[Geysers] RE: Model Geysers

[Davis, Brian L.]

> How high does this model go, like how high does the single
> chamber go?  How high does the Multiple chamber go in
> minors and major?

It's hard to tell. First, because most of the modeling I've done I cover the top of the catch basin with a lid or saran wrap or something similar. I'm doing these, for the most part, in my kitchen, so not hitting the ceiling is a very good idea. Also, how high the model will go depends a lot on the size of the vent - put in a smaller cross-sectional area vent (a constriction), and conservation of mass is going to produce much higher ejection velocities. I tried this outside and video-taped the results once however, just to determine potential height (& ejection velocity). The model was a 1 L flask with a 3/4" standpipe above it, reducing to 1/2" very near the top. Right at the vent it reduced to 8 mm in diameter, and the entire conduit was about 2 meters tall (base of flask to tip of nozzle). The system erupted in a rapid multi-burst fashion, with the 1st burst hitting 20", the 2nd burst hitting 26", and at least one later burst rocketing water 54" above the vent (almost 70% of the conduit depth). From the video it's clear it would have gotten higher if not for the falling water crashing directly back down on the next rising jet (I should have had it at a slight angle I guess).

The problem is I can almost always make a "taller" eruption by swapping in a smaller nozzle, and since I'm doing it inside I usually don't want a tall, messy eruption either, so it's not something I've studied a lot.

As to systems with majors & minors... which system? There are some systems with single chambers and single conduits that show this sort of behavior; I also see it in dual-chamber, single conduit models where the chambers join near the base of the conduit, two very different cases.

As just another single example, putting two 500 ml flasks on similar heat fluxes with a shared conduit results in majors (both chambers end up erupting together, with one triggering the other) that raise the pool temperature 6° C in my model, with a post-eruption interval of about 2 minutes. But there's also  a minor mode (on chamber erupting but being suppressed by interactions with the 2nd chamber) that occurred about twice as frequently, where the pool temperature only warmed 0.8 °C and the interval was about 0.8 minutes. So in this model, minors were roughly 8 times "weaker" than majors, but happened twice as frequently. The intervals in this model were very clearly bimodal, with a histogram showing two clearly separate peaks. In addition majors had a tendency to follow majors, while minors had a tendency to follow minors. By shifting the two chambers on the hotplate (and thus changing the heating rate independently) a lot of variations on this could be generated.

Putting in a "bedding plane" (a double section of horizontal conduit) also ended up producing major/minor behavior, but major were less frequent (I didn't have enough for statistics). Putting a wide (1") section nearer the top of the narrow (1/2") conduit also resulted in majors (4 °C pool temperature rise) & minors (0.6 °C pool temperature rise).

There is a *large* "phase space" of geyser plumbing to play around in here, and I'm not positive where it's best to look next. I did try a 15' tall one today, but couldn't get it to work (twice it got close, before vibrations from the steam collapses dislodged the rubber stopper from the top of the 2 L flask: 110° C water flashing to steam it really impressive... preferably from a safe distance. It tends to do bad things to the monitoring electronics as well).

-- 
Brian "sorry for the long answer" Davis