U.S. Army Corps of Engineers Bay Model (en.wikipedia.org)
147 points by tosh 2 days ago
Lammy an hour ago
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, and Marin City at 09:23.
nonethewiser a minute ago
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.
LucasLanglois 6 hours ago
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 4 hours ago
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 3 hours ago
Someone should do a follow up episode with a person dressed up as Godzilla.
NoSalt 3 hours ago
vlad-asis 10 minutes ago
Their models HEC-HMS and HEC-RAS are really great hydraulic models. Unfortunately, with Windows native interfaces...
hirpslop 3 hours ago
The bay’s first LLM (large liquid model) was invented in the 1950s.
WillAdams 6 hours ago
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 5 hours ago
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.
carderne 5 hours ago
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 2 hours ago
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 an hour ago
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 an hour ago
Autodesk was founded in Marin and later moved down. This model is 10km^2 so it's not moving anywhere.
dieselgate an hour ago
karlgkk 2 hours ago
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
Robdel12 5 hours ago
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 3 hours ago
>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.
e40 2 hours ago
Took my son there when he was young (6?) and we all loved it. What a great day trip.
nkrisc 6 hours ago
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 5 hours ago
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 2 hours ago
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.,
WillAdams 5 hours ago
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 5 hours ago
I think a model this size full of alcohol would also be quite hazardous for several reasons.
btrettel 4 hours ago
redm 6 hours ago
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 4 hours ago
This is a hidden gem in the Bay Area. Go check it out if you live near by.
youngtaff 3 hours ago
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 3 hours ago
https://en.wikipedia.org/wiki/United_States_Army_Corps_of_En... has a good overview. Note that 97% of the employees are civilians.
wbl 3 hours ago
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.
bumby 3 hours ago
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.
nxobject 2 hours ago
They're decentralized enough as well that some of their local offices have hilarious online presences. For example, Portland...
obvioustourist 5 hours ago
See also the Mississippi River Basin model built by German engineer POWs during WWII: https://en.wikipedia.org/wiki/Mississippi_River_Basin_Model
contingencies 6 hours ago
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 5 hours ago
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 2 hours ago
>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.
supertroop 5 hours ago
Don’t show something good the government has done or the POTUS will cancel it!!!