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Re: Sloshing Damping

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Aha !  What a Wright-eous FABLE !  Indeed a quagmire for anyone wanting to look up the word quagmire.

Yes, a 3-D element takes alot of understanding.  they are not very robust elements.  they are short-sighted suckers.  one needs many of them to make them work. 

can you tell us about a 3-D element modeling scenario that would work?  actually i have never modelled fluids as I suggest.  but it seems very possible.  one just needs to be able to input the properties in a way that can make it work.

however, thinking about the tiger, he is probably the computer, and when one jumbles so many elements into a computer and tries to make it work in dynamic mode, one probably gets the skewer over and over again. 

with computers as they are becoming, it may be very easy to run such a calculation, no?  why not exactly?  it could be an interesting exercise to say the least.

On 11/22/06, Christopher Wright <chrisw(--nospam--at)> wrote:

On Nov 22, 2006, at 2:20 PM, refugio rochin wrote:

> why not throw aside the equations, and run a discreet FE model trying
> to match actual activity in a tank.
One reason is that the problem isn't trivial. Anyone who thinks a good
3D element makes him king of the world should pay heed to the

FEA is like a sharp stick. The newbie may pick up such a stick and heft
it a little and try out the sharp point on his finger. 'My, what a nice
stick,' he thinks. He waves it around and people step aside; he uses it
to spear ants, then beetles and even tiny lizards. He finds the stick
useful as a lever for moving large objects with comparative ease.
Picking up a book he sees duellists overcoming their enemies, obtaining
free drinks and sexual favors with things that resemble sharp sticks.
So the newbie says to himself, 'This stick makes me powerful and
superior to others who have no stick. The stick allows me to overcome
nature and force people to do my bidding. I shall become a duellist and
win free drinks and sexual favors because I am a cool stick-master.'

Now engineering is like a tiger. Both are powerful and elegant but when
mishandled they can be very dangerous. An engineering project, like a
tiger, requires judgement and a respectful approach because small
errors can have catastrophic results. Like the large energetic objects
encountered in engineering practice, the tiger is also large and
energetic and behaves according to its nature, not always as we think
proper. A wise person makes allowances for such behavior and acts
cautiously and thinks over each move carefully.

As for the newbie, as he strolled along the forest path waving his
stick and spearing beetles, he encountered a dead tiger. 'Ha!,' says
he. 'I shall illustrate my power over nature by poking this dead
creature with my stick and thus gain many free drinks and sexual
favors.' Fortunately for the tiger, but unfortunately for the newbie,
the tiger was merely napping, and at the first poke it swatted the
newbie and killed him with a single blow. And after lunch, the tiger
amused itself by batting around the stick and the remains of the newbie
before urinating on both and raking leaves and dirt over the mess.

The lesson, O beloveds, is this: The wise newbie does not mistake
marginal skill with a useful tool for knowledge, and takes a stepwise
approach to large energetic objects  with due regard for the
consequences of poor judgement.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania

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