11.21.06
Posted in Computational Fluid Dynamics, Dissertation Research, Tex, LaTeX, and ConTeXt at 2:04 pm by Brooks
The 2006 annual conference of the American Physical Society’s Division of Fluid Dynamics just ended a few hours ago, here in Tampa. As usual, I’ve put the slides from my talk up on dpdx.net/research/papers. Direct links: abstract, Slides in PDF form, and ConTeXt source for the slides. It’s a fun conference; unlike most, the talks are only ten minutes long, so it’s pretty easy to hit information overload by the end.
I’ll post some more about these results once I get home. I’ve been working pretty hard on this for the last few months, and haven’t had time to post much about it here, but things should be a bit less hectic soon. My code is finally producing results (luckily just in time for the conference!), and the results are considerably more dramatic than I was expecting — a pleasant surprise!
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05.06.06
Posted in Computational Fluid Dynamics, Dissertation Research at 10:21 am by Brooks
I just added the slides from my presentation at the 58th annual November meeting of the APS’s Division of Fluid Dynamics to my publications page. This is largely a modified version of the presentation I gave at the ILASS meeting last May.
Presentations at APS meetings are only 10 minutes long, instead of the 25 at most other conferences, so these slides are much tighter and more concise than the ILASS slides. I think there are definite advantages to the format; most of the presentations still seemed to contain all of the critical aspects of the research, and most of what seemed to get cut was excessive belaboring of points, and recitations of the same justifications and basic background that we’ve all heard dozens of times before. And, of course, it means that there’s time to see more than twice as many presentations in a day; when the conference packs over a thousand talks into a three-day block, that’s quite important.
One unfortunate thing about the APS DFD meeting is that the talks don’t come accompanied by papers that one can look up and read afterwards. For my presentation, though, my paper from the ILASS meeting covers most of the same results.
Oh, and at some point I’ll work out an appropriate Creative Commons license for this stuff. In the interim, if you want to borrow one of the slides or figures for something, just send me an email.
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03.17.06
Posted in Computational Fluid Dynamics, Dissertation Research at 12:31 am by Brooks
(This is a continuation of Why Simulating Free-Surface Flow is Difficult, Part 1.)
In Part 1 of this series, I talked about why it’s difficult to do an accurate computer simulation of a single drop dripping from a faucet. That’s a very simple example of a free-surface flow, however, and many of the flows that are relevant to other scientific or engineering questions are far more complicated.
One general class of more complicated free-surface flows are “sprays”, also referred to as “spray flows” or “atomization” – a liquid is forced at relatively high pressure through a small nozzle (or set of nozzles), and when it comes out it breaks up into tiny droplets. Sprays are nearly ubiquitous in any handling of liquids; for instance, in my day-to-day life, I might take a shower in the morning (under a spray of water from the showerhead), wash the shower walls with a cleaner in a spray-bottle, use an aerosol spray can of cooking oil to oil the pan to cook my eggs in, and wash the pan using the spray attachment on my sink. My car has a fuel-injected engine, which means that there are nozzles in it that spray the fuel into the air intake. If I were to paint the (sadly rusting) hood on it, I’d use a spray can. The train that I take to work has a diesel engine; the term “diesel” means that in it the fuel is sprayed directly into the engine’s cylinder, where it burns immediately as it’s being sprayed in.
In every one of those cases, it’s important to get the spray “right”. The shower-cleaner, cooking-oil, and paint sprays need to provide an even coating on the walls without spraying any off to the sides. The shower head needs to produce rather large drops that act like rain rather than fog. The fuel injectors in my car need to produce tiny droplets that will evaporate quickly, while the ones on the diesel locomotive need to produce droplets of the right size to get to the middle of the cylinder before they burn up. Thus, it would be very useful to be able to simulate the spray that comes out of a new nozzle design, so that it can be tested and improved without needing to do costly experiments.
As an example to talk about, here’s a fairly typical spray that’s easy to photograph – water being squirted through the nozzle from a Windex® bottle. I should credit my wife for patiently helping me take the picture; it took quite a few tries before I managed to get the flash timed correctly with the spray!
(click on the photo for a larger version)
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03.03.06
Posted in Computational Fluid Dynamics, Dissertation Research at 10:08 pm by Brooks
“Free-surface flows” are fluid flows that involve a surface that can move freely in response to the flow, such as the surface of the ocean, which is moved by the waves. This is contrasted to flows where all of the surfaces are fixed, such as water in a rigid pipe – or, alternately, a submarine deep under the ocean, where the only relevant surfaces are the rigid surfaces of the submarine which can only move as a solid piece.
As an example of a simple free-surface flow, consider water slowly dripping from a faucet. The surface of water across the bottom of the faucet moves downward, forming a drop, which eventually becomes heavy enough to fall and break off. I’ll use this to illustrate a couple of the reasons why computer simulations of free-surface flows are difficult.
(click on the photo for a larger version)
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