train aerodynamics

Rohang

hi friends,
can any one gimme a link describing the aerodynamic effect of a moving train on its vicnity space. a study about how the air around it becomes when the train moves.

mshinavar

If you can find "An Album of Fluid Motion" a picture book of windand water tunnel experiments, im sure there is a picture of a rectangular (or square block) in a flow on a "ground".

essentially, there will be hig pressure in front of the train as the flow stagnates or stops as it hits the front of the train. probably separation will occur as it comes over the top of the front of the train. the various features on the train along its length (cylindrical handrails, spaces between cars, etc) will create tons of drag, and at the back of the train, the flow will separate. Luckily, trains generally move slow, so aerodynamic effects are quite small. however, above say 45 mph, it starts to take a larger effect proportional to V^2

DaveC426913

Mythbusters! If they didn't test it, it didn't happen! Yay!

mshinavar

I think it would be better to adapt the drafting - truck and car in a windtunnel to this question rather than the stroller into the train experiment.

of course, if that is what you are referring to, which I think you are

mgb_phys

You're in USA/Canada I take it?
They generaly have to slow down to go through stations, but the aerodynamic effect of a pair of 250km/h trains passing each other or entering a tunnel is not negligible. For their effects on other objects http://www.redwingengineering.com/vehicle_aero.html

mshinavar

yes, I live in the land of slow trains. I fully understand what you are referring to, hence the comment that aerodynamics start to pick up at 45 mph.

In my local region the fastest trains go 70mph, most staying at 45mph or under

DaveC426913

It is kind of funny how train speeds (/some highway speeds) and size-of-country have a somewhat reciprocal relationship.

mshinavar

i was just thinking about that, while responding to the truck wind tunnel thread here. how the truck in this non-American country is going 40mph, but the trains probably 150mph, and we go 80mph on the freeway and the trains go 45mph.

you would think America being a big country by land size would have developed high speed freight trains. probably too much pollution a la SST

mgb_phys

Europe is about the same size ( area and population ) as the USA.
Part of this is historical, europe ended up with a dense network of railway lines in the C19, in the 1950 and 60s these were extended and updated in most countries as a national pride type project. In the US the interstate system was built for the same reasons - but there the goal of enabling individual businesses ( entrepreneurial truckers) rather than goverment monopolies meant roads were built. Britain of course closed 75% of it's rail links!
The reason passenger trains caught on in europe while flights caught on in the USA is probably due to geography, Norway to Spain might be the same distance as New York - LA but not many people in Norway needed to regularly go to spain, they needed to go to Sweden. Trains are better if you have more local connections.
The effect is even more pronounced in Japan, you have a small densely populated country where it is difficult to build roads. As a result they built an excellent rail system.

Trains (even high speed ones) are very efficent - and since most are electric they can be powered by nuclear/hydro if you have it.
I suspect in the next few decades the ability to go accross Europe at 300km/h in something that doesn't need oil wil become usefull.
There is under construction a series of express freight links which will allow freight to travel at 150mph accross most of europe with tunnels accross the English channel and links to scandanavia.

mshinavar

In Europe. the US would have to build a huge infrasturcture of cantanary (sp?) wires for electric trains. only small inter/intra city trains are electric.

That is something we really lack, a good rail system. I drive 60 miles to work every day. I would much rather take a train, but alas, there is no rail service within 50 miles of my workplace. we have a subway system in LA, but its like the size of something disneyland would make

sorta disappointing

DaveC426913

mshinavar

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