General > General Technical Chat
Newton's third law problem.
fourfathom:
--- Quote from: Nominal Animal on November 23, 2022, 12:21:18 am ---Where the insistence of energy storage being involved here stems from, I can only imagine.
--- End quote ---
Here's the genesis:
* Because of electro's unwillingness to properly consider frames of reference, he believes that it is impossible for a wind-powered vehicle travel directly downwind FTTW (Faster Than The Wind).
* So, he presumes that energy used for this physically demonstrated FTTW speed has been stored as pressure behind the vehicle while it was travelling slower TTW.
* When presented with simple physical or conceptual models that demonstrate analogous behavior he clings to the "energy storage" model, invoking things like "slip-stick hysteresis". (this does exist in some cases, but is irrelevant here).
So it all goes back to the original propeller/wheel vehicle that violates electro's misunderstood laws of physics.
electrodacus:
--- Quote from: fourfathom on November 23, 2022, 04:26:11 pm ---Here's the genesis:
* Because of electro's unwillingness to properly consider frames of reference, he believes that it is impossible for a wind-powered vehicle travel directly downwind FTTW (Faster Than The Wind).
* So, he presumes that energy used for this physically demonstrated FTTW speed has been stored as pressure behind the vehicle while it was travelling slower TTW.
* When presented with simple physical or conceptual models that demonstrate analogous behavior he clings to the "energy storage" model, invoking things like "slip-stick hysteresis". (this does exist in some cases, but is irrelevant here).
So it all goes back to the original propeller/wheel vehicle that violates electro's misunderstood laws of physics.
--- End quote ---
You're confusing things.
There are two vehicles
a) the direct upwind discussed in this thread as it should be simpler to explain and has analog version using just wheels and this one uses small capacity energy storage and stick slip hysteresis to trigger when energy is being charged and discharged.
b) the direct downwind faster than wind not discussed here that uses a large capacity energy storage called pressure differential and created by the propeller.
The only way wind interacts with any vehicle is through collisions between air particles and vehicle and depending on direction vehicle gains or loses kinetic energy.
That is why the equation for wind power has no variable related to the vehicle design so all wind powered vehicles have access to the same amount of wind power.
WindPower = 0.5 * air density * (area * coefficient of drag) * (wind speed - vehicle speed)3
This above equation is universal for any wind powered vehicle so for direct downwind equation shows there is zero wind power available when vehicle speed equals wind speed.
And for direct upwind discussed in this thread the equation shows the power that winds acts against the vehicle as well as the theoretical max power available to vehicle and so since this two are ideal case equal the vehicle can not move unless it first store energy then uses that stored energy to move a little bit against the wind direction and then repeat this cycle as many times as you want.
So that equation is the only prove I need to show that any vehicle powered only by wind requires energy storage in order to drive faster than wind directly downwind or at any speed directly upwind.
If you want to contradict what I say you will need to provide a wind power equation that matches what is observed and measured in reality.
And my best example of what happens and it is measured in reality was the one about the power needed to overcome drag (same equation) is the same for a vehicle driving at 30m/s with no wind as it is for the same vehicle driving at 10m/s with a 20m/s head wind.
The basic physics law that you try to violate is Newton's third law the subject of this thread and by extension the energy conservation.
AVGresponding:
Never been sailing? You can tack into the wind, effectively using wind power to propel you in the direction the wind is coming from.
electrodacus:
--- Quote from: AVGresponding on November 23, 2022, 05:06:32 pm ---Never been sailing? You can tack into the wind, effectively using wind power to propel you in the direction the wind is coming from.
--- End quote ---
I have never been on a sailboat but I can explain how it works.
A sailboat can not sail directly upwind but it can sail at an angle to gain kinetic energy then rotate to direct upwind and use that kinetic energy to sail for a small amount of time upwind then it will need to change direction again to recharge the kinetic energy.
So it can take advantage of kinetic energy storage if it is allowed to change direction but if that is not allowed it can not sail directly upwind.
A vehicle perpendicular to wind direction will always have access to max wind power no matter the vehicle speed as wind speed relative to vehicle is always the same.
AndyBeez:
--- Quote from: AVGresponding on November 23, 2022, 05:06:32 pm ---Never been sailing? You can tack into the wind, effectively using wind power to propel you in the direction the wind is coming from.
--- End quote ---
And if you're using a hydrofoil, you can do it faster than the wind is blowing at you. Wrong but true. Google America's Cup. On the subject of friction reduction, is anyone using the downward force of gravity g in their equations? Does this thing still work in microgravity?
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