How are you changing the volume of ‘A’?


Without some mechanism (and energy input) the transition between steps 2 & 3 will not occur in the manner as stated.


“unlocking” the width of A, will simply compress ‘A’ to its’ minimum width at any point in the diagram. Water pressure at every depth = > 1 ATM
This forces air out through the tube and ‘A’ will remain at its minimum volume.

In your opinion will object A move up, down or remain stationary based on calculating Fb1, Fb2 and any other factors which you believe are relevant?

https://www.youtube.com/watch?v=PZ4Ri2l4W8w

This guy tried to use the same principle... No pressure on the sides. It didn't work.

The important thing about buoyancy, it is the result of water moving downward with gravity. If Mass moves downwards, it will move. If it can't, it won't. Mass can't move downwards throughout the entire cycle unless you are filling it back up at the top and releasing some from the bottom.

Identify when in your system mass moves downwards and when water mass moves upwards. Then you will know when it isn't going to move.

some observations...

panyuming design would function given that..

1. Seeping of the fluid into in between the fixed wall and the outer
surface of the pontoons can be prevented without creating to much friction.
2. The exception to Archimedes's is a valid exception.

A rubber like surface on the outside surfaces of the pontoons and upon the
inner face of the fixed wall might prevent the fluid's seepage.

The design referenced by Tarsier-79 in the video

@ https://www.youtube.com/watch?v=PZ4Ri2l4W8w

is only, in part, the same principle as is the Novus's design.
The design referenced by Tarsier-79 in that video does not
incorporate the bottom or side case exception to Archemedes's principle,
in that the sides are missing from the floats, at all times during its operation.

i.e. during both the submersion and the rising.

 

Does that actually make any difference?

Do you mean...

1. is the Archimedes principle exception valid ?
   or
2. that, assuming the Archimedes principle exception is valid, "does that actually
make any difference ?"

Answer to # 1. I don't know if the Archimedes principle exception is valid or not.

It is an idea I myself pondered in the past, but didn't have enough balls to consider
that I might actually be correct / had not heard of it from any source / had not the means
to test the idea.
                            It makes sense to me.

Answer to # 2. Yes, it makes a difference,

In the Panyuming design @

https://overunity.com/19459/buoyancy-calculations-making-use-of-an-exception-to-archimedes-principle/msg577132/#msg577132

the aluminum pontoons touching the fixed wall, will be less buoyant than the
pontoons that have all sides exposed to the liquid.  The wheel will have an
imbalance in the forces causing pontoons to rise and therefore, the wheel will
have a tendency to rotate clockwise, if the Archimedes principle exception is valid.

The question remains if the object in the example given in my earlier post will move up, down or remain stationary, preferably supported by calculations rather then general concepts on buoyancy, water displacement etc.

Anyone knows the answer to this question?

Let me know if the question is not clear and/or if relevant information is missing.

Thanks.

Novus, I don't know the answer. I suspect if there was no seal on the sides it would lift.

Given that the density of the object is less than the density of the fluid the standard Archimedes principle is applicable and the object would rise.

I suspect if you don't interrupt the seal, it will stay put,

I find this hard to believe since it would need to apply to any given depts, surface areas and density of the object in relation to the density of the fluid.

The following factors relate to the question raised in relation to the example scenario;
1.   There are no lateral forces on the trapezium shaped object when the exception to Archimedes’ principle applies to both sites?
2.   The force on the bottom of ‘A’ = h2*p*g*A which in the example given equates to Fb2 = 6*p*g*8 = 48pg
The force on the top of ‘A’ = h1*p*g*A which in the example given equates to Fb1 = 4*p*g*10 = 40pg
Since Fb2>Fb1 the result would be a net upwards buoyancy force? Since ‘the density of object A is slightly less than the fluid’ the object would start to rise and increase in volume? As per below picture 1 we would exchange a loss in Fb for an increase in volume?
3.   Any other forces/factors which are applicable to the scenario?

Your other problem, to get it down to start with you need to make the assembly denser than water. It sinks to the bottom and wedges itself against the sides and somehow we seal it. Then to move back upwards, it needs to be less dense to float up and expand..... I think that is a killer of your design.

See picture 2 below based on the initial post which would result in a net gain when the answer to the example would be that the object rises upwards and increases in both volume and buoyancy.
As for the practical implications and the challenges with sealing the sites water tight and lock and unlock the seals I propose to leave this aside for now and focus on why this should fail even in theory.

Information on the internet on the bottom (and side) case exception to Archimedes’ principle which I have been able to find is limited with no example found when the exception applies to both sides of an object:

https://arxiv.org/pdf/1110.5264.pdf

"The existence of exceptions to Archimedes’ law has been observed in some simple experiments in which the force predicted by AP is qualitatively incorrect for a body immersed in a fluid and in contact to the container walls. For instance, when a symmetric solid (e.g., a cylinder) is fully submerged in a liquid with a face touching the bottom of a container, a downward BF is observed, as long as no liquid seeps under the block [2, 13, 14, 15, 17]. Indeed, the experimental evidence that this force increases with depth (see, e.g., Refs. [2, 15, 16, 17]) clearly contrasts to the constant force predicted by AP. These disagreements led some authors to reconsider the completeness or correctness of the AP statement, as well as the definition of BF itself [2, 14, 15, 16, 18], which seems to make the things more confusing yet."

@ Tarsier (and anyone else who wants to join the discussion) – can you maybe have an other look at this since we both agree that a gravity/buoyancy based design will never work.