Re: Scientific Errors (Proof)



Dennis B wrote:
Dennis B wrote:
blair.houghton@xxxxxxxxx wrote:
Dennis B wrote:
To further prove that a fluid exerts an increased force of pressure as
the velocity of the fluid increases, take for example a water powered
piston. Water is an incompressible fluid and therefore cannot (easily)
change in density. Therefore, as the water enters the piston, most of
the force of the fluid is then translated into moving the piston. If the
flow of water into the piston is increased (in other words if the fluid
velocity is increased) the water exerts a greater force or pressure upon
the piston, does it not?

It does not. In general, when trying to get a greater force into
such a volume, it is necessary to increase the volume more slowly.

TEll that to racecar engineers and they'l laugh you off of the
racetrack. There is some truth in what you say though in that a lower
velocity is more efficient at transfering force because a higher
velocity results in higher viscous head or friction losses. And by the
way, how do you get more force at a lower volume? I would imagine by
using a large pump with a piston having a large surface area?


Or rather, with a hydraulic press? Of course, that is not how a race
carengine functions. A racecar engine uses a combustible fuel which
expands when it is converted from a liquid to a gas as it burns. To get
more force and therefore more power from a racecar engine you have to
use fuels that push the piston harder by having more explosive force.
The greater the explosive force of the fuel, the greater the velocity
and pressure it imparts. Furthermore, a more explosive fuel fills the
chamber more quickly when it explodes.

Same thing happens when you want to increase leverage. You can't
raise an object as fast, but you can raise a heavier object.
Same
thing
happens when trying to impart knowledge to a denser skull. Speak
slowly. Speak clearly. Repeat the idea several times, a little
different
each time.

Conversely, only when water is withdrawn from
the piston does the force of pressure decrease, in which case the water
and the piston move in the opposite direction. SUCK ON THAT all you
adherents of the Bernoulli Principle myth!

How can you believe that it's a myth when it's clear that you have
no experience with the data?

I know enough to see that there are some obvious errors in the existing
theories. As for the accusation that I have no experience with the
data, you are very mistaken. I know what the observed facts are. I have
a basic understanding of the processes involved. Not to say I haven't
much yet to learn. Learning never ends. Yet, I have a right to speak my
mind. And I call it as I see it.

How can you speak about it in any
way when it's clear that you have never actually read the statement
of the theorem?


You are making false accusations. I am VERY familar with Bernoulli's
principle. My understanding is internally consistent. Yours is not.
Your beliefs violate the conservation of momentum and energy laws, the
fundamental laws of motion (ma = F), *AND* doe not agree with observed
phenomena. If pressure decreased as velocity increased, there would not
be any increase in friction loss. In other words, there would be no
friction. Of course, Bernoulli's equation does not apply to viscous
fluids such as air or water and therefore does not include friction in
it's pure form. This is not because there are no friction losses with a
viscous fluid. It's because Bernoulli's principle applies only to
inviscid fluids. In other words it only applies to super-fluids.
Therefore, one could rightly call Bernoulli's principle a myth (with a
seed of truth in it), although my original point was that Bernoulli's
principle as it is COMMONLY taught (being used to explain the function
of an airplane wing) is a myth.

In the steady state - constant velocity - if the external load is
constant, the pressure in the piston is the same whether you
are increasing or decreasing the volume. There will only be an
increase or decrease in the transient phase, when the velocity
is changing. And the assumed conditions for Bernoulli's principle
do not apply to transients.

I hesitate to say this because I know it will blow your tiny, ossified
mind, but, because of Bernoulli's principle, in the steady, nonzero-
velocity state, the pressure in the feed tube for the piston is lower
than the pressure in the piston body - no matter which direction
the piston is moving.

But wait! you say. How can I start it moving without increasing
the force on the distal end of the feed tube? Increasing the force
must increase the pressure! Well, it does. But that's the transient
phase. By the time the transients end and the steady state is
reached, the boundary condition for the pressures has changed
from equal pressure in both places to a lower pressure in the
feed tube. In the case of a perfectly incompressible fluid, this
transition takes zero time. Real fluids aren't incompressible, but
they're close. So what happens is huge shockwaves transit the
system. And we've discovered the property of "water hammer".

I'll say it again (for reasons I've outlined above): when the
piston is moving in the steady state, the pressure in
the feed tube is lower than the pressure in the piston, no
matter which direction it is moving. Bernoulli applies.


I presume this is because of inertia in the piston? It keeps the piston
going even though the fluid flow from the feed tube has stopped?

Before you try to tell me I'm wrong about this, which I may be,

Only because it is difficult to understand your explanations...

I
should emphasise one again that this seems to me a trivial detail which
is irrelevant to the discussion of basic fluid dynamics...

-Dennis B

.

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