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Newton's third law problem.

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james_s:

--- Quote from: PlainName on November 29, 2022, 06:20:27 pm ---
--- Quote ---This equation alone is proof that no vehicle can exceed wind speed directly downwind as equation shows wind power available is zero.
--- End quote ---

You are applying it by ignoring the propeller output and power sink, so the equation is useless for this vehicle. I've shown you how the missing things fit in and you can't even say why that is wrong, other than "it's all incorrect".

--- End quote ---

That's because he's a troll, he's succeeding in wasting your time and frustrating you which is exactly what trolls seek to do. We already know that he's wrong because multiple people have built vehicles that do exactly what he says is not possible, there's no point in arguing.

PlainName:
You're right, of course. I thought it useful to me to crystalise my thinking in that post, so not completely wasted.

electrodacus:

--- Quote from: PlainName on November 29, 2022, 06:20:27 pm ---You are applying it by ignoring the propeller output and power sink, so the equation is useless for this vehicle. I've shown you how the missing things fit in and you can't even say why that is wrong, other than "it's all incorrect".

--- End quote ---

Propeller is powered by wind so it will not add up.
All you have as input is wind power.

Equation for available wind power cares only about the vehicle shape (coefficient of drag) and projected frontal area.

electrodacus:

--- Quote from: james_s on November 29, 2022, 06:28:37 pm ---
That's because he's a troll, he's succeeding in wasting your time and frustrating you which is exactly what trolls seek to do. We already know that he's wrong because multiple people have built vehicles that do exactly what he says is not possible, there's no point in arguing.

--- End quote ---

Where I ever claimed any of those vehicles do things that are not possible?
They all work as shown but not for the reasons you think they do.

They will also not work as you will predict they will based on flawed theory.

For example the direct downwind faster than wind vehicles both the large blackbird and the small treadmill model will accelerate to a max speed (can be 2x or even 3x the wind speed) and then they will slow down as there is no longer any stored energy to cover the friction losses.

Kleinstein:

--- Quote from: electrodacus on November 29, 2022, 05:48:48 pm ---
--- Quote from: PlainName on November 29, 2022, 05:35:34 pm ---
Stop with the putting in values until you have a proper equation to insert them into, and currently you don't. All you're doing is confusing things by having some arbitrary number you need to distribute somewhere, but you don't really know where.

--- End quote ---

I use values as people do not see a limit.


--- End quote ---

Doing much of the math with numbers can be confusing, but it can sometimes also help. Getting obviously wrong resucts (e.g. reduculous numbers that contradict experiance) is one way to show that a claimed equation is obviously wrong. However this still does not work with electrodacus: he refuses to see how rediculous his claims are (e.g. walking against a 30 km/h head wind would need some 400 W of power and thus be a kind of heavy sports).



--- Quote from: electrodacus on November 29, 2022, 05:48:48 pm ---There is only wind power as input. There is absolutely nothing else.
There is a single equation describing the amount of power available to any wind powered vehicle and as you started to realize it is proportional with wind speed minus vehicle speed.

This equation alone is proof that no vehicle can exceed wind speed directly downwind as equation shows wind power available is zero.
And also same equation shows that no vehicle can drive directly upwind because in order to move upwind you need more than wind power.

So there is nothing to discuss other than if this equation is the correct one or not. Once you agree with that equation the conclusion is clear.

Now if you want to know how those vehicle work because they work then that is a separate discussion and involves energy storage.

--- End quote ---

The problem is that AFAIK there is no such simple, easy to accept equation for the maximum available power.  At least I don't see such an equation that I would take for granted. So it would still need a proof or at least good plausibile explaination. 
Aerodynamics can be be quite tricky and I would consider getting such an euqation and proving it rather hard. So the way via the available power is a hard one.
The equation claimed by electrodacus is known to be wrong. AFAIR his reasoning kind of works for a simple sail, but it does not apply for the fan/ porp case. There are cases when a prop can be more efficient than a sail.  The calculations for the prop drivne vehicle show that one can get more power and one can go faster than the wind. So the equation claimed by electrodacus is proven wrong - it is just that he refuses to accept (and maybe understand - though it is relatively easy) the proof.

Beside the calculation there are also videos to show that it is possible to go faster than the wind / or the equivalent case of moving against the moving treadmil, driven by a prop. With the plausible forms of ernergy storage the times shown are well long enough to consider them to show a stationary case - so the energy storrage argument / read herring is dead. :horse:

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