[Geysers] Blog post about geyser mechanisms

[Carlton Cross]

Well, I neglected to describe the size of this one.  It's made from 8 
in well casing.  The water chamber is 9 ft long with a 2 in exit pipe 
that is about 6 ft long.  It holds about 25 gal of water with 6  2 kW 
heating elements.  So, this is not a starting point.

Long ago, I wrote some instructions for making a small geyser from a 
juice can and some copper tubing, but I can't find them now.  It 
requires soldering to seal the exit tube into the can lid.  Pineapple 
juice cans last longer because they have a coating to protect from 
corrosion.  The exit tube can be 1/4 in or 3/8 in copper about 3 ft 
long.  It's also nice to have a funnel on top to catch most of the 
erupted water although the eruption will be much higher without a 
funnel.  You have to catch the erupted water if you want to get a 
true cycle.  Otherwise, you have to refill the system after each eruption.

I think there are other people who have made small models more 
recently than I have, so maybe they'll chime in.

Carlton Cross
cross at bmi.net


At 01:24 PM 9/9/2013, you wrote:
>Have you got a detailed description of your set-up that could be 
>posted? Zayne's old enough now that we could attempt to have Webb 
>family driveway experiments, and this looks like a neat set-up if 
>you can compare overflowing/non-overflowing and vertical vs. horizontal.
>Karen
>
>[]
>
>
>On 9/8/2013 10:33 PM, Carlton Cross wrote:
>>What you describe sounds like what I remember.  Jeff may have 
>>something to add if my memory needs correction.  (I haven't had 
>>time to dig up our old data.)
>>
>>There are many features of a geyser's plumbing that will affect the 
>>frequency of oscillation, the main ones being the combined volume 
>>of the bubbles, the mass of the water above the bubbles, and the 
>>size and friction of the passage leading to the surface.  Smooth 
>>pipes that are cooled by the outside air are not very good models 
>>of geyser plumbing, but I think it's interesting that the behavior 
>>of the models can be seen in some natural geysers.   I don't 
>>remember finding a geyser that displayed the rapid bouncing, but 
>>that is no surprise because the friction in a natural geyser tube 
>>is much greater than in a smooth pipe and the mass of the moving 
>>water is generally greater.  As the friction increases, the 
>>frequency of oscillation will decrease; and, as the moving mass 
>>increases, the frequency will decrease.  I can't think of any 
>>reason why a natural geyser would oscillate faster than the models.
>>
>>Carlton Cross
>><mailto:cross at bmi.net>cross at bmi.net
>>
>>From: 
>><mailto:geysers-bounces at lists.wallawalla.edu>geysers-bounces at lists.wallawalla.edu 
>>[mailto:geysers-bounces at lists.wallawalla.edu] On Behalf Of Demetri Stoumbos
>>Sent: Sunday, September 08, 2013 5:24 PM
>>To: Geyser Observation Reports
>>Subject: Re: [Geysers] Blog post about geyser mechanisms
>>
>>I find it interesting that your experiments produced two distinct 
>>patterns of water column bouncing.  In my backyard modeling 
>>experiments, I have found that the system starts out with the 
>>"rapid" form of bouncing, and then progressively shifted to the 
>>"slow" form.  I noticed this both in models which overflowed 
>>between eruptions, and those in which the water level naturally sat 
>>a little bit below overflow.  As the eruption neared, the bouncing 
>>would decrease in bounces per second, increase in amplitude, and 
>>become more erratic.  That is to say that a water level vs time 
>>graph would start out looking like a sinusoidal wave, but then the 
>>ordered nature of the curve would deteriorate as time went on as 
>>the water level stalled for split seconds or bounce around at peaks 
>>and troughs.  Of course in the overflowing systems, the actual 
>>water level was constant at vent level, so I went off of how much 
>>water overflowed per unit time.  In these systems, as the bouncing 
>>progressed to "slow" form and its amplitude grew during an 
>>interval, the low parts of the bouncing would become low enough 
>>that overflow would momentarily stop (think Depression or Oblong).
>>
>>I guess my end question is: did your models show an either/or 
>>pattern in relation to the two forms of bouncing, or did they start 
>>out with the "rapid" form, then at one point flip over to "slow" form?
>>
>>Demetri Stoumbos
>>
>>On Sun, Sep 8, 2013 at 2:32 PM, Carlton Cross 
>><<mailto:cross at bmi.net>cross at bmi.net> wrote:
>>A quote from the below link,
>>
