Received: from hpoclrf.sj.hp.com by opus.hpl.hp.com with SMTP (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA23204; Fri, 25 Aug 1995 13:17:45 -0700 Return-Path: <kirk@hpmsd3.sj.hp.com-DeleteThis> Received: by hpmsd3.sj.hp.com (1.37.109.16/15.5+IOS 3.22) id AA201631863; Fri, 25 Aug 1995 13:17:43 -0700 Date: Fri, 25 Aug 1995 13:17:43 -0700 From: Kirk Lindstrom <kirk@hpmsd3.sj.hp.com-DeleteThis> Message-Id: <199508252017.AA201631863@hpmsd3.sj.hp.com-DeleteThis> To: Geoffrey.Boehm@wj.com-DeleteThis, wind_talk@opus.hpl.hp.com-DeleteThis Subject: Re: Re[2]: WIND_TALK digest 63
Well, I'm in an onary mood and want to bore those that don't care and
get better understanding for those that do. I might even be wrong, has
happened in the past, but I think I'm right on this.
Don'r read on if you are sick of talking about currents....
----------------------
Well, I DID give a spring model which is more intuitive, but the EE
model is more accurate at the expense of ease of understanding.
> How ironic that there are actually windsurfers who find electrical
> objects more intuitive than water. Only in silicon valley.
>_________________________ Reply Separator _________________________________
> Subject: Re: WIND_TALK digest 63
> Author: James.Paugh@Eng.Sun.COM-DeleteThis (Jim Paugh) at INTERNET
> Date: 8/25/95 11:17 AM
> > "What I would like to hear is an explanation of why slack current occurs
> > after say, a low tide. For instance, today, low tide at Crissy is at
> > 5:03pm, but low slack is at 7:29pm! How is it that slack current occurs
> > 2.5 hours after low tide? "
>
> > The best explanation I have heard on this was Ken Poulton's a few
> > months ago on the wind_talk list. He compared tidal dynamics to
> > electron flow within a wire. At the outside, resistance to the flow
> > is greater than in the middle. So at the point where the flow stops
> > on the outside, the flow is still moving at the center.
> >
BzzzzzP.....
I don't remember Ken stating it this way....
In truth, electricity flows uniformally thru a wire until the freuency
is high enough for "the skin effect" and this sez the electrons travel
on the "outside" of the wire and NOT in the center.....
excuse me for boreing the rest of you...8-)
> > Consider the analogy to the Bay: at the edges we have relatively
> > shallow mud flats that offer a lot of resistance to the current. In
> > the center you have a deep shipping channel where the water flows more
> > freely. So at the low tide, the resistance of the mud flats on the
> > edges just matches the current flow, and you have a zero current at the
> > edge. But in the middle of the channel the ebb is still continuing,
> > and it doesn't stop until a later time, because there is less
> > resistance to stop the outward flow.
>
No. Way off. Doesn't explain the lag time. Must be a software guy or
a shoe salesman....8-)
> Kirk Lindstrum writes:
>
> > It has to do with the shape of the bay. If you are an EE, then you can
> > model the bay as a bunch of capacitors in each big, deep section and
> > each "straight" as an inductor with the largest inductor at the Golden
> > Gate. The "system" is driven by tide height (Voltage input) at the
> > Golden Gate. Voltage is the same as tide height and current is the same for
> > both with one being water and the other electrons.
>
> Oh, NO! The dreaded EE analogy! Picture a blank stare on my face, eyes
> glazed over, mouth agape :^o
>
> Thanks guys, for trying, but I think I'll stick to the tidal wave rolling
> through the Golden Gate analogy!
>
Problem with this analogy, I believe, is that it is WRONG!
Think a bit. 6 hrs from San Diego (or Hawaii or Equador) to get to the
Gate and then it slows down enough to take 6 hours to only go a few
miles? I don't think so. Why would it slow down? What absorbed the
energy? Tides are explained well by Relativity.
you can think of tides as a blanket over a bed where you, acting as
gravity, pull on the center of the blanket and it rises towards you.
The parts of the blanket all move just a bit towards you, but they don't
really flow far. Relativity explains why we get two peaks and not
just one (the way I understand it....).
yet another spring analogy:
It is really very simple. loop several rubber bands together. Tie
something to the end and loop the other end around your hand. Hold your
hand out suspending the object by the rubber-band-spring. Now drop your
hand 1 ft and observe that the object on the end of the rubber band
drops further than one ft. unless you do it VERY slowly.
> ~Jim
>
enough! 8-)
until I feel the need to bore more....
Kirk out
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