Not saying it can't be done, but like one of the earlier contributors noted from his previous work in modeling fluid flow systems with Navier-Stokes, I'd be astonished if a numerical simulation of water draining out of a sink (through a slotted grate no less) produced results that were verifiably correct. I'm also working with PSC, btw on an NIGMS-funded project. This might make for an interesting discussion topic for them: modeling approach, boundary condition definitions, physical container geometry, measures of "correctness" for evaluating results.
I actually think weather modeling is a much easier problem, if for no other reason than the complicated sink topography. Heck, go ahead and take the grate out: it's still a difficult problem. Note that I changed the topic subject line... --Doug On Tue, Jul 5, 2011 at 4:43 PM, Frank Wimberly <[email protected]>wrote: > > - First, you asked a question that probably can't be answered, even > with the most powerful, sophisticated tools available to us today.**** > > Doug,**** > > ** ** > > At the Pittsburgh Supercomputing Center we had users who modeled the Gulf > Stream and the formation of tornadoes. The latter, Kelvin Droegemeir, > monopolized our biggest machines every morning in June to predict, with some > success, the locations of that afternoon’s tornadoes in Oklahoma. Is it > really too difficult to model water running out of a household sink? Wasn’t > that Nick’s question?**** > > ** ** > > Frank**** > > ** ** > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Douglas Roberts > *Sent:* Tuesday, July 05, 2011 2:01 PM > > *To:* The Friday Morning Applied Complexity Coffee Group > *Subject:* Re: [FRIAM] Experiment and Interpretation**** > > ** ** > > I must say Nick, that was a rather immature response, even by my standards. > **** > > ** ** > > Let's look back at this thread for a moment:**** > > - First, you asked a question that probably can't be answered, even > with the most powerful, sophisticated tools available to us today.**** > - Several of us tried to explain why this was so.**** > - Some of us joked with you.**** > - You persisted, even implying that an unnamed few of us were being > snobs by refusing to answer your simple little question.**** > - We pushed back.**** > - You left in a huff.**** > > Think about it for a bit...**** > > ** ** > > --Doug**** > > ** ** > > ** ** > > On Tue, Jul 5, 2011 at 1:47 PM, Nicholas Thompson < > [email protected]> wrote:**** > > Ok. I got it. You guys don’t want to talk about this subject, you don’t > want ME to talk about it, and nobody else really wants to talk about it. > So, I declare this thread closed. Please don’t post any more responses to > this thread. You want to make off color remarks, find you own damn thread. > **** > > **** > > N**** > > **** > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Douglas Roberts > *Sent:* Tuesday, July 05, 2011 1:05 PM**** > > > *To:* The Friday Morning Applied Complexity Coffee Group > *Subject:* Re: [FRIAM] Experiment and Interpretation**** > > **** > > Simply titillating, Pamela.**** > > **** > > --Doug**** > > On Tue, Jul 5, 2011 at 11:01 AM, Pamela McCorduck <[email protected]> wrote: > **** > > I find this discussion fascinating, especially because it mirrors an > ongoing discussion between me (liberal arts trained) and my beloved (applied > mathematician/computer scientist). In over forty years, we've found that we > can talk to each other at some level about these issues, but I don't expect > him to read a novel the way I do, and he doesn't expect me to understand > physics (and God knows, not fluid dynamics) the way he does. We speak in a > kind of pidgin. It's okay.**** > > **** > > Tangentially, one of my favorite tee shirts has a bit of the Navier Stokes > equation on it. People without any knowledge of physics just laugh. (Idea > is: Which part of .... do you not understand?) Physicists scrutinize my > chest and eventually say (to a man): Uhm, there's a syntax error there.*** > * > > **** > > P.**** > > **** > > **** > > On Jul 5, 2011, at 10:35 AM, Douglas Roberts wrote:**** > > ** ** > > Interesting, Bruce, thanks.**** > > **** > > BTW: on the subject of being of use to Nick re: his burning question of why > water goes down the sink drain the way it does, Nick appears to have > rejected the characterization of this phenomenon as a "really, really hard" > fluid flow systems problem requiring graduate-level studies in the specialty > areas of fluid dynamics sciences as the necessary basis for developing an > answer.**** > > **** > > Which leaves us where? **** > > **** > > Apparently with Nick bitching that no one will answer his question. I > mean, it's a simple question, right?