3016: Cold Air

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Cold Air

Title text: We also should really have checked that the old water tower was disconnected from the water system before we started filling it with compressed air.

Explanation

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Tornadoes generally create winds of about 40-400 mph [1] (about 60-640 km/h) which causes damage to buildings. Cueball proposes a method to essentially blow tornadoes away from cities by keeping enough "tornado repelling" air in a tank. It is not clear if the compressed air will be used to "blow away" the whole tornado, to try to exactly counteract the tornado itself (through applied counter-rotation) or to remove the conditions that cause the development of the tornado's system. The last of these is heavily implied, as replacing any troublesome hot and humid air will remove the conditions required to invoke a nascent tornado. Whether this would work is questionable, since it's precisely the mixing of warm and cold air that produces the swirling motion that creates tornadoes. Rather than dissipating the threat, the very act of displacement could create atmospheric mixing and tornado-generating turbulence in its own right. Several years later, Cueball admits that (for one reason or another) this plan increased wind damage instead of decreasing it.

Cueball proposes keeping the tank at the pressure of a typical scuba tank to counteract the tornado. The title text confirms that at least one tower is a repurposed water tower, which, if using 16 inch pipes as is common, would produce much stronger winds than those of the tornado, because flow speed is inversely proportional to the diameter of the pipes and even a "wide" 16 inch pipe is very narrow for this purpose indeed.

The formula for the velocity of a fluid (air is considered a fluid in physics) is V=√(2*P/ρ) where V is the velocity, P is the pressure, and ρ is the density of the fluid. The density of the fluid is given by the formula ρ=P/(RT) for a given constant R and a Temperature T. In this case, ρ is 0.245 g/cm^3 assuming room temperature, meaning the V=√(2*3000psi/ 0.245 g/cm^3)=410.9 m/s, which is just under 1500 km/h, almost three times faster than the max speeds of the tornados Cueball is trying to prevent. It's also faster than the speed of sound, so anything it touches will generate a sonic boom.

The air needing to be dry might involve a dehumidification process on the air being pumped into storage. But the stipulation that it be cold will probably be more than provided for by adiabatic expansion, so much so that unwise or uncontrolled release of sufficient air to affect a weather system could produce severe cooling effects in the vicinity. To mitigate this could require heat-exchange systems to redistribute heat from the surroundings (which could have the extra beneficial effects of converting external warm and humid air into cool air that has had its excess humidity condensed out), or by unchilling the outflow by heaters, but the handling of the technical challenges and the other means of operation (e.g. any power used) are not covered by what we see of Cueball's plan.

Further, pressurised vessels are liable to bursting, an issue harder to mitigate the larger the internal volume. Cueball's proposal would put particularly large ones in the center of dense cities, creating the possibility for further damage. Especially, if the proposal diagram is to be believed, with the tank itself being twice the height of the tallest surrounding buildings (drawn to resemble skyscrapers, so probably tens of stories tall), being elevated high above them upon by base that also dwarfs them, and dominating the area and its skyline. Assuming a volume of 75 million cubic meters for the tank (based on a rough scaling from the sizes of the buildings), that corresponds to a stored energy of about 700 kilotons of TNT, about 50 times the energy of the nuclear bomb dropped on Hiroshima.

Finally, even if Cueball's air tanks produce winds no faster than a normal tornado, they are now being produced in the centers of heavily built-up areas, significantly increasing the potential for damage.

The result is a quadrupling in damage caused by wind, since now, not only are the tornadoes causing heavy winds, but the tanks — when functioning properly and when malfunctioning — are causing heavy winds too.

In the title text, it is revealed that the water tower they were using to store the compressed air was still plumbed in to the water mains. Given the pressure required for the tower to work properly against tornadoes and the fact that water is nearly incompressible, the pressure from the tower would have been nearly instantly transmitted into the water distribution system. The best case scenario would have been 'just' to have dangerously highly-pressurised water jetting into sinks, bathtubs and toilet cisterns whenever they were used; more severe consequences could be catastrophic failures of pipes and plumbing.

Using technology to disrupt tornadoes before they form was a plot element in Liu Cixin's novel Ball Lightning, and other works. In reality, fringe scientist Prokop Diviš (1698-1765) proposed a weather-control machine to disrupt thunderstorms before they form, and there are occasionally discredited ideas made to control other weather events.

Transcript

This transcript is incomplete. Please help editing it! Thanks.

[Cueball is in front of a diagram of a tornado with a pointer in his right hand. The diagram has arrows flowing from the bottom toward the tornado at the top, and from the tornado toward the rain below it.]

