[Geysers] Model geysers - a video

[Davis, Brian L.]

Well, as it gets colder and  in situ gazing gets more difficult, I thought I'd pop up some in vitro gazing. Here's a YT video of a few of the little geysers I've made going off, as well as some explanations (I know the people on this list don't need my rather poor commentary, but I get tired of answering the same questions over & over on YT so I try to provide some background):

http://www.youtube.com/watch?v=9WxUJ6fNRCA

(and the web page with directions: http://mypage.iusb.edu/~brdavis/GeyserModel.html )

For those of you who have asked, here's a few interesting points in the video.

1) The "cone style" geysers (the first one for instance) shown actually do recycle their water: the cone is a screw-on female adaptor, with four small holes drilled around the lower edge (below the water line), so that water slowly drains back into the conduit after the eruption but the pool water does not interfere with the eruption itself. This works really well, and allows for a variety of screw-on vent types to be tried out (usually swapped in and out while the geyser is running actually).

2) At 3:05, you can see the laser light shining through the flask, as well as hitting the sensor in the upper left corner of the frame. This has proven to be a remarkably accurate way to monitor conditions in the flask, including temperature actually (as the water temperature changes the refraction of the laser changes enough to be detectable).

3) The steam bubbles collapsing after 4:01 are fascinating to watch, with that characteristic "flickering" look even in the tiny 1" glass tube. I may invest in some short but larger diameter glass tubes when I figure out how to make larger diameter systems (CPVC goes up to about 1", and while PVC is available much wider, it does *not* handle the temperatures well... not well at all. Anyone want to twist a piece of PVC into a pretzel?). 1" systems and wider *do* show conduit warming to the point where it looks like you can initiate a "top down" eruption like OF's (but the one example I've managed was not properly instrumented, and collapsed over the kitchen floor due to too much water in collecting in the basin and 1/5" PVC pipe failure under high temperature).

4) The tall outdoor models (at 4:41 and beyond; two models actually) did not both erupt; the first blew the rubber stopper out just as boiling began in the chamber on two separate attempts. The second did erupt, more than once, but I was not able to get it on video for a variety of reasons. The trick was using a flexible rubber coupling (seen at the bottom of the frame at 4:49) to lock the outside of the flask to the outside of the CPVC pipe above it using hose clamps. This works *very* well, far better than rubber stoppers actually, but mates only wide (large) flasks with wide pipes. They're really interesting models to try to set up, however, and heat losses are such that I'm not going to be able to run them during the winter (Hmm, unless Laura let's me run them in the 2-story entryway... no, probably not).

5) At 5:01, the big chunk of styrofoam behind the vent is cantilevered onto a force sensor: s the water in the basin rises, more of the styrofoam is under water, so it pushes up harder on the force sensor. That actually allows water level sensing with a resolution of about 0.5 mm, rather useful for these models (you can determine the amount of water pushed out of the vent).

6) The odd "breathing" behavior at 5:27 is what happens when you use a galvanized 1" pipe wrapped in a high-temperature heating tape as the heat source, instead of a flask heated from below. There were a number of interesting models using this heating tape, but they suffered from a much lower heating rate (which caused problems with heat loss) and expense (the smallest, cheapest tape I could find was $100). Using this "heated pipe" model did allow simulation of Jeff Cross's hypothesis of how systems like Turban-Grand function, with insteresting results. I just need more power to pull off significant eruptions.

7) I'd love to know who the gazer was that you hear at 6:31, but at the time I had no idea who you guys were... I was just following around a bunch of extremely knowledgable folks in floppy hats who for some bizarre reason were carrying various umbrellas on a spotless, hot, rain-free July day. I understand now :).

I've done probably about 40 different models in the last year, but the attraction of "bigger" is getting hard to ignore...

-- 
Brian Davis