Astro Hacker News - U.S. Army Corps of Engineers Bay Model

Lammy |next [-]

Big fan of this thing. It's one of my favorite places to take friends who visit the Bay Area.

Something that's not mentioned in the article is that the building they occupy is a former warehouse of Marinship, a World War Ⅱ shipyard that made Liberty Ships and T2 oil tankers used to supply fuel in the Pacific Theater: https://en.wikipedia.org/wiki/Marinship

The Bay Model building has a Marinship museum in a front room. For anyone who wants to see Marinship's full story in motion, here's my HEVC encode of ‘“Tanker” — 1942–1945 War Time History of Marinship Corporation’ https://mega dot nz/file/lgtmlKIA#asrzuwGOxi6l8I5BmgyAxfKkm1zFcxvY4SYS1SxqtZk

See also Marin City, which is the remains of Marinship's on-site worker housing: https://en.wikipedia.org/wiki/Marin_City,_California

e: the Bay Model building is the big square one that is center-frame starting at 04:30 in the video, Marin City at 09:23, and some beginnings of modern-day international oil politics at 12:28.

Wistar |root |parent |next [-]

I used to live in Tam Junction, close to Sausalito. I had lived there at least a year before I discovered the Bay Model and was amazed when I visited it. It is huge.

nonethewiser |root |parent |previous [-]

I went to SF once for a few days and this is one of the things my friend showed me in my limited time there. I remember it from time to time. It's pretty cool.

Im trying to reflect on why it was so memorable. I thought it was interesting at the time but it wasnt mind-blowing or something. I think it is just just such a unique oddity and a relic of the past. There was so much effort and space devoted to this. You'd never do something like that today.

LucasLanglois |next |previous [-]

If you don't know Tom Scott, he has done a great video 4mn vide on the model where you can see it in action: https://www.youtube.com/watch?v=i70wkxmumAw

MontagFTB |root |parent [-]

Yes, that’s a great video. The Mythbusters used the same model to understand Bay Area current flows during their Alcatraz escape attempt episode.

rbanffy |root |parent [-]

Someone should do a follow up episode with a person dressed up as Godzilla.

NoSalt |root |parent [-]

I am ... confused by your statement.

rbanffy |root |parent [-]

To simulate a Godzilla incursion and check if the movie where Godzilla attacks San Francisco makes an accurate depiction of what would happen.

For science.

hnav |root |parent [-]

The real question is would a Godzilla incursion be good for property values (novelty, tourism attraction, remove some housing stock) or decimate them (safety concerns, change the spirit of neighborhoods).

gumby271 |root |parent [-]

Depends on the cost of Godzilla insurance, which currently is quite low. Lock in now!

hirpslop |next |previous [-]

The bay’s first LLM (large liquid model) was invented in the 1950s.

WillAdams |next |previous [-]

It's a shame that there isn't a series of articles on such models --- saw the Chesapeake Bay model (mentioned in a footnote) on a field trip when I was much younger (and it was still in active use for research I believe, yes, as my kids constantly tell me, I'm old).

Simulation used to be essentially impossible, something one dreamed of, or had to pay for time on a Cray or similar supercomputer/cluster.

Apparently, the Chesapeake Bay model was built just as that was becoming feasible:

https://easternshorebrent.com/2017/11/30/doomed-progress-the...

and has since been dismantled and a business park built on the site.

mattlong |next |previous [-]

I highly recommend a visit. It’s only a beautiful ferry ride and nice walk along the waterfront away from San Francisco. A refreshingly retro and analog experience.

taco_emoji |next |previous [-]

There's a similar model for the entire Great Lakes watershed at Discovery World in Milwaukee. You can even press a button to make it rain!

carderne |next |previous [-]

John McPhee talks about a similar model for the Mississippi River in “The Control of Nature” Well worth a read. Fun stories about Hawaii and Los Angeles too, iirc.

msisk6 |next |previous [-]

I haven't been there in awhile.

Back in the 90's the Autodesk tech office was next door to the Bay Model and we'd occasionally pop over for lunch and tour the place.

Great to see it still around and open to the public.

dieselgate |root |parent [-]

Was it displayed at the Civic Center or did Autodesk have an office location in Sausalito? I had never heard of this Bay Model and believe to only have seen a model at the (new location) of the Exploratorium - this was over a decade ago so don't quite recall

hnav |root |parent [-]

Autodesk was founded in Marin and later moved down. This model is 10km^2 so it's not moving anywhere.

dieselgate |root |parent [-]

Yes, the Marin Civic Center in Terra Linda is what I'm referring to.

Edit: above said "next door" so I'm curious how literal they meant this

Robdel12 |next |previous [-]

This is neat to see. US army crops of engineers is a negative “word” to me after growing up in FL and they destroyed so many ecosystems. And the entire Everglades. They’re still at it now. My family has basically spent the past 30 years fighting a ware they put in on our natural creek. It killed the creek, it shrunk the flow to the size of the culvert.

So, It’s neat to see something competent! Imagine if they modeled what cutting off the natural draining to the Everglades would do :p

bumby |root |parent [-]

>It’s neat to see something competent!

The existence of negative externalities or tradeoffs does not inherently imply incompetence.

