Capturing Wake Energy Without Drag ?

[Questor]

Every time I see a boats wake I can't help but believe that there is 1,000 times more energy in the wake than propelling the boat.Long after the riverboat has disappeared wave after wave crashes against the shore. As a child I lived on a farm with a mirror smooth pond. I would drop the tiniest rock onto the pond and watch wave after wave travel across the pond, lifting and pushing hundreds of leaves , sticks and lily pads. After what seemed an eternity,when stillness returned, I'd drop another tiny pebble and watch the the ensuing chaos that lifted and pushed thousands of objects floating on the pond and growing on the shore.

These observations lead me to believe that there must be some way to mount an electrical generator on a boat that produces more lift than drag while producing electricity from wake energy. Does this concept seem feasible ? Nothing would be more fun than returning to the dock with more energy than you left with.

[wardd]

No, it's not feasible

we couldn't exist in a universe without entropy.

[Questor]

The concepts of entropy entrenched in the second law of thermodynamics seem to have undergone some major revision since the last time I reviewed them. We now have the concept of Maximum Entropy Production leading to the production of order from disorder. Chemists now talk about unleashing the latent heat of creation to unleash more energy from a reaction than is humanly vested in the original action.

No one will ever convince me that there is less energy in a boats wake than propelling the boat.

Back when I was 9 years old I used to gather heavy arm loads of sticks to float on the pond. In moments of stillness I'd drop those tiny pebbles and watch my armada rising and falling on the pond.The total lift captured by my floating armada as it repeatedly rose and fell greatly exceeded the energy of the falling pebble.

People living in the real worlds of experience and observation have no difficulty grasping the concept of the greater energy that acted upon my floating armada in the pond. University graduates on the other hand , deny what they can clearly see while blindly quoting concepts of entropy and thermodynamics.

[Ad Hoc]

I'm a bit confused. Can you explain what you mean by your statements:

Originally Posted by Questor

... I can't help but believe that there is 1,000 times more energy in the wake than propelling the boat.

and

Originally Posted by Questor

The total lift captured by my floating armada as it repeatedly rose and fell greatly exceeded the energy of the falling pebble.

Questor, may I introduce Quark? Quark, Questor.

[Easy Rider]

I think we've heard enough out of you today Mark.

Questor,
At or a bit below hull speed the bow wave comes back, up under the stern and if the angle of the stern wave is very similar to the QBBL the stern wave should put the vessel in a surfing mode and some of the power that made the bow wave should be recovered. This is the only way that I know of that energy lost creating a wake is recovered. I'm sure this happen's but it must be small as I have never seen the resistance curve of a hull that shows a dip in the curve at that speed. A steep QBBL and a speed of about .9 S/L ratio should produce the most effect. This is all imagineering on my part as I've never heard if it out of my mind. Now I've probably stepped right into someth'in there.

Easy Rider

Have you, now? Who do you think you are?

[Questor]

Originally Posted by Ad Hoc

I'm a bit confused. Can you explain what you mean by your statements:



and

When I look at the volume of water in a boats wake and the wakes velocity as it travels away from the boat, I believe that there is more kws of energy to be harvested from the boats wake than the boat is using to travel across a body of water.

As a child on the farm I gathered the largest weight of heavy sticks that I could physically lift. I launched them slowly into the pond and waited for them to stall. When I saw that they were motionless I would drop a small pebble into the pond . When the waves from the pebble struck the sticks they would rise upon each wave and fall as the waves passed them. Each wave striking the sticks carried them closer to the other side of the pond.With a lot of patience a small handful of pebbles could create enough wave action to carry all of the sticks across the pond. In addition to the energy necessary to carry my armada of sticks across the pond there was a lot of surplus energy in the waves that moved everything they touched that was growing in the pond or floating on the pond.

In the almost fifty years since my childhood I've shown this experiment to quite a few highly educated people of science. Their typical reaction is " I don't believe what I am seeing." " This contradicts the second law of thermodynamics." They cling to their dogmas and deny what they can clearly see.