Cueball: Tornado supercells are powered by the inflow of warm, moist surface air.

[Cueball is now in front of a representation of his compressed air tank with a PSI of 3000 next to smaller buildings, appearing to be high-rise buildings or skyscrapers, on both sides of the tank.]

Cueball: Compressed air tanks could produce artificial pools of cold, dry air on demand, disrupting tornado inflow to protect cities.

[Cueball is in front of a line graph labeled "Wind Damage over Time". Wind damage has spiked constantly after a point on the graph labeled "Giant experimental compressed air tanks installed in the middle of every major city"). In a frame in the top left corner, there is a label:]

Several years later:

Cueball: In retrospect, I can see how my plan went wrong.

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Discussion

Back In The Day, one of the idiot youngsters in a first-year chemistry lab, before leaving at the end of the afternoon, connected a water faucet to a natural-gas line (used for Bunsen burners) with a rubber hose, and opened both taps. By the next morning, much of the natural-gas network in the heart of the city was flooded. It took a while to get everything working again, and the cleanup wasn't cheap. BunsenH (talk) 22:50, 25 November 2024 (UTC)

You have the right username to mention this! ;)

Also, the 'big trick', back in my day, was to be at the (correct end of) the science-lab bench and briefly blow into a pipe (temporarily unplugged from the burner) just as you turn your tap on. Then watch as the rest of the row (downstream of your connection to the supply) have their active flames go out. ...but I leave it to your imagination the three main problems (and various other less major ones) with trying that, with the benefit of hindsight. 172.69.195.201 00:02, 26 November 2024 (UTC)

Anyone understand the physics here? It seems clear that adding tanks of cool, dry air will make storms (and particularly tornados) far worse, not better, as the incoming hot, wet air will react with any released air to make even worse/dramatic weather patterns. But is there more to it? If the tanks are sealed, then effect could be muted by simply not releasing the stored air once the problem is realized, but this would be countered by at least two factors: First, the title text indicates that an additonal error was made resulting in it beingg impossible to seal the stored air completely (it escapes through the water system). But also, any time weather got bad enough to open leaks in the system, I think this would produce a catastrophic result as the storm mixed with all the cold dry air at once? Mneme (talk) 23:01, 25 November 2024 (UTC)

My understanding is generally that explosive failure of a container with sufficient "anti-tornado" air inside is going to be non-trivial (and you face this threat constantly, in the settlement that has an "air tower", whereas tornados are relatively infrequent and mostly cross countryside). post-edit: And the editor who set up the current explanation seems to have had much the same idea... gratifying to know I'm on the same wavelength as at least one person!

And the water-connection would be bad due to (first) extremely pressurised water and (immediately afterwards) almost as pressurised air pushing through the areas plumbing systems, with unknown secondary effects such as effectively blowing empty any water-heaters that really shouldn't be left to be 'boiled dry' (after enough air bubbles in, the remaining water will soak up the burner heat and evaporate beyond design limitations, adding to the gas pressure and no longer moderating the effects on the boiler body itself; not sure exactly what will go wrong, but it may not be pretty). 172.69.195.201 00:02, 26 November 2024 (UTC)

Without knowing which 'city' the diagram might be of (or, indeed, how figurative Cueball's illustrative figure might be), I checked the first "tornado alley" city I could think of and came up with One Kansas City Place as how tall the taller buildings might be. In that case, just shy of 200m (with spire on top) and 40-odd floors. The dimensions of the 3000psi tank (external, but ignoring support infrastructure) is somewhere around 400m in height, perhaps 600m side to side, presumably oblate spheroidal, so approaching (less thickness of container walls) 75 million m³ of compressed air. Which is compressed, and would otherwise be around 15,000 million m³ (15 km³!) of atmosphere if ever released. As a very vague upper limit. Notwithstanding the apparent use of an existing (ex-)water-tower in the titletext. But obviously there's possibly abstract and definitely reinterpretable alternative interpretations of the quantities that might be involved. 172.69.195.225 00:48, 26 November 2024 (UTC)

It seems that the wiki math package

<math> </math>

Does not work properly, and returns an error Failed to parse

(Missing <code>texvc</code> executable. Please see math/README to configure.):

when I attempted to add the math describing the speed of the air using LaTeX 172.68.22.92 01:06, 26 November 2024 (UTC)

This is a long-standing error (at some point, one bit of update invalidated the rendering process, and nobody is currently able to update the other component/configuration).