I remember reading that the USACE said the NOLA levees would not adequately protect against a category 5 hurricane but the powers that be didn’t think the added cost for a more robust design was worth the risk. If true, it doesn’t imply USACE was incompetent but that we live in an uncertain world with tough tradeoffs.

vlad-asis |next |previous [-]

Their models HEC-HMS and HEC-RAS are really great hydraulic models. Unfortunately, with Windows native interfaces...

karlgkk |next |previous [-]

I’d gone here as a young child in school, and then went as part of a team building afternoon. Massive Deja Vu in front of all of my coworkers

nkrisc |next |previous [-]

The distortion is interesting and something I didn’t realize the model included. I assume that it’s necessary because the effects of surface tension and the viscosity of water (and other effects?) change its behavior at this scale relative to the features of the model?

lorenzohess |root |parent |next [-]

If I recall correctly, at an undistorted scale, the water would be so shallow that surface tension and viscosity would dominate, so the depths are exaggerated to keep the flow realistic.

More specifically, tidal flow obeys Froude similarity, not Reynolds. Matching the model's Froude number to the real Bay's requires enough depth for gravity waves and tides to scale correctly, which the vertical exaggeration provides.

But the distortion makes the flow too efficient, so copper strips are added throughout to achieve the right frictional resistance.

bumby |root |parent |next |previous [-]

Have you ever watched a movie with a fire or explosion just didn't look right because it was a scale replica? At a subconscious level, you may have picked up on how the dynamics of the smoke or debris didn't fit right with the scale. It's because the fluids in the model lacked "similitude" at the adjusted scale.

When building scaled models, adjustments have to be made to create that similitude, usually done by comparing some dimensionless number at the real scale and model scale. If you're using water, maybe you can't adjust the viscosity, so you may you have to adjust the velocity to get the same dimensionless number. Everything doesn't just scale linearly; you tweak the variables to achieve the dimensionless value so the whole system dynamics remain faithful.

E.g.,

https://en.wikipedia.org/wiki/Froude_number

https://en.wikipedia.org/wiki/Rayleigh_number

WillAdams |root |parent |previous [-]

Yes. Another technique was to use alcohol rather than water since it has lower surface tension, but that was only workable for smaller models (which were usually enclosed).

nkrisc |root |parent [-]

I think a model this size full of alcohol would also be quite hazardous for several reasons.

btrettel |root |parent [-]

Even if it wasn't a large size, it likely wouldn't be great. During my PhD on sprays, I did some (unpublished) experiments using isopropyl alcohol to reduce the surface tension. The nozzles I used were around 1 mm in diameter as I recall. I did not anticipate that the room would fill up with isopropyl alcohol vapor and (probably) tiny droplets. I wore a mask and maybe left the room while each trial was running. Breathing that likely wasn't great for my lungs.

lstodd |root |parent [-]

You just get drunk from the vapour way faster than it can have a measurable impact on the lungs.

(you can actually drink it if it's reasonably pure. it's even less toxic than ethanol, but the hangover is terrible)

e40 |next |previous [-]

Took my son there when he was young (6?) and we all loved it. What a great day trip.

redm |next |previous [-]

These are the kinds of interesting engineering challenges that were solved with human ingenuity and grit; I wish we were talking more about them to our youth to inspire imagination about what's possible.

eezing |next |previous [-]

This is a hidden gem in the Bay Area. Go check it out if you live near by.

obvioustourist |next |previous [-]

See also the Mississippi River Basin model built by German engineer POWs during WWII: https://en.wikipedia.org/wiki/Mississippi_River_Basin_Model

youngtaff |next |previous [-]

Why do the Army Corps of Engineers get so involved in civil infrastructure in the US - thinking of the Mississippi in particular?

In other countries the government would be involved but it would be a civilian rather than military role

macintux |root |parent |next [-]

https://en.wikipedia.org/wiki/United_States_Army_Corps_of_En... has a good overview. Note that 97% of the employees are civilians.

bumby |root |parent |next |previous [-]

Not sure about the exact thrust of your question but a few points:

- flood management is not easy to monetize so there is not much incentive for private industry. The timelines for design decisions (100 year, 500 year) often don’t mate well with private incentives

- it crosses many property boundaries which makes it hard to manage unless you have the rights of a government

- much of the work is still done by private companies but managed by the government, just like other infrastructure works like roads, bridges etc.

wbl |root |parent |next |previous [-]

The US did not have a civilian engineering school for a few decades after the founding. West Point was the only institution creating engineers. Given they had responsibility for port defenses the civil engineering of waterways was an easy addition.

nxobject |root |parent |previous [-]

They're decentralized enough as well that some of their local offices have hilarious online presences. For example, Portland...

https://www.instagram.com/corpsofengineers_portland/

contingencies |next |previous [-]

The fellow who lived next door to me told me of a similar model system used to model Sydney Harbour which he worked on in the 1970s. IIRC it was instrumented with electronics and linked to a VAX or similar early machine.

emmelaich |root |parent [-]

The Aus Navy had a computer simulation of Sydney Harbour, dating from the 70s or maybe 80s. One particular feature of the system was a disk drive about 1m in diameter with about 12 heads. Cost a bomb, but I guess it was worth it.

When I saw a demo, they had an easter egg of a Loch-Ness type monster in it.

There's also a topographical map of the harbour at St Ives showground but it's purely non-hydrographical. But it's almost disappeared now through neglect.

cucumber3732842 |root |parent [-]

>The Aus Navy had a computer simulation of Sydney Harbour, dating from the 70s or maybe 80s. One particular feature of the system was a disk drive about 1m in diameter with about 12 heads. Cost a bomb, but I guess it was worth it.

Meanwhile the Soviets probably found a little inlet somewhere that was "close enough", evicted anyone who lived there and excavated it to match.

Some junior engineer probably had to wake up at 1am to take a kayak out to "Little Kotlin Island" to change the tape in the recording equipment in time for the tide change.

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supertroop |previous [-]

Don’t show something good the government has done or the POTUS will cancel it!!!