>>"There, after an eruption, more and more steam can accumulate 
>>between the surface of the water and the roof of the cavity, 
>>gradually building up pressure. When the pressure grows too high, 
>>the steam and water escape through the geyser's vertical shaft."
>>
>>and
>>
>>"They found that pressure builds up in a bubble trap there between 
>>geyser eruptions, just as in the Russian study."
>>
>>I haven't had time to locate and read the referenced sources,  but 
>>I think it's important to note that pressure build-up is not what 
>>causes an eruption.  Also, the Cross driveway experiments have 
>>produced geyser models that demonstrate eruptions from an entirely 
>>vertical system with no places for trapping steam.  Pressure gages 
>>along the water column show clearly that the pressure everywhere 
>>decreases continuously once the eruption has started.  The 
>>temperature also drops because the steam carries heat out of the 
>>system.  Eruptions in a vertical system were not noticeably 
>>different from those of a horizontal system.
>>
>>The static pressure within a fluid system is determined by the 
>>depth below the surface.  When you dive into water, you feel 
>>greater pressure as you go deeper.  It doesn't matter whether 
>>you're in a chamber with vapor or not.  In a horizontal chamber, 
>>the static pressure will be determined by the pressure at the 
>>chamber exit to the surface, and the pressure at the exit will be 
>>determined by the depth below the surface.  As a geyser system 
>>fills after an eruption, the depth of the water increases until the 
>>start of overflow.  After that, the temperature will increase, but 
>>not the static pressure.
>>
>>Steam within a horizontal chamber will displace water from the 
>>chamber.  That water must exit through whatever passage leads to 
>>the surface where overflow will occur.  Hence, the effective depth 
>>of the water above the chamber will not change and the static 
>>pressure will NOT increase.
>>
>>Once a geyser system has reached overflow, it can and does continue 
>>to heat, and, at some point, a small section of upward-moving water 
>>will rise until it reaches a place where the static pressure is low 
>>enough for the water to boil and produce steam.  The expansion of 
>>the steam will displace water from that region, and, 
>>simultaneously, the steam bubbles will begin to rise.  As the 
>>bubbles rise in the water column, the static pressure at all points 
>>below the bubbles will decrease because water with bubbles weighs 
>>less than water without bubbles.  Finally, when the pressure drops, 
>>the boiling point drops and more water will boil which produces 
>>more bubbles which allows more water to boil, etc.  The system has 
>>gone unstable and the expanding steam will begin to rush toward the 
>>surface exit - an eruption.
>>
>>So far, I have talked only about the static pressure which is 
>>determined by the depth within the system.  There are, of course, 
>>dynamic pressure changes related to water movement.  Once steam has 
>>accumulated within a chamber or the water column, the whole column 
>>can bounce up and down because the steam below is 
>>compressible.  When the column rises, the steam expands and the 
>>pressure drops eventually to the point where the upward motion will 
>>decrease, possibly until it stops and then begins to fall.  The 
>>downward motion will compress the steam below and the pressure will 
>>rise, possibly causing the steam to condense into water.  When the 
>>pressure is finally great enough to stop the downward motion, 
>>expansion can begin again, pushing the water upward.
>>
>>Our driveway experiments clearly produced two forms, rapid and 
>>slow, of a bouncing water column as the system neared an 
>>eruption.  In the rapid form, there was only slight movement of the 
>>water at about one cycle per second with no overflow.  The slow 
>>form was more like a series of overflow surges separated by many seconds.
>>
>>Carlton Cross
>><mailto:cross at bmi.net>cross at bmi.net
>>
>>
>>
>>
>>At 07:38 PM 9/7/2013, you wrote:
>>Thinking this might interest some gazers who do not read geological 
>>magazines or journals, I'll send along the URL to a post I just put 
>>up about some interesting new studies on geysers:
>><<http://www.yellowstonetreasures.com/author-blog/>http://www.yellowstonetreasures.com/author-blog/>http://www.yellowstonetreasures.com/author-blog/
>>
>>
>>Happy geyser gazing to those of you who get to enjoy the late season!
>>
>>Janet Chapple
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