There are plenty of alternate ways to format a newly needed formula, without TeX, and anything that's the same as when it was pre-rendered will continue to show as the inline "formula image" (which I think is potentially worse, anyway, when it comes to accessibility issues). It's really not too hard to do it without the math-tag extension working properly, though. e.g.

p1•v1	=	p2•v2
t1		t2

...as quick example with just a little bit of fine tuning applied. 172.70.160.134 01:44, 26 November 2024 (UTC)

The statement that 3000PSI is 6x higher than known high pressure systems is false. Scuba tanks contain air at this pressure (240bar/3000psi) and the systems used to fill scuba tanks are twice that. 172.71.26.101 (talk) 09:28, 26 November 2024 (please sign your comments with ~~~~)

Perform the wiki magic and add that source!--FrankHightower (talk) 15:04, 26 November 2024 (UTC)

Done. Deleted the reference to one specific product, and just noted that it's a pressure typical of scuba tanks.162.158.154.34 15:00, 27 November 2024 (UTC)

My calculator (Google) says 400MPH is 644 KPH (not 500). Also 40 Bar seems to be well on the high side of 500psi (580psi).

"winds of about 40-400 mph [1] (about 50-500 kph)" "about 40 bar [2] (about 500 psi)."

--PRR (talk) 01:11, 26 November 2024 (UTC)

The source says tornadoes go up to 318 mph (512 kph) but the strongest tornado on record exceeded that. I couldn't confirm when I wrote whether that was actually the strongest, and since the only purpose of the number is to say "Cueball's windspeeds are way, way worse", I decided an upper bound of 400 covered it.--FrankHightower (talk) 15:04, 26 November 2024 (UTC)

"I decided an upper bound of 400 covered it." Somebody edited my words and omitted the key point: ARITHMETIC. English to Metric is NOT 4:5. --PRR (talk) 23:32, 26 November 2024 (UTC)

Hmmm... "English to Metric". Strange phrase, for various reasons. ;) 172.69.195.200 00:13, 27 November 2024 (UTC)

So my brief wikihole dive has me doubting again; but is the part about requiring refrigeration accurate? By my understanding, pressurising the air in the first place would raise its temperature. It then goes back to equilibrium with the environment while it's stored at pressure, and temperature drops when it's released. 172.71.99.67 (talk) 08:19, 27 November 2024 (please sign your comments with ~~~~)

Possibly the editor concerned got confused about the liquefaction of gases (compression by cooling). I agree that (after any amount of compressed equilibreum), released compressed air will likely by cool be default. The 200x expansion would mean heat energy originally stored in the 3000psi container would reduce the effective temperature of the final state by an eye-watering (and then probably flash-freezing!) amount, in the main release plume.

But you might want to apply refrigeration to the compression mechanism, or just after, to take the edge off the concentrated heat and rise in temperature you generate within the pressure vessel whilst filling (assuming you don't do it tediously slowly). 141.101.98.50 14:05, 27 November 2024 (UTC)

Just heard on the BBC Science in Action podcast 21November - the USA research group Climate Action, has shown that the damage due to wind goes up with the eighth power of the speed. Thus 9% increase results in twice the damage! Would help to explain some of the magnitude of the peaks on the graph! RIIW - Ponder it (talk) 09:12, 27 November 2024 (UTC)

So, not a fluid dynamics expert here, but are we sure that using a naive equation for fluid flow will provide the right figure here? My understanding is that near the speed of sound, fluid flow becomes choked and limited to ~ the speed of sound. Although in the past I was mainly investigating this in the context of STP air flowing into a vacuum, so maybe the high pressure changes it. - Buggy, not a registered user 172.69.71.160 (talk) 09:41, 27 November 2024 (please sign your comments with ~~~~)

The comparison to Hiroshima is based on a compressed gas energy calculation, U = PV/(g-1) * {1 - (p/P)^[(g-1)/g]}, where P is the stored pressure, p is the outside pressure, V is the volume of the storage vessel, and g is the ratio of specific heats (1.4 for air). Took V = 75 million m^3, as estimated above.162.158.154.34 15:00, 27 November 2024 (UTC)

I like the Prokop Diviš mention but was he really a fringe scientist for also being a theologist and suggesting weather control in the 1700s? Some of his ideas were functional: he invented the lightning rod around the same time and independently of Benjamin Franklin but spectacularly failed with its marketing by underestimating how superstitious his village was (they thought it was causing a drought and took it down; later in storm season some houses burned down and vilagers changed their mind but Diviš refused to reinstate it). ChaoticNeutralCzech (talk) 17:43, 27 November 2024 (UTC)