**** > > **** > > Also, as to Nick's suggestion that this list should refocus on complexity > issues: I don't think I've ever worked on a more complex problem than when > I was developing simulations of fluid flow systems. **** > > **** > > But, it was just a simple question, right?**** > > **** > > --Doug**** > > On Tue, Jul 5, 2011 at 10:21 AM, Bruce Sherwood <[email protected]> > wrote:**** > > I can offer some historical context on why physicists at least are, on > average, unlikely to give Nick much help. > > In the 1950s Halliday and Resnick, then at Pitt, created a new-style > intro university-level ("calculus-based") physics textbook, for the > freshman/sophomore course taken by engineering and science students. > Their motives included emphasizing depth rather than breadth, as > existing textbooks tended to be shallow surveys of a vast field. At a > conference at RPI honoring Resnick upon his retirement, Resnick > explained that in the service of the laudable goal of emphasizing > depth they had to eliminate some topics, and one of the topics they > mostly dropped was fluids, reasoning that the basics were covered in > the high school survey course. > > With time, the book universally referred to as "Halliday and Resnick" > gathered a huge audience and is still at this very late date the most > widely used university textbook (now "Halliday , Resnick, and > Walker"). There was a trickle-down effect, because high school physics > is strongly influenced by university physics."Since Halliday and > Resnick downplay fluids, so will we", and as Resnick ruefully > acknowledged in his retirement address, fluids basically disappeared. > Fluids even disappeared from the curriculum taken by physics majors. > It is not much of an exaggeration to say that most physicists today > know very little about fluids (with exceptions, of course). > Occasionally there are clarion calls for bringing fluids back into the > education of physicists, but I've not seen any significant movement in > that direction. > > In our own university intro physics textbook ("Matter & Interactions"; > see matterandinteractions.org), Ruth Chabay and I emphasize starting > analyses from a small number of fundamental principles rather than > from one of a very large number of secondary formulas, and we > emphasize the insights available from exploiting simple atomic models > of matter. In the first chapter we comment that in the service of > these emphases we'll analyze solids and gases but not liquids. Solids > have the simple property that the atoms don't move around very much, > and gases have the simple property that the atoms interact rather > seldom, whereas in liquids the atoms move around a lot AND they > continually interact. So in our own small way we contribute to the > continuing absence of fluid mechanics in physics curricula. > > I'll add that my own perception is that fluid dynamics is really > really hard. It is a fiercely complex phenomenon. I don't think I've > ever seen a popular-science treatment of fluids, whereas there are > lots of good books on "simple" stuff like quantum mechanics.... > > Bruce > > P.S. My own undergraduate education was in engineering at Purdue, and > I had a wonderful aeronautical engineering course on fluid dynamics > taught by Paul Lykoudis and using the textbook by Prandtl. Alas, I > never used this knowledge and it atrophied, so I'm no use to Nick.**** > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org**** > > > > > -- > Doug Roberts > [email protected] > [email protected]**** > > http://parrot-farm.net/Second-Cousins**** > > > 505-455-7333 - Office > 505-670-8195 - Cell**** > > **** > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org**** > > **** > > > "In humans, the brain is already the hungriest part of our body: at 2 > percent of our body weight, this greedy tapeworm of an organ wolfs down 20 > percent of the calories that we expend at rest."**** > > **** > > Douglas Fox, Scientific American**** > > **** > > **** > > > ============================================================**** > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org**** > > > > > -- > Doug Roberts > [email protected] > [email protected]**** > > http://parrot-farm.net/Second-Cousins**** > > > 505-455-7333 - Office > 505-670-8195 - Cell**** > > ** ** > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org > -- Doug Roberts [email protected] [email protected] http://parrot-farm.net/Second-Cousins <http://parrot-farm.net/Second-Cousins> 505-455-7333 - Office 505-670-8195 - Cell
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