodynamics and starts turning in a clockwise direction. Again, the vehicle is stationary. The only energy is the wind. The only means to harness it is the prop, and the prop begins its rotation in the opposite direction that aerodynamics dictate. So, I call buII$hit.

I believe you need to look at the problem from an alternative perspective. Look at it from an energy perspective. At the point at which the wind and vehicle speed match (and aren't imparting energy to each-other if they are matched), what point in this system DOES have a moving plane of reference? The drive for the prop.

 

[endlessplane]

so the wind turns the propeller, which turns the wheels and moves the blackbird forward.

No, the aerodynamic torque at the propeller never turns the propeller, but rather always opposes its rotation. The aerodynamic force at propeller pushes the entire vehicle forward, thus indirectly turning the wheels.

 

[Drunkskunk]

so the wind turns the propeller, which turns the wheels and moves the blackbird forward.

No, the aerodynamic torque at the propeller never turns the propeller, but rather always opposes its rotation. The aerodynamic force at propeller pushes the entire vehicle forward, thus indirectly turning the wheels.

Oh! Ok, I think I am getting this now. The wheels turn the propeller, maintaining the difference in pressures between the front and rear of the vehicle. So the wind speed is irrelevant to the vehicle speed, the only factor that matters is the difference in kinetic energy between the air and the ground.
Am I close?