Author Topic: Big brain exercise! Vector based bouyancy wheel (Read 8622 times)

Low-Q · « **on:** November 21, 2010, 05:13:13 PM »

I have been thinking of a bouyancy wheel which isn't harnessing a weight based inbalance, but rather a vector based inbalance.

If you see the picture, there are two objects inside a tank of water. Both objects are placed on the bottom, so no water can access the very bottom of each object. This example are for reference only - and hard to achieve in real life (However theoretically possible)

One of these objects have no horizontal surface which the water can press upwards, but that has the other object due to the scewed "boxes". So this last object appears as lighter than the other object even if the mass and volume are identical.

Can these two objects be applied to a wheel so it can run under water, but not above water?

There is no weight of water we have to move upwards, there are no forces that prevents the "boxes" to move perfectly inline with eachother in order to loose its bouyancy effect. This actions will change the bouyancy force without applying energy - we have to find out a way to do this in practice.

broli · « **Reply #1 on:** November 21, 2010, 05:45:26 PM »

There's always the same amount of surface area that is seeing the same pressure in opposite direction.

Low-Q · « **Reply #2 on:** November 21, 2010, 07:52:33 PM »

OK. I see the problem. Now to a more complicated thing. Which of these two objects have the most bouyancy?

I can rotate elements to increase bouyancy?

They both have the same weight and volume, and are under the same conditions as in the previous picture. The gap between the elements are big for better visuality.

Vidar

broli · « **Reply #3 on:** November 21, 2010, 09:04:43 PM »

Good one

. So far have no objections.

spinn_MP · « **Reply #4 on:** November 21, 2010, 09:11:30 PM »

Think about the "center of gravity" as the "center of buoyancy". And the losses while rotating that floats (friction, water drag,..)

broli · « **Reply #5 on:** November 21, 2010, 09:33:25 PM »

Quote from: spinn_MP on November 21, 2010, 09:11:30 PM

Think about the "center of gravity" as the "center of buoyancy". And the losses while rotating that floats (friction, water drag,..)

The point is rule out conceptual or "theoretical" errors not engineering problems.

spinn_MP · « **Reply #6 on:** November 21, 2010, 09:43:05 PM »

Quote from: broli on November 21, 2010, 09:33:25 PM

The point is rule out conceptual or "theoretical" errors not engineering problems.

OK.
Which conceptual problems do you have in mind?

fritznien · « **Reply #7 on:** November 21, 2010, 11:46:27 PM »

Quote from: Low-Q on November 21, 2010, 07:52:33 PM

OK. I see the problem. Now to a more complicated thing. Which of these two objects have the most bouyancy?

I can rotate elements to increase bouyancy?

They both have the same weight and volume, and are under the same conditions as in the previous picture. The gap between the elements are big for better visuality.

Vidar

if i can assume the same displacement in each case the the buoyancy is equal.
the bottom 2 will always have the same buoyancy.
the top one will only change if its displacement changes.
next question please.
fritznien

Low-Q · « **Reply #8 on:** November 21, 2010, 11:47:08 PM »

Quote from: spinn_MP on November 21, 2010, 09:43:05 PM

OK.
Which conceptual problems do you have in mind?

Sorry for "taking" this question, but the general rule is to point out what's possible and what's not, according to Newtons laws of thermodynamics. Friction and drag are an engeneering problem rather than an impossible law-breaking issue to solve.

In my last drawing (previous in the thread) I have possibly prooved that bouyancy of two systems can be different even if they are finding themself in the same depth, having the same shapes, weight and volume. Just by rearrange the shapes we suddenly got more bouyancy force on the system to the right than the system on the left. This concept applies only for items which is fixed at the bottom - sealing the water and pressure out at the very bottom.

I am now hoping that someone can help me find a way to transfer this rearrangement into a wheel so it can start to run without braking any laws of thermodynamics... maybe letting those two be linked as a belt. See picture below.

Low-Q · « **Reply #9 on:** November 21, 2010, 11:57:15 PM »

Quote from: fritznien on November 21, 2010, 11:46:27 PM

if i can assume the same displacement in each case the the buoyancy is equal.
the bottom 2 will always have the same buoyancy.
the top one will only change if its displacement changes.
next question please.
fritznien

If the item on the left was in one solid piece, the replacement of water would be the same as the item on the right. Anyways, the item on the right has distributed the pressure vertically which is not the case in item to the left.

The gaps between the elements in items to the left are so close, so the water pressure are allmost equal both upwards and downwards. In the item on the right, the spacing are increased. Even if the displacements are the same, the difference in pressure on each surface is much different - or is it not?

I do not claim that I'm right, but this is how I see it anyways - probably until I understand more

My only claim is that this is true, only if the bottom surface are free of pressure.

fritznien · « **Reply #10 on:** November 22, 2010, 01:58:42 AM »

Quote from: Low-Q on November 21, 2010, 11:57:15 PM

If the item on the left was in one solid piece, the replacement of water would be the same as the item on the right. Anyways, the item on the right has distributed the pressure vertically which is not the case in item to the left.

The gaps between the elements in items to the left are so close, so the water pressure are allmost equal both upwards and downwards. In the item on the right, the spacing are increased. Even if the displacements are the same, the difference in pressure on each surface is much different - or is it not?

I do not claim that I'm right, but this is how I see it anyways - probably until I understand more My only claim is that this is true, only if the bottom surface are free of pressure.

an object is buoyed up by a force equal to the weight of the fluid displaced.
this a volume thing, the orientation is not a factor.
the buoyancy force is the difference in pressure between the top and the bottom times the area.
having a differant pressure top and bottom as the object turns dose not change the buoyancy because the area changes to compensate.
fritznien

Low-Q · « **Reply #11 on:** November 22, 2010, 08:35:04 PM »

Quote from: fritznien on November 22, 2010, 01:58:42 AM

an object is buoyed up by a force equal to the weight of the fluid displaced.
this a volume thing, the orientation is not a factor.
the buoyancy force is the difference in pressure between the top and the bottom times the area.
having a differant pressure top and bottom as the object turns dose not change the buoyancy because the area changes to compensate.
fritznien

You are perfectly right. Sometimes whishes are blocking elementary math and reasonable thinking

I did a quick math yesterday, and there is no bouyancy greater than the other. It ended up in zero in both cases. if there was not pressure that was applied to the very bottom of the items.
Greater bouyancy are only achieved if the volume increase, but that requires energy.

So much for the brain exercise

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Author Topic: Big brain exercise! Vector based bouyancy wheel (Read 8622 times)

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Big brain exercise! Vector based bouyancy wheel

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