It takes a lot of energy to move water by a machine. As an example , a large pond of water about 400 feet long by 100 feet wide and an average of about 12 inches deep formed above a frozen sewer inlet next to a community hall I was managing. As cars drove down the alley beside the hall, the wake they created rose above the bottom of the halls basement windows and filtered around the windows and into the hall.I purchased a 1500 watt water pump and placed it in the pond with a section of hose leading towards an open sewer inlet.I only had to lift the water a few inches and transport it about 20 feet, after which gravity would carry the water the rest of the way to the open sewer. Over the space of 48 hours a pump I bought didn't make a noticeable dent in the body of water I was trying to move. A neighbours building was also being threatened by the wake of passing cars so he added a pump of his own to the venture.During the two days that my neighbour and I watched the pumps I told a number of people " I wish a powerboat could drive by, a couple of teaspoons of gas and all this water would be gone . " They all knew what I was talking about.They had all seem the incredible force of a powerboats wake. Some people that stopped by even brought up the subject of powerboat wakes without me mentioning it.

As I write this, I wonder if a small remote control power boat travelling in small circles , powered with a couple of triple A batteries, might have moved more water towards the other sewer inlet than our 2 useless electric water pumps did.

[Ad Hoc]

I’m sorry but I still don’t really understand what you are saying other than you keep dropping stones into a pond. I think you have left out too much from what you are trying to describe to make any sense.

The same with the car story. Cars don’t have wake. So perhaps there is also an issue of not using the correct terminology that is confusing me too.


But addressing this:

Originally Posted by Questor

When I look at the volume of water in a boats wake and the wakes velocity as it travels away from the boat, I believe that there is more kws of energy to be harvested from the boats wake than the boat is using to travel across a body of water.

What makes you “believe” this?.. do you have anything more than a belief?...and what does the volume of water have to do with it?

This is absolutely ridiculous. I didn't find a good shallow water animation for you (the one I did find has errors) but in water deeper than half the wavelength, if the wave isn't cresting there is no forward sustained momentum of water molecules nor anything resting on the water. It is simply how waves propagate... http://www.classzone.com/books/earth...=visualization
Decrease wavemaking or work with it to increase efficiency but you will never retrieve more energy from a wave than you put into it.

[peter radclyffe]

http://www.youtube.com/watch?v=H0K2dvB-7WY

[CDK]

Originally Posted by Questor

When I look at the volume of water in a boats wake and the wakes velocity as it travels away from the boat, I believe that there is more kws of energy to be harvested from the boats wake than the boat is using to travel across a body of water.

You already dropped pebbles in the pond and could have learned from such experiments that the visible effects are misleading.
The energy introduced to the pond is mass times speed of the pebble, so almost nothing. That is distributed over the whole surface of the pond, it should be clear that there is nothing to recover.

Originally Posted by CDK

, it should be clear that there is nothing to recover.

.......except sanity? perhaps?

We have just another Kistinie here.

Well, once a week.......................

[Questor]

Originally Posted by Ad Hoc

I’m sorry but I still don’t really understand what you are saying other than you keep dropping stones into a pond. I think you have left out too much from what you are trying to describe to make any sense.

The same with the car story. Cars don’t have wake. So perhaps there is also an issue of not using the correct terminology that is confusing me too.


But addressing this:



What makes you “believe” this?.. do you have anything more than a belief?...and what does the volume of water have to do with it?

When the pebble first strikes the lake it creates a small hole which closes and forms a fountain that launches several small bodies of water into the air. As the water in the fountain falls back into the pond a series of ripples are formed . As the first ripple travels away from the original point of turbulence the volume of water contained in the ripple grows exponentially. Eventually the first ripple has enough energy to cause all the floating sticks in the pond to move towards the opposite shore. The first ripple is followed by several others, each of which pushes more sticks than I can carry across the pond.
( Eventually I had a half dozen armloads of sticks in the pond. )

If the weight of the sticks being transported across the pond weighs more than the energy of the falling pebble then the energy of the reaction exceeds the energy of the original action.

[wardd]

when you drop a pebble in a pond do the waves keep getting bigger and